Search

Relatively little is known about the taxonomy and ecology of deep-sea nematode species inhabiting cold seep habitats. The available data show that cold seep nematode communities are typically characterized by low diversity and are often dominated by a single species, although no nematode taxon appears to have a strong association with methane seepage. In July 2019, a research voyage to New Zealand’s Hikurangi Margin provided an opportunity to characterize the nematode species communities of New Zealand cold seeps, which had not been investigated until now. Here, six new species and two new nematode genera of the class Chromadorea are described from macrofauna cores obtained at three seep sites (Mungaroa, Glendhu, and Uruti South) on Hikurangi Margin from 1227 to 2077 m depth. The species described here represent a wide range of feeding groups, ranging from deposit feeders (Linhomoeus pycnocricus sp. nov., Deraionema barbatum gen. et sp. nov.) to microvores (Aulostomonema abyssum gen. et sp. nov., Aegialoalaimus magnus sp. nov.) and epigrowth feeders (Desmodora parapilosa sp. nov.). The diet of Siphonolaimus curtisensillus sp. nov., which is characterized by an unusual stylet-like feeding apparatus, remains to be determined, however the presence of several different feeding modes in the species described here indicates that a range of food sources are exploited by macrofaunal nematodes at the study sites. Desmodora, Linhomoeus, and Aegialoalaimus have been reported from cold seep habitats previously, however no records of Siphonolaimus from cold seeps could be found in the literature. Aulostomonema gen. nov. does not appear to have a close association with seeps, whilst Deraionema gen. nov. appears to be restricted to the centre of the seep sites where methane seepage is likely strongest. Ongoing work on the ecology and distribution of nematode communities at the Hikurangi Margin seep sites will help determine spatial patterns in abundance and species distributions in more detail, including the identification of any species/taxa with affinities with methane seepage.

Aegialoalaimus magnus sp. nov. urn:lsid:zoobank.org:act: 4D4BD1F6-70E8-4E2B-BF6C-530389C772AA Figs 13–15, Table 6 Diagnosis Aegialoalaimus magnus sp. nov. is characterized by body length 2.8–3.3 mm, papilliform cephalic sensilla, amphids with strongly cuticularized outline and central region with pitted appearance, radiating, cuticularized processes surrounding junction of pharyngostome and cheilostome, secretory-excretory pore located at or near level of nerve ring and ventral gland well posterior to cardia, spicules 1.4–1.6 cloacal body diameters long, well-developed gubernacular apophyses, 11–12 inconspicuous precloacal supplements, and conical tail 2.8–3.5 cloacal or anal body diameters long. Differential diagnosis The new species differs from all other species of the genus in the longer body (2.8–3.3 vs magnus ʼ meaning ʻlargeʼ, ʻgreatʼ and refers to the relatively large size of the species. Material examined Holotype NEW ZEALAND • ♂; Hikurangi Margin, Mungaroa cold seep site; 41.9376° S, 175.3110° E; 2075 m water depth; collected on 7 Jul. 2019; sandy mud sediment (97% silt/clay, mean particle size 19 µm), voyage TAN1904, station 18; NIWA154918. Paratypes NEW ZEALAND • 2 ♀ ♀; same collection data as for holotype; NIWA 154920 • 1 ♂; Glendhu cold seep site; 41.7695° S, 176.0882° E; 1993 m depth; collected 10 Jul. 2019; sandy mud sediment (88% silt/clay, mean particle size 27 µm), voyage TAN1904, station 40; NIWA 154919. Type habitat and locality New Zealand continental slope, Hikurangi Margin, Mungaroa and Glendhu cold seeps. Description Male Body colourless, cylindrical along most of its length, tapering slightly towards both extremities. Cuticle with fine transverse striations without lateral differentiation. Body pores and epidermal glands absent. A few sparse, short somatic papillae, 1 µm long, present in anterior pharyngeal region. Cephalic region slightly rounded; lip region poorly developed, continuous with body contour, lips fused. Inner labial papillae not observed; six short outer labial papillae, Female Similar to males, but with excretory pore located at or slightly anterior to level of nerve ring. Reproductive system didelphic with two opposed and reflexed ovaries both located ventrally or to the left of intestine; spermatheca absent. Vulva situated at mid-body. Proximal portion of vagina surrounded by constrictor muscle, small vaginal glands present. Uterus wall not cuticularized., Published as part of Leduc, Daniel, 2023, New nematode species and genera (Nematoda: Chromadorea) from cold seeps on Hikurangi Margin, New Zealand, pp. 1-45 in European Journal of Taxonomy 856 on pages 29-34, DOI: 10.5852/ejt.2023.856.2025, http://zenodo.org/record/7522913

Setoplectus minor sp. nov. (Figures 5–6 and Table 2) Type material One male and one female were found and measured. Holotype male on slide NHS74-279-1, paratype female on slide NHS79-289-7. Type locality and habitat Holotype was found in muddy clay sediment at Station S 74 in the South China Sea (10.013° N, 115.147°E, water depth 1951 m). Paratype female was found in muddy clay sediment at Station S 79 in the South China Sea (10.751°N, 114.983°E, water depth 2390 m). Etymology The species name is derived from the Latin adjective minor (minute), referring to its tiny body size relative to other members of the genus. Measurements All measurement data are given in Table 2. Description Holotype male. Body elongate spindle, anterior third of pharyngeal region attenuated. Cuticle annulated, annules smooth. Inner and outer labial sensilla papilliform, located on the anterior surface of lips. Four cephalic setae each 2 µm long, located posteriorly to the labial region. Amphidial aperture circular, located at more posterior position of 5 times head diameters from the anterior end. Secretory–excretory system absent. Tubular buccal cavity long and narrow, occupying one-third of the total length of the pharynx. Pharynx guitar shaped, with a middle bulb and a basal bulb, with strongly developed cuticular lining. Mid-pharyngeal bulb rugby ball shaped and basal bulb pear shaped. Cardia cylindrical, partly enveloped by the intestinal tissue in its posterior part. Tail elongate conical with tapered terminus, without terminal setae, 4.3 times abd in length. Three caudal glands present. Spinneret functional. Reproductive system diorchic. Spicules symmetrical, slightly arcuate, with cephalated proximal end and tapered distal end, 21 µm long. Gubernaculum rod-like, slightly curved, 8 µm long. A papilliform midventral precloacal supplement located at 9 µm in front of cloaca. Female. Similar to males in most morphological characteristics except amphidial aperture larger and oval in outline. Reproductive system didelphic with two opposed, outstretched ovaries. Spermatheca unseen. Vulva located at mid-body, 52% of body length from the anterior end. Vulval lips slightly raised. Vagina straight., Published as part of Lu, Yang, Sui, Xinxin & Huang, Yong, 2022, Three new species of free-living marine nematodes from the central basin of the South China Sea, pp. 1091-1107 in Journal of Natural History 56 (17 - 20) on page 1103, DOI: 10.1080/00222933.2022.2102446, http://zenodo.org/record/7012374

Updated key to species of the genus Setoplectus (based on; Andrássy 1973) 1 Body slender (a = 70–90), longer than 1.3 mm....................................................................... 2 - Body plumper (a = 20–35), shorter than 1 mm....................................................................... 3 2 Head spherical, body 1.4 mm long, tail elongate conical, 4 abd long, male with 14 precloacal supplements.................................................................... S. riemanni Andrássy, 1973 - Head conical (narrow), body 2.1–2.4 mm long, tail shorter than 2 abd, male with one precloacal supplement...................................................... S. proceroviscerali Andrássy, 1973 3 Cephalic sensilla longer than 1 hd, situated farther than 1 hd from the anterior end.................................................................. S. amphibulbosus (Gerlach, 1955) Vitiello, 1970 -1971 - Cephalic sensilla shorter than 1 hd, situated close to the anterior end....................... 4 4 Body longer than 0.7 mm, tail conico-cylindrical, 2–3 abd long, male with 4–5 precloacal supplements............................................................... S. gerlachi Vitiello, 1970 -1971 - Body shorter than 0.5 mm, tail conical, longer than 4 abd, male with one precloacal supplement.................................................................................................................. S. minor sp. nov., Published as part of Lu, Yang, Sui, Xinxin & Huang, Yong, 2022, Three new species of free-living marine nematodes from the central basin of the South China Sea, pp. 1091-1107 in Journal of Natural History 56 (17 - 20) on page 1106, DOI: 10.1080/00222933.2022.2102446, http://zenodo.org/record/7012374, {"references":["Andrassy I. 1973. Nematoden aus strand-und hohlenbiotopen von Kuba. Acta Zool Acad Sci Hungaricae. 19 (3 - 4): 233 - 270."]}

Genus Leptolaimus de Man 1876 Diagnosis (Holovachov 2014) Cuticle annulated. Lateral alae present. Cephalic sensilla papilliform or setiform. Amphideal fovea ventrally unispiral (circular in outline). Buccal cavity elongate and tubular. Male reproductive system diorchic, usually having both tubular and alveolar precloacal supplements. The number of supplements varies from zero to 40 for alveolar and zero to 11 for tubular. Female has two opposed and reflexed ovaries, may also have tubular supplements in some species.

Leptolaimus boucheri sp. nov. (Figures 1���3 and Table 1) Type material Three males and four females were collected from the Bohai Sea, China. Holotype male on slide DST151-98. Paratypes on slides DST2-7, DST151-99, DST151-86, DST151-81, DST151- 92 and DST151-87. Type locality and habitat All specimens were found in muddy sediments of the 0���2 cm and 2���5 cm layers, intertidal zone of Tianjin Bay along the Bohai Sea, China (39.209��N, 117.955��E). Etymology The species is named in honour of Dr Guy Boucher, in recognition of his contributions to nematode taxonomy. Measurements All measurement data are given in Table 1. Description Males. Body slender, 545���602 ��m long, tapering towards anterior and posterior ends, greatest body diameter at middle of body. Cuticle distinctly annulated along the body; annuli 2���3 ��m wide, without ornamentation. Lateral alae present, 2 ��m wide at mid-body, originating in the middle of the pharynx and extending along the body to almost half of tail length. Numerous body pores present in sublateral position at both sides of lateral field. Anteriormost body pore located at lateral field and level of buccal cavity base, about 30 ��m from the cephalic apex. Somatic setae not observed. Labial region truncate, slightly offset from body contour. Inner labial sensilla and outer labial sensilla not visible. Cephalic sensilla papilliform. Amphideal fovea circular, 62.5% of corresponding body diameter, situated 9���10 ��m from the cephalic apex. Buccal cavity long, cylindrical, 35���38 ��m deep, 40���44% of pharyngeal length. Pharynx slender, posterior region swollen and forming oval basal bulb. Cardia cylindrical, with posterior part embedded in intestine. Nerve ring surrounding pharynx at 66 ��m from the anterior end. Secretory-excretory system indistinct. Tail conico-cylindrical, 3.8���4.5 cloacal body diameter in length, anterior conical portions gradually transforming to posterior slender cylindrical portions, posteriorly swollen. Caudal glands indistinct. Spinneret present. Caudal setae sparse, and usually six to eight caudal setae distributing subventral and subdorsal sides of tail. Reproductive system with two opposed testes. Anterior testis outstretched, posterior one reflexed. Spicules slender, slightly arcuate, proximally cephalated and distally pointed. Gubernaculum plate-like, curved to spicules, without apophyses. Accessory apparatus composed of a papilla, four evenly spaced tubular supplements and 15���21 successive alveolar supplements. A papillary supplement just anterior to the cloaca. Tubular precloacal supplements almost straight, with tapered tip, 11 ��m long. Winged alveolar supplements with cuticularised wall. The most anterior alveolar supplement located at level of posterior portion of pharynx, 102���112 ��m from the anterior end. The posteriormost one situated about 20 ��m anterior to the anteriormost tubular supplement, 371���417 ��m from the anterior end. Four evenly spaced tubular supplements extending for 82���87 ��m from cloaca forward. The posteriormost tubular supplements 23���25 ��m in front of cloaca. Females. Similar to males in most aspects except body slightly thicker (24���27 ��m vs 18���19 ��m), amphideal fovea slightly smaller (3 ��m vs 5 ��m wide in males) and having a single ventral pre-anal supplements. Supplement tubular, 6���8 ��m long, situated 36��� 50 ��m anterior to anus. Reproductive system didelphic, with two opposed, reflexed ovaries, located to the left side of intestine. Mature eggs large, oval-shaped. Spermathecae not observed. Vagina straight, 0.25 times vulval body diameter long. Vulva midventral, slightly raised, located at mid-body length, 51���53% of total body length from the anterior end., Published as part of Geng, C. X., Hao, Y. D. & Huang, Y., 2022, Description of Leptolaimus boucheri sp. nov. (Nematoda: Leptolaimidae) from the Bohai Sea, China, pp. 2951-2960 in Journal of Natural History 55 (47 - 48) on pages 2953-2954, DOI: 10.1080/00222933.2022.2033868, http://zenodo.org/record/6351778

Genus Aegialoalaimus de Man, 1907 = Tubuligula Boucher & Helléuët, 1977 op. Jensen, 1978 Diagnosis (from Holovachov (2015)): See family diagnosis. Remarks. The genus was revised by Holovachov (2015) who provided a key to all four valid species of the genus.

Aegialoalaimus tereticauda n. sp. (Figs 1 & 2) Measurements. See Table 1. Type specimens. Holotype male (139255), collected 3 December 2017 (voyage TAN1711, station 25, site 3). One paratype male and two paratype females (139256), same data as holotype. Type habitat. Kermadec Trench (30.3815�� S, 176.6417�� W), water depth: 9540 m, sediment depth: 4���5 cm. Etymology. The species name is derived from the latin teretis (= rubbed off, rounded, cylindrical) and cauda (= tail). Description. Males. Body slender, cylindrical over most of its length, tapering slightly towards anterior extremity. Cuticle with transverse striations, without lateral differentiation; somatic setae not observed. Body pores and epidermal glands not observed. Labial region rounded, continuous with rest of body, lips fused. Inner and outer labial sensilla indistinct. Four papilliform cephalic sensilla, located close to anterior body extremity. Subcephalic setae absent. Amphideal fovea large, circular, with lightly cuticularized outline, its anterior end located well posterior to cephalic sensilla bases. Ocelli absent. Oral opening terminal. Buccal cavity narrow, tubular, undistinguishable from cuticularized lumen of the pharynx. Pharynx divided into two sections: anterior tubular part and posterior bulb. Tubular part of pharynx is 97���105 ��m long, 1.3 ��m wide at base and gradually narrowing to 0.8���0.9 ��m anteriorly, surrounded by thin sheath of tissue. Posterior bulb is muscular, with dorsal pharyngeal gland sometimes visible in middle of dorsal sector of posterior bulb. Subventral pharyngeal glands indistinct. Nerve ring located near middle or slightly anterior to middle of pharynx. Secretory-excretory system difficult to distinguish; excretory pore located slightly anterior to posterior bulb, renette cell not observed. Cardia 4���5 ��m long, not embedded in intestine. Reproductive system with two testes. Anterior testis outstretched, located to the left or right of intestine; posterior testis located on same side of intestine as anterior testis, may be directed posteriorly and outstretched, or possibly directed anteriorly and reflexed (with proximal portion obscured). Mature sperm globular, 3�� 4 ��m. Spicules paired, equal, 1.5���1.6 cloacal body diameters long, arcuate, tapering distally and slightly swollen proximally. Gubernaculum small, plate-like, without lateral pieces, without apophyses. Precloacal supplements absent. Ejaculatory glands not observed. Tail cylindrical with rounded tip; three caudal glands present in posterior half of tail with common opening. Female. Similar to males but excretory pore located 1 cbd anterior to nerve ring and slightly longer tail. Reproductive system with two opposed and reflexed ovaries both located to the right of intestine. Vulva located slightly posterior to middle of body length. Vagina perpendicular to body surface; vaginal glands not observed. Diagnosis. Aegialoalaimus tereticauda n. sp. is characterised by body length 755���864 ��m, cephalic sensilla papilliform (A. leptosoma Gagarin, 2012 in the short body length (versus 3���5 precloacal papillae in A. leptosoma), tail shape (cylindrical versus conical in A. leptosoma) and position of caudal gland nuclei (in posterior half of tail versus anterior half of tail in A. leptosoma). Other minor differences include the longer tail (c�� = 4.4���5.3 versus 3.1���4.0 in A. leptosoma), shorter cephalic sensilla (versus 1.5���2.0 ��m in A. leptosoma), and shorter spicules (18���22 versus 23���24 ��m in A. leptosoma). The new species is also similar to A. bratteni Holovachov, 2015 in having papilliform cephalic sensilla and in lacking precloacal supplements, but can be differentiated from the latter by the shorter body (versus 1491��� 1754 ��m), longer tail (c�� = 4.4���5.3 versus 4.2 in A. bratteni), spicule shape (arcuate versus straight in A. bratteni), presence of gubernaculum (versus absent in A. bratteni), and tail shape (cylindrical versus conical in A. bratteni). Molecular phylogenetic relationships. Near full-length SSU (1506���1571 bp) and D2���D3 of LSU sequences (685���720 bp) were obtained for Aegialoalaimus sp., Manganonema sp., and Daptonema amphorum. For Metasphaerolaimus constrictus, partial SSU (850 bp) and near full length D2���D3 of LSU sequences (762 bp) were obtained. Among the orders included in our SSU phylogenetic analysis, only the Desmodorida, Desmoscolecida and outgroup Chromadorida were recovered as monophyletic (Figure 3). The two Aegialoalaimus sequences formed a distinct, well supported clade (100% posterior probability and 98% bootstrap support) without clear relationships with the Plectida, Araeolaimida, Monhysterida, Isolaimiida, or any of the orders included in our analysis. The Xyalidae sequences, including Manganonema sp. and Daptonema amphorum, formed a moderately to well-supported monophyletic clade (100% posterior probability and 69% bootstrap support). Within the Xyalidae, Daptonema amphorum was grouped with sequences of Daptonema Cobb, 1920 spp., Zygonemella striata Cobb, 1920 and Metadesmolaimus Schuurmans Stekhoven, 1935 sp. with 98% posterior probability but less than 50% bootstrap support. Manganonema sp. was most closely related to Theristus agilis (de Man, 1880) Filipjev, 1918 (93% posterior probability and 60% bootstrap support). Metasphaerolaimus constrictus and the other Sphaerolaimidae sequences formed a well-supported monophyletic clade (100% posterior probability and bootstrap support). The Monhysterida was not monophyletic due to the placement of taxa belonging to the Siphonolaimoidea Filipjev, 1918 (Monhysterida II and III; Figure 3) outside of the main monhysterid clade (Monhysterida I; Figure 3)., Published as part of Leduc, Daniel & Zhao, Zeng Qi, 2021, Molecular characterization of free-living nematodes from Kermadec Trench (Nematoda: Aegialoalaimidae, Xyalidae) with description of Aegialoalaimus tereticauda n. sp., pp. 341-352 in Zootaxa 4949 (2) on pages 344-347, DOI: 10.11646/zootaxa.4949.2.7, http://zenodo.org/record/4636488, {"references":["Gagarin, V. G. (2012) Thalassomonhystera pygmaea sp. n. and Aegialoalaimus leptosoma sp. n. (Nematoda, Chromadorea) from Vietnam Seashore. Zoologicheskii Zhurnal 91, 1155 - 1160. [in Russian]","Holovachov, O. (2015) Description of Aegialoalaimus bratteni sp. n. from Skagerrak and a review of the genus (Aegialoalaimidae, Nematoda incertae sedis). Biodiversity Data Journal, 3, e 5738. https: // doi. org / 10.3897 / BDJ. 3. e 5738","Cobb, N. A. (1920) One hundred new nemas (type species of 100 new genera). Contributions to a Science of Nematology, 9, 217 - 343.","Schuurmans Stekhoven, J. H. Jr. (1935) Nematoda: Systematischer Teil, Nematoda Errantia. Die Tierwelt der Nord- und Ostsee, 28, 1 - 173.","De Man, J. G. (1880) Die einheimischen, frei in der reinen Erde und im sussen Wasser lebende Nematoden monographisch bearbeitet. Tijdschrift der Nederlandse Dierkundige Vereeniging, 5, 1 - 104.","Filipjev, I. N. (1918) Free-living marine nematodes of the Sevastopol area. Transactions of the Zoological Laboratory and the Sevastopol Biological Station of the Russian Academy of Sciences Series, 2, 1 - 203."]}

Shimada, Daisuke, Suzuki, Atsushi C., Tsujimoto, Megumu, Imura, Satoshi, Kakui, Keiichi (2021): Two New Species of Free-living Marine Nematodes (Nematoda: Axonolaimidae and Tripyloididae) from the Coast of Antarctica. Species Diversity 26 (1): 49-63, DOI: 10.12782/specdiv.26.49, URL: http://dx.doi.org/10.12782/specdiv.26.49

Anaplectus labiosulcus sp. nov. (Figs. 3, 4) Measurements. Table 2. Description. Female: Body arcuate, more so towards posterior extremity. Outer cuticle annulated, 1.5–2.0 μm thick, relatively loose in lip region; annules 1.5 μm wide; inner cuticle not striated. Somatic setae indistinct. Lat-eral fields extending from nerve ring up to middle of tail length, ca 1/5 th– 1/6 th corresponding body diameter wide, appearing as three lines under LM as the two lateral alae are closely placed. Amphidial aperture a transverse or elliptical slit, located at 3 rd or 4 th body annule. Sub-cuticular sublateral, round to ovoid, hypodermal glands, opening through 115–123 conspicuous, cuticularised pores; running from anterior to posterior body end laterodorsally and lateroventrally. Except for the anteriormost 5–6 hypodermal glands, which lie in a single row laterally, the glands run in two rows with opposite as well as alternate positions and with the laterodorsals usually larger than the lateroventrals. First hypodermal gland opens 2–3 μm posterior to amphidial opening. Lip region low, slightly offset from adjoining body. Cephalic setae 3–4 μm long, arising at level of 3 rd annule. Lips six, closely placed or amalgamated with cuticularised semicircular interlabial grooves. Stoma comprising of non-cuticularised cheilostom, strongly arched, C-shaped gymnostom, and parallel-walled stegostom surrounded by pharyngeal sleeve; gymnostom wall often bends before joining the stegostom, giving the gymnostom an appearance of double-arched structure. Pharynx differentiated into anterior corpus, a somewhat indistinct isthmus and a pyriform basal bulb with post-bulbar extension surrounded by cardia. Basal pharyngeal bulb ovoid, 23–26 µm long and 17–20 μm wide in dimension with a grinder comprising of 5–7 pairs of denticulate ridges and a haustrulum. Nerve ring encircling corpus at 51–53% of pharyngeal length; pharyngeal region narrow and compressed at level of nerve ring. Secretory-excretory pore posterior to nerve ring at 56–60% of pharyngeal length, duct cuticularised and coiled extending to a posteriorly located uninucleate excretory cell. One pair of ovoid pseudocoelomocytes present posterior to cardia. Intestine appearing granular and thin-walled. Rectum thick-walled, smaller than anal body diameter, without rectal glands. Reproductive system didelphic, amphidelphic. Ovaries well developed, reflexed; anterior ovary on right and posterior on left side of intestine. Oocytes arranged in 2–3 tiers distally; intra-uterine eggs present with spinose shells. Sperms not observed in genital tract. Vagina straight, 1/4 th of vulval body diameter, provided with two pairs of muscles appearing elliptical in cross section. Vulval lips flush with the main body or slightly protruding. Tail plump, conoid, ventrally arcuate with four caudal setae. Three caudal glands arranged in a group and opening through a conspicuous, cuticularised spinneret. Male: Not found. Type habitat and locality. Sample containing Anaplectus labiosulcus sp. nov. was collected from soil from the grass at the bank of a drain at Khair, Aligarh, India at coordinates N 27° 56’ 24.38”, E 77° 50’ 34.54”. Type material. Holotype female on slide Anaplectus labiosulcus sp. nov. NOK/1 deposited in the Nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh. Five paratype females on slides Anaplectus labiosulcus sp. nov. NOK/2–6 deposited in the Nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh. Diagnosis and relationship. Anaplectus labiosulcus sp. nov. is characterised by medium-sized females having thick, annulated cuticle; 115–123 sublateral hypodermal glands on each side of body with dorsals usually larger than ventrals; 5–6 anteriormost glands unpaired arranged linearly; slightly offset labial region; lips with cuticularised, semicircular interlabial grooves; amphids located in anterior part of stoma; gymnostom arched, occasionally double-arched; stegostom parallel-walled; ovoid to rounded basal bulb; vulval lips slightly protruded; four caudal setae and caudal glands grouped opening through a cuticularised spinneret. The new species most closely resembles A. eurycerus in most of the morphometric details and the absence of males but differs in having smaller a (19.2–23.2 vs 25) value; slightly offset lip region with cuticularised semicircular interlabial grooves (vs lip region usually continuous, cuticularised interlabial grooves absent); relatively anterior position of amphids (located at anterior vs middle level of stoma) and stoma 2.5 [vs 3.5 times lip region diameter long in A. eurycerus (Massey, 1964)]. The new species also resembles A. octo in most of the morphometric details and in absence of males but differs in having smaller a (19.2–23.2 vs 26–27) and ć (1.8–2.2 vs 3.3) values; greater c (13.9–16.4 vs 11–13) and V (53.9–55.6 vs 51) values; gymnorhabdia single or double-arched (vs always double-arched or hourglass-shaped) and relatively larger stoma [25–27 μm vs 23–24 μm in A. octo (Zullini,1973)]. A. labiosulcus sp. nov. further resembles A. granulosus in most of the morphometric details but differs in having relatively smaller individuals (0.7–0.8 mm vs 0.7–1.5 mm); relatively lower a (19.2–23.2 vs 20–39) and b (4.0–4.3 vs 4–6) values; smaller number of hypodermal glands (115–123 vs 160); dorsolaterals usually larger than dorsoventrals (vs no size differences observed); greater number (five to six vs one) of unpaired hypodermal glands in the anterior region; four pairs (vs three pairs) of caudal setae and male absent [vs present in A. granulosus (Bastian, 1865) De Coninck & Schuurmans Stekhoven, 1933]. Etymology. The name of the species labiosulcus stands for labial grooves which are conspicuously cuticularised. Anaplectus granulosus (Bastian, 1865) De Coninck & Schuurmans Stekhoven, 1933 (Fig. 5) - Plectus granulosus Bastian, 1865 - Plectus schneideri de Man, 1880 - Plectus tubifer Cobb, 1914 - Plectus blanci Hofmänner in Hofmänner & Menzel, 1914 - Marinoplectus tetrapapillatus Kreis, 1963 - Anaplectus arenicola Killick, 1964 Measurements. Table 3. Description. Female: Body more or less C-shaped after fixation, more ventrally arcuate towards posterior extremity with maximum body width observed in the mid-region. Outer cuticle coarsely annulated, 2.0–3.0 μm thick, annules 1.5 μm wide; inner cuticle not striated. Lateral fields consist of three lateral lines under LM originating near the anterior pharyngeal region and extending almost to tail terminus. Amphid aperture a transverse slit, located at 8 th or 9 th body annule. Sub-cuticular hypodermal glands distinct, opening through conspicuous, cuticularised pores; running from anterior to posterior body end laterodorsally and lateroventrally (except for the 1 or 2 anteriormost linearly-arranged glands). Laterodorsals and lateroventrals large and of almost similar size, running in two rows with opposite as well as alternate positions comprising a total of 120–125 lateroventral and laterodorsal pores on each side. First hypodermal gland opens 2–3 μm posterior to amphid opening. Cervical papillae located just posterior to amphid or near to first lateral pore. Lip region slightly offset from adjoining body. Lip region consists of six separate lips; labial sensilla indistinct. Cephalic setae 2–4 μm long, arising at level of 2 nd or 3 rd annule. Stoma comprising of non-cuticularised cheilostom bordered by lips, arcuate cuticularised gymnostom, shorter than wide; stegostom surrounded by thin pharyngeal sleeve, subdivided into two parts: anterior broad cylindrical tube comprising of fused pro-, meso- and metastegostom and posterior narrow telostegostom, enveloped by muscular pharyngeal tissue. Pharynx differentiated into anterior corpus, a somewhat distinct isthmus and basal bulb. Corpus gradually widening posteriorly. Isthmus narrower and slightly demarcated from corpus. Basal pharyngeal bulb rounded, 25–28 µm long and 18–24 μm wide in dimensions with grinder composed of 5–7 pairs of denticulate ridges and haustrulum. Postbulbar extension elongate or conoid, enveloped by cardia. Nerve ring encircling corpus at 54–57% of pharyngeal length. Secretory-excretory pore posterior to nerve ring at 58–62% of pharyngeal length, duct cuticularised extending to a posteriorly located uninucleate excretory cell. Deirids papilliform; located inside lateral field posterior to nerve ring or adjacent to secretory-excretory pore. Intestine thin-walled without distinct lumen. Rectum thickwalled, smaller than anal body diameter. Reproductive system didelphic, amphidelphic. Ovaries well developed, reflexed; anterior ovary on right and posterior on left side of intestine. Each genital branch possesses a prominent spermatheca, and crustaformeria followed by spacious uterus. Single intra-uterine egg present measuring 62 μm long x 37 μm wide in dimension with spinose shell. Sperms not found in genital tract. Vagina straight, 1/3 th -1/4 th of vulval body diam. Vulval lips slightly protruding. Tail conoid, ventrally arcuate, with bluntly rounded terminus. Caudal glands three, distinct. Cuticularised spinneret present. Two pairs of small caudal setae observed in the posterior half of the tail length. Male: Not found. Habitat and locality. The sample containing Anaplectus granulosus was collected from manure at Java, Aligarh, Uttar Pradesh, India at coordinates 27.9392° N, 77.8424° E. Voucher specimens. Four females on slide Anaplectus granulosus RJ-JV 2/1–3 deposited in the Nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh, Uttar Pradesh, India. Remarks. Allen and Noffsinger (1968) provided a detailed description of the poorly known type species A. granulosus The original description (Bastian 1865) of A. granulosus was based upon females, however, Allen and Noffsinger (1968) described the male, and also collected from the type locality and designated the neotype from soil around stubble from Broadmoor, England. They also synonymised A. areniocola Killick, 1964 with A. granulosus on the basis of slit-like amphid apertures. The specimens described here agree well with the redescription of A. granulosus as given by Allen and Noffsinger (1968) in morphological as well as morphometric characteristics. A few minor differences were observed, including a relatively smaller body (L = 0.7–0.9 mm vs 0.7–1.5 mm); smaller a (19.2–24.6 vs 20.0–39.0) value; smaller number of hypodermal glands (120–125 vs 160) and two pairs of caudal setae (vs three pairs). This population also conforms well with the population of A. granulosus described by Holovachov et al. (2004), with some minor differences, including lower a (19.2–24.6 vs 24.0–29.9) and c (14.5–17.5 vs 17.2–20.0) values. The present population lacks males as also reflected by spermathecae with no sperms.

Anaplectus sudhausi sp. nov. (Figs. 1, 2) Measurements. Table 1. Description. Female : Body C-shaped; slightly narrowing in anterior region; ventrally arcuate, more so towards posterior extremity. Outer cuticle annulated, 1.5–2.0 μm thick, annules 0.5 μm wide; inner cuticle not striated. Lat-eral field with two wings, marked by four incisures; starting from the middle or posterior part of corpus region and extending almost up to tail terminus; and about 1/6 th corresponding body diameter wide. Somatic setae not discernible. Sublateral hypodermal glands more or less equally sized, ca 1/5–1/6 of corresponding body diameter, arranged in two rows with opposite or alternate positions (except for the anteriormost three unpaired laterally-placed glands) comprising a total of 120–132 lateroventral and laterodorsal pores on each lateral side. Another set of 5–8 small, unpaired laterodorsal glands, approximately 1/7 th of corresponding body diameter, present on the outer side of subdorsal glands dispersed along the entire body length. First hypodermal gland opening 2–3 μm posterior to amphidial aperture. Lip region truncate, continuous or slightly offset from adjoining body. Lip region consists of six separate leaf-shaped lips interspersed by interlabial liplets; apices of lateral lips appear bifid compared to conical apices of submedians. Labial sensilla indistinct. Cephalic sensilla post-labial, stumpy with wide base ca 2–3 μm long, arising at level of 2 nd or 3 rd annule. Amphidial aperture a transverse slit, located at 8 th or 9 th body annule. First hypodermal gland opens ca 2–3 μm posterior to amphidial opening. Cervical papillae located just posterior to amphid or near to first lateral pore. Stoma comprising of non cuticularised cheilostom with straight walls; Gymnostom shorter than wide, with sclerotized arcuate gymnorhabdia and stegostom surrounded by pharyngeal tissue and subdivided into cylindrical pro-, meso- and metastegostom and posterior narrower telostegostom. Stoma with curved/bent walls in some specimens. Stomal lumen opening into pharyngeal lumen marked by pharyngeal tubes. Pharynx differentiated into anterior corpus, a fairly distinct isthmus and an oval to rhomboid-shaped basal bulb with post-bulbar extension leading to a cardia. Basal pharyngeal bulb 20–24 µm long and 18–19 µm wide in dimension with grinder. Nerve ring encircling the isthmus posterior to corpus, at 57–59% of pharyngeal length. Secretory-excretory pore posterior to nerve ring, at 62–63% of pharyngeal length; duct cuticularised and looped extending to a posteriorly located uninucleate excretory cell. One pair of ovoid pseudocoelomocytes present posterior to cardia. Intestine thin-wailed, granular without distinctly demarcated cells. Rectum thick-walled, shorter than anal body diameter without rectal glands. Reproductive system didelphic, amphidelphic. Ovaries well developed, reflexed; anterior ovary on right and posterior on left side of intestine. Oocytes arranged in 2–3 tiers distally; spermatheca with globular sperm cells; columella distinct. Intra-uterine eggs 60–62 µm long and 31–34 µm wide in dimension present with spinose shells. Vagina perpendicular to main body axis, with distinct vagina vera and vagina uterina, extending inward 1/3 rd of vulval body diameter; vulval lips slightly protruding; epiptygma absent. Tail conoid, ventrally arcuate, acutely pointed terminally. Three pairs of caudal setae present; caudal glands reduced, opening through a weakly cuticularised spinneret. Male: Similar to female in general morphology. Reproductive system diorchic, anterior testis outstretched, posterior testis reflexed. Anterior testis and vas deferens on right-hand side and posterior testis on left-hand side of intestine. Three sclerotized preanal tubular supplements or tubuli present: the first one opening at 11–13 µm, the second one at 27–31 µm and the third one 47–51 µm anterior to cloacal opening. Tail short, ventrally arcuate. Spicules arcuate, with oval or round manubrium slightly wider than adjoining calomus or blade. Gubernaculum plate-like with a dorsal projection perpendicular to corpus; large triangular lateral sleeve with a wide base arising from corpus enveloping spicules for about 1/3 rd their length distally and elongated caudal apophyses present. Genital papillae comprising of three precolacals with one ventrolateral pair and a single median papilla close to anterior cloacal lip, five pairs of post cloacal papillae with three lateral in the mid tail region and two subventral pairs close to tail tip. Type habitat and locality. Soil containing Anaplectus sudhausi sp. nov. was collected from the lawn of Institut für Zoologie, Freie Universitat Berlin, Germany at coordinates N 52° 27’ 33.12”, E 13° 18’ 23.80”. Type specimens. Holotype female on slide Anaplectus sudhausi sp. nov. GER/1 deposited in the Nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh. Four paratype females and two paratype males on slides Anaplectus sudhausi sp. nov. GER/2–5 deposited in the Nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh. Diagnosis and relationship. Anaplectus sudhausi sp. nov. is characterised by its medium-sized body, with finely annulated cuticle; labial region slightly offset from body contour; amphid located near anterior part of stoma; leaf-shaped lips interspersed by interlabial liplets; lateral lips with bifid apices; cheilostom with non-cuticularised walls; gymnostom with cuticularized, arcuate walls; basal bulb oval to rhomboid; 120–132 sublateral hypodermal glands on each body side with an additional 5–8 smaller subdorsal hypodermal glands; vulval lips protruding; female tail with three caudal setae and a weakly cuticularised spinneret; males with arcuate spicules with manubrium slightly wider than calomus and blade; last median tubulus or supplement about half spicule length; gubernaculum with a dorsal projection perpendicular to corpus; large triangular lateral sleeve and elongated caudal apophyses and tail terminus with a weakly cuticularised spinneret. Anaplectus sudhausi sp. nov. resembles A. atubulatus in most morphometric details but differs in having an additional row of smaller, subdorsal hypodermal glands (vs additional row not reported), three pairs (vs two pairs) of caudal setae in females; males with gubernaculum having crura or lateral sleeve with a wide base (vs narrow base); closely spaced (vs more widely spaced) tubuli; three precloacal and five pairs of postcloacal (vs three precloacal and seven pairs of postcloacal) genital papillae and spinneret present [vs absent in A. atubulatus (Holovachov et al. 2004)]. The new species also resembles A. brzeskii in most of the morphometric details but differs in having an additional row of smaller subdorsal hypodermal glands (vs additional row not reported); males with three precloacal and five pairs of postcloacal (vs one precloacal and thirteen pairs of postclocal) genital papillae and spinneret weak [vs strongly cuticularised in A. brzeskii (Holovachov et al. 2004)]. A. sudhausi sp. nov. differs from A. granulosus in having relatively smaller-sized (0.81–0.86 mm vs 0.7–1.5 mm) females; fewer (120–132 vs 160) hypodermal glands; an additional row of smaller, subdorsal hypodermal glands (vs additional row not reported); three pairs (vs four pairs) of caudal setae; males with arcuate spicules with manubrium wider but continuous (vs separated by a notch) with calomus; gubernaculum with prominent (vs weak) conical sleeve; lesser (vs greater) number of genital papillae and spinneret weak [vs strongly cuticularised in A. granulosus (Allen & Noffsinger 1968, Holovachov et al. 2004)]. The new species further differs from another gonochoristic species, A. varicaudatus in most of the morphometric details but differs in having lateral fields with four (vs three) lines under LM; greater number (120–132 vs 98) of hypodermal glands; an additional row of smaller, subdorsal hypodermal glands (vs additional row not reported); gubernaculum with a conspicuous triangular lateral sleeve or crura and dorsal apophyses [vs lateral sleeve or crura and apophyses not reported in A. varicaudatus (Allen & Noffsinger 1968)]. Etymology. The new species is named after Prof. Walter Sudhaus acknowledging his valuable contributions to nematode systematics.

Antomicron holovachovi sp. nov. (Figures 1–3 and Table 1) Type material One male and two females were obtained. Holotype: male, on slide number JZW(17–8). Paratypes: ♀ 1 and ♀ 2, on slides numbered JZW(17–7) and JZW(47–31), respectively. (The holotype specimen is deposited in the Marine Biological Museum of Chinese Academy of Sciences, Qingdao, and the paratype specimens are deposited in the biodiversity laboratory of Liaocheng University.) Type locality and habitat Specimens were collected from the surface 0–2 cm sublittoral silt sediment in Jiaozhou Bay (JZW-17: 36.119°N, 120.217°E). Water depth of 11 m. Etymology The species is named in honour of Dr Oleksandr Holovachov, Swedish Museum of Natural History, for his contributions to nematode taxonomy. Measurements All measurement data are given in Table 1. Description Male. Body cylindrical, tapering anteriorly in cervical region and posteriorly on tail. Cuticle with widely spaced transverse striation, 2.2 µm apart, without ornamentation. Lateral field present, consists of single ala (two incisures), 2 µm wide at mid-body; originating at base of amphideal fovea and extending posteriorly to anterior part of tail. Some body pores situated at both sides of lateral field in pharyngeal region. Labial region bluntly rounded, continuous with body contour, lips fused. Cephalic capsule obvious. Anteriormost body annule, which demarcates labial region, located at level of middle of amphid. Inner and outer labial sensilla indistinct. Cephalic sensilla setiform, 1.5 µm long. Amphidial fovea elongate, loop-shaped, 11 µm long and 4.5 µm wide (2.4 times as long as it is wide), 8 µm from the anterior end. Nerve ring surrounding pharynx at level of anterior to excretory pore. Secretory-excretory system present; ventral gland cell large, located anterior part of intestine (230 µm from the anterior end), extends anteriorly along ventral side of pharynx and forms an excretory ampulla just anterior to pharyngeal bulb, and opens to the exterior via a pore just posterior to nerve ring. Buccal cavity uniformly tubular. Pharynx cylindrical anteriorly, with distinct oval basal bulb with strong cuticular internal lining. Cardia cylindrical, its posterior part embedded in intestine. Tail conicocylindrical, gradually narrowing to posterior cylindrical part. Unstriated tail tip swollen. Caudal setae scattered. Three caudal glands present. Spinneret distinct. Reproductive system diorchic; anterior testis outstretched; posterior one reflexed. Spicules slender, slightly ventral curved, with cephalated proximal end and tapered distal end. Gubernaculum rectangular, with a dorsal caudal apophysis, 5 µm long. Accessory apparatus composed of five 11–11.5 µm midventral straight tubular supplements extending for 122 µm from cloaca towards anterior end, and 41 evenly spaced alveolar supplements extending anteriorly. Anteriormost alveolar supplement located at level of cardia, 124 µm from anterior end,posteriormost alveolar supplement 21 µm from the anteriormost tubular supplement (i.e. 143 µm anterior to cloaca). Posteriormost tubular supplement 18 µm anterior to cloaca, anterior to spicules. One pair of subventral precloacal setae and one pair of postcloacal setae present, 2–3 µm long. Female. Similar to male in most respects except slightly shorter body length. Reproductive system didelphic, with two opposed and reflexed ovaries. Oviduct a narrow tube. Two oval, saclike spermathecae located on each side (anterior and posterior) of vulva. Spermathecae filled with oval spermatozoa. Uterus a wide tube. Vagina straight, 0.3 times vulval body diameter in length. Vulva located just before middle of body. Three females of Antomicron were found in sublittoral sediment of Jiaozhou Bay. One of them was found with a male of Antomicron holovachovi sp. nov. in the same locality, and its main measurement data match with the male of Antomicron holovachovi sp. nov. Therefore, the female was identified as Antomicron holovachovi sp. The other female, which was from the locality where the male of another new species was found, and which had a thicker body and slightly longer amphideal fovea, was identified as Antomicron chinensis sp. nov. The third female, which matches the first female, was identified as Antomicron holovachovi sp. nov. The female of Antomicron holovachovi sp. nov. differs from the female of Antomicron chinensis sp. nov. by a slender body (maximum body diameter 23–26 µm vs 33 µm), slightly shorter amphideal fovea (10–12 µm vs 14 µm) and anterior position of vulva (40–45% vs 51%). Differential diagnosis and discussion Antomicron holovachovi sp. nov. is characterised by loop-shaped amphideal fovea, central elevation ridge-like; male with five straight tubular and 41 alveolar supplements; short cephalic setae; one pair of precloacal subventral setae; slightly curved slender spicules with cephalated proximal end and tapered distal end; rectangular gubernaculum with a short dorsal caudal apophysis. The new species belongs to a group of species the males of which have both tubular and alveolar supplements. The new species is morphologically close to Antomicron intermedius Gagarin and Nguyen Vu Thanh, 2005 in most aspects, but differs from the latter species in having elongated loop-shaped amphideal fovea (vs doughnut-shaped amphideal fovea; 2.4 vs 1.6 times as long as its width), central elevation ridge-like (vs oval), many more alveolar supplements (41 vs 29–36) and the shape of tubular supplements. The new species differs from the similar species A. profundum Vitiello, 1971 by longer body length (747–813 vs 512–575 µm), longer spicules (20 vs 17.5 µm) and many more alveolar supplements (41 vs 0–14). Further differences between Antomicron holovachovi sp. nov. and other congeners are specified in Table 2 and the key below.

ORDER ARAEOLAIMIDA De Coninck & Schuurmans Stekhoven, 1933 Family Axonolaimidae De Coninck & Schuurmans Stekhoven, 1933 Odontophora bermudensis Jensen & Gerlach, 1976 Odontophora sp. Parodontophora cobbi (Timm, 1952) Timm, 1963 Parodontophora sp. Parodontophora xenotricha Boucher, 1973 Family Bodonematidae Jensen, 1991 Bodonema vossi Jensen, 1991 Family Comesomatidae Filipjev, 1918 Cervonema macramphis Jensen, 1979 Comesoma arenae Gerlach, 1956 Comesoma sp. Dorylaimopsis pellucidum (Cobb, 1920) Jensen, 1979 Dorylaimopsis punctata Ditlevsen, 1918 Dorylaimopsis sp. Hopperia muscatensis Warwick, 1973 Hopperia sp. Laimella longicauda Cobb, 1920 Metacomesoma sp. Paracomesoma dubium (Filipjev, 1918) Schuurmans Stekhoven, 1950 Paracomesoma hexasetosum (Chitwood, 1937) Schuurmans Stekhoven, 1950 Paracomesoma inaequale Jensen & Gerlach, 1977 Paracomesoma sipho (Gerlach, 1956) Jensen & Gerlach, 1977 Paracomesoma sp. Pierrickia decasetosa Vitiello, 1970 Pierrickia sp. Sabatieria armata Gerlach, 1952 Sabatieria praedatrix de Man, 1907 Sabatieria pulchra (Schneider, 1906) Riemann, 1970 Sabatieria sp. Setosabatieria hilarula (de Man, 1922) Platt, 1985 Setosabatieria sp. Vasostoma sp. Family Diplopeltidae Filipjev 1918 Araeolaimus boomerangifer Wieser, 1959 Araeolaimus elegans de Man, 1888 Campylaimus sp. Diplopeltis cirrhatus (Eberth, 1863) Cobb, 1891 Diplopeltula sp. Intasia nojii (Jensen, 1991) Leduc, 2017 Pseudaraeolaimus sp. Southerniella allometrica Vitiello, 1971 Southerniella sp., Published as part of Pérez-García, José Andrés, Ruiz-Abierno, Alexei & Armenteros, Maickel, 2020, A checklist of aquatic nematodes from Cuban Archipelago, pp. 301-320 in Zootaxa 4731 (3) on pages 306-307, DOI: 10.11646/zootaxa.4731.3.1, http://zenodo.org/record/3653534

Genus Odontophora Bütschli, 1874 Diagnosis (modified from Leduc & Zhao 2016) Tapering anterior end with rounded cephalic region. Cuticle smooth or finely striated. Cephalic setae long; 4–12 subcephalic setae present. Amphidial fovea loop-shaped, longitudinally elongated or with almost circular outline. Buccal cavity deep and funnel shaped, with six odontia in anterior portion. One or two circles of cuticularized accessory buccal structures often present, alternating with odontia and often oval- or kidney-shaped or denticulate. Pharynx gradually widening posteriorly or with weak posterior bulb. Female with two outstretched ovaries, male with two opposed testes. Spicules arcuate, bent or L-shaped, gubernacular apophyses usually present. Pore-like or tubular precloacal supplements present or absent. Tail conical or conico-cylindrical. Type species: Odontophora marina Bütschli, 1874 (= species inquirenda), Published as part of Pinto, Taciana Kramer & Neres, Patricia Fernandes, 2020, Four new species of free-living nematodes from shallow continental shelf of Portugal, pp. 1-33 in Zootaxa 4722 (1) on page 17, DOI: 10.11646/zootaxa.4722.1.1, http://zenodo.org/record/3603616, {"references":["Butschli, O. (1874) Zur Kenntniss der freilebenden Nematoden, insbesondere der des Kieler Hafens. Abhandlungen, Herausgegeben von der Senckenbergischen Naturforschenden Gesellschaft, 9, 236 - 292.","Leduc, D. & Zhao, Z. Q. (2016) Review of the genus Odontophora (Nematoda: Axonolaimidae), with a key to valid species and description of Odontophora atrox sp. n. from the New Zealand coast. Nematology, 18 (10), 1125 - 1139. https: // doi. org / 10.1163 / 15685411 - 00003018"]}

Odontophora sinapophysis sp. n. (Figures 10–13, Table 5) urn:lsid:zoobank.org:act: 292388EA-5980-43A3-8B2B-7ABB8F693831 Type material. Five males and one female were collected at station 38. Holotype (♂) MUHNAC / MB 26–000026. Paratype (♀) MUHNAC / MB26–000027. Other paratypes: UFALPEN/ LEB 0010–0013 Type locality. Sandy sediments adjacent to an artificial reef (Shipwreck) (Table 1) Etymology. The specific epithet “ sinapophysis ” (sine —meaning without or lacking) is given because this species is the first to have gubernaculum without apophysis. Measurements. Table 5. Description. Male. Body cylindrical 4440–4950 µm long. Anterior region slightly attenuated, head diameter corresponding to 62–88% of body diameter in pharynx end. Cuticle finely striated, striations sometimes difficult to observe. Somatic setae present in pharynx region (4–8.5 µm), distributed in four rows, two lateroventral and two laterodorsal. Some caudal setae present. Anterior sensilla arranged according to the pattern 6+6+4: inner labial and outer labial papilliform, cephalic setae setiform (0.95–1.2 times corresponding body diameter). Single mediolateral subcephalic seta immediately posterior to each amphidial fovea. Other subcephalic setae present (9–12.5 µm) located near middle of funnel shaped portion of buccal cavity. Amphidial fovea loop shaped, rounded (27–39% of corresponding body diameter) located between cephalic setae and 2.5–5 µm behind anterior end. Buccal cavity separated into two portions: anterior portion with six strongly cuticularized and eversible odontia, 9–10 µm long; posterior portion funnel shaped and with cuticularized walls, 18.5–20 µm deep and 7–8.5 µm wide at anterior extremity. Cylindrical pharynx (192–200 µm or 3–4% of the total body length), posterior end slightly enlarged. Cardia completely inserted into intestine. Secretory–excretory pore not observed. Ventral gland posterior to the pharynx end. Never ring 83.4–128 µm from anterior end. Two testes left of intestine, one branch extended and one reflexed. Spicules strongly bent in their proximal third (1.2–1.34 times cloacal body diameter), cephalate proximally and distal portion rounded. Gubernaculum (12.5–14 µm) without apophyses. Precloacal supplements absent. Tail conical (4.9–6.1 times cloacal body diameter). Three caudal glands and triangular spinneret present. Female. Largely similar to male. Cephalic setae (1.17 times corresponding body diameter). Amphidial fovea loop shaped, rounded, 31% of corresponding body diameter, located 3.5 µm behind anterior end. Two opposed outstretched ovaries, anterior branch (360 µm) left of intestine and posterior branch (432 µm) right of intestine. A mass of sperm is attached to the vulva with something like a mucosal clump. Vulva located slightly posterior to mid-body (57% of total length). Large seminal receptacle. Tail conical, slightly smaller than in male (3.6 times anal body diameter), with three caudal glands and triangular spinneret. Diagnosis. The new species presents as main characteristics: cuticle finely striated, cephalic setae setiform about one corresponding body diameter, single mediolateral subcephalic seta immediately posterior to each amphidial fovea and other subcephalic setae at about middle region of the funnel shaped portion of the buccal cavity; amphidial fovea loop shaped, rounded, very close to the anterior end (27–39% of corresponding body diameter); spicules strongly bent in their proximal third (1.2–1.4 time cloacal body diameter), cephalate proximally and with distal portion rounded; gubernaculum without apophyses measuring 0.3 times spicule length, precloacal supplements absent, tail conical (5–6 times cloacal body diameter) in male and 3.6 times anal body diameter in female; female with large seminal receptacle. Differential diagnosis. The new species differs from all the others already described in the genus by the absence of apophysis in the gubernaculum; therefore, an amendment in the genus diagnosis is necessary. In Leduc & Zhao (2016), the authors subdivided Odontophora species according to the position of the subcephalic setae and the spicule shape. The species described here belong to the group that has single mediolateral subcephalic seta immediately posterior to each amphidial fovea, just like O. wieseri Luc & De Coninck 1959, O. octoseta Boucher & Helléouët 1977 and O. tenuicaudata Allgén, 1935. However, these species possess gubernaculum with apophysis and other characteristic different from new species. O. wieseri presents cephalic setae 2 times corresponding body diameter, almost twice as long as in new species; O. octoseta present spicules strongly bent and without capitulum and O. tenuicaudata has spicules arcuate and with capitulum, while the new species has spicules L-shaped and capitulum. Females have a well-developed seminal receptacle as in O. falcifera Ott, 1972. The accessory buccal structures in anterior portion of buccal cavity, as described in Leduc & Zhao (2016), were not observed because the odontia were retracted in the buccal cavity. Systematics (According to De Ley et al. 2006)

The genus Campylaimus is a broadly distributed but relatively uncommon genus of marine and brackish nematodes with 20 nominal species and one nomen nudum. Many species descriptions and redescriptions are based on very few (single) individuals, which limits our understanding of inter- and intra-specific variability and morphology-based species boundaries. Two new species were found in the Skagerrak off the west coast of Sweden. Campylaimus triclados sp. n. is characterised by body 0.59–0.69 mm long; cuticle without longitudinal striation; anteriormost edge of the amphid anterior to the oral opening; dorsal limb of the amphid equal to 1.6–2.5 labial region diameters in male, 1.9 labial region diameters in female; ventral limb of the amphid extends towards anterior part of the intestine in male and midpharynx in female, 4.3–5.5 times the length of the dorsal limb in male and 2.2–2.8 times the length of the dorsal limb in female; ventral limb of the amphid is as wide as the dorsal limb; interamphideal space extends further than the posterior end of the dorsal limb but not reaching the posterior end of the ventral limb; secretory-excretory pore opens posterior to the cardia; spicules 19–24 µm long; two precloacal supplements; tail equal to 4.3–5.6 anal body diameters in length, with conoid terminal part. Campylaimus longispiculus sp. n. is characterised by body 0.56–0.65 mm long; cuticle without longitudinal striation; anteriormost edge of the amphid anterior to the oral opening; dorsal limb of the amphid equal to 1.8–2.1 labial region diameters in male; ventral limb of the amphid extends towards anterior part of the intestine in male, 2.8–3.5 times the length of the dorsal limb in male; ventral limb of the amphid is as wide as the dorsal limb; interamphideal space absent; secretory-excretory pore opens posterior to the cardia; spicules 28–35 µm long; two precloacal supplements; tail equal to 4.9–5.3 anal body diameters in length, with clavate terminal part. In addition, following nine species are new records for the fauna of Sweden: Campylaimus amphidialis, C. inaequalis, C. lefeverei, C. minutus, C. orientalis, C. rimatus, C. siwaschensis, C. striatus and C. tkatchevi.

Chronogaster africana Heyns & Coomans, 1980 Figures 9 & 10 Measurements: Table 4 ......continued on the next page The female specimen was identified as Chronogaster africana based on morphometrics and morphology, especially the morphology of the tail terminus displaying a mucro with six short spines, and the absence of no crystalloids in the body cavity. The female specimen found in Telperion Nature Reserve (no males found) matches that of the original description by Heyns & Coomans (1980) with only difference being the length of the post-uterine branch (12.5 µm vs 6–9.5 µm). First time SEM observations on this species revealed the following: Lip region three annules long with four cephalic setae and amphid openings on second annule with their posterior margins protruding slightly. Amphid aperture with two protrusions towards inside. Cuticle shows distinct annules, no lateral field. Excretory pore located 140 µm from anterior end its opening one body annule wide. Lateral caudal pore on tail 30 µm posterior from anus on lateral side of body. This pore indicates two openings, one in the anterior and one in the posterior margin (Figure 10 B). Tail terminus consists of six small projections on the base of one larger mucro. In some instances, an extra projection noticed on larger mucro (Figure 10 C–F). Annules at the base of the tail tip showed some anastomoses / breaks in striations on lateral sides (Figure 10 F). Discussion. Chronogaster africana was first described in South Africa in 1980 from water sediment samples in Boskop Dam and The Kloof (North West Province), Natalspruit (Gauteng Province), and Krom River (Western Cape Province). It was then again reported in South Africa in 1992 from sand near the weir in the Sabie River near Lower Sabie (Mpumalanga Province) (Botha & Heyns 1992). As this species has been reported in this country only, it is considered endemic to South Africa. Locality and material examined: In the Telperion Nature Reserve a female specimen of C. africana was collected at the Wetland site (Table 1) with locality number MP00043 and deposited in the National Collection of Nematodes (ARC—Plant Health and Protection, Biosystematics, Pretoria) on slide number 50567., Published as part of Girgan, Chantelle, Marais, Mariette, Fourie, Hendrika, Tiedt, Lourens & Swart, Antoinette, 2019, Description of two new species, Aphanolaimus strilliae n. sp. (Nematoda: Aphanolaimidae) and Makatinus africanus n. sp. (Nematoda: Aporcelaimidae), and SEM observations on three known species from freshwater sources in the Telperion Nature Reserve (Mpumalanga, South Africa), pp. 201-234 in Zootaxa 4651 (2) on pages 216-217, DOI: 10.11646/zootaxa.4651.2.1, http://zenodo.org/record/3363080, {"references":["Heyns, J. & Coomans, A. (1980) Freshwater nematodes from South Africa 5. Chronogaster Cobb, 1913. Nematologica, 26 (2), 187 - 208. https: // doi. org / 10.1163 / 187529280 X 00080","Botha, A. & Heyns, J. (1992) Further records and descriptions of nematodes from rivers in the Kruger National Park (orders Enoplida, Chromadorida, Monhysterida, Mononchida and Araeolaimida). Koedoe, 35 (2), 11 - 25."]}

Genus Rhabdolaimus de Man, 1880 Pseudorhabdolaimus Soós, 1937: 323. Diagnosis (modified from Siddiqi 2012) Cuticle transversely striated. Lateral alae, body pores and epidermal glands absent. Somatic sensilla absent. Labial region truncated, lips indistinct. Inner labial sensilla indistinct. Six outer labial pore-like sensilla, located on periphery of labial region. Four cephalic papilliform sensilla, located just behind labial region. Amphid stirrup-shaped with transverse slit-like opening. Stoma tubular, cheilostom minute, stegostom with weakly cuticularised walls and three small denticles located at same level at its anterior edge. Pharynx cylindrical anteriorly, with distinct basal bulb; valves absent. Cardia small, partially embedded into intestinal tissue. Secretory-excretory system absent. Female reproductive system didelphic, amphidelphic, ovary branches reflexed antidromously. Vulva a transverse slit. Vagina straight, without pars refringens vaginae or epiptygmata. Spermatheca absent. Male reproductive system unknown. Spicules arcuate, symmetrical. Gubernaculum, supplements and caudal alae absent. Tail elongate. Caudal glands and spinneret present. Type species Rhabdolaimus terrestris de Man, 1880. syn. Rogerus rosea Ali, Suryawanshi & Chisty, 1971. Included species Rhabdolaimus alpestris Siddiqi, 2012. Rhabdolaimus annulatus Siddiqi, 2012. Rhabdolaimus antiquus Siddiqi, 2012. Rhabdolaimus aquaticus de Man, 1880. syn. Rhabdolaimus terrestris aquaticus de Man, 1880. Rhabdolaimus brachyuris Meyl, 1954. Rhabdolaimus directistomus Gagarin, 2000. Rhabdolaimus hasani Siddiqi, 2012. Rhabdolaimus limnophilus (Soós, 1937). syn. Pseudorhabdolaimus limnophilus Soós, 1937. Rhabdolaimus medius Siddiqi, 2012. Rhabdolaimus minor Cobb, 1914. Rhabdolaimus nannus (Hoeppli, 1926). syn. Chromadora nanna Hoeppli, 1926. Rhabdolaimus parvulus Siddiqi, 2012. Rhabdolaimus porifer Siddiqi, 2012. Rhabdolaimus porosus Siddiqi, 2012. Rhabdolaimus sclerorectum Tahseen, Chowdhary, Kulsum, Ahmad & Jairajpuri, 2005. Rhabdolaimus strialaimus Siddiqi, 2012. Rhabdolaimus thornei Siddiqi, 2012.

Family Rhabdolaimidae Chitwood, 1951 Diagnosis As for the superfamily Campydoroidea, except stoma with three denticles. Included subfamilies Subfamily Monochromadorinae Andr��ssy, 1958. Subfamily Rhabdolaiminae Chitwood, 1951., Published as part of Holovachov, Oleksandr, 2019, Campydoroides manautei gen. et sp. nov. from New Caledonia and a reappraisal of the suborder Campydorina (Nematoda), pp. 1-23 in European Journal of Taxonomy 518 on page 14, DOI: 10.5852/ejt.2019.518, http://zenodo.org/record/2649833

Subfamily Monochromadorinae Andr��ssy, 1958 Udonchinae Eyualem & Coomans, 1996: 213. Diagnosis Cheilostom with twelve longitudinal rugae; stoma with three denticles, which are arranged in two separate groups at two levels; female reproductive system monodelphic. Type and only genus Udonchus Cobb, 1937., Published as part of Holovachov, Oleksandr, 2019, Campydoroides manautei gen. et sp. nov. from New Caledonia and a reappraisal of the suborder Campydorina (Nematoda), pp. 1-23 in European Journal of Taxonomy 518 on page 15, DOI: 10.5852/ejt.2019.518, http://zenodo.org/record/2649833, {"references":["Eyualem A. & Coomans A. 1996. Aquatic nematodes from Ethiopia VII. The family Rhabdolaimidae Chitwood, 1951 sensu Lorenzen, 1981 (Chromadorida: Nematoda) with the description of Udonchus merhatibebi n. sp. Hydrobiologia 341: 197 - 214. https: // doi. org / 10.1007 / BF 00014685"]}

Genus Rogerus Hoeppli & Chu, 1934 Diagnosis Cuticle transversely striated. Lateral alae, body pores and epidermal glands absent. Somatic sensilla absent. Labial region truncated, lips indistinct. Inner labial sensilla papilliform. Six outer labial sensilla papilliform or setiform, located on periphery of labial region. Four cephalic setiform sensilla, at level with outer labial sensilla. Amphid oval (transverse ovoid). Stoma tubular, cheilostom minute, stegostom with weakly cuticularised walls and three small denticles located at same level at its anterior edge. Pharynx cylindrical anteriorly, with distinct basal bulb; valves absent. Cardia small, partially embedded into intestinal tissue. Secretory-excretory system absent. Female reproductive system didelphic, amphidelphic, ovary branches outstretched. Vulva circular. Vagina straight, without pars refringens vaginae or epiptygmata. Spermatheca absent. Male reproductive system monorchic. Spicules arcuate, symmetrical. Gubernaculum, supplements and caudal alae absent. Tail elongate. Caudal glands and spinneret present. Type and only species Rogerus orientalis (Hoeppli & Chu, 1932). syn. Greenia orientalis Hoeppli & Chu, 1932; Greeninema orientalis (Hoeppli & Chu, 1932). Included species Rogerus rajastanensis Khera, 1966. syn. Rhabdolaimus rajastanensis (Khera, 1966)., Published as part of Holovachov, Oleksandr, 2019, Campydoroides manautei gen. et sp. nov. from New Caledonia and a reappraisal of the suborder Campydorina (Nematoda), pp. 1-23 in European Journal of Taxonomy 518 on page 17, DOI: 10.5852/ejt.2019.518, http://zenodo.org/record/2649833, {"references":["Hoeppli R. & Chu H. J. 1932. Free-living nematodes from hot springs in China and Formosa. The Hong Kong Naturalist Supplement 1: 15 - 29."]}

The new genus and species Campydoroides manautei Holovachov gen. et sp. nov. is placed in the suborder Campydorina and is characterised by a transversely striated cuticle without lateral alae, body pores or epidermal glands; somatic sensilla only on pharyngeal region and on tail; a truncate labial region with papilliform inner labial, outer labial and cephalic sensilla; a stirrup-shaped amphid with transverse slit-like opening; a conoid stoma with strongly cuticularised walls and large protrusible dorsal tooth; a cylindrical pharynx with distinct basal bulb but without valves; a large ovoid cardia; didelphic, amphidelphic female gonads with antidromously reflexed ovaries and without spermatheca; a transverse vulva; a straight vagina without pars refringens vaginae or epiptygmata; an elongate tail with caudal glands and spinneret. The new genus is similar to the genera Campydora Cobb, 1920 and Udonchus Cobb, 1913 in having papilliform labial and cephalic sensilla, a stirrup-shaped amphid with a transverse slit-like opening, a stoma with a well-developed protrusible dorsal tooth, and a muscular pharynx with a strongly developed basal bulb, but can be easily separated from both in details of a stoma morphology. The systematics of the suborder Campydorina is revised. Halirhabdolaimus Siddiqi, 2012 is synonymised with Syringolaimus de Man, 1888.

Genus Syringolaimus de Man, 1888 Halirhabdolaimus Siddiqi, 2012: 65 syn. nov. Diagnosis (after Tchesunov 2017) Cuticle visually smooth or transversely striated. Lateral alae absent. Somatic sensilla undescribed. Labial region truncated. Inner labial sensilla indistinct. Morphology of inner and outer labial sensilla unclear. Four cephalic small papilliform sensilla. Amphid stirrup-shaped with transverse slit-like opening. Stoma cylindrical, with cuticularised walls and three protrusible bifid teeth located at same level at anterior edge of stegostom. Pharynx cylindrical anteriorly, with distinct basal bulb; valves absent. Cardia large, ovoid, partially embedded into intestinal tissue. Secretory-excretory system present. Female reproductive system didelphic, amphidelphic, ovary branches reflexed antidromously. Morphology of vulva and vagina unknown. Male reproductive system monorchic, testis outstretched. Spicules arcuate, symmetrical. Gubernaculum present. Precloacal supplements papilliform, in single midventral row. Caudal alae absent. Tail elongate. Caudal glands and spinneret present or absent. Type and only species Syringolaimus striatocaudatus de Man, 1888. syn. Syringolaimus striatocaudatus aberrans Micoletzky, 1924. syn. Syringolaimus striatocaudatus steineri Micoletzky, 1924. syn. Dolicholaimus propinquus Allg��n, 1933. syn. Dolicholaimus tenuicaudatus Allg��n, 1932. Included species Syringolaimus annae Lima, Lins, Da Silva & Esteves, 2009. Syringolaimus elegans Tchesunov, 2017. Syringolaimus filicaudatus Vitiello, 1970. Syringolaimus loofi Gourbault & Vincx, 1985. syn. Halirhabdolaimus loofi (Gourbault & Vincx, 1985). Syringolaimus renaudae Gourbault & Vincx, 1985. Syringolaimus smolae Lima, Lins, Da Silva & Esteves, 2009. Syringolaimus striatocaudatus de Man, 1888. Syringolaimus taniae Lima, Lins, Da Silva & Esteves, 2009. Species inquirenda Syringolaimus brevicaudatus Micoletzky, 1922. Syringolaimus caspersi Gerlach, 1951. Syringolaimus lichenii (Nasira & Turpeenniemi, 2002). syn. Trissonchulus lichenii Nasira & Turpeenniemi, 2002. Syringolaimus marisalbi Platonova & Mokievsky, 1994. Syringolaimus smarigdus Cobb, 1928. Nomina nuda Syringolaimus gladiatus Bussau, 1993. Syringolaimus ingens Bussau, 1993. Syringolaimus nitidus Bussau, 1993. Syringolaimus venustus Bussau, 1993. Remarks See Tchesunov (2017) for the most recent and comprehensive revision of the genus. The genus Halirhabdolaimus was proposed by Siddiqi (2012) for a single species, Syringolaimus loofi, and was only compared with the genus Rhabdolaimus. However, the author did not compare Halirhabdolaimus with Syringolamus. The differential diagnoses of both genera match perfectly and thus the proposal of the new genus was entirely unjustified., Published as part of Holovachov, Oleksandr, 2019, Campydoroides manautei gen. et sp. nov. from New Caledonia and a reappraisal of the suborder Campydorina (Nematoda), pp. 1-23 in European Journal of Taxonomy 518 on pages 17-18, DOI: 10.5852/ejt.2019.518, http://zenodo.org/record/2649833, {"references":["Siddiqi M. R. 2012. Ten new species of Rhabdolaimus de Man, 1880, with the proposal for Halirhabdolaimus gen. n. (Nematoda: Haliplectidae). International Journal of Nematology 22: 47 - 66.","Tchesunov A. V. 2017. Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss. Zootaxa 4306: 478 - 500. https: // doi. org / 10.11646 / zootaxa. 4306.4.2"]}

Genus Mediolaimus Tahseen, Sultana, Khan & Hussain, 2012 Diagnosis (after Tahseen et al. 2012) Cuticle transversely striated. Lateral alae absent. Somatic sensilla not described. Labial region flattened. Inner labial sensilla not described. Six outer labial pore-like sensilla. Four cephalic papilliform sensilla. Amphid with elliptical slit-like opening (transverse ovoid). Stoma tubular, cheilostom minute, stegostom with weakly cuticularised walls and three small denticles located at same level at its anterior edge. Pharynx cylindrical anteriorly, with distinct basal bulb; with thickened valve plates. Cardia small. Secretory-excretory system present. Female reproductive system didelphic, amphidelphic, ovary branches outstretched. Vulva a transverse slit. Vagina straight, with weak pars refringens vaginae, without epiptygmata. Spermatheca undescribed. Male reproductive system unknown. Tail elongate. Caudal glands and spinneret absent. Type and only species Mediolaimus obtusicaudatus Tahseen, Sultana, Khan & Hussain, 2012., Published as part of Holovachov, Oleksandr, 2019, Campydoroides manautei gen. et sp. nov. from New Caledonia and a reappraisal of the suborder Campydorina (Nematoda), pp. 1-23 in European Journal of Taxonomy 518 on page 16, DOI: 10.5852/ejt.2019.518, http://zenodo.org/record/2649833, {"references":["Tahseen Q., Sultana R., Khan R. & Hussain A. 2012. A new genus and species of the family Rhabdolaimidae (Nematoda), with descriptions of two known species and taxonomic discussion. Journal of Nematology 44: 302 - 312."]}

Aphanolaimus strilliae n. sp. and Makatinus africanus n. sp. are described from freshwater sources in the Telperion Nature Reserve, Mpumalanga, South Africa. Aphanolaimus strilliae n. sp. is characterised by a body length of 1240–1613 μm, more than 800 body annules, lateral field originating between the first and second lateral body pore at the 34th–46th annule, first lateral body pore located at the 25th–35th annule, vagina V-shaped and bent anteriorly, 142–195 µm long uterus and 165–207 µm long tail with spinneret offset. This species is ovoviviparous and no males were found. Makatinus africanus n. sp. is characterised by a large, thick body (3228–4128 μm long, a = 30–39 wide), slightly set off lip region with amalgamated lips; 31–34 μm long odontostyle; long tongue-shaped cardia, and stout, short tail (30–43 μm long) with a small peg / digitate extension and male absent. Populations of three known species, Chronogaster africana, Eutobrilus annetteae and Neotobrilus ampiei, from fresh water at the Telperion Nature Reserve are described and scanning electron microscope graphs of these species published for the first time.

Neodiplopeltula incisa (Southern, 1914) gen et. comb. nov. Figs 1–4; Table 2 Diagnosis (based on combined data) Neodiplopeltula incisa gen. et comb. nov. is characterised by a 1.52–2.24 mm long body; refractive plates underlying cephalic cuticle around amphids present, irregular in shape, not joined, 28–33 µm long and 21–25 µm wide; cephalic setae 8–14 µm long; amphidial fovea 22–28 µm long and 5.5–7 µm wide; oral opening 1–3 µm from anterior end, posterior to cephalic setae bases; secretory-excretory pore located opposite to posterior part of pharynx; tail 2.5–3.9 anal body diameters long; vagina with epiptygmata; spicules 66–79 µm long. Material examined SWEDEN: 4 ♀♀, 3 ♂♂, Skagerrak, 58°12′37″ N, 11°18′53″ E, shells and sand at a deep of 15–22 m, 10 Oct. 2012, O. Holovachov leg. (SMNH-169255); 1 ♀, 1 ♂, Skagerrak, 58°20′21″ N, 11°12′42″ E, coarse shell sand at a deep of 14–17 m, 19 Aug. 2014, O. Holovachov leg. (SMNH-169258). Description Adult Body cylindrical, posteriorly tapering in tail region, straight or weakly ventrally curved upon fixation. Cuticle finely transversely striated along entire body as seen under SEM (striation can be observed under LM but very fine and shallow and cannot be measured with confidence), except for visually smooth labial region and terminal part of tail; longitudinal striation not observed under the light microscope, but distinct under the scanning electron microscope, covers cuticle over entire body length. Somatic sensilla visible along pharyngeal region (cervical setae, see below) and on tail. Labial region bluntly rounded, lips fused. Refractive plates underlying cephalic cuticle around amphids present (periamphideal), extending from level of anteriormost edge of amphid posteriorly some distance behind posteriormost edge of amphid; refractive plates irregular in shape (with incised edges), not connected with each other on ventral and dorsal sides. Inner labial sensilla small pore-like, located on anterior surface of lips, discernible under SEM only. Outer labial sensilla papilliform, located on anterior surface of lips, clearly visible under SEM only. Cephalic sensilla setiform, bases of dorsosublateral setae located posterior to oral opening. Cervical sensilla papilliform, arranged in four sublateral rows starting at level with middle of amphid and ending at level with posterior edge of refractive plate, two or three per row. Amphids similar in shape and size between sexes: amphidial fovea inverted U-shape with dorsal branch 0.5–3.5 µm longer than ventral branch. Oral opening shifted towards dorsal side of body. Stoma barrel-shaped: cheilostom broad; gymnostom barrel-shaped, with weakly cuticularised walls; stegostom short conoid, its lining uniform with lining of pharynx. Pharyngeal tubes absent. Pharynx subcylindrical, muscular, with evenly distributed myofilaments, gradually expanding towards posterior end; not subdivided in distinct sections; pharyngeal lumen uniform in thickness along entire pharynx length; valves absent. Cardia ovoid, almost entirely embedded into intestinal tissue. Secretory-excretory system present; secretory-excretory pore located along ventral body line opposite to posterior 3/5 th of pharynx; secretory-excretory duct very short, leading from pore to ampulla; renette cell small, its body adjacent and ventral to posterior part of pharynx. Tail cylindro-conical with bluntly rounded terminus. Caudal glands opening via three separate subterminal openings, spinneret absent. Female Reproductive system didelphic, amphidelphic, ovary branches outstretched and symmetrical, on opposite sides of intestine. Anterior genital tube 248–280 µm long, situated to either right (n = 1) or left (n = 4) of intestine; posterior genital tube 224–259 µm long, situated to either left (n = 1) or right (n = 4) of intestine. Vulva a transverse slit, located posterior to midbody. Vagina straight, with developed sphincter muscle surrounding proximal part and distinct epiptygmata in distal part; pars refringens vaginae absent. Sack-like spermatheca present, filled with oval spermatozoa in fertilized specimens. Rectum short. Male Reproductive system diorchic, testes opposed; anterior testis 162–286 µm long, outstretched and posterior testis 117–162 µm long, reflexed. Spicules paired and symmetrical, strongly curved, with ovoid manubrium and subcylindrical shaft. Gubernaculum plate-like, with pair of strong, closely set caudal apophyses variable in shape (Fig. 4 C–E). Caudal setae present, several ventrosublateral and dorsosublateral pairs arranged in rows along entire tail length (often difficult to observe). Remarks Despite the fact that the original description by Southern (1914) is rather brief, the present population closely resembles the type specimens in most morphological and morphometric features, including the shape of the refractive plates underlying the amphids (described as “shield shaped” with “front and lateral walls are notched”). Spicules are slightly shorter in the type specimens (66 µm vs 75–79 µm in recent specimens). Neodiplopeltula barentsi (Steiner, 1916) gen. et comb. nov. Figs 5–7, 14–15; Table 3 Diagnosis (based on combined data) Neodiplopeltula barentsi gen. et comb. nov. is characterised by a 0.94–1.67 mm long body; refractive plates underlying cephalic cuticle around amphids present, elongated ovoid in shape, not joined, 23.5– 32 µm long and 12–16 µm wide; cephalic setae 3.5–7.5 µm long; amphidial fovea 21–32 µm long and 4–7 µm wide; oral opening 1–2 from anterior end, posterior to cephalic setae bases; secretory-excretory pore located opposite to posterior part of pharynx; tail 1.6–3.3 anal body diameters long; vagina with epiptygmata; spicules 45–73 µm long. Material examined SWEDEN: 1 ♀, 1 ♂, Skagerrak, 58°20′06″ N, 11°09′24″ E, muddy sediment at a deep of 53 m, 9 Aug. 2011, O. Holovachov leg. (SMNH-169264); 1 ♀, 1 ♂, Skagerrak, 58°22′19″ N, 11°04′55″ E, muddy sediment at a deep of 55– 70 m, 9 Aug. 2011, O. Holovachov leg. (SMNH-169266); 3 ♀♀, 1 ♂, Gullmarn Fjord near Östersidan, 58°15′09″ N, 11°27′54″ E, shells, gravel sand and mud, 14 Aug. 2014, O. Holovachov leg. (SMNH-169268); 1 ♀ lectotype of Diplopeltis asymmetricus, Öresund, west of Valgrundet, at a deep of 30– 36 m, Zostera and Echinocardium, 7 Aug. 1926 (SMNH Type-9015). GREENLAND: 1 ♀, holotype of Diplopeltis ovalis, Godhavn, mud, 17 Aug. 1926, Reisinger and Steinböck leg. (NHMD 102171). Description Adult Body cylindrical, posteriorly tapering in tail region, straight or weakly ventrally curved upon fixation. Cuticle finely transversely striated along entire body, except for visually smooth labial region and terminal part of tail (striation can be observed under LM but very fine and shallow and cannot be measured with confidence); longitudinal striation not observed. Somatic sensilla visible along pharyngeal region (cervical sensilla, see below) and on tail. Labial region bluntly rounded, lips fused. Refractive plates underlying cephalic cuticle around amphids present (periamphideal), extending from level of anteriormost edge of amphid posteriorly some distance behind posteriormost edge of amphid; refractive plates elongated ovoid in shape (plate edges not incised), not connected with each other on ventral and on dorsal sides. Inner labial sensilla indistinct. Outer labial sensilla papilliform, located on anterior surface of lips. Cephalic sensilla setiform, bases of dorsosublateral setae located posterior to oral opening. Cervical sensilla papilliform, arranged in four sublateral rows starting at level with middle of amphid and ending at level with posterior edge of refractive plate, one or two per row. Amphids similar in shape and size between sexes: amphidial fovea inverted U-shape with dorsal branch usually 0.5–2.0 µm longer than ventral branch (in two specimens ventral branch 0.5–1.0 µm longer than dorsal branch). Oral opening shifted towards dorsal side of body. Stoma barrel-shaped: cheilostom broad; gymnostom subcylindrical, with weakly cuticularised walls; stegostom short conoid, its lining uniform with lining of pharynx. Pharyngeal tubes absent. Pharynx subcylindrical, muscular, with evenly distributed myofilaments, gradually expanding towards posterior end; not subdivided in distinct sections; pharyngeal lumen uniform in thickness along entire pharynx length; valves absent. Cardia ovoid, entirely embedded into intestinal tissue. Secretoryexcretory system present; secretory-excretory pore along ventral body line opposite to 3/5 th of pharynx; secretory-excretory duct very short, leading from pore to ampulla; renette cell small, its body adjacent and ventral to posterior part of pharynx. Tail conoid with bluntly rounded terminus. Caudal glands opening via three separate subterminal openings, spinneret absent. Female Reproductive system didelphic, amphidelphic, ovary branches outstretched and symmetrical, on opposite sides of intestine. Anterior genital tube 179–269 µm long, situated to either right (n = 3) or left (n = 2) of intestine; posterior genital tube 173–286 µm long, situated to either left (n = 3) or right (n = 2) of intestine. Vulva transverse slit, located posterior to midbody. Vagina straight, with developed sphincter muscle surrounding proximal part and distinct epiptygmata in distal part; pars refringens vaginae absent. Sacklike spermatheca present, filled with oval spermatozoa in fertilized specimens. Rectum short. Male Reproductive system diorchic, testes opposed; anterior testis 145–314 µm long, outstretched and posterior testis 117–207 µm long, reflexed. Spicules paired and symmetrical, strongly curved, with weakly defined elongated manubrium and shaft, cylindrical along most of its length. Gubernaculum plate-like, with pair of strong, closely set caudal apophyses variable in shape (Fig. 7 C–E). Caudal setae present, several ventrosublateral and dorsosublateral pairs arranged in rows along entire tail length (often difficult to observe). Remarks The original description of this species by Steiner (1916) is rather short, with a few measurements given. The present population has a shorter pharynx and tail compared to the type specimen, but in all other respects both match very well, including the position of the oral opening and the shape of the underlying refractive plates. Neodiplopeltula onusta (Wieser, 1956) gen. et comb. nov. Figs 8–10; Table 4 Diagnosis (based on combined data) Neodiplopeltula onusta gen. et comb. nov. is characterised by a 0.99–1.48 mm long body; refractive plates underlying cephalic cuticle around amphids present and joined, 32.5–48 µm long and 18.5–24 µm wide; cephalic setae 3–6.5 µm long; amphidial fovea 32–44 µm long and 5–8 µm wide; oral opening 2–5 from anterior end, at level with cephalic setae bases; secretory-excretory pore located opposite to posterior part of pharynx; tail 1.4–2.3 anal body diameters long; vagina with epiptygmata; spicules 52–77 µm long. Material examined SWEDEN: 1 ♀, Skagerrak, 58°19′15.6″–20.9″ N, 10°29′33.5″–34.0″ E, soft bottom at a deep of 352–374 m, 10 Sep. 2012, “Inventering Bratten” leg. (SMNH-169284); 1 ♂, Skagerrak, 58°23′00.8″– 22′00.8″ N, 10°20′28.8″–38.3″ E, soft bottom at a deep of 390–428 m, 10 Sep. 2012, “Inventering Bratten” leg. (SMNH-169280); 1 ♂, Skagerrak, 58°28′21.2″–19.2″ N, 10°29′35.6″–43.6″ E, soft bottom at a deep of 248–316 m, 11 Sep. 2012, “Inventering Bratten” leg. (SMNH-169281); 3 ♀♀, 1 ♂, Skagerrak, 58°27′36.7″–43.3″ N, 10°32′52.0″–59.4″ E, soft bottom at a deep of 232–240 m, 12 Sep. 2012, “Inventering Bratten” leg. (SMNH-169282 – SMNH-169283). Description Adult Body cylindrical, posteriorly tapering in tail region, straight or weakly ventrally curved upon fixation. Cuticle finely transversely striated along entire body, except for visually smooth labial region and terminal part of tail (striation can be observed under LM but very fine and shallow and cannot be measured with confidence); longitudinal striation not observed.Somatic sensilla visible along pharyngeal region (cervical setae, see below) and on tail. Labial region bluntly rounded, lips fused. Refractive plates underlying cephalic cuticle around amphids present (periamphideal), extending from level of anteriormost edge of amphid posteriorly some distance behind posteriormost edge of amphid; refractive plates connected with each other on ventral and on dorsal sides. Inner labial sensilla indistinct. Outer labial sensilla papilliform, located on anterior surface of lips. Cephalic sensilla setiform, bases of dorsosublateral setae located at level with oral opening. Cervical sensilla papilliform, arranged in four sublateral rows at level with amphid, one or two per row. Amphids similar in shape and size between sexes: amphidial fovea inverted U-shape with dorsal branch 1.0–2.0 µm longer than ventral branch. Oral opening shifted towards dorsal side of body. Stoma subcylindrical: cheilostom broad; gymnostom barrel-shaped, with weakly cuticularised walls; stegostom short conoid, its lining uniform with lining of pharynx. Pharyngeal tubes absent. Pharynx subcylindrical, muscular, with evenly distributed myofilaments, gradually expanding towards posterior end; not subdivided in distinct sections; pharyngeal lumen uniform in thickness along entire pharynx length; valves absent. Secretory-excretory system present; secretory-excretory pore located along ventral body line opposite to 3/5 th of pharynx; secretory-excretory duct very short, leading from pore to ampulla; renette cell small, its body adjacent and ventral to posterior part of pharynx. Tail conoid with bluntly rounded terminus. Caudal glands opening via three separate subterminal openings, spinneret absent. Female Reproductive system didelphic, amphidelphic, ovary branches outstretched and symmetrical, on opposite sides of intestine. Anterior genital tube 109–180 µm long, situated to either right (n = 3) or left (n = 1) of intestine; posterior genital tube 109–145 µm long, situated to either left (n = 3) or right (n = 1) of intestine. Vulva transverse slit, located posterior to midbody. Vagina straight, with developed sphincter muscle surrounding proximal part and distinct epiptygmata in distal part; pars refringens vaginae absent. Sack-like spermatheca present, filled with oval spermatozoa in fertilized specimens. Rectum short. Male Reproductive system diorchic, testes opposed; anterior testis outstretched and posterior testis reflexed (poorly discernible in most specimens due to highly granular and dark content of overlapping intestine and cannot be measured). Spicules paired and symmetrical, strongly curved, with elongated ovoid manubrium and subcylindrical shaft. Gubernaculum plate-like, with pair of strong closely set caudal apophyses variable in shape (Fig. 10 E–G). Caudal setae present, several ventrosublateral and dorsosublateral pairs arranged in rows along entire tail length. Remarks The single female used by Wieser (1956) to describe this species has a slightly broader labial region and longer cephalic setae than the population from Sweden, but the specimens described under the name Diplopeltula tchesunovi fill this gap. The position of the oral opening is at level with the cephalic setae bases and the shape of the refractive plates underlying the cephalic cuticle around the amphids (joined along the dorsal and ventral body sides) in both type female and recent specimens are identical and confirm the conspecificity.

The new genus Neodiplopeltula gen. nov. is proposed to accommodate those species from the genus Diplopeltula Gerlach, 1950 that possess the following morphological characters: amphids in the shape of an elongated loop, a well-developed subcylindrical stoma and outstretched ovaries. The genus Diplopeltula is considered genus inquirendum et incertae sedis . Four species placed in Neodiplopeltula gen. nov. are redescribed. The following taxonomic changes are proposed: Neodiplopeltula asymmetrica (Allgen, 1935) gen. et comb. nov.; Neodiplopeltula barentsi (Steiner, 1916) gen. et comb. nov.; Neodiplopeltula bathmanni (Jensen, 1991) gen. et comb. nov.; Neodiplopeltula cuspidiboja (Leduc, 2017) gen. et comb. nov.; Neodiplopeltula indica (Gerlach, 1962) gen. et comb. nov.; Neodiplopeltula intermedia (Gerlach, 1954) gen. et comb. nov.; Neodiplopeltula obesa (Nguyen Vu Thahn, Nguyen Thahn Hien & Gagarin, 2012) gen. et comb. nov.; Neodiplopeltula onusta (Wieser, 1956) gen. et comb. nov.; Neodiplopeltula ovalis (Ditlevsen, 1928) gen. et comb. nov. and Neodiplopeltula tchesunovi (Fadeeva & Mordukhovich, 2013) gen. et comb. nov. New synonyms include: Diplopeltis asymmetricus Allgen, 1935 and Diplopeltis ovalis Ditlevsen, 1928 are synonimised with Neodiplopeltula barentsi (Steiner, 1916) gen. et comb. nov.; Diplopeltula tchesunovi Fadeeva & Mordukhovich, 2013 is synonimised with Neodiplopeltula onusta (Wieser, 1956) gen. et comb. nov.; the male of Diplopeltula cuspidiboja Leduc, 2017 is synonimised with Neodiplopeltula barentsi gen. et comb. nov. and the female with N. bathmanni gen. et comb. nov. A key to the species of Neodiplopeltula gen. nov. is provided.

Genus Neodiplopeltula gen. nov. urn:lsid:zoobank.org:act: B1D9F161-1903-4227-8F97-5A2D6715F2CA Type species Neodiplopeltula incisa (Southern, 1914) gen. et comb. nov. = Diplopeltis incisus Southern, 1914 = Diplopeltula incisa (Southern, 1914) = Diplopeltis incisus sensu Gerlach, 1950 partim (note #1) = Diplopeltula incisa sensu Voronov, 1982 partim (note #2) Diagnosis Cuticle transversely striated; striae visibly smooth under light microscope, may have fine longitudinal incisures visible under SEM. Lateral alae absent. Body pores and epidermal glands absent. Somatic sensilla present, most prominent along anterior part of pharyngeal region and on tail. Labial region bluntly rounded; lips fused. Six inner labial sensilla small, pore-like, located on anterior surface of lips, discernible under SEM only. Six outer labial sensilla papilliform, located on anterior surface of lips. Four cephalic sensilla setiform; their bases located at base of labial region, at level with anteriormost part of amphid. Bases of dorsosublateral setae often located more posteriorly than bases of ventrosublateral setae. Subcephalic sensilla absent. Cervical sensilla present in some species, setiform or papilliform, arranged in dorsosublateral and ventrosublateral rows at level with amphid and subcuticular periamphideal plates. Deirid and ocelli absent. Amphids in some species on strongly refractive lateral subcuticular periamphideal plates that can be connected together on ventral and dorsal sides forming a ���cephalic framework���. Amphidial fovea loop-shaped (inverted U-shaped), dorsal branch often longer than ventral branch; both branches of amphideal fovea closely adjacent. Secretory- excretory system present; renette cell located opposite to posterior part of pharynx or anterior part of intestine. Secretory-excretory ampulla present, located at level of pharynx. Cuticularised secretoryexcretory duct very short, opens to exterior either anterior or posterior to nerve ring level. Oral opening apical or shifted towards dorsal side of body. Buccal cavity usually well developed, subcylindrical and often asymmetrical: cheilostom usually broad, flexible; gymnostom subcylindrical, with weakly cuticularised walls; stegostom short conoid, its lining is uniform with lining of pharynx.Pharyngeal tubes absent. Pharynx subcylindrical, muscular, with evenly distributed myofilaments, gradually expanding towards posterior end; not subdivided into distinct sections; pharyngeal lumen uniform in thickness along entire pharynx length; valves absent. Cardia glandular, variable in shape and size, its posterior part embedded in intestinal tissue. Female reproductive system didelphic-amphidelphic, with equally developed branches, ovaries outstretched. Spermatheca present. Vulva equatorial or postquatorial. Vagina straight; pars proximalis vaginae encircled by large sphincter muscle; pars refringens vaginae absent, epiptygmata present or absent. Male reproductive system diorchic, testes opposed (anterior testis outstretched and posterior testis reflexed). Spicules symmetrical, arcuate; gubernaculum present, usually with strongly developed apophyses. Supplements, precloacal and postcloacal sensilla absent. Three caudal glands present, open via three separate openings, their cells and nuclei incaudal. Spinneret absent. Etymology The genus name is composed of a prefix ���neo������, meaning ���new��� and Diplopeltula, and defines a new taxon proposed to accommodate species formerly placed in the genus Diplopeltula. Relationships The new genus differs from all other taxa currently included in the family Diplopeltidae (Holovachov 2017) in having amphids in the shape of an elongated loop, a well-developed subcylindrical stoma and outstretched ovaries. It is proposed in order to accommodate a number of species previously placed in the genus Diplopeltula and to solve a long lasting taxonomic conundrum (Vincx & Gourbault 1992; Holovachov et al. 2009; Holovachov 2017; Holovachov & Bostr��m 2017). The description of Diplopeltula breviceps, type species of the genus Diplopeltula, does not include clear descriptions of several important taxonomic characters (see Table 1) and the absence of such data prevents an unequivocal placement of the species D. breviceps and the genus Diplopeltula in the classification system of Nematoda. As a result, D. breviceps is considered species inquirenda et incertae sedis and the genus Diplopeltula is accordingly considered genus inquirendum et incertae sedis. The second species, D. longiceps, is also considered species inquirenda et incertae sedis for the same reasons (incomplete description and unclear systematic position). Valid species Neodiplopeltula barentsi (Steiner, 1916) gen. et comb. nov. = Diplopeltis barentsi Steiner, 1916 = Diplopeltis ovalis Ditlevsen, 1928 syn. nov. (note #3) = Neodiplopeltula ovalis (Ditlevsen, 1928) gen. et comb. nov., syn. nov. = Diplopeltis asymmetricus Allg��n, 1935 syn. nov. (note #4) = Neodiplopeltula asymmetrica (Allg��n, 1935) gen. et comb. nov., syn. nov. = Diplopeltis incisus sensu Gerlach, 1950 partim (note #1) = Diplopeltula incisa sensu Voronov, 1982 partim (note #2) = Diplopeltis ovalis sensu Sergeeva, 197 7 (note #5) = Diplopeltula cuspidiboja Leduc, 2017 partim syn. nov. (note #6) = Neodiplopeltula cuspidiboja (Leduc, 2017) gen. et comb. nov., syn. nov. Neodiplopeltula bathmanni (Jensen, 1991) gen. et comb. nov. = Diplopeltis bathmanni Jensen, 1991 = Diplopeltula bathmanni (Jensen, 1991) = Diplopeltula incisa sensu Vitiello, 1972 (note #7) = Diplopeltula incisa sensu Voronov, 1982 partim (note #2) = Diplopeltula cuspidiboja Leduc, 2017 partim syn. nov. (note #8) = Neodiplopeltula cuspidiboja (Leduc, 2017) gen. et comb. nov., syn. nov. Neodiplopeltula indica (Gerlach, 1962) gen. et comb. nov. (note #9) = Diplopeltula indica Gerlach, 1962 Neodiplopeltula intermedia (Gerlach, 1954) gen. et comb. nov. (note #9) = Diplopeltula intermedia Gerlach, 1954 Neodiplopeltula obesa (Nguyen Vu Thahn, Nguyen Thahn Hien & Gagarin, 2012) gen. et comb. nov. = Diplopeltula obesa Nguyen Vu Thahn, Nguyen Thahn Hien & Gagarin, 2012 (note #9) Neodiplopeltula onusta (Wieser, 1956) gen. et comb. nov. = Diplopeltis onustus Wieser, 1956 = Diplopeltula onusta (Wieser, 1956) = Diplopeltula incisa sensu Voronov, 1982 partim (note #2) = Diplopeltula tchesunovi Fadeeva & Mordukhovich, 2013 syn. nov. (note #10) = Neodiplopeltula tchesunovi (Fadeeva & Mordukhovich, 2013) gen. et comb. nov., syn. nov. Species inquirenda et incertae sedis Diplopeltula breviceps Gerlach, 1950 Diplopeltula longiceps Gerlach, 1950 Species incertae sedis Diplopeltula striolata Vincx & Gourbault, 1992 (note #11) Diplopeltula ostrita Boucher & Hell��ou��t, 1977 (note #12) Nomenclatorial changes and notes 1) The description of Diplopeltis incisus sensu Gerlach, 1950 is based on specimens collected in several localities in the Kiel Bay and is likely to be a mixture of at least two different species: based on the oval shape and relatively small size of the periamphideal refractive plate, the position of cephalic setae posterior to the oral opening, and the position of the oral opening close to the anterior end, N. barentsi gen. et comb. nov. can be identified on fig. 3h, 3k & 3m in Gerlach (1950), while fig. 3b likely depicts N. incisa sensu stricto, based on the irregular shape and relatively large size of the periamphideal refractive plate, the position of cephalic setae posterior to the oral opening, and the position of the oral opening close to the anterior end. Unfortunately, exact measurements of morphological characters cannot be attained from the figures in Gerlach���s publication due to the absence of proper scale bars. Thus, our hypothesis on the taxonomic identity of specimens studied by Gerlach (1950) must solely rely on illustrations and cannot be verified any further. 2) The description of Diplopeltula incisa sensu Voronov, 1982 is based on specimens collected in six different locations from the White Sea, within an area of more than 100 �� 200 km in size and ranging in depth from 50 to 250 meters. Many measurements given by Voronov vary within 2�����4�� range. Morphological features of the anterior end also show a considerable variability (noted by Voronov himself) suggesting that his description is based on more than one morphospecies. Here we suggest that there are four different species of Neodiplopeltula gen. nov. illustrated in Voronov���s publication: fig. 1a likely depicts N. bathmanni gen. et comb. nov. with very narrow periamphideal plates and an oral opening located at level with the cephalic setae bases; both specimens depicted on fig. 1б and 1в match our concept of N. barentsi gen. et comb. nov. with relatively broad oval periamphideal plates and an oral opening located close to the anterior terminus, anterior to the cephalic setae bases; the presence of irregularly shaped periamphideal plates and an oral opening located close to the anterior terminus, anterior to cephalic setae bases in specimen depicted on 1г suggest it to belong to N. incisa gen. et comb. nov.; while the anterior end shown on fig. 1д completely matches with N. onusta gen. et comb. nov. (and confirmed by Voronov in his figure caption) in having periamphideal plates merging on the dorsal and ventral body sides and an oral opening located at level with the cephalic setae bases. 3) The holotype of Diplopeltis ovalis described by Ditlevsen (1928) from Greenland is available in the collection of the Natural History Museum of Denmark in Copenhagen and is in rather acceptable shape. Some morphological features, such as cephalic setae and the spinneret cannot be seen due to deterioration, while the vagina and rectum are difficult to observe since the specimen is not in perfect lateral position on the slide. Morphological and morphometric features that are visible and measurable, show no differences from N. barentsi gen. et comb. nov. ��� in particular, the position of the oral opening and morphology of refractive plates underlying the amphids are identical (Figs 14A, 15 A���B). Consequently, Diplopeltis ovalis is being transferred to the genus Neodiplopeltula gen. nov. and synonimised with N. barentsi gen. et comb. nov. 4) The lectotype of Diplopeltis asymmetricus described by Allg��n (1935) from ��resund was found in the collection and is in poor shape. The specimen is partly dried, thus making it impossible to observe and measure smaller features such as cephalic setae, spinneret and rectum. It is also slightly flattened, which affects a- and c���-ratios. Morphological features that are visible, show no differences from N. barentsi gen. et comb. nov. ��� in particular, the position of the oral opening and the morphology of refractive plates underlying the amphids are identical (Figs 14B, 15C). Consequently, Diplopeltis asymmetricus is being transferred to the genus Neodiplopeltula gen. nov. and synonimised with N. barentsi gen. et comb. nov. 5) Diplopeltis ovalis sensu Sergeeva, 1977 is similar to N. barentsi gen. et comb. nov. in the position of the oral opening on the dorsal side of the body but close to the anterior end, length and arrangement of the cephalic setae (7.5 ��m vs 3.5���7.5 ��m in present specimens), and the shape of refractive plates (elongated ovoid, not connected). 6) The male of Diplopeltula cuspidiboja gen. et comb. nov. is identical to N. barentsi gen. et comb. nov. in the position of the oral opening, size and shape of refractive plates and the great majority of quantitative characters (see Table 3), except for a slightly longer amphid (32 ��m vs 21���25.5 ��m) and gubernaculum (20 ��m vs 10���11.5 ��m). 7) Diplopeltula incisa sensu Vitiello, 1972 is similar to D. bathmanni in the position of the oral opening, length and the arrangement of the cephalic setae, the size and position of the periamphideal refractive plate, length of the tail and position of the caudal gland openings. 8) The female of Diplopeltula cuspidiboja gen. et comb. nov. is identical to N. bathmanni gen. et comb. nov. in the position of the oral opening, the position of the cephalic sensilla, the size and shape of the refractive plates (Leduc 2017); as a result of having a larger body (2076 ��m vs 1270���1673 ��m), many morphometric characters of the female of D. cuspidiboja are also outside the measurement range of both Nordic populations, which can be attributed to geographic variability. 9) Diplopeltula indica and Diplopeltula intermedia both match the diagnostic characters of the genus Neodiplopeltula gen. nov.: amphids in the shape of an elongated loop, a well-developed subcylindrical stoma and outstretched ovaries. Diplopeltula obesa also has amphids in the shape of an elongated loop and outstretched ovaries, however, the structure of the stoma in this species is described as ���not expressed���, leaving some doubts as to its exact morphology. 10) Diplopeltula tchesunovi is identical to D. onusta in all qualitative and quantitative characters (Table 4), with the exception of longer refractive plates (41���48 ��m vs 32���38 ��m), which can be attributed to geographic variability. 11) Diplopeltula striolata is described based only on one male, thus the structure of the female reproductive system remains unknown, questioning its systematic affinities. It is similar to the genus Neodiplopeltula gen. nov. in the morphology of the amphid (in the shape of an elongated loop) and stoma (small but well developed, subcylindrical). The morphology of the pharynx (uniformly cylindrical) also matches that of Neodiplopeltula gen. nov. However, D. striolata strongly differs from Neodiplopeltula gen. nov. in having a strongly annulated cuticle, the position of the excretory pore at the level with the anterior part of the intestine, the presence of a spinneret, the absence of a gubernaculum. Although this species can easily be identified, and its validity is unquestionable, its taxonomic position remains unresolved as it cannot be assigned to any of the existing genera with confidence (species incertae sedis). 12) All available type specimens of Diplopeltula ostrita were examined, but not all morphological characters can be observed. That includes the female reproductive system and the structure of the ovaries. However, D. ostrita strongly differs from Neodiplopeltula gen. nov. in having a strongly annulated cuticle, a minute buccal cavity, weak spicules and gubernaculum. Similar to Diplopletula striolata, D. ostrita is here considered to be a valid species, which, however, cannot be assigned to any existing genus with confidence and must be considered species incertae sedis., Published as part of Holovachov, Oleksandr & Bostr��m, Sven, 2018, Neodiplopeltula gen. nov. from the west coast of Sweden and reappraisal of the genus Diplopeltula Gerlach, 1950 (Nematoda, Diplopeltidae), pp. 1-34 in European Journal of Taxonomy 458 on pages 3-7, DOI: 10.5852/ejt.2018.458, http://zenodo.org/record/3826987, {"references":["Southern R. 1914. Nemathelmaia, Kinorhyncha, and Chaetognatha (Clare Island Survey, Part 54). Proceedings of the the Royal Irish Academy 31: 1 - 80.","Gerlach S. A. 1950. Die Diplopeltiden, eine Gruppe freilebender Nematoden. Kieler Meeresforschungen 7: 138 - 156.","Voronov D. A. 1982. [Free-living nematodes of the genus Diplopeltula Gerlach, 1950 (Araeolaimida, Axonolaimidae) from the White Sea.] Sovremennye problemy biogeografii: 189 - 197. [in Russian.]","Vincx M. & Gourbault N. 1992. Six new species of the genus Diplopeltula (Nematoda: Diplopeltidae) with remarks on the heterogeneity of the taxon. Hydrobiologia 230: 165 - 178. https: // doi. org / 10.1007 / BF 00036563","Holovachov O., Tandingan De Ley I., Mundo-Ocampo M., Gingold R &, De Ley P. 2009. Nematodes from the Gulf of California. Part 3. Three new species of the genus Diplopeltoides Gerlach, 1962 (Nematoda: Diplopeltoididae) with overviews of the genera Diplopeltis Gerlach, 1962 and Diplopeltula Gerlach, 1950. Russian Journal of Nematology 17: 43 - 57.","Holovachov O. & Bostrom S. 2017. Three new and five known species of Diplopeltoides Gerlach, 1962 (Nematoda, Diplopeltoididae) from Sweden, and a revision of the genus. European Journal of Taxonomy 369: 1 - 35. https: // doi. org / 10.5852 / ejt. 2017.369","Steiner G. 1916. Freilebende Nematoden aus der Barentssee. Zoologische Jahrbucher. Abteilung fur Systematik, Geographie und Biologie der Tiere 39: 511 - 664.","Ditlevsen H. 1928. Free-living marine nematodes from Greenland waters. Meddelelser om GrOnland 23 (Suppl.): 199 - 250.","Allgen C. 1935. Die freilebenden Nematoden des Oresunds. Capita Zoologica 6: 1 - 192.","Leduc D. 2017. Four new nematode species (Araeolaimida: Comesomatidae, Diplopeltidae) from the New Zealand continental slope. Zootaxa 4237: 244 - 264. https: // doi. org / 10.11646 / zootaxa. 4237.2.2","Jensen P. 1991. Nine new and less known nematode species from the deep-sea benthos of the Norwegian Sea. Hydrobiologia 222: 57 - 76. https: // doi. org / 10.1007 / BF 00017500","Vitiello P. 1972. Sur quelques especes de Diplopeltula (Nematoda, Araeolaimida). Vie et Milieu 21: 535 - 544.","Wieser W. 1956. Free-living Nematodes and Other Small Invertebrates of Puget Sound Beaches. University of Washington Press.","Fadeeva N. & Mordukhovich V. 2013. Some new and poorly known nematode species from the Sea of Japan. Deep-Sea Research II 86 - 87: 119 - 123. https: // doi. org / 10.1016 / j. dsr 2.2012.07.044","Sergeeva N. G. 1977. Free-living nematoda, new for the Black Sea. Vestnik Zoologii 1: 36 - 44."]}

Amendment to the key to the genera of Diplopeltidae (from Holovachov 2017) 10. Stoma subcylindrical; caudal glands open via three separate pores.......... Neodiplopeltula gen. nov. – Stoma small and undifferentiated; caudal glands open via common spinneret...............................11 11. Amphid located on a well-developed refractive subcuticular plate.............................................................................................................................................. Diplopeltis Cobb in Stiles & Hassal, 1905 – Refractive subcuticular plate absent.......................................... Pseudaraeolaimus Chitwood, 1951

Neodiplopeltula bathmanni (Jensen, 1991) gen. et comb. nov. Figs 11–13; Table 5 Diagnosis (based on combined data) Neodiplopeltula bathmanni gen. et comb. nov. is characterised by a 0.85–2.08 mm long body; refractive plates underlying cephalic cuticle around amphids present, not joined, 19–29 µm long and 12–16.5 µm wide; cephalic sensilla 2–3.5 µm long; amphidial fovea 20–32 µm long and 4–7 µm wide; oral opening 6–16 µm from anterior end, at level with or posterior to cephalic setae bases; secretory-excretory pore located opposite to posterior part of pharynx; tail 1.5–2.2 anal body diameters long; vagina with epiptygmata; spicules 52–66 µm long. Material examined SWEDEN: 1 ♀, 4 ♂♂, Skagerrak, 58°19′15.6″–20.9″ N, 10°29′33.5″–34.0″ E, soft bottom at a deep of 352–374 m, 10 Sep. 2012, “Inventering Bratten” leg. (SMNH-169274 and SMNH-169284); 1 ♀, Skagerrak, 58°22′17.8″–19.4″ N, 10°23′50.8″–24′03.2″ E, soft bottom at a deep of 351–387 m, 10 Sep. 2012, “Inventering Bratten” leg. (SMNH-169275); 1 ♀, 1 ♂, Skagerrak, 58°34′21.3″–16.6″ N, 10°38′11.2″–29.4″ E, soft bottom at a deep of 139–153 m, 12 Sep. 2012, “Inventering Bratten” leg. (SMNH-169277). Description Adult Body cylindrical, posteriorly tapering in tail region, straight or weakly ventrally curved upon fixation. Cuticle finely transversely striated along entire body, except for visually smooth labial region and terminal part of tail (striation can be observed under LM but very fine and shallow and cannot be measured with confidence); longitudinal striation not observed. Somatic sensilla visible along pharyngeal region (cervical setae, see below) and on tail. Labial region bluntly rounded, lips fused. Refractive plates underlying cephalic cuticle around amphids present (periamphideal), extending from level of anteriormost edge of amphid posteriorly some distance behind the posteriormost edge of amphid; refractive plates are elongated ovoid in shape (plate edges not incised), not connected with each other on ventral and on dorsal sides. Inner labial sensilla indistinct. Outer labial sensilla papilliform, located on anterior surface of lips. Cephalic sensilla setiform, bases of dorsosublateral setae located at level with or anterior to oral opening. Cervical sensilla absent; small papilliform somatic sensilla visible posterior to amphid and refractive plate. Amphids similar in shape and size between sexes: amphidial fovea inverted U-shape branches unequal in length with either dorsal or ventral branch 1.0–2.0 µm longer than opposite branch. Oral opening shifted towards dorsal side of body. Stoma subcylindrical: cheilostom broad; gymnostom barrel-shaped, with weakly cuticularised walls; stegostom short conoid, its lining uniform with lining of pharynx. Pharyngeal tubes absent. Pharynx subcylindrical, muscular, with evenly distributed myofilaments, gradually expanding towards posterior end; not subdivided in distinct sections; pharyngeal lumen uniform in thickness along entire pharynx length; valves absent. Secretory-excretory system present; secretory-excretory pore located along ventral body line opposite to 4/5 th of pharynx; secretory-excretory duct very short, leading from pore to ampulla; renette cell small, its body adjacent and ventral to posterior part of pharynx. Tail conoid with bluntly rounded terminus. Caudal glands opening via three separate subterminal openings, spinneret absent. Female Reproductive system didelphic, amphidelphic, ovary branches outstretched and symmetrical, on opposite sides of intestine. Anterior genital tube 97–242 µm long, situated to either right (n = 2) or left (n = 1) of intestine; posterior genital tube 103–245 µm long situated to either left (n = 2) or right (n = 1) of intestine. Vulva transverse slit, located posterior to midbody. Vagina straight, with developed sphincter muscle surrounding proximal part and distinct epiptygmata in distal part; pars refringens vaginae absent. Sacklike spermatheca present, filled with oval spermatozoa in fertilized specimens. Rectum short. Male Reproductive system diorchic, testes opposed; anterior testis outstretched and posterior testis reflexed (cannot be measured). Spicules paired and symmetrical, strongly curved, with ovoid manubrium and fusiform shaft. Gubernaculum plate-like, with pair of strong closely set caudal apophyses variable in shape (Fig. 13 C–E). Caudal setae present, several ventrosublateral pairs arranged in rows along entire tail length, one dorsosublateral pair located close to tail terminus (not always visible). Remarks No morphological or morphometric differences can be found between the recent specimens and the original description of this species (Jensen 1991).

Syringolaimus magdae Lima, Lins, Da Silva & Esteves, 2009. Lima et al., 2009: p. 125-127, figs 3���4 (South���West Atlantic, off coast of Brazil, Campos Basin, 1050 m, siltclay), one male. Cuticle smooth along the entire body or striations not easily observed. Ventral pore situated at 35.2% of pharynx length from anterior end; ventral gland cell body present. Caudal glands and spinneret present. Monorchic. No supplementary organs mentioned. Syringolaimus marisalbi Platonova & Mokievsky, 1994 sp. inq. Platonova & Mokievsky, 1994: p. 9���10, figs 9���14 (White Sea, upper intertidal zone, fine sand with clay), males, females and juveniles. Body cuticle largely smooth but striated on tail. Spinneret present. Ovaries are described as straight (erroneously?). Amphids, ventral pore and ventral gland, male gonads, supplementary organs and caudal glands not mentioned. Apparently, close or may be identical to S. striatocaudatus. Syringolaimus nitidus Bussau, 1993 nom. nud. Bussau, 1993: p. 501���505, Abb. 216, 217. (South���East Pacific / Peru Basin/, 4100���4200 m, dark brown ooze with manganese nodules), males and females. Body cuticle with extremely fine annulations. Metanemes not observed. Ventral pore at a distance of 60 ��m from anterior end (in a male), a bit anterior to the nerve ring. Spinneret evident but no caudal glands found. Monorchic. No supplementary organs mentioned., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on pages 481-482, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097, {"references":["Lima, R. C. C., Lins, L., Da Silva M. R., & Esteves, A. M. (2009) Four new species of Syringolaimus De Man, 1888 (Nematoda: Ironidae) from the Southeast Atlantic (Brazil), with redefinition of valid species and the proposal of a new key. Zootaxa, 2096, 119 - 136.","Platonova, T. A. & Mokievsky, V. O. (1994) Revision of the marine nematodes of the family Ironidae (Nematoda: Enoplida). Zoosystematica Rossica, 3 (1), 5 - 17.","Bussau, Ch. (1993) Taxonomische und okologische Untersuchungen an Nematoden des Peru-Beckens. Dissertation zur Erlangen des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultat der Christian-Albrechts-Universitat zu Kiel, Kiel, 621 pp."]}

Syringolaimus renaudae Gourbault & Vincx, 1985. Gourbault & Vincx, 1985: p. 109���114, fig. 1���2 (SW Atlantic, Cape Basin, 3694���4180 m, deep-sea ooze), males and females. Cuticle finely annulated close to both extremities. Anterior end demarcated by a distinct collar. Amphidial fovea 40% of the corresponding body width in male. Ventral pore at the level of posterior end of the buccal cavity. Monorchic. No supplementary organs mentioned. Spinneret and caudal glands present. Syringolaimus smarigdus Cobb, 1928 sp. inq. Cobb, 1928: p. 249���253, fig. 1 (USA east coast, Massachusetts, from shells of gastropod molluscs Alectrion obsoleta feeding on algae Ralfsia). De Coninck & Schuurmans Stekhoven, 1933: p. 58 (junior synonym of S. striaticaudatus). Chitwood, 1951: p. 646, fig. 9 I ���K (Texas, from Sargassum algae). Description and brief redescriptions of this species are poorly detailed. Since neither measured values nor structural features contradict characteristics of S. striatocaudatus, I follow the opinion of De Coninck & Schuurmans Stekhoven (1933) and adopt synonymy of the species., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on page 482, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097, {"references":["Gourbault, N. & Vincx, M. (1985) Deux especes nouvelles d'Ironidae marins; observations sur les spermatozoides \" flagelles \" des Nematodes. Bulletin du Museum national d'Histoire naturelle, Paris, 4 e Serie, 7, Section A, n o 1, 109 - 118.","Cobb, N. A. (1928) A new species of the nemic genus Syringolaimus with a note on the fossorium of nemas. Journal of the Washington Academy of Sciences, 18, 249 - 263.","De Coninck, L. A. & Schuurmans Stekhoven, J. H. (1933) The free-living marine nemas of the Belgian coast II. Memoires du Musee royal d'Histoire naturelle de Belgique, 58, 1 - 163.","Chitwood, B. G. (1951) North American marine nematodes. Texas Journal of Science, 3, 617 - 672."]}

Syringolaimus taniae Lima, Lins, Da Silva & Esteves, 2009. Lima et al., 2009: p. 130���133, figs 7���8 (South���West Atlantic, off coast of Brazil, Campos Basin, 1050���1350 m, silt-clay), males and female. Body cuticle with faint striation not easily detected. Ventral pore just posterior to the buccal cavity, ventral gland cell body at the level of cardia. Tail with anterior portion rounded and clearly set apart from distal filliform cylindrical part. Caudal glands present, spinneret long, representing 12.9% of tail length. Monorchic. No precloacal papilla present. Syringolaimus venustus Bussau, 1993 nom. n., sp. inq. Bussau, 1993: p. 505���507, Abb. 218 (South���East Pacific, Peru Basin, 4100���4200 m, dark brown ooze with manganese nodules), female and juveniles. Body cuticle extremely finely annulated. Metanemes not found. Amphidial fovea 25% of the corresponding body width in female. Neither ventral pore nor ventral gland cell body found. Spinneret evident but no caudal glands found., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on page 482, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097, {"references":["Lima, R. C. C., Lins, L., Da Silva M. R., & Esteves, A. M. (2009) Four new species of Syringolaimus De Man, 1888 (Nematoda: Ironidae) from the Southeast Atlantic (Brazil), with redefinition of valid species and the proposal of a new key. Zootaxa, 2096, 119 - 136.","Bussau, Ch. (1993) Taxonomische und okologische Untersuchungen an Nematoden des Peru-Beckens. Dissertation zur Erlangen des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultat der Christian-Albrechts-Universitat zu Kiel, Kiel, 621 pp."]}

Identification of Syringolaimus species Species of Syringolaimus are pretty similar, but differ from one another in morphometrics and especially in relative length and shape of the tail. Other characters such as length of the buccal cavity and position of the amphidial aperture are also important for species discrimination and hence they are included in tables 1 and 2. Position of the ventral pore and presence/absence of preanal supplementary papilla, caudal glands and spinneret should also have significance for species identification but unfortunately they are very unevenly characterized in all species and hence it is impossible to present these traits for every species as icons in a pictorial key. Lima et al. (2009) provided a dichotomous key for fourteen Syringolaimus species designated by them as valid. Since some changes in the list of valid species are made and one new species is here described, I complement the key with morphometric characteristics (tables 1 and 2) and schematic icons of the tails (Fig. 1)., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on page 483, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097, {"references":["Lima, R. C. C., Lins, L., Da Silva M. R., & Esteves, A. M. (2009) Four new species of Syringolaimus De Man, 1888 (Nematoda: Ironidae) from the Southeast Atlantic (Brazil), with redefinition of valid species and the proposal of a new key. Zootaxa, 2096, 119 - 136."]}

Southerniella parasimplex sp. n. (Figs. 7���9, Table 2) Diagnosis. Southerniella parasimplex sp. n. is characterised by 840���1130 ��m body length, cephalic setae 0.3 cbd long, amphids 0.5���0.6 cbd wide and situated immediately posterior to the cephalic setae, buccal cavity ~12 ��m deep, secretory-excretory system with three renette cells, presence of progaster consisting of densely granulated cells, conicocylindrical tail, female with two outstretched ovaries and single anterior spermathecum, and male with outstretched anterior testis and reflexed posterior testis directed anteriorly, and gubernaculum surrounding spicules distally and with apophyses directed dorsally. Etymology. The species name refers to the similarity between the new species and Southerniella simplex. Holotype. Male (NIWA 115454), collected 15 April 2010 (voyage TAN 1004, station 4), Hikurangi Margin (1046 m water depth), 41.6837 ��S, 175.6642 ��E, mean grain size: 12 ��m, %silt/clay particles: 94.7%. Paratype. Female (NIWA 115455), same data as holotype. Description. Males. Colourless cylindrical body tapering slightly towards anterior end, with rounded anterior extremity and conicocylindrical tail. Cuticle with faint transverse striations; no somatic setae observed. Walls of numerous epidermal cells visible throughout length of body; content of epidermal cells transparent. Cephalic region narrow and set off from rest of body. Inner and outer labial sensilla not observed; four cephalic setae, 0.3 cbd long. Subcephalic setae absent. Circular amphideal fovea and aperture, situated immediately posterior to cephalic setae. Buccal cavity cylindrical, narrow, ~12 ��m deep, weakly cuticularised, surrounded by pharyngeal tissue. Cylindrical pharynx with anteriormost portion (corpus) thinner than the rest of pharynx, and with slight posterior bulb; pharyngeal tubes present but difficult to observe. Nerve ring at ~60% of pharynx length from anterior. Secretory-excretory system with three renette cells situated immediately posterior to pharynx; pore not observed. Anteriormost portion of intestine differentiated as enlarged, densely granulated cells surrounding cardia (progaster). Reproductive system diorchic with anterior outstretched testis located to the left of intestine and anteriorly oriented and reflexed posterior testis situated ventrally relative to intestine. Mature sperm cells globular, 5 �� 7 ��m, with oval nuclei. Spicules paired, equal, strongly bent, almost L-shaped, 1.2 cloacal body diameters long, without capitulum. Gubernaculum surrounding distal ends of spicules, with pair of apophyses directed dorsally and parallel with proximal end of spicules. Four rectal glands present; two glands situated laterally and slightly anteriorly to spicules, one gland situated dorsally relative to spicules, and one gland immediately posterior to spicules. Three pairs of ejaculatory glands also present further anteriorly. Precloacal supplements and precloacal seta not observed. Tail conicocylindrical, with short cylindrical terminal portion. Three caudal glands and spinneret present. Species Diplopeltula cuspidiboja sp. n. Southerniella parasimplex sp. n. Female. Similar to male, but with walls of epidermal cells not as conspicuous, slightly smaller amphid, pharyngeal tubes conspicuous in anterior half of pharynx, and slightly shorter tail. Reproductive system didelphic, with anterior outstretched ovary to the left of intestine and posterior outstretched ovary to the right of intestine. Single anterior spermathecum present with several sperm cells. Vulva located slightly posterior to mid-body. A single posterior granular vaginal gland present, proximal portion of vagina uterina surrounded by constrictor muscle. Differential diagnosis. Southerniella parasimplex sp. n. is most similar to S. simplex in having relatively large amphids located immediately or almost immediately posterior to the cephalic setae, as well as a relatively short buccal cavity. Southerniella parasimplex sp. n. can be differentiated from S. simplex by the orientation of the gubernacular apophyses (dorsally-directed and parallel to spicules in S. parasimplex sp. n. versus dorso-caudally directed and perpendicular to spicules in S. simplex), and the shape of the tail (conicocylindrical in S. parasimplex sp. n. versus conical in S. simplex). The new species is also similar to S. conicauda in having a relatively short buccal cavity but can be differentiated from the latter by the presence of a gubernaculum (absent in S. conicauda) and the shape of the tail (conicocylindrical in S. parasimplex sp. n. versus usually conical and sometimes conicocylindrical in S. conicauda). Remarks. The progaster in Southerniella conicauda, Intasia amblynema and Intasia lympha usually comprises four enlarged and non-granular cells. Progaster cells in Southerniella parasimplex sp. n. have an unusual granulated appearance, and their number could not be determined with certainty. Jensen (1991) noted the presence of a progaster in other genera of the Order Araeolaimida, namely Cylindrolaimus de Man, 1880 (Diplopeltidae) and Bodonema Jensen, 1991 (Bodonematidae), as well as in some Monhysteridae., Published as part of Leduc, Daniel, 2017, Four new nematode species (Araeolaimida: Comesomatidae, Diplopeltidae) from the New Zealand continental slope, pp. 244-264 in Zootaxa 4237 (2) on pages 254-259, DOI: 10.11646/zootaxa.4237.2.2, http://zenodo.org/record/343781, {"references":["Jensen, P. (1991) Bodonematidae fam. n. (Nematoda, Monhysterida) accommodating Bodonema vossi gen. et sp. n. from the deep-sea benthos of the Norwegian Sea. Sarsia, 76, 11 - 15."]}

Diplopeltula cuspidiboja sp. n. (Figs. 10���12, Table 2) Diagnosis. Diplopeltula cuspidiboja sp. n. is characterised by 1150���2080 ��m body length, a striated cuticle, the presence of amphideal plates, a dorsally oriented mouth opening, cup-shaped buccal cavity with pointed ring giving appearance of small teeth, arcuate spicules and gubernaculum with strongly cuticularised apophyses, vulva located at three quarters of body length from anterior, and short conical tail. Etymology. The species name is derived from the Latin cuspidis (= pointed end) and boja (= collar), and refers to the pointed ring projecting into the buccal cavity of this species. Holotype. Male (NIWA 115456), collected 20 February 2011 (voyage TAN1103, station 69), crest of Chatham Rise (350 m water depth), 43.331�� S, 178.288�� E, mean grain size: 55���59 ��m, %silt/clay particles: 43���45%. Paratype. Female (NIWA 115457), collected 17 April 2010 (voyage TAN1004, station 17), Hikurangi Margin (1514 m water depth), 41.6288 ��S, 175.8682 ��E, mean grain size 9.0 ��m, % silt/clay particles: 97.8%. Description. Male. Colourless cylindrical body tapering slightly towards anterior and posterior ends, with rounded anterior and posterior extremities and conical tail. Cuticle with light transverse striations and sparse somatic setae restricted to anteriormost and posteriormost body regions, 1���2 ��m long. Six minute inner labial papilla present on lip region; six outer labial papilla in a separate circle and four cephalic setae situated further posteriorly, 0.3 cbd long. Loop-shaped amphideal fovea and aperture, situated on cuticularised amphideal plate immediately posterior to cephalic setae. Mouth opening oriented dorsally; buccal cavity cup-shaped, lightly cuticularised, with pointed ring giving appearance of small teeth in optical cross-section. Cylindrical pharynx partially surrounding buccal cavity and widening posteriorly without forming a true bulb; pharyngeal tubes not observed. Nerve ring at about 40% of pharynx length from anterior. Secretory-excretory system present, excretory pore slightly posterior to nerve ring; small ampulla and renette cell located immediately anterior to posterior swelling of pharynx. Cardia 5 ��m long, partially surrounded by intestine. Reproductive system diorchic with anterior outstretched testis located to the left of intestine and posterior outstretched testis to the right of intestine. Mature sperm cells indistinct. Spicules paired, equal, arcuate, 1.8 cloacal body diameters long, with weakly defined capitulum and short central cuticularised projection (lamella) at proximal end. Gubernaculum surrounding distal ends of spicules, with pair of strongly cuticularised apophyses directed dorso-caudally. Rectal and ejaculatory glands not observed. Tubular precloacal supplements and precloacal seta not observed. Tail short, conical, with rounded distal tip sometimes with sparse lateroventral setae. Three caudal glands with three separate outlets. Female. Similar to males, but with longer and wider body, and pharynx with well-defined posterior bulb and pharyngeal gland visible. Reproductive system didelphic, with anterior outstretched ovary to the left of intestine and posterior outstretched ovary to the right of intestine. Mature eggs not observed. Spermatheca present in both genital branches, both with numerous sperm. Vulva located at three quarters of body length from anterior. Vaginal glands not observed, proximal portion of vagina uterina surrounded by constrictor muscle. Differential diagnosis. Diplopeltula cuspidiboja sp. n. resembles other species of the genus with a dorsally oriented mouth opening, namely D. bathmanni, D. belgica, D. dulcis, D. incisa, D. longiloba, D. ostrita, D. striolata and D. tenuis. It is most similar to D. incisa in the body dimensions, presence of amphideal plates, shape and size of the copulatory apparatus, and short conical tail. The new species can be differentiated from D. incisa by the presence of a pointed and lightly cuticularised ring projecting into the buccal cavity (versus unarmed buccal cavity in D. incisa), and the position of the vulva located further posteriorly (74% versus 62���64% of body length from anterior extremity in D. incisa). In the original description of D. incisa by Southern (1914), the buccal cavity is almost terminal and only slightly displaced dorsally in the drawings (although this is not noted in the description), the buccal cavity is cylindrical and without teeth, the amphideal plate is characterised by notches laterally and anteriorly, and the vulva is described as being some distance behind the middle of the body. Subsequent descriptions of the species show some variation in these traits, such as the absence of notches in the amphideal plate (Vitiello 1972, Warwick 1998), a larger, ovoid buccal cavity (Gerlach 1950, Warwick 1998), and a mouth situated far dorsally resulting in a displacement of the cephalic setae (Vitiello 1972). The descriptions of Gerlach (1950), Vitiello (1972), and Warwick (1998), however, all show the vulva to be at 62���64% of body length from the anterior extremity, and none show any buccal cavity armature., Published as part of Leduc, Daniel, 2017, Four new nematode species (Araeolaimida: Comesomatidae, Diplopeltidae) from the New Zealand continental slope, pp. 244-264 in Zootaxa 4237 (2) on pages 260-263, DOI: 10.11646/zootaxa.4237.2.2, http://zenodo.org/record/343781, {"references":["Southern, R. (1914) Nemathelmia, Kinorhyncha, and Chaetognatha (Clare Island Survey, Part 54). Proceedings of the Royal Irish Academy, 31, 1 - 80.","Vitiello, P. (1972) Sur quelques especes de Diplopeltula (Nematoda Araeolaimida). Fie et Milieu, 21, 535 - 544.","Warwick, R. M., Platt, H. M. & Somerfield, P. J. (1998) Free-living Marine Nematodes Part III Monhysterids. In: Synopses of the British fauna. New Series. Fol. 53. Field Studies Council, Shrewsbury, pp. 1 - 296.","Gerlach, S. A. (1950) Die Diplopeltiden, eine gruppe freilebender nematoden. Kieler Meeresforschungen, 7, 138 - 156."]}

Family Rhabdolaimidae Chitwood, 1951 4. Rhabdolaimus terrestris de Man, 1880 ��� {25} (0, 4, 0, 0; 1) Population structure and abundance. One juvenile individual and two females (~1 x10 3 /m2). Ecology and distribution. Amphibiont. Occurs in various aquatic and terrestrial biotopes. Presumably cosmopolitan. Widely distributed in Europe, Asia and Africa; noted in some countries of North and South America and Oceania (Andr��ssy 2005). Observed in diverse aquatic and soil biotopes in northern Vietnam (Gagarin & Nguyen 2005a; Nguyen & Nguyen 2005; Nguyen 2007; Gagarin & Nguyen 2008a, 2012). 5. * Udonchus tenuicaudatus Cobb, 1913 ��� {2, 20, 31, 58, 62} (11, 4, 8, 9; 7) Population structure and abundance. From 1 to 6 females (including those with eggs) and sporadic juveniles at the majority of sites (up to 4 x10 3 /m2), with 27 specimens (two juveniles, 15 females and 10 gravid females) at site 2 (10 x10 3 /m2). Ecology and distribution. Amphibiont. Until recently considered a hydrobiont as it was noted only from water bodies of several European and African countries, and in some countries of Central (Jamaica) and South (Colombia) America and Asia (Sumatra) (Andr��ssy 2005). However, a 2012 paper (Tahseen et al. 2012) reported U. tenuicaudatus populations from the soils of various regions of northern India. Until the beginning of our studies on meiobenthos, this genus had not been recorded in Vietnam (Gusakov et al. 2014). Remarks. Males are unknown (Tahseen et al. 2012). In our earlier paper (Gusakov et al. 2014), we described this taxon under the name U. cf. merhatibebi. This was because we could not conclusively assign any of our initial specimens to U. merhatibebi Eyualem & Coomans, 1996, described from Ethiopia (Eyualem & Coomans 1996), and were unaware of the morphologically similar U. tenuicaudatus. Further analysis of Vietnamese samples has shown that a majority of the adult specimens found (as assessed on the basis of a set of features) conform to descriptions of U. tenuicaudatus (Eyualem & Coomans 1996; Andr��ssy 2005; Tahseen et al. 2012). At the same time, even within a single habitat we found specimens displaying in various combinations the diagnostic features of both species (shapes of the lip region, cardia and associated gland cells, and of the tail tip, amphid position, etc.). Without considering the whole range of variation in these features, some individuals of these populations could be identified as U. merhatibebi. A similar mixing of the features of these two species was noted in the description of soil populations of U. tenuicaudatus from India (Tahseen et al. 2012), where this phenomenon is discussed and illustrated in detail. Those authors suggest that U. tenuicaudatus is a widespread and morphologically variable species depending on geographical location and that the few diagnostic features that distinguish it from the presumably close species U. merhatibebi are unreliable. Our study on populations of U. tenuicaudatus from Vietnamese inland waters has led us to a similar opinion., Published as part of Gusakov, Vladimir A. & Gagarin, Vladimir G., 2017, An annotated checklist of the main representatives of meiobenthos from inland water bodies of Central and Southern Vietnam. I. Roundworms (Nematoda), pp. 1-43 in Zootaxa 4300 (1) on page 12, DOI: 10.11646/zootaxa.4300.1.1, http://zenodo.org/record/837117, {"references":["Andrassy, I. (2005) Free-living nematodes of Hungary (Nematoda Errantia). I. Pedozoologica Hungarica, No. 3, 1 - 518.","Gagarin, V. G. & Nguyen, V. T. (2005 a) Free-living nematodes from some fresh water bodies of Northern Vietnam. Biologiya Fnutrennih Fod, No. 1, 18 - 23. [in Russian]","Nguyen, T. T. & Nguyen, V. T. (2005) Comparison on Free-living Nematode Compositions of the Cau, Day, Cam and Nhue Rivers. T ap chi Sinh H oc, 27, 36 - 42. [in Vietnamese]","Nguyen, V. T. (2007) Free-living nematodes Monhysterida, Araeolaimida, Chromadorida, Rhabditida, Enoplida, Mononchida, Dorylaimida. In: Dang, N. T. (Ed.), Fauna of Fietnam. Fol. 22. Science and Technics Publishing House, Hanoi, 455 pp. [in Vietnamese]","Gagarin, V. G. & Nguyen, T. T. (2008 a) Free-living nematodes from the Chu River, Northern Vietnam. Inland Water Biology, 1, 14 - 18.","Tahseen, Q., Sultana, R., Khan, R. & Hussain, A. (2012) A New Genus and Species of the Family Rhabdolaimidae (Nematoda), with Descriptions of Two Known Species and Taxonomic Discussion. Journal of Nematology, 44, 302 - 312.","Eyualem, A. & Coomans, A. (1996) Aquatic nematodes from Ethiopia VII. The family Rhabdolaimidae Chitwood, 1951 sensu Lorenzen, 1981 (Chromadorida: Nematoda) with the description of Udonchus merhatibebi n. sp. Hydrobiologia, 341, 197 - 214."]}

Syringolaimus filicaudatus Vitiello, 1970 Vitiello, 1970: p. 206���207, figs 51 a���j (Mediterranean, Gulf of Lion, 310���580 m). Body cuticle finely striated only in anterior and caudal regions. Ventral pore at 37% of pharynx length from anterior length. Caudal glands and spinneret present. Male gonads not described. No preanal supplementary papilla. Gubernaculum vestigial. Among other things, the species is distinguished from other species by fine striations of anterior cuticle and distinctly narrow arcuate spicules. Syringolaimus gladiatus Bussau, 1993 nom. nud. Bussau, 1993: p. 492���497, Abb. 211, 212, 213 (South-East Pacific, Peru Basin, 4100���4200 m, dark brown ooze with manganese nodules), males and females. Body cuticle with fine annulations. Metanemes present. Ventral pore situated between buccal cavity base and nerve ring, in male at a distance 87 ��m posterior to the anterior end; ventral gland cell body not found. Caudal glands and spinneret absent. Monorchic. No supplementary organs mentioned. Syringolaimus ingens Bussau, 1993 nom. nud. Bussau, 1993: p. 498���501, Abb. 214, 215 (South���East Pacific, Peru Basin, 4100���4200 m, dark brown ooze with manganese nodules), male and females. The largest (by body length) species of the genus. Body cuticle with extremely fine annulations. Metanemes present. Neither ventral pore nor ventral gland cell body found. Spinneret evident but no caudal glands found. Monorchic. No supplementary organs mentioned. Syringolaimus lichenii (Nasira & Turpeenniemi, 2002) Tahseen & Mehdi, 2009 sp. inq. Nasira & Turpeenniemi, 2002: p. 2���4, fig. 1 A���I, table 1 (Trissonchulus lichenii) (Pakistan, Karachi, beach, lichens), males and females. Unusual elongate cardia. Diorchic. Original diagnosis is very brief, anterior sensilla (besides amphid), supplementary papillae, caudal gland and spinneret are not mentioned. Tahseen & Mehdi (2009) noted that the species is inadequately described and better fits within the genus Syringolaimus on account of nonoffset lip region, presence of pharyngeal bulb and conical tail with caudal glands and terminal spinneret. However, presence of two testes does not correspond to the genus Syringolaimus., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on page 481, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097, {"references":["Vitiello, P. (1970) Nematodes libres marins des vases profondes du Golfe du Lion. I. Enoplida. Tethys, 2, 139 - 210.","Bussau, Ch. (1993) Taxonomische und okologische Untersuchungen an Nematoden des Peru-Beckens. Dissertation zur Erlangen des Doktorgrades der Mathematisch-Naturwissenschaftlichen Fakultat der Christian-Albrechts-Universitat zu Kiel, Kiel, 621 pp.","Nasira, K. & Turpeenniemi, T. A. (2002) Description of Trissonchulus licheniii n. sp. and Halalaimus gidanensis n. sp., with observations on three known species (Nematoda: Enoplida) from northern Arabian Sea. Pakistan Journal of Nematology, 20 (2), 1 - 16.","Tahseen, Q. & Mehdi, S. J. (2009) Taxonomy and relationships of a new and first continental species of Trissonchulus Cobb, 1920 along with two species of Ironus (Nematoda: Ironidae) collected from coal mines. Nematologia Mediterranea, 37, 117 - 132."]}

Syringolaimus annae Lima, Lins, Da Silva & Esteves, 2009 (Figures 2���3) Labels. Male: DIVA 1, M 48/1, st 346/2, Muc 3; female: DIVA 1, M 48/1, st 346/1, Muc 3. Material and conditions. One male, one female and two juveniles. All specimens are slightly compressed and have broken tail tips; the slightly shortened tails reduce tail lengths and body lengths, and raise body indices to a certain extent. Description. Body nearly cylindrical, but tapered to the anterior end. Male: L=1553 �� m, a=31.1, b=6.19, c=6.47, c'=5.71; body diameter at the level of: labial region 15 �� m, nerve ring 33 �� m, cardia 53 �� m, midbody 50 �� m, cloaca 39 �� m. Female: L=1236 �� m, a=35.7, b=5.57, c=8.83, c'=5.83, V=58.7%; body diameter at the level of: labial region 13 �� m, nerve ring 26 �� m, cardia 28 �� m, midbody 35 �� m, anus 24 �� m. Cuticle smooth along the entire body. Metanemes not visible. Head apex truncate. Anterior sensilla (besides amphids) not seen. Amphid as a rather broad transverse slit, amphidial fovea shallow and hardly discernible. In male, width of the amphidial aperture 6 �� m or 33% of the corresponding body diameter, distance from the head apex to the aperture 12 �� m. The same measurements in female are 4 �� m, 22%, 13 �� m, respectively. No somatic sensilla visible along the body. Three double teeth of the anterior stoma everted. Each tooth consists of two slightly unequal claws. Teeth length is 5 �� m in male and 3 �� m in female. Pharyngostom long, cylindroid, its length is 72 �� m in male and 32 �� m in female. In juveniles, replacing teeth are present just below the functioning teeth. Replacing teeth are distinctly double, consisting of two separate claws. Pharyngostom surrounded by narrow cuff with nonevident muscular striation. Pharynx nearly cylindrical up to terminal swelling, with transverse muscular striation and thick internal cuticular lining. There is a rounded terminal swelling with stronger muscular striation at posterior pharynx. Internal lining of the swelling not modified. In male, terminal bulb is 47 �� m long and 44 �� m wide; the same in female���31 �� m and 26 �� m, respectively. Cardia muscular, small, 12 �� m long, its posterior half surrounded by intestinal tissue. Ventral gland not found. In male, a poorly discernible structure resembling ventral pore situated at half distance between pharyngostom base and nerve ring. Tail consists of two distinct portions, anterior conical and posterior slim cylindrical parts; tail tip broken. No evident caudal glands. Since tail tip is broken in both specimens, spinneret can not be described. Females didelphic, amphidelphic; ovaries antidromously reflexed. Anterior ovary ventral and slightly to the right of the intestine, posterior ovary ventral to the intestine. Males monorchic, anterior testis outstretched and situated ventral to the intestine. Spicules half drawn out from the cloacal opening, short, arcuate, broad and weakly cuticularized, 49 �� m long. Gubernaculum as a pair of weakly cuticularized bars perpendicular to the body axis, with curved distal ends, 15 �� m long. There is a midventral precloacal supplementary papillum just anterior to the cloacal opening; there is also one more or less prominent anterior midventral elevation devoid of an internal canal, likely a cuticular fold. A pair of conical lateroventral papillae at the end of conical portion of the tail. Diagnosis. Body length 1236���1553 ��m, a=31���36. Tubular pharyngostom 32���72 ��m long. Terminal pharyngeal bulb 31���47 ��m long and 17���34 ��m wide. Spicules 49 ��m, weakly cuticularized. Precloacal supplementary papillum present. Tail cylindro-conical, with posterior cylindrical portion comprising 72���85% of entire tail; no terminal tube or spinneret. TABLE]. Morphometry of Syringolaimus species, males (valiđ species in bolđ, values rounđeđ). Species Characters Source Bođy a b c c' Distal Buccal Amphiđ wiđth as Distance from Length of Length of length, �� m slenđer tail cavity % of heađ apex to terminal spicules part as % of length, �� m corresponđing amphiđ, �� m pharyngeal along arc, entire tail bođy điameter bulb, �� m �� m length morphometric value calculateđ from đrawings of publisheđ species đescriptions. sex not specifieđ in the source citeđ. Species Characters Source Bođy a b c c' Distal slenđer Buccal Amphiđ wiđth as Distance Length of length, �� m tail part as % cavity % of from heađ terminal of entire tail length, corresponđing apex to pharyngeal length �� m bođy điameter amphiđ, �� m bulb, �� m morp hometric value calculateđ from đrawings of publisheđ species đescriptions. sex not specifieđ in the source citeđ. Discussion. This species fits well with the description of S. annae except for index a in males (31 vs. 41���73, likely because of compression of the body) and greater length of spicules (49 �� m vs. 17���34 �� m, spicules can be inaccurately measured because of their weakness and indistinctness), indices c and c' in females (c 8.8 vs. 4.8���7.4, c' 5.8 vs. 7.3���10.8, because of broken tail tip). Length of the buccal cavity differs notably in male and femalehowever, these values vary considerably in type specimens as well (28���55 �� m in males and 27���57 �� m in females, Lima et al., 2009). According to the original diagnosis of Lima et al. (2009), a spinneret is absent in this species (tail tips of our specimens are broken). Postcloacal lateroventral papillae are not indicated in the original diagnosis (Lima et al., 2009), probably because these small structures are poorly visible and hence could be overlooked., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on pages 483-489, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097, {"references":["Lima, R. C. C., Lins, L., Da Silva M. R., & Esteves, A. M. (2009) Four new species of Syringolaimus De Man, 1888 (Nematoda: Ironidae) from the Southeast Atlantic (Brazil), with redefinition of valid species and the proposal of a new key. Zootaxa, 2096, 119 - 136."]}

Family Bastianiidae de Coninck, 1935 12. * Bastiania parexilis de Coninck, 1935 ��� {27, 29} (0, 7, 0, 0; 3) Population structure and abundance. At site 27���14 females (including one with egg), two males and a single juvenile (18x10 3/m2), at site 29 (qualitative sample)���alone female. Ecology and distribution. Amphibiont. Occurs both in terrestrial and aquatic biotopes (Jacobs 1984). Rare species, apparently, until recently noted only in two regions: Central Africa (Zaire) and in Russian Far East (Jacobs 1984; Andr��ssy 1991). Remarks. In the fullest identification handbook to date on free-living nematodes of Vietnam (Nguyen 2007), the genus Bastiania is not listed. At the same time, B. exilis Cobb, 1914 was found in one river in the north (Nguyen & Nguyen, 2005). The same species was also reported from Hainan Island (China), situated close to Vietnam (Wu & Liang 2000)., Published as part of Gusakov, Vladimir A. & Gagarin, Vladimir G., 2017, An annotated checklist of the main representatives of meiobenthos from inland water bodies of Central and Southern Vietnam. I. Roundworms (Nematoda), pp. 1-43 in Zootaxa 4300 (1) on page 14, DOI: 10.11646/zootaxa.4300.1.1, http://zenodo.org/record/837117, {"references":["Jacobs, L. J. (1984) The free-living inland aquatic nematodes of Africa-a review. Hydrobiologia, 113, 259 - 291. https: // doi. org / 10.1007 / bf 00026614","Andrassy, I. (1991) The free-living nematode fauna of the Batorliget nature reserves. In: Mahunka, S. (Ed.), The Batorliget Nature Reserves - after forty years, Hungarian Natural History Museum, Budapest, 129 - 197.","Nguyen, V. T. (2007) Free-living nematodes Monhysterida, Araeolaimida, Chromadorida, Rhabditida, Enoplida, Mononchida, Dorylaimida. In: Dang, N. T. (Ed.), Fauna of Fietnam. Fol. 22. Science and Technics Publishing House, Hanoi, 455 pp. [in Vietnamese]","Nguyen, T. T. & Nguyen, V. T. (2005) Comparison on Free-living Nematode Compositions of the Cau, Day, Cam and Nhue Rivers. T ap chi Sinh H oc, 27, 36 - 42. [in Vietnamese]","Wu, J. & Liang, Y. (2000) Inland Free-Living Nematodes in China: A Historical Review of Taxonomic Studies with Descriptions of Aphanonchus orientalis sp. nov. (Chromadorida: Leptolaimidae) and Daptonema limnobia sp. nov. (Monhysterida: Xyalidae). Annales Zoologici, 50, 307 - 319."]}

Syringolaimus striatocaudatus de Man, 1888 De Man, 1888: p. 35���36, pl. III, IV, figs 16���16c (North Sea, the Netherlands, Walcheren, male and female). De Coninck, 1932: p. 17���20, figs 7���9 (North Sea, West Flanders, males and females). De Coninck & Schuurmans Stekhoven, 1933: p. 58, fig. 28���29 (Belgian coast, on Enteromorpha, one male and one juvenile). Hopper, 1969: p. 673���674, figs 7���10. Nova Scotia, East Canada, marsh grass). Ventral gland cell present but ventral pore is not always observed. Spinneret and caudal glands are evident. Midventral precloacal papilla is indicated in some descriptions. Hopper (1969) found a small lateral pore (���phasma���) at posterior end of conoid portion of the tail. Body size varies considerably in different descriptions. A complete set of morphometric data is provided only by Hopper (1969). The most obvious distinguishing character is prominent annulation of the tail cuticle while other body cuticle looks smooth. Synonymy: see Gerlach & Riemann, 1973. The most common and widespread species of Syringolaimus., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on page 482, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097, {"references":["de Man, J. G. (1888) Sur quelques Nematodes libres de la mer du Nord nouveaux ou peu connu. Memoires de la Societe Zoologique de France, 1, 1 - 51.","De Coninck, L. A. (1932) Nieuwe bijdrage tot de kennis der vrijlevende nematoden van Belgie. Bulletin du Musee Royal d'Histoire Naturelle de Belgique, 8, 1 - 30.","De Coninck, L. A. & Schuurmans Stekhoven, J. H. (1933) The free-living marine nemas of the Belgian coast II. Memoires du Musee royal d'Histoire naturelle de Belgique, 58, 1 - 163.","Hopper, B. E. (1969) Marine nematodes of Canada. II. Marine nematodes from the Minas Basin-Scots Bay area of the Bay of Fundy, Nova Scotia. Canadian Journal of Zoology, 47, 671 - 690. https: // doi. org / 10.1139 / z 69 - 114","Gerlach, S. A. & Riemann, F. (1973) The Bremerhaven checklist of aquatic nematodes. A catalogue of Nematoda Adenophorea excluding the Dorylaimida. Part 1. Veroffentlichungen des Instituts fur Meeresforschung in Bremerhaven, 4 (Supplement), Heft 1, 1 - 404."]}

Syringolaimus smolae Lima, Lins, Da Silva & Esteves, 2009 (Figures 4���6, Table 3) Material. Ten males and four females from both stations 325 (st. 325/4 Muc 8, 325/7 Muc8) and 346 (st. 346/1 Muc 3, 346/2 Muc 3). Description. Body slim and graceful. Cuticle smooth and moderately thick, fine cross striations visible only on ventral side of cylindrical part of the tail. Anterior cuticle between apex and amphidial fovea forming a circular thickening. There are three equal cheilostomatal teeth just out from the mouth opening. All the teeth are double (split from base) and thus consist of two claw-like parts. The claws of each tooth are slightly unequal; in most specimens, dorsal tooth composed of larger left and smaller right claws, smaller and bigger claws in ventrosublateral pairs more variable in position. Length of teeth is 2.3���3.5 ��m in males and 2.3���3.6 ��m in females. Sensilla around the mouth opening not visible. Amphidial aperture a large transverse slit posterior to the cheilostomal teeth. Amphidial fovea as a pocket with a wisp of ciliary processes within. In males, width of the amphidial aperture is 4.2 ��m or 29���45% of the corresponding body diameter, distance from the cephalic apex to the aperture is 13���18.4 ��m; same figures in a female with discernible aperture are 4.2 ��m, 35% and 16.6 ��m, respectively. There are scarce and hardly visible tiny papillae along the body. Metanemes not visible. Pharyngostom a rather long tube, with sclerotized lumen but flexible. Pharynx slender and muscular throughout its length, with thick internal cuticular lining. Pharyngostom surrounded with narrow, non-muscular tissue. Posterior part of the pharynx enlarged in an oval bulb; its internal cuticular lining not modified but distinctly set off from the lining of the major part of the pharynx. Cardia external, shaped as a truncate cone. Anteriormost intestinal cells with homogeneous content different from other intestinal cells that make them similar to progaster of Monhysteridae. Intestine with internal glycocalyx layer partly detached. Tail consists of anterior conical and posterior cylindrical parts not sharply differentiated from one another. Tail curved dorsally in all male and female specimens. Tail end rounded, no indication of spinneret; however, one or more caudal gland cell bodies discernible in some specimens (Fig. 6 A). Female reproductive system didelphic, amphidelphic; anterior ovary to the left, posterior ovary to the left of the intestine. Males monorchic, outstretched testis situated to the right or to the left and ventral of the intestine. Spermatozoa tadpole-like or drop-shaped, situated with knob-like nuclear part turned towards anterior end and tail-like part towards posterior end of the body, 13���16 ��m long, transparent, with dense nucleus in the thick end. Vas deferens with granular walls, its anterior part narrowed, posterior part enlarged. Spicules weak and arcuate, broad, with truncate anterior end and knobbed posterior end. Gubernaculum small (8���12 ��m), in a shape of a slightly curved bar. A small midventral supplementary organ is visible as a small mound with an internal canal situated just anterior (3.4���9.2 ��m) to the cloacal opening. In some males, structures similar to sublateral precloacal and a postcloacal papillae are visible. Diagnosis. Body length 900���1190 ��m, a=30���62. Tubular pharyngostom 39���60 ��m long. Terminal pharyngeal bulb 28���40 ��m long and 16���31 ��m wide. Spicules 17���30 ��m, weak and flexible. Precloacal supplementary papillum present. Tail cylindro-conical, with posterior cylindrical portion (47���80% of entire tail) always curved dorsally in both sexes; no terminal tube or spinneret. Discussion. The species fits well the description of S. smolae Lima et al., 2009 in dimensions and shape of the tail but differs by: absence of visible secretory-excretory pore at the level of the nerve ring, absence of a terminal spinneret on the tail tip, rather broad and weak spicules versus ���setiform��� spicules mentioned for S. smolae. Character Males (n=10) Females (n=4) Despite verbal statements about presence of the spinneret and setiform spicules in the text of the original diagnosis, the figures correspond well to respective organs of our specimens. Gut content. Intestine may be empty or contain a sausage of medium-coarse-granular material with sparse light-refractive particles as well as spherical homogeneous and slightly heterogeneous drops., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on pages 489-494, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097, {"references":["Lima, R. C. C., Lins, L., Da Silva M. R., & Esteves, A. M. (2009) Four new species of Syringolaimus De Man, 1888 (Nematoda: Ironidae) from the Southeast Atlantic (Brazil), with redefinition of valid species and the proposal of a new key. Zootaxa, 2096, 119 - 136."]}

Syringolaimus elegans sp. n. (Figures 7���9) Material: DIVA 1, M 48/1, st 325/4, Muc 8. Holotype male and paratype juvenile with vestigial ovaries. The slides are deposited in Senckenberg Museum (Frankfurt am Main, Germany) under the inventory numbers SMF 17055 (holotype) and SMF 17056 (paratype). Male. Body slender, filiform. Body length 2718 �� m, a=98.8, b=8.47, c=11.8, c���=8.41. Body diameter at the level of: anterior sensilla 17 �� m, nerve ring 34.5 �� m, cardia 35.8 �� m, midbody 27.5 �� m, cloaca 24.1 �� m. Cuticle smooth along the entire body except numerous irregular transversal fissures or chaps like in cervical region. No metanemes found. Anterior sensilla hardly discernible as six papillae or pores. Amphidial aperture a transverse slit; fovea poorly visible. Width of the amphidial aperture 5.9 �� m or 31% of the corresponding body diameter, distance from anterior apex to aperture 11.5 �� m. No somatic sensilla along the body. Apical cuticle around the mouth opening widened and its internal sublayer sclerotized. There are three equal doubled cheilostomatal teeth about 4.6 �� m long. The teeth joined movably to the sclerotization of the internal layer of the apical cuticle. Each tooth consists of two parts (subteeth) fused basally; both parts isomorphic claw-like, one part somewhat bigger than another. Dorsal tooth consists of left bigger and right smaller parts. Pharyngostom 79 �� m long and 3.4 �� m wide, tubular, with sclerotized walls, but flexible. Pharyngostom enveloped by a cuff (manchette) with obliquely directed muscular striation. Pharynx evenly muscular throughout its length, with distinct thick internal cuticular lining. Posterior part of the pharynx slightly enlarged into an elongate ovoid bulb 70 �� m long and 32 �� m wide; however, its internal cuticular lining not modified. Cardia conical, with radial striation. Intestine with glycocalyx layer detached. Nerve ring distinct, at the middle of the pharynx. No clear indication of a ventral gland; however, a ventral pore and a thin intracuticular canal present at a distance of 36 �� m anterior to the nerve ring. Male monorchic, male genital branch 1156 �� m long, situated to the right of the intestine. Spermatozoa (or spermatids?) fiber-like. Vas deferens consists of anterior slender and posterior thicker portions. Spicules slender, arcuate, 32 �� m long, weakly sclerotized, their anterior (proximal) knobs not pronounced (underdeveloped?). Gubernaculum vestigial, hardly visible. There is one midventral precloacal supplementary papillum with a thin internal canal located at a distance of 8 �� m anterior to the cloacal opening; two other supplements situated a bit closer to the cloaca, are questionable and may actually represent cuticular folds. No other sensilla in pericloacal region. Tail long, its proximal conical part gradually transforms to thin whip-like part constituting about 67% of the total tail length. No indication of spinneret and caudal glands. IV juvenile stage (slightly compressed). Body length 2786 �� m, a=68.0, b=8.55, c=11.9, c'=8.1. Body diameter at the level of: anterior sensilla 12 �� m, nerve ring 38 �� m, cardia 51 �� m, midbody 48 �� m, cloaca 30 �� m. Width of the amphidial aperture 3.5 �� m or 24% of the corresponding body diameter, distance from anterior apex to aperture 9.3 �� m. Buccal cavity 61 �� m long. Replacing teeth present just posterior to the functional teeth. Terminal bulb 60 �� m. Vestigial female branches present but no vagina could be found. Posterior cylindrical portion of the tail 69% of the total tail length. Diagnosis. Body length of male 2718 �� m, a=98.8, b=8.5, c=11.8, c'=8.4. Distance from head apex to the amphidial aperture 11.5 �� m. Buccal cavity 79 �� m. Basal pharyngeal bulb 70 �� m long and 32 �� m wide. No ventral gland. Monorchic with single anterior outstretched testis. Spicules arcuate, very weak, 32 �� m. A single evident midventral precloacal supplementary organ as a papillum with an axial canal. Tail with cylindrical posterior portion constituting 67% of the entire tail. No evident spinneret and caudal glands. Differential diagnosis. Syringolaimus elegans sp. n. differs from all other species of Syringolaimus by slimmer body (a 99 vs. 30���73) and from all species except S. ingens by its greater body length (2718 �� m vs. 760��� 1750 �� m), longer buccal cavity (79 �� m vs. 28���58 �� m), and longer terminal pharyngeal bulb (70 �� m vs. 29���53 �� m). S. elegans sp. n. differs from S. ingens nom. nud., the largest species within the genus, by smaller and slimmer body (L=2718 �� m versus 3735 �� m, a=99 vs. 43), relatively longer tail (c'=8.4 vs. 4.0), smaller spicules (32 �� m vs. 70 �� m) and by presence of a precloacal supplementary papillum (not mentioned for S. ingens)., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on page 494, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097

Syringolaimus loofi Gourbault & Vincx, 1985 Gourbault & Vincx, 1985: p. 114���17, fig. 3 (coast of the Netherlands, in sponge Halichondria), males and females. Cuticle finely striated. Ventral pore at the posterior end of buccal cavity. Tail elongate, conical. Caudal glands present, spinneret short, conical. Monorchic. Preanal midventral papilla distinct., Published as part of Tchesunov, Alexei V., 2017, Free-living nematodes of the genus Syringolaimus de Man, 1888 (Nematoda, Enoplida, Ironidae) from the Angola Basin, South-East Atlantic Abyss, pp. 478-500 in Zootaxa 4306 (4) on page 481, DOI: 10.11646/zootaxa.4306.4.2, http://zenodo.org/record/845097, {"references":["Gourbault, N. & Vincx, M. (1985) Deux especes nouvelles d'Ironidae marins; observations sur les spermatozoides \" flagelles \" des Nematodes. Bulletin du Museum national d'Histoire naturelle, Paris, 4 e Serie, 7, Section A, n o 1, 109 - 118."]}

Order Araeolaimida De Coninck & Schuurmans Stekhoven, 1933 Diagnosis. (Modified from Fonseca & Bezerra (2014) and Lorenzen (1994).) Cuticle smooth, striated, or with transverse rows of punctations. Inner labial sensilla papilliform or not visible; outer labial sensilla and cephalic setae usually in two separate circles. Buccal cavity varies from minute, to cup-shaped or tubular, sometimes equipped with 3���9 odontia (teeth). Amphideal fovea usually loop-shaped or spiral, less commonly bowl-shaped or pore-like. Pharyngeal tubes present in the Comesomatidae and Axonolaimidae and some Diplopeltidae. Pharynx usually cylindrical, sometimes with posterior bulb. Female reproductive system usually with two outstretched ovaries, in some cases only one posterior ovary is present. Males with one or two testes; precloacal supplements sometimes present., Published as part of Leduc, Daniel, 2017, Four new nematode species (Araeolaimida: Comesomatidae, Diplopeltidae) from the New Zealand continental slope, pp. 244-264 in Zootaxa 4237 (2) on page 245, DOI: 10.11646/zootaxa.4237.2.2, http://zenodo.org/record/343781, {"references":["Fonseca, G. & Bezerra, T. N. (2014) Order Araeolaimida De Coninck & Schuurmans Stekhoven, 1933. In: Shmidt-Rhaesa, A. (Ed.), Handbook of Zoology, Gastrotricha, Cyclioneura and Gnathifera. Fol. 2. Nematoda. De Gruyter, Hamburg, pp. 467 - 486."]}

Genus Diplopeltula Gerlach, 1950 Type species. Diplopeltula breviceps Gerlach, 1950 Diagnosis. (Modified from Fonseca & Bezerra (2014).) Striated cuticle, sometimes with longitudinal bars. Loopshaped and elongated amphideal fovea, may be located on cuticularised amphideal plate. Ocelli absent. Buccal cavity cup- or barrel-shaped, sometimes minute, situated terminally or slightly dorsally. Pharynx cylindrical, with or without posterior bulb. Female reproductive system with two outstretched ovaries. Tail usually conical, sometimes conicocylindrical. Remarks. The taxonomy of the genus Diplopeltula was most recently reviewed by Holovachov et al. (2009). They considered D. botula Wieser (1959) Gerlach, 1962, D. lucanica Boucher & Hell��ou��t, 1977 and D. striata Gerlach, 1956 to be species inquirendae due to lack of information on pharynx morphology and female reproductive system. They also transferred the species Diplopeltis bathmanni Jensen, 1991 to the genus Diplopeltula, Diplopeltula curtus Vincx & Gourbault, 1992 to the genus Pararaeolaimus, and Diplopeltula pulcher and Diplopeltula sundensis to the genus Diplopeltoides Gerlach, 1962. More recently, Diplopeltula nellyae Vincx & Gourbault, 1992 was transferred to the genus Mudwigglus by Leduc (2013). Some species described by Bussau (1993), namely D. mollis Bussau, 1993 and D. peruensis Bussau, 1993, lack information on the female reproductive system and are therefore considered species inquirendae., Published as part of Leduc, Daniel, 2017, Four new nematode species (Araeolaimida: Comesomatidae, Diplopeltidae) from the New Zealand continental slope, pp. 244-264 in Zootaxa 4237 (2) on page 259, DOI: 10.11646/zootaxa.4237.2.2, http://zenodo.org/record/343781, {"references":["Gerlach, S. A. (1950) Die Diplopeltiden, eine gruppe freilebender nematoden. Kieler Meeresforschungen, 7, 138 - 156.","Fonseca, G. & Bezerra, T. N. (2014) Order Araeolaimida De Coninck & Schuurmans Stekhoven, 1933. In: Shmidt-Rhaesa, A. (Ed.), Handbook of Zoology, Gastrotricha, Cyclioneura and Gnathifera. Fol. 2. Nematoda. De Gruyter, Hamburg, pp. 467 - 486.","Holovachov, O., De Ley, I. T., Mundo-Ocampo, M., Gingold, R. & De Ley, P. (2009) Nematodes from the Gulf of California. Part 3. Three new species of the genus Diplopeltoides Gerlach, 1962 (Nematoda: Diplopeltoididae) with overviews of the genera Diplopeltis Gerlach, 1962 and Diplopeltula Gerlach, 1950. Russian Journal of Nematology, 17, 43 - 57","Jensen, P. (1991) Bodonematidae fam. n. (Nematoda, Monhysterida) accommodating Bodonema vossi gen. et sp. n. from the deep-sea benthos of the Norwegian Sea. Sarsia, 76, 11 - 15.","Leduc, D. (2013) Mudwigglus gen. n. (Nematoda: Diplopeltidae) from the continental slope of New Zealand, with description of three new species and notes on their distributions. Zootaxa, 3682 (2), 351 - 370.","Bussau, C. (1993) Taxonomische und okologische Untersuchungen an Nematoden des Peru-Beckens. PhD thesis, Christian- Albrechts-Universitat zu Kiel, Kiel, 621 pp."]}

Key to species of Pseudaraeolaimus Chitwood, 1951 See Table 3 for additional diagnostic characters. 1. Body 2 mm long; amphidial fovea with transverse striation............................................................................................................................................................. P. laminata (Vitiello, 1972) comb. nov. ��� Body shorter than 1.5 mm long; amphidial fovea without transverse striation................................ 2 2. Ocelli present.................................................................................................. P. ocellatus Kito, 1981 ��� Ocelli absent..................................................................................................................................... 3 3. Amphidial fovea a broad loop, less than 1.5 times long as it is wide... P. perplexus Chitwood, 1951 ��� Amphidial fovea a narrow loop, more than 3 times long as it is wide............................................. 4 * ��� not available, specimens of particular sex are unknown 4. Cervical setae short, only two pairs at level with amphidial fovea....................................................................................................................................... P. cassidaigniensis (Vitiello, 1972) comb. nov. ��� Cervical setae long, two pairs at level with amphidial fovea and 4���5 pairs at level with midpharynx.................................................................... P. cylindricauda (Allg��n, 1932) comb. nov. Family Diplopeltidae Filipjev, 1918 Diagnosis (emended after Fonseca & Bezerra 2014) Cuticle visually smooth, finely striated or coarsely annulated.Lateral alae absent.Somatic sensilla present. Inner and outer labial sensilla papilliform. Cephalic sensilla setiform; their bases located at the base of the labial region, anterior to amphidial fovea. Cervical (paramphidial) sensilla present in some genera, located at the level of the amphid and posterior to it. Deirid absent. Ocelli present or absent. Amphidial fovea unispiral or loop-shaped. Secretory-excretory system present. Oral opening apical or shifted either to dorsal or ventral body side. Buccal cavity tubular, cylindrical or undifferentiated. Teeth-like structures absent. Pharynx variable in shape; pharyngeal lumen uniform in thickness along the entire pharynx length; valves absent. Female reproductive system didelphic-amphidelphic or monodelphic-prodelphic. Ovaries outstretched or reflexed antidromously. Male reproductive system diorchic. Posterior testis is either anteriorly oriented and reflexed in the anterior section (reflexed terminal section of the germinal zone) or is posteriorly directed. Spicules symmetrical; gubernaculum present. Precloacal sensilla present in some genera. Three caudal glands present, their nuclei are incaudal. Caudal glands open separately via three pores, or together via a common spinneret. Valid genera Araeolaimus de Man, 1888 = Araeolaimoides de Man, 1893 = Coinonema Cobb, 1920 = Parachromagaster Allg��n, 1929 Belgopeltula gen. nov. Campylaimus Cobb, 1920 Cylindrolaimus de Man, 1880 Diplopeltis Cobb in Stiles & Hassal, 1905 = Dipeltis Cobb, 1891 = Discophora Villot, 1875 Diplopeltula Gerlach, 1950 Edalonema Andr��ssy, 2007 = Adelonema Holovachov & Sturhan, 2003 Intasia Tchesunov & Miljutina, 2008 Metaraeolaimoides De Coninck, 1936 Morlaxia Vincx & Gourbault, 1988 Mudwigglus Leduc, 2013 Pararaeolaimus Timm, 1961 Pseudaraeolaimus Chitwood, 1951 Southerniella Allg��n, 1932 Family Diplopeltidae Filipjev, 1918 Diagnosis (emended after Fonseca & Bezerra 2014) Cuticle visually smooth, finely striated or coarsely annulated.Lateral alae absent.Somatic sensilla present. Inner and outer labial sensilla papilliform. Cephalic sensilla setiform; their bases located at the base of the labial region, anterior to amphidial fovea. Cervical (paramphidial) sensilla present in some genera, located at the level of the amphid and posterior to it. Deirid absent. Ocelli present or absent. Amphidial fovea unispiral or loop-shaped. Secretory-excretory system present. Oral opening apical or shifted either to dorsal or ventral body side. Buccal cavity tubular, cylindrical or undifferentiated. Teeth-like structures absent. Pharynx variable in shape; pharyngeal lumen uniform in thickness along the entire pharynx length; valves absent. Female reproductive system didelphic-amphidelphic or monodelphic-prodelphic. Ovaries outstretched or reflexed antidromously. Male reproductive system diorchic. Posterior testis is either anteriorly oriented and reflexed in the anterior section (reflexed terminal section of the germinal zone) or is posteriorly directed. Spicules symmetrical; gubernaculum present. Precloacal sensilla present in some genera. Three caudal glands present, their nuclei are incaudal. Caudal glands open separately via three pores, or together via a common spinneret. Valid genera Araeolaimus de Man, 1888 = Araeolaimoides de Man, 1893 = Coinonema Cobb, 1920 = Parachromagaster Allg��n, 1929 Belgopeltula gen. nov. Campylaimus Cobb, 1920 Cylindrolaimus de Man, 1880 Diplopeltis Cobb in Stiles & Hassal, 1905 = Dipeltis Cobb, 1891 = Discophora Villot, 1875 Diplopeltula Gerlach, 1950 Edalonema Andr��ssy, 2007 = Adelonema Holovachov & Sturhan, 2003 Intasia Tchesunov & Miljutina, 2008 Metaraeolaimoides De Coninck, 1936 Morlaxia Vincx & Gourbault, 1988 Mudwigglus Leduc, 2013 Pararaeolaimus Timm, 1961 Pseudaraeolaimus Chitwood, 1951 Southerniella Allg��n, 1932, Published as part of Holovachov, Oleksandr, 2017, Belgopeltula belgica (Vincx & Gourbault, 1992) gen. et comb. nov. and Mudwigglus micramphidium sp. nov. from the west coast of Sweden, and reappraisal of the genus Pseudaraeolaimus Chitwood, 1951 (Nematoda: Araeolaimida: Diplopeltidae), pp. 1-21 in European Journal of Taxonomy 383 on pages 15-17, DOI: 10.5852/ejt.2017.383, http://zenodo.org/record/3839807, {"references":["Vitiello P. 1972. Sur quelques especes de Diplopeltula (Nematoda, Araeolaimida). Vie et Milieu 21: 535 - 544.","Allgen C. 1932. Weitere Beitrage zur Kenntnis der marinen Nematodenfauna der Campbell-insel. Nyt Magazin for Naturvidenskaberne 70: 97 - 198.","Fonseca G. & Bezerra T. N. 2014. 7.15 Order Araeolaimida De Coninck & Schuurmans Stekhoven, 1933. In: Schmidt-Rhaesa A. (ed) Handbook of Zoology. Gastrotricha, Cycloneuralia, Gnathifera. Volume 2: Nematoda: 467 - 486. de Gruyter, Gottingen.","Cobb N. A. 1920. One hundred new nemas. (Type species of 100 new genera). Contributions to a Science of Nematology 9: 217 - 343.","Gerlach S. A. 1950. Die Diplopeltiden, eine Gruppe freilebender Nematoden. Kieler Meeresforschungen 7: 138 - 156.","Tchesunov A. V. & Miljutina M. A. 2008. A new free-living nematode Intasia monohystera gen. n., sp. n. (Nematoda, Araeolaimida, Diplopeltidae) from the Barents Sea and the White Sea, with a key to genera of Diplopeltidae. Russian Journal of Nematology 16: 33 - 48.","Leduc D. 2013. Mudwigglus gen. n. (Nematoda: Diplopeltidae) from the continental slope of New Zealand, with description of three new species and notes on their distribution. Zootaxa 3682: 351 - 370. https: // doi. org / 10.11646 / zootaxa. 3682.2.8","Timm R. W. 1961. The marine nematodes of the Bay of Bengal. Proceedings of the Pakistan Academy of Sciences 1: 1 - 88."]}

Key to genera of Diplopeltidae See Table 4 for additional diagnostic characters. 1. Amphidial fovea a transverse slit; cuticle with ten longitudinal ridges.... Edalonema Andr��ssy, 2007 ��� Amphidial fovea double-loop-shaped in male, unispiral in female.................. Belgopeltula gen. nov. ��� Amphidial fovea unispiral................................................................................................................ 2 ��� Amphidial fovea loop-shaped........................................................................................................... 4 2. Basal bulb absent; freshwater or terrestrial........................................ Cylindrolaimus de Man, 1880 ��� Basal bulb present; marine................................................................................................................ 3 3. Single anterior ovary................................................................ Intasia Tchesunov & Miljutina, 2008 ��� Two ovaries (anterior and posterior)....................................................... Southerniella Allg��n, 1932 4. Oral opening shifted to the ventral body side............................ Morlaxia Vincx & Gourbault, 1988 ��� Oral opening apical or shifted to the dorsal body side..................................................................... 5 5. Basal pharyngeal bulb present; ovaries antidromously reflexed............... Mudwigglus Leduc, 2013 ��� Basal pharyngeal bulb absent; ovaries outstretched......................................................................... 6 6. Lateral alae present, in some species fused with the ventral limb of the amphid.................................................................................................................................................. Campylaimus Cobb, 1920 ��� Lateral alae absent............................................................................................................................ 7 7. Amphid in a shape of rounded loop.................................................................................................. 8 ��� Amphid in a shape of elongated loop............................................................................................. 10 8. Anterior body region abruptly narrowing; amphid at a distance equal to more than five labial region diameters from the anterior end............................................. Metaraeolaimoides De Coninck, 1936 ��� Anterior body region cylindrical or subcylindrical; amphid at a distance equal to less than two labial region diameters from the anterior end............................................................................................. 9 9. Buccal cavity cup-shaped; pronounced sexual dimorphism in the amphid size (large in males and small in females).................................................................................. Pararaeolaimus Timm, 1961 ��� Buccal cavity conical; no sexual dimorphism in the amphid size.......... Araeolaimus de Man, 1888 10. Cervical (paramphideal) setae absent; caudal glands open via three separate pores........................................................................................................................................... Diplopeltula Gerlach, 1950 ��� Cervical (paramphideal) setae present; caudal glands open via common spinneret........................11 11. Amphid located on a well-developed refractive subcuticular plate.............................................................................................................................................. Diplopeltis Cobb in Stiles & Hassal, 1905 ��� Refractive subcuticular plate absent.......................................... Pseudaraeolaimus Chitwood, 1951, Published as part of Holovachov, Oleksandr, 2017, Belgopeltula belgica (Vincx & Gourbault, 1992) gen. et comb. nov. and Mudwigglus micramphidium sp. nov. from the west coast of Sweden, and reappraisal of the genus Pseudaraeolaimus Chitwood, 1951 (Nematoda: Araeolaimida: Diplopeltidae), pp. 1-21 in European Journal of Taxonomy 383 on pages 17-19, DOI: 10.5852/ejt.2017.383, http://zenodo.org/record/3839807, {"references":["Tchesunov A. V. & Miljutina M. A. 2008. A new free-living nematode Intasia monohystera gen. n., sp. n. (Nematoda, Araeolaimida, Diplopeltidae) from the Barents Sea and the White Sea, with a key to genera of Diplopeltidae. Russian Journal of Nematology 16: 33 - 48.","Allgen C. 1932. Weitere Beitrage zur Kenntnis der marinen Nematodenfauna der Campbell-insel. Nyt Magazin for Naturvidenskaberne 70: 97 - 198.","Leduc D. 2013. Mudwigglus gen. n. (Nematoda: Diplopeltidae) from the continental slope of New Zealand, with description of three new species and notes on their distribution. Zootaxa 3682: 351 - 370. https: // doi. org / 10.11646 / zootaxa. 3682.2.8","Cobb N. A. 1920. One hundred new nemas. (Type species of 100 new genera). Contributions to a Science of Nematology 9: 217 - 343.","Timm R. W. 1961. The marine nematodes of the Bay of Bengal. Proceedings of the Pakistan Academy of Sciences 1: 1 - 88.","Gerlach S. A. 1950. Die Diplopeltiden, eine Gruppe freilebender Nematoden. Kieler Meeresforschungen 7: 138 - 156."]}

Genus Mudwigglus Leduc, 2013 Type species Mudwigglus patumuka Leduc, 2013 Diagnosis (emended after Leduc 2013) Cuticle transversely striated; striae without ornamentation. Lateral alae absent. Body pores and epidermal glands present. Somatic sensilla present. Labial region bluntly rounded; lips fused. Inner labial sensilla invisible if present. Outer labial sensilla papilliform, located on the anterior surface of lips. Cephalic sensilla setiform; their bases located at the base of the labial region, anterior to amphid. Subcephalic and cervical sensilla, deirid and ocelli absent. Amphidial aperture loop-shaped (inverted U-shaped). Secretory-excretory system present; renette cell located opposite to the posterior part of the pharynx and anterior part of intestine. Cuticularised secretory-excretory duct very short, opens to the exterior at the level of the posterior part of pharynx. Oral opening apical. Buccal cavity small but distinctly subdivided into three sections: cheilostom narrow tubular; gymnostom barrel-shaped or truncate conoid, with weakly cuticularised walls; stegostom short conoid, its lining is uniform with the lining of the pharynx. Pharyngeal tubes absent. Pharynx subdivided into anterior corpus and posterior bulbus; corpus cylindrical, muscular, with evenly distributed myofilaments; bulbus muscular; pharyngeal lumen uniform in thickness along the entire pharynx length; valves absent. Dorsal gland orifice penetrates pharyngeal lumen at the base of the stoma, ventrosublateral gland orifices indistinct. Dorsal gland nucleus is visible in the basal bulbus. Female reproductive system didelphicamphidelphic with equally developed branches, ovaries antidromously reflexed. Spermatheca absent. Vulva equatorial. Vagina straight or oblique; pars proximalis vaginae encircled by single sphincter muscle; pars refringens vaginae and epiptygmata absent. Male reproductive system diorchic; anterior testis outstretched, posterior testis outstretched, with posteriorly reflexed terminal section of the germinal zone. Spicules symmetrical, arcuate; gubernaculum present. Supplements and precloacal sensilla present. Setae in caudal region of males arranged in subventral and subdorsal pairs along the tail. Three caudal glands present, their nuclei are incaudal. Caudal glands open separately via three pores (this structure is obscure in some species). Valid species Mudwigglus macramphidium Leduc, 2013 Mudwigglus micramphidium sp. nov. Mudwigglus minutus (Vitiello, 1972) comb. nov. = Diplopeltula minuta Vitiello, 1972 Mudwigglus nellyae (Vincx & Gourbault, 1992) = Diplopeltula nellyae Vincx & Gourbault, 1992 Mudwigglus patumuka Leduc, 2013 Mudwigglus plebeius Leduc, 2013 Nomenclatorial change Diplopeltula minuta Vitiello, 1972 is here transferred to the genus Mudwigglus based on its close morphological affinities to M. plebeius, from which it can only be separated by features of male accessory apparatus (one or two setae in M. minutus vs one setae and two tubular supplements in M. plebeius)., Published as part of Holovachov, Oleksandr, 2017, Belgopeltula belgica (Vincx & Gourbault, 1992) gen. et comb. nov. and Mudwigglus micramphidium sp. nov. from the west coast of Sweden, and reappraisal of the genus Pseudaraeolaimus Chitwood, 1951 (Nematoda: Araeolaimida: Diplopeltidae), pp. 1-21 in European Journal of Taxonomy 383 on pages 9-10, DOI: 10.5852/ejt.2017.383, http://zenodo.org/record/3839807, {"references":["Leduc D. 2013. Mudwigglus gen. n. (Nematoda: Diplopeltidae) from the continental slope of New Zealand, with description of three new species and notes on their distribution. Zootaxa 3682: 351 - 370. https: // doi. org / 10.11646 / zootaxa. 3682.2.8","Vitiello P. 1972. Sur quelques especes de Diplopeltula (Nematoda, Araeolaimida). Vie et Milieu 21: 535 - 544.","Vincx M. & Gourbault N. 1992. Six new species of the genus Diplopeltula (Nematoda: Diplopeltidae) with remarks on the heterogeneity of the taxon. Hydrobiologia 230: 165 - 178. https: // doi. org / 10.1007 / BF 00036563"]}

Genus Belgopeltula gen. nov. urn:lsid:zoobank.org:act: C016D9A9-F945-4320-A549-9180F7E3CF80 Type and only species Belgopeltula belgica (Vincx & Gourbault, 1992) gen. et comb. nov. = Diplopeltula belgica Vincx & Gourbault, 1992 Diagnosis Cuticle transversely striated; striae without ornamentation. Lateral alae absent. Body pores and epidermal glands absent. Somatic sensilla indistinct. Labial region bluntly rounded; lips fused. Inner labial sensilla invisible if present. Outer labial sensilla papilliform, located on the anterior surface of lips. Cephalic sensilla setiform; their bases located at the base of the labial region, anterior to amphid. Subcephalic and cervical sensilla, deirid and ocelli absent. Amphidial fovea unispural (circular) in female and double-loop-shaped in male (starting from the porus amphidialis, fovea extends anteriorly for a short distance, makes a loop towards ventral side of the body and extends posteriorly for the full length of the amphidial fovea, makes another loop towards dorsal side of the body and extends anteriorly almost to the level of the porus amphidialis). Secretory-excretory system present; renette cell located opposite to the anterior part of intestine. Cuticularised secretory-excretory duct very short, opens to the exterior at the level of cephalic setae bases. Oral opening shifted towards the dorsal side of the body. Buccal cavity small and narrow, cheilostom short, remaining part of stoma undifferentiated; its lining is uniform with the lining of the pharynx. Pharyngeal tubes absent. Pharynx subdivided into anterior corpus and posterior postcorpus; corpus fusiform, muscular, with evenly distributed myofilaments; postcorpus narrow and long, weakly muscularised; pharyngeal lumen uniform in thickness along the entire pharynx length; valves absent. Pharyngeal gland orifices penetrate pharyngeal lumen as the base of the stoma. Postcorpus is surrounded by six large pseudocoelomocyles. Female reproductive system didelphic-amphidelphic, with equally developed branches, ovaries reflexed antidromously. Spermatheca present. Vulva equatorial. Vagina straight; pars proximalis vaginae encircled by single sphincter muscle; pars refringens vaginae and epiptygmata absent. Male reproductive system diorchic, testes opposed (anterior testis outstretched, posterior testis reflexed). Spicules symmetrical, arcuate; gubernaculum present. Supplements, precloacal and postcloacal sensilla absent. Three caudal glands present, their cells and nuclei are incaudal. Spinneret present.������ Etymology The name ��� Belgopeltula ��� combines parts of the original binomen: ���Belg������ comes from species name belgica, and ������opeltula��� ��� from Genus name Diplopeltula. Relationships The new genus is proposed to accommodate the single species Diplopeltula belgica and is particularly characterised by following unique characters: amphidial fovea circular in female and double-loop-shaped in male; secretory-excretory pore located at the level of cephalic setae bases; oral opening subterminal, located on the dorsal side of the body; pharynx subdivided into strongly muscularised fusiform corpus and weakly muscularised narrow and long postcorpus; female didelphic with antidromously reflexed ovaries; male diorchic with opposed testes; pre- and postcloacal supplements absent. The morphology of the pharynx in Belgopeltula gen. nov. needs to be clarified. In the original publication, the pharynx is described as: ���muscular with an elongated terminal bulb���. The drawing shows rather cylindrical anterior part of the pharynx that rapidly widens short distance posterior to the amphideal fovea; the nerve ring is drawn immediately in front of this pharyngeal expansion, at 54% of the pharynx length. The only other known record of the same species published by Fadeeva & Mordukhovich (2013) describes the pharynx as follows: ���pharynx terminates in a small bulb-like expansion���. Nerve ring is not depicted in the figure but is said to encircle pharynx at 77% of its length. Videos of the pharyngeal region of the holotype of Diplopeltula belgica were examined. Morphology of the pharynx and surrounding tissues in the holotype confirms well with observations of pharyngeal region in recent specimens: fusiform corpus and narrow postcorpus; large pseudocoelomocyles surrounding anterior part of postcorpus and glandular cells surrounding posterior part of it. Photographs of the specimen from the Sea of Japan also show most of the features observed in specimens from the coast of Sweden, despite it being not in the best quality: distinct fusiform corpus and narrower postcorpus; large pseudocoelomocyles surrounding postcorpus along most of its length; basal part of the pharynx surrounded by small glandular cells. The unique shape of the male amphid (starting from the porus amphidialis, fovea extends anteriorly for a short distance, makes a loop towards ventral side of the body and extends posteriorly for the full length of the amphid, makes another loop towards dorsal side of the body and extends anteriorly almost to the level of the porus amphidialis) separates Belgopeltula gen. nov. from all other genera classified in the family Diplopeltidae (Leduc 2013; Fonseca & Bezerra 2014), which have unispiral or single loopshaped amphid. Belgopeltula gen. nov. and Mudwigglus Leduc, 2013 are the only two genera in the family Diplopeltidae with antidromously reflexed ovaries, while the rest of the genera are characterised by outstretched ovaries. In this respect, both genera show similarities to the family Diplopeltoididae Tchesunov, 1990 (Tchesunov 1990) (currently placed in the order Plectida Gadea, 1973 (Gadea 1973)). However, as discussed in Leduc (2013), the morphology of female ovaries (outstretched vs reflexed) may not always be consistent in all species within large taxonomic categories, and in some cases may not have diagnostic value. To make things more complicated, the morphology of female ovaries has not been described in large number of species placed in the genus Diplopeltula, including its type species D. breviceps. In having oral opening located on the dorsal side of the body, the new genus resembles the genus Campylaimus Cobb, 1920 (Cobb 1920) and some species of the genus Diplopeltula. It can be easily separated from both genera in the morphology of the amphidial fovea (circular in female and characteristic double-loop-shaped in male vs single loop in both females and males in Diplopeltula and Campylaimus), the female reproductive system (ovaries reflexed in Belgopeltula gen. nov. vs ovaries outstretched in Diplopeltula and Campylaimus), the pharynx (subdivided into fusiform corpus and narrow postcorpus in Belgopeltula gen. nov. vs cylindrical in Diplopeltula and Campylaimus) and the position of excretory pore (located at the level of cephalic setae bases in Belgopeltula gen. nov. vs at the level of posterior part of pharynx or anterior part of intestine in Diplopeltula and Campylaimus)., Published as part of Holovachov, Oleksandr, 2017, Belgopeltula belgica (Vincx & Gourbault, 1992) gen. et comb. nov. and Mudwigglus micramphidium sp. nov. from the west coast of Sweden, and reappraisal of the genus Pseudaraeolaimus Chitwood, 1951 (Nematoda: Araeolaimida: Diplopeltidae), pp. 1-21 in European Journal of Taxonomy 383 on pages 2-4, DOI: 10.5852/ejt.2017.383, http://zenodo.org/record/3839807, {"references":["Vincx M. & Gourbault N. 1992. Six new species of the genus Diplopeltula (Nematoda: Diplopeltidae) with remarks on the heterogeneity of the taxon. Hydrobiologia 230: 165 - 178. https: // doi. org / 10.1007 / BF 00036563","Fadeeva N. & Mordukhovich V. 2013. Some new and poorly known nematode species from the Sea of Japan. Deep-Sea Research II 86 - 87: 119 - 123. https: // doi. org / 10.1016 / j. dsr 2.2012.07.044","Leduc D. 2013. Mudwigglus gen. n. (Nematoda: Diplopeltidae) from the continental slope of New Zealand, with description of three new species and notes on their distribution. Zootaxa 3682: 351 - 370. https: // doi. org / 10.11646 / zootaxa. 3682.2.8","Fonseca G. & Bezerra T. N. 2014. 7.15 Order Araeolaimida De Coninck & Schuurmans Stekhoven, 1933. In: Schmidt-Rhaesa A. (ed) Handbook of Zoology. Gastrotricha, Cycloneuralia, Gnathifera. Volume 2: Nematoda: 467 - 486. de Gruyter, Gottingen.","Tchesunov A. V. 1990. A critical analysis of the family Aegialoalaimidae (Nematoda, Chromadoria), trends in evolutionary development of marine nematode pharynx and a proposal of two new families. Zoologicheskii Zhurnal 69: 5 - 18.","Gadea E. 1973. Sobre la filogenia interna de los Nematodos. Publicaciones del Instituto de Biologia Aplicada 54: 87 - 92.","Cobb N. A. 1920. One hundred new nemas. (Type species of 100 new genera). Contributions to a Science of Nematology 9: 217 - 343."]}