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Key to genera of Platycominae 1. Amphidial aperture with two flat setae on its posterior edge in males........................... Platycoma ��� Amphidial aperture with no setae on its posterior edge............................................... 2 2. Amphidial aperture with a flap on its posterior edge in males............................... Proplatycoma ��� Amphidial aperture without a flap................. 3 3. Gubernaculum with dorsal apophyses, precloacal ventromedian supplements tubular..... Pseudoplatycoma ��� Gubernaculum without apophyses, precloacal ventromedian supplements papilliform........ Platycomopsis, Published as part of Shimada, Daisuke & Kakui, Keiichi, 2020, A New Species of Free-living Marine Nematode, Proplatycoma tsukubae sp. nov. (Enoplida: Leptosomatidae), from Japan, pp. 205-211 in Species Diversity 25 on page 210, DOI: 10.12782/specdiv.25.205, http://zenodo.org/record/5738672

Shimada, Daisuke, Kakui, Keiichi (2020): A New Species of Free-living Marine Nematode, Proplatycoma tsukubae sp. nov. (Enoplida: Leptosomatidae), from Japan. Species Diversity 25: 205-211, DOI: 10.12782/specdiv.25.205

Subfamily Platycominae Platonova 1976 Description (from Platonova 1976). Body long, tapering little toward both ends. Some forms with well-developed labial cuticular outgrowths and long cephalic setae. Cervical setae numerous and situated in clusters or transverse rows. Amphids usually large and often sexually dimorphic: amphids significantly larger or more complex in males than in females. Renette cell not developed. Nerve ring situated at approximately mid-length of esophagus. Tail rather short and wide, often pointed at end. Spicules usually small or reduced; gubernaculum highly developed. Additional copulatory armature always present and represented by one to two papillate accessory organs. Postanal papillae with setae may also be present., Published as part of Chen, Cheng-Ann, 2015, A new marine nematode genus Pseudoplatycoma with a new species from the Sulu Sea and revision of the subfamily Platycominae (Enoplida: Leptosomatidae), pp. 233-244 in Zootaxa 3905 (2) on page 234, DOI: 10.11646/zootaxa.3905.2.5, http://zenodo.org/record/240544, {"references":["Platonova, T. A. (1976) Lower Enoplida of the seas of the Soviet Union. In: Platonova, T. A. & Gal'tsova, V. V. (Eds.), Nematodes and their role in the meiobenthos. Studies on Marine Fauna, 15 (23), pp. 1 - 214. [Nauka, Leningrad]"]}

Chen, Cheng-Ann (2015): A new marine nematode genus Pseudoplatycoma with a new species from the Sulu Sea and revision of the subfamily Platycominae (Enoplida: Leptosomatidae). Zootaxa 3905 (2): 233-244, DOI: http://dx.doi.org/10.11646/zootaxa.3905.2.5

Genus Pseudoplatycoma n. gen. Description. Male Body long, diameter uniform except near anterior and posterior ends. Cuticle smooth. Ocelluslike paired pigment spots throughout the body from posterior to the nerve ring to the anterior of the spicule. Labial papillae not clearly observed. Eight cephalic setae. Three stout cervical setae near the posterior of the amphid. Four somatic setae on the left side but absent on the right side. One seta on esophageal region (as well as three stout cervical setae). Virtually no buccal cavity; mouth opening merging into oesophagus. Oesophagus cylindrical; length approximately one sixth of the total body length. Amphids pocket-like. Tail conical. Spicules paired, slightly curved ventrally. Proximal end of spicule bluntly rounded. Distal end of spicule forming a screw-like pattern. Gubernaculum with paired dorsal apophyses, caudally directed. Paired subventral setae present at the cloaca. A small pre-cloacal supplement present. One caudal seta present at the tail region. Six pairs of heavily cuticularized paired tubular supplements. Female. Similar to male except for reproductive structures and larger body which is also longer relative to diameter. Head diameter and amphid smaller than male. First pigment spot further from anterior and nerve ring compared to the male. Vulva near mid body length. Reproductive system didelphic amphidelphic. Tail relatively longer than in male. Diagnosis. The characteristics most distinguishing the new genus from the other genera in subfamily Platycominae are the presence of paired heavily cuticulatized tubular precloacal supplements, spicules bluntly rounded at the proximal end, and ocellus-like paired pigment spots throughout the body from posterior to the nerve ring to the anterior of the spicule. No other genus in the subfamily has these characteristics, together with cupshaped or pocket-like amphids with posterior cervical setae. The genus Platycomopsis Ditlevsen 1926 has cupshaped or pocket-like amphids with posterior cervical setae, but has spicules funnel-shaped at the proximal end and ocelli-like paired pigment spots are absent throughout the body. In the presence of a group of cervical setae situated close together and posterior to the amphids, but not immediately so, Pseudoplatycoma n. gen. closely resembles the genus Platycoma (as defined in Table 2). However, Platycoma has oval or slit-like amphids with posterior cervical setae. Proximally bluntly rounded spicules, together with gubernaculum apophyses which are caudally directed are only reported in the genus Proplatycoma, as is a pre-cloacal supplement followed by six subventral papillae. Proplatycoma has a conical pointed, arrowhead-shaped or branched amphid in males, unlike Pseudoplatycoma n. gen.. Etymology. The genus name refers to the dissimilarity with the genus Platycoma., Published as part of Chen, Cheng-Ann, 2015, A new marine nematode genus Pseudoplatycoma with a new species from the Sulu Sea and revision of the subfamily Platycominae (Enoplida: Leptosomatidae), pp. 233-244 in Zootaxa 3905 (2) on page 234, DOI: 10.11646/zootaxa.3905.2.5, http://zenodo.org/record/240544, {"references":["Ditlevsen, H. (1926) Free-living nematodes. The Danish Ingolf Expedition, 4 (6), 1 - 42."]}

Pseudoplatycoma malaysianis n. gen. n. sp. (Fig. 1���5, Table 1) Material examined. One male and one female. Holotype Male, collected on 15 September 2012, Sulu Sea (15 m) depth, 7 �� 16 ' 57.68 "N, 117 �� 1 ' 37.79 "E. Sandy bottom. (BMRI.NEM 0003). Allotype Female (BMRI.NEM 0003- 1), same collection data as holotype. Description. Male Body long (6686 ��m). Body diameter uniform except near anterior and posterior ends; maximum about 150 ��m. Head diameter about 26���27 ��m. Cuticle smooth. Mouth surrounded by four low lips. Labial papillae not clearly observed. Eight cephalic setae. Three stout cervical setae at the posterior of the amphid. Four somatic setae on the left side (Fig. 1) which are absent on the right side. One seta on esophageal region (as well as three stout cervical setae). Virtually no buccal cavity; mouth opening merging into oesophagus. Oesophagus cylindrical; length approximately one sixth of the total body length. Nerve ring about 340 ��m from anterior. Amphids pocket-like and slightly pointed in the centre. Ocellus-like pigment spots present throughout the body region from posterior of the nerve ring (370 ��m from anterior) to the anterior of the spicule. Pigment spot c.d. ranging from 31 ��m to 41 ��m. Tail conical. Spicules paired, 100 ��m long and slightly curved ventrally. Proximal end of spicule bluntly rounded. Distal end of spicule forming a screw-like pattern. Gubernaculum with paired dorsal apophyses, caudally directed. Paired subventral setae present at the cloaca. Three additional subventral setae located near a small pre-cloacal supplement. One caudal seta present at the tail region. Six pairs of heavily cuticularized paired tubular supplements located from 240 ��m anterior to the cloaca. Female. body larger than the male (Table 1). Body shape similar to male but longer relative to length. Head diameter and amphid smaller than male. First pigment spot further from anterior and nerve ring compared to the male. Smaller pigment spots (23���25 ��m). Vulva about 3700 ��m from anterior, or 54 % of total body length. a.b.d. 71 ��m. Reproductive system didelphic amphidelphic. Tail relatively longer than in male. Characters Holotype Allotype Total body length 6686.0 6971.9 Head diameter 26.5 25.6 Length of cephalic setae 12.2 14.3 Amphid diameter 10.6 5.9 Amphid diameter / corresponding body diameter (%) 36.8 27.6 Nerve ring from anterior extremity of body 337.3 365.9 Oesophagus length 1169.6 1326.0 Oesophagus c.d. 70.1 69.9 Maximum body diameter 146.0 149.0 First pigment spot from anterior 373.1 449.1 First pigment spot from nerve ring 13.7 61.7 ......continued on the next page Diagnosis. P. malaysianis n. gen. n. sp. is characterized by having four low lips, pocket-like amphids that are slightly pointed in the center, six pairs of heavily cuticularized paired tubular supplements, pigment spots throughout the body, a bluntly rounded spicule, gubernaculum apophyses caudally directed and a conical tail. There are no other species of the genus. Etymology. The species name refers to the name of the country, Malaysia, where the species was found., Published as part of Chen, Cheng-Ann, 2015, A new marine nematode genus Pseudoplatycoma with a new species from the Sulu Sea and revision of the subfamily Platycominae (Enoplida: Leptosomatidae), pp. 233-244 in Zootaxa 3905 (2) on pages 235-238, DOI: 10.11646/zootaxa.3905.2.5, http://zenodo.org/record/240544

Family Leptosomatidae Filipjev, 1916 Diagnosis (from Smol & Coomans (2006)). Large nematodes (2���50 mm). Two circles of anterior sensillae: six inner labial sensilla mostly papilliform, six outer labial and four cephalice setae, often short. Amphids pocketshaped. Large number of metanemes with caudal filaments. Many species with ocelli. Buccal cavity usually narrow, sometimes with tooth-like thickenings. Pharynx inserts onto the body cuticle in the region of the buccal cavity, the cephalic capsule is variable in form. Three pharyngeal glands open in the buccal cavity. Pharynx always smooth in outline. Secretory-excretory system, if present, restricted to the pharyngeal region. Female reproductive system didelphic-amphidelphic with antidromously reflexed ovaries. Males with two opposed testes. Subventral or ventral pre-cloacal papillae (never tubules) often present. Caudal glands mostly present, extending into the precaudal region., Published as part of Leduc, Daniel, 2013, Deontostoma tridentum n. sp. (Nematoda, Leptosomatidae) from the continental slope of New Zealand, pp. 483-492 in Zootaxa 3722 (4) on page 484, DOI: 10.11646/zootaxa.3722.4.3, http://zenodo.org/record/222721

Deontostoma tridentum n. sp. (Table 1, Fig. 1���4) Material examined. Holotype male (NIWA 88367), collected on 11 November 2011 (NIWA cruise TAN 1116, station 68), southern flank Chatham Rise (44.221 �� S, 178.882 �� E), water depth: 1007 m, sediment total organic matter content (0���5 cm): 2.9 %, sediment CaCO 3 content (0���5 cm): 21.8 %. Three paratype males and two paratype females (NIWA 88368), same data as holotype. One paratype female (NIWA 88369), collected on 6 November 2011 (NIWA cruise TAN 1116, station 33), southern flank Chatham Rise (43.389 �� S, 174.175 �� E), water depth: 570 m, sediment total organic matter content (0���5 cm): 2.7 %, sediment CaCO 3 content (0���5 cm): 7.8 %. Etymology. The species name is derived from the Latin tres (= three) and dens (= tooth), and refers to the presence of three onchia in the buccal cavity of this species. Description. Male. Body large, cylindrical, gradually tapering from mid���body to anterior end. Cuticle thick, thinnest in anterior pharyngeal region (~ 14 ��m) and gradually thickening posteriorly (up to ~ 19���21 ��m thick), comprising several distinct layers as seen under light microscope (Figure 2 A); light transverse striations anterior to amphid and oblique striations crossing at angle of ca 120 �� in anterior pharyngeal region (Figure 2 B and 3 D), smooth elsewhere. Head blunt, rounded, set-off by slight constriction at level of amphideal aperture. Six small inner labial papillae with conspicuous ducts at base; six outer labial setae and four cephalic setae in one circle, equal in length, 10���12 % cbd long, with nerve process often visible. Eight rows of somatic setae (two subventral, two subdorsal, two lateral, one ventral and one dorsal) in anterior pharyngeal region, sometimes in clusters of two or three, with conspicuous ducts; somatic setae short and sparse elsewhere. Cephalic capsule without prominent anterior lobes or tropis; six posterior lobes present. Interlobar incisions wide, simple, without posteriorly-directed arms; posterior lobe margin smooth, with shallow incisions. Intralobar lacunae mostly absent. Amphids pocketshaped with relatively small aperture, 16���17 ��m wide by 3���5 ��m high. Species Deontostoma tridentum n. sp. Males Females Mouth opening wide, triangular (en face view), enclosed by one dorsal and two subventral microlabia (Figure 3 A and B). Subventral microlabia completely divided by mandibular ridge; dorsal microlabium only partially divided by mandibular ridge (Figure 4 C). Odontia reduced to minute ridges and not visible with light microscopy (Figure 3 B), appear completely absent in some specimens (Figure 4 A). Buccal cavity with large dorsal onchium and two smaller subventral onchia. Pharynx widening gradually posteriorly, ocelli not observed. Nerve ring at 22 % of pharynx length from anterior. Pharyngeal glands and secretory-excretory system not observed. Male reproductive system diorchic with opposed testes. Two rows of subventral pre-cloacal supplements consisting of 14���17 setae beginning slightly posteriorly to cloaca followed by 6���7 pairs of papilloid supplements bearing setae (Figure 2 E and 3 C). Transition between setae and papillae bearing setae is gradual and distinction between the two not always clear. Distance between papilloid supplements increases anteriorly from ca 60 to 120 ��m. One ventral supplement situated 200���215 ��m anterior to cloaca, consisting of a central oval projection flanked by two lateral ridges with rounded outline; central projection with minute opening (Figure 3 E). Spicules paired, slightly curved, 1.2���1.4 abd long, with central lamina extending along almost entire length of spicules. Gubernaculum with broad proximal ends without ornamentation and curving laterally; triangular crurae extending from middle portion. Proximal portion of gubernaculum is rounded, appears to consist of glandular tissue surrounded at base by cuticularised portion of gubernaculum. Copulatory musculature well-developed, extends ca 2000 ��m anterior to cloaca. Tail short, cylindrical, with blunt, rounded tip. Three caudal glands extending anterior to cloaca; spinneret present (Figure 2 C). Eight rows of short somatic setae present (two subventral, two subdorsal, two ventrosublateral, and two dorsosublateral). Females. Similar to males, but with smaller amphids and slightly longer tails. Reproductive system amphidelphic with two opposed and reflexed ovaries situated to the left of intestine. Vulva situated at ~ 2 / 3 of body length, surrounded by small intracuticular granules (Figure 2 D). Up to seven mature eggs present, 250���290 ��m wide by 735���810 ��m long. Diagnosis and relationships. Deontostoma tridentum n. sp. is characterised by large buccal cavity with greatly reduced or inconspicuous odontia, one large dorsal onchium and two smaller subventral onchia, cephalic capsule without interlobar incisions with posteriorly���directed arms, ventral pre-cloacal supplement situated 200���215 ��m anterior to cloaca, and gubernaculum with triangular crurae and curved proximal portion. Deontostoma tridentum n. sp. can be differentiated from all species of the genus based on the presence of two subventral onchia in the buccal cavity (absent in all other species). It is most similar to D. coptochilus in the presence of a large buccal cavity with a prominent dorsal onchium, structure of the cephalic capsule, and structure of the microlabia (i.e., subventral microlabia completely divided by mandibular ridge and dorsal microlabium not completely divided by mandibular ridge). Deontostoma tridentum n. sp. differs from the latter in the presence of crurae (absent in D. coptochilus), absence of ocelli (present in D. coptochilus), and in the position and structure of the ventral pre-cloacal supplement (> 200 ��m anterior to cloaca, central longitudinal ridge absent in D. tridentum n. sp. vs D. coptochilus). Deontostoma tridentum n. sp. is also similar to D. parantarcticum in the presence of more than one onchia in the buccal cavity and absence of ocelli, but can be differentiated from the latter by smaller values of a (36���52 vs 60���73), longer cephalic setae (7���8 vs 3���4 ��m), absence of conspicuous odontia (vs 2 large odontia on dorsal microlabium present in D. parantarcticum), and presence of 6���7 subventral pre-cloacal papillae (vs 3 in D. parantarcticum). Remarks The Brenke sledge was primarily designed to sample organisms present in the benthic boundary layer, i.e., suprabenthic organisms (Brandt & Barthel 1995), but re-suspended benthic organisms are also often sampled (e.g., L��rz et al. 2011). Deontostoma tridentum n. sp. specimens were found in core samples obtained from the type localities (D. Leduc, unpublished data), which suggests that the presence of specimens in the sledge nets was due to re-suspension of sediments. Association of this species with larger organisms such as sponges could also have increased its chance of capture by the sledge nets, but an association of D. tridentum n. sp. with other organism(s) has yet to be verified., Published as part of Leduc, Daniel, 2013, Deontostoma tridentum n. sp. (Nematoda, Leptosomatidae) from the continental slope of New Zealand, pp. 483-492 in Zootaxa 3722 (4) on pages 485-491, DOI: 10.11646/zootaxa.3722.4.3, http://zenodo.org/record/222721

Genus Deontostoma Filipjev, 1916 Diagnosis (modified from Hope (1967)). Cephalic capsule without ventral tropis. Mouth opening enclosed by one dorsal and two sub-ventral microlabia; buccal cavity with or without dorsal onchium. Pharyngeal pigment spot usually present, and when present, always cyathiform and with lens-like structure. Gubernaculum parallel to spicules, with paired apophyses directed dorsally or anterodorsally, never at right angle to corpus; often with elongated, anteriorly-directed crurae near distal end or middle region of corpus. Caudal glands extending anterior to anus/cloaca. Remarks. The genus Deontostoma was last revised by Hope (1967), who argued that the presence or absence of the tropis (a process arising from the internal surface of the ventral side of the cephalic capsule) is the most reliable character for differentiating between Deontostoma and the closely related genus Thoracostoma Marion 1870. In an earlier revision, Platonova (1962) suggested that differences in spicule shape may also help differentiate the two genera, but Hope (1967) noted that several exceptions exist, and spicule shape is therefore not considered a useful character. The following list of valid Deontostoma species is based on the revisions of Platonova (1962) and Hope (1967), as well as subsequent species descriptions by Hope (1974; 1977), Vitiello (1975), Coles (1977), Pastor de Ward (1995), and Gagarin (2008). The list follows Wieser (1953), who considered D. anchorilobatum Allg��n 1947 and D. elongatum Ditlevsen 1926 synonymous with D. arcticum Saveljev 1912, and D. polare Cobb 1914 synonymous with D. antarcticum Linstow 1892. Deontostoma montredonense Marion 1870 was considered doubtful by Wieser (1953), and is therefore not included in the list., Published as part of Leduc, Daniel, 2013, Deontostoma tridentum n. sp. (Nematoda, Leptosomatidae) from the continental slope of New Zealand, pp. 483-492 in Zootaxa 3722 (4) on pages 484-485, DOI: 10.11646/zootaxa.3722.4.3, http://zenodo.org/record/222721

Leduc, Daniel (2013): Deontostoma tridentum n. sp. (Nematoda, Leptosomatidae) from the continental slope of New Zealand. Zootaxa 3722 (4): 483-492, DOI: http://dx.doi.org/10.11646/zootaxa.3722.4.3

Two newLeptosomatidae species are described:Deontostoma conicum sp. nov., characterized by two conical odontia and transversal striae on the distal end of the gubernaculum — andDeontostoma duanei sp. nov., characterized by laterally directed odontia, specific measurements and gubernaculum morphology. Additional information is given onDeontostoma antarcticum (Linstow, 1892) andDeontostoma campbelli (Ditlevsen, 1921).

Nematode diversity may seriously be underestimated when taking into account cryptic speciation. Thoracostoma trachygaster is commonly found in kelp holdfasts along the California coastline and was recently shown to consist of at least two distinct molecular clades (I and II). Here, we provide detailed morphological analysis of both clades, based on measurements taken from video vouchers of respectively eight and 16 individuals from the previous study, as well as 80 newly collected specimens from four Californian beaches. The latter were vouchered, measured, and then subjected to molecular analyses of the mitochondrial cytochrome oxidase c subunit I (COI) gene, and the ribosomal D2D3 and internal transcribed spacer (ITS) regions. This integrative approach shows that the three molecular clades are phylogenetically and morphologically distinct species, but a combination of morphological characters is needed to distinguish them. Two new species, Thoracostoma fatimae sp. nov. and Thoracostoma igniferum sp. nov., are identified and described. The spicule length of T. fatimae sp. nov. is significantly shorter than that of T. trachygaster. Thoracostoma igniferum sp. nov. can be distinguished by the irregular posterior edge of the cephalic capsule and the two internal subdorsal tropis-like projections in the wall of the cephalic capsule, which are lacking in T. fatimae sp. nov. and T. trachygaster.

The nematode Pseudoplatycoma malaysianis n. gen. n. sp. is described from the Sulu Sea (Malaysia). The new genus is classified in the subfamily Platycominae Platonova 1976. Revision of the new genus and four other genera in Platycominae, resulted in four species from the genus Platycomopsis being transferred to other genera: P. dimorphica and P. mazjatzavi to the genus Platycoma ; P. effilata to the genus Micoletzkyia ; and P. gibbonensis to the genus Anticoma . Pilosinema is regarded as a asynonym of Platycomopsis and Platycomopsis paracobbi is regarded as a synonym for P. cobbi . A key for identification of the genera and species of Platycominae is presented.

Leptosomatum bacillatum (Enoplida: Leptosomatidae) occurs in high densities in the sponge Halichondria panicea. Previously observed fluctuations in modal length suggested an annual reproductive cycle which in this study is confirmed by monthly samplings. Eggs are deposited in July and August and L. bacillatum reaches maturity after one year. Mature females continue growing, their length being season dependent. The bionomics, mucus trap hypothesis and nematode-sponge relationship are discussed.

Leptosomatum ranjhai Timm, 1960 can no longer be assigned to Leptosomatum sensu Bongers, 1983 because the sexual dimorphism in the amphids of Leptosomatum is absent in L. ranjhai. The new genus proposed for this species, Orthophallonema, is characterized by the presence of serially oriented lateral epidermal glands, ortho- and loxometanemes (Lorenzen, 1978), and ventral and subventral pre-cloacal sensilla in the male.

Summary Two new species of Leptosomatidae (Nematoda) from Lambert's Bay, South Africa, are described. Deontostoma parantarcticum n.sp. differs from D. antarcticum (Von Linstow 1892) in the absence of oesophagal pigment spots and the different shape of the spicules. Thoracostoma ancorarium n.sp. is characterized by the absence of ocellar pigment and the presence of posteriorly-directed arms on the fenestrae of the cephalic capsule.

The structure of a proprioceptor in the lateral hypodermal chords of Deontostoma californicum has been studied by light and electron microscopy. It is comprised of a sensory cell provided with a cilium situated in a terminal invagination. An accompanying dendrite forms a synaptic junction at the distal end of the sensory cell. This is the first fine structural description of this proprioceptor in the Enoplida.