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Alaimus parvus Thorne, 1939. Dimensions of five females: L = 0.51-0.57 mm; a = 30-44; b = 3.5-4. 1; c = 8.3- 8.8; V = 4 1-45 12- 20. Length of tail equal to 7 -8 anal body widths. Tail curved strongly to ventral side; terminus narrowly rounded. Samples 26 and 27., Published as part of P. A. A. LOOF, 1971, FREELIVING AND PLANT PARASITIC NEMATODES FROM SPITZBERGEN, COLLECTED BY MR. H. VAN ROSSEN, pp. 1-86 in Mededelingen Landbouwhogeschool Wageningen 71 on page 61, DOI: 10.5281/zenodo.8152982

Eudorylaimus vanrosseni n.sp. (Fig. 27; Diagram 6). Dimensions: Females (n = 8): L = 1.03-1.25 mm; a = 23- 29; b = 3.5-4.3; c = 35-40; V = 1 3 _ 1 854 - 5713 - 1 8. Female, holotype: L = 1.05 mm; a = 27; b = 3.6; c = 38; V = 135615. Male unknown. Body rather stout, curved ventrad slightly in death. Cuticle 2.5- 3.0 [x thick, increasing to 6 u, on ventral side of tail; with thin, sharply demarcated outer layer which shows fine but distinct transverse striae. Lateral chord about 30 % of body width. Lip region offset by a shallow constriction; lips separate, angular. Amphid aperture about 60 % of corresponding body width. Length of odontostyle 16-17 (JL, i.e. slightly more than width of lip region, the aperture occupying about one-third of its length. Basal portion about 25 \i long. Guiding ring 'single'. The nerve ring surrounds the oesophagus at about 35 % of its length from head end. Cardia conspicuous, subglobular, variable in size (12-20 X 15- 27(1). Oesophageal characters (two females): The oesophagus begins to widen at 51- 53 % and attains its full width at 57- 60 % of its length from head end. DO lies at, or just anterior to the latter level, the distance DO- DN is 13 -14 \i. The SiN lie a small distance apart, behind the middle of the distance DN - S2N; the anterior one is small and indistinct, the posterior one large and conspicuous. The S2N are well developed and lie rather close to the base of the oesophagus. Locations: DO 57 -59 %; SjN^ 77-78 %; S2N 90-93 %; K = 85 - 93; D N 62 -63 %; SjN2 79- 80 %; S20 92- 93 %; K ' = 94. DO- DN 4.6 %; dist. 1.6-2.7 %; Vulva of the transverse type, vagina wide, half body width deep. Gonads two, opposed, reflexed, without sperm; with constriction between uterus and oviduct. Tail shaped as in E.monohystera: convex-conoid, indented dorsally, tip round­ ed; its length 1.0-1.3 anal body widths. Rectum 1.2 - 1.3 anal body widths long, prerectum one to two times as long as rectum. Tail with a row of (usually 6) small ventral saccate bodies. Holotype: Female on slide WT 1134. Paratypes: Seven females on slides WT 1221-1224. Type habitat and locality: Sample 55. Paratypes also from sample 53. Diagnosis: This species resembles E.pratensis (de Man, 1880) in tail shape, but this species has a much longer and thinner odontostyle. From E. nitidus (Thorne & Swanger, 1936) it differs by the well-developed, separate lips; from E.obesus (Thorne & Swanger, 1936) by the distal part of the tail ventrally not being offset, and by the shorter odontostyle (against 22 \x) with shorter aperture; from E.albionensis (van der Linde, 1938) by the non-sinuate ventral tail contour, lower lip region, post-equatorial vulva and lower ratio odontostyle/lip region (1.5 in albionensis)., Published as part of P. A. A. LOOF, 1971, FREELIVING AND PLANT PARASITIC NEMATODES FROM SPITZBERGEN, COLLECTED BY MR. H. VAN ROSSEN, pp. 1-86 in Mededelingen Landbouwhogeschool Wageningen 71 on pages 76-77, DOI: 10.5281/zenodo.8152982

14. Eudorylaimus pratensis (de Man. 1880) Andrássy, 1959 Località: Le Gobbie l ♀. ♀: L = 1.62 mm; n: 25; b: 3,7; e = 54,5; V = 51 %. Il corpo, arcuato veutralmeute, possiede una cutícula liscia asumamule e debalmente stxiala internamente, een delle striatum più evienti nella regime caudale. La regione labiale è distinta dal resto del arpa da una wstrizione; sono evidenti le papille estatua. Lo atiletta è mgo 27 μm, cioè 1,3 volte il diametro oefalieo, ed è piuttosto suttile, Jisurando iu larghezza solo 1 /15 dello spessore del corpn alla sua base d 1 /7- 1/8 del diametro cefaljeo; la sua apertura è pari ad 1/ 3 della ua lunghaza; Panella guida è sempliee. Uesofago si slarga a circa la ¡età della sua lungliezza. Gli ovari sono pari, opposti e riflessi; ciascun amo x-iflesso è pari a circa 1/3 delPimeı-a ganada. La vulva è in poııione equatorial: e presenta le lablu-a ispessite; la vagina, che lia forma ilindiica, si addentra fin quasi a meta nella spessore del corpo. Non si otario sperruatazai nella gonads femminile. Il prereuo è lungo cima ne value il rena, elle, a ma volta, è un pom pin lung« del diametro nale. La cada, di forma conìca, ha Festi-eniità subdigitata e presenta dei orpi saccifnmıi; non è visibile invece La ‹‹ corda t-enuale a segnalata in no degli esemplari di De Man (Leer, 1961). La specie è nuova per la fauna italiana. 5, Published as part of Maria Teresa Vinciguerra & Marcella De Francisci, 1973, Nematodi muscicoli delle Alpi Apuane, pp. 8-13 in Bollettino delle Sedute dell'Accademia Gioenia di Scienze Naturali in Catania 11 on pages 8-9, DOI: 10.5281/zenodo.8143879

1 a. Rhyssocolpus microdorııs (Schiemer, 1965) Andrássy, 1971 (Fig. 3) Localìtà: Le Gobbie; Monte Sumbra 2 ♀. 1 ♂. ♀: L = 0,908-0, mm.; a = 21 -22,7; b = 4,5; c = 21 -22,7; V = 51- 63 % ♂: L = 0,690 mm; a = 23,2; b = 3,4; c = 19. Nel 1965 ScmEMEa ha istituim e descritto la specie Enchndelus micradorus basanvlusi su esemplari esclusivamente di sexso ınıwclıile. Successivamente ANDBÃSSY nel 1971 ha istituito il genere Rhyssaoalpus, genera molto vieino alPEııchadelııs, ma different: du esso pa- alcuni caraueri, quali sopııınutm un caratleristioo raggrinzimento della cutícula in prussimilå della vulva e Ia lunghezza dello stiletto sempre iníeriore al diametro cefalico, ed ha atlribuita al nuovo genere anche la specie di SCHnzMBx, basandosi però soltanto sui caratteri dei masehi. Ora il ritrovamentu della femmina dl questa specie, Elle presenta il caraum più peculiar; del genera, e cioè Là striatura della uma vulvare, confermı ulteriorrnente la validinä della interpretazione di Aıvıııılssv., Published as part of Maria Teresa Vinciguerra & Marcella De Francisci, 1973, Nematodi muscicoli delle Alpi Apuane, pp. 8-13 in Bollettino delle Sedute dell'Accademia Gioenia di Scienze Naturali in Catania 11 on page 13, DOI: 10.5281/zenodo.8143879

Enchodelus parvus n.sp. (Fig. 23; Diagram 3). Dimensions: Females (n = 5): L = 0.59- 0.79 mm; a = 18 - 22; b = 3.9 -4.7; c = 37 -45; V = i 2 - " 52 _ 54 i 4 - i9. Female, holotype: L = 0.70 mm; a = 22; b = 4.0; c = 41; V = 165415. Body curved ventrad about 90° in death. Cuticle consisting of two sharply demarcated layers of equal thickness; total thickness 1.5 jx, increasing to 2 ji, in neck region and to 3.5 JJ. (chiefly through thickening of the inner layer) on the tail. Outer layer with fine but distinct transverse striation. Lateral chord one-quarter of body width. Lip region slightly offset by a shallow constriction: lips somewhat separate, the papillae protruding slightly. Walls of buccal cavity not conspicuously thick. Length of odontostyle 8 -10 pi, of basal portion 9-11 pi; aperture short. Length of odontostyle about equal to width of lip region. Basal portion linear, weakly sclerotized. The nerve ring surrounds the oesophagus at 43 % of its length from head end. Cardia small. Oesophageal characters (one female): The oesophagus begins to widen at 66 % and attains its full width at 74 % of its length from head end, DO lies anterior to the latter level; the distance DO-DN is 7 pi. The SjN are invisible, but the St O are distinct, located halfway between DN and S 2N. The latter are well developed. Locations: DO 72 %; 8,082 %; S2N 98 %; DN 76 %; S2092 %. DO-DN 4.1 %; Vulva depressed, probably not quite transverse. Vagina slightly sclerotized, one-halfbody width deep. Gonads two, opposed, reflexed; uteri without sperm. A distinct sphincter is present. An intra-uterine egg measures 78 x 27 pi. Ovaries with few oocytes. Tail elongate-hemispheroid, as long as anal body width, with a few saccate bodies. Rectum as long as anal body width, prerectum about twice as long. Holotype: Female on slide WT 1229; paratypes: Four females on slides WT 1230-1231. Type habitat and locality: Sample 28. Paratypes also from samples 16 and 63. This species resembles E.vesuvianus (Cobb, 1893), from which it differs by the longer tail, shorter odontostyle and posterior vulva., Published as part of P. A. A. LOOF, 1971, FREELIVING AND PLANT PARASITIC NEMATODES FROM SPITZBERGEN, COLLECTED BY MR. H. VAN ROSSEN, pp. 1-86 in Mededelingen Landbouwhogeschool Wageningen 71 on page 67, DOI: 10.5281/zenodo.8152982

Eudorylaimus parvus (de Man, 1880) Andrâssy, 1959. Six females. Dimensions: L = 0.69-0.83 mm; a = 28 - 33; b = 3.5- 3.8; c = 15-19; V = 9 - 1153- 51 ll ~ 13 ; odontostyle = 11-12(1. One male: L = 1.00 mm; a = 32; b = 3.7; c = 27; VD = 1 5 41 13; odontostyle = 13 [i; spicules = 32 [i; supplements = 4. Lip region offset by a shallow constriction. Length of spear slightly more than width oflip region. Oesophagus expanded about halfway. Body diameter at base of oesophagus about 2.5 X width of lip region. Vulva transverse. Tail length 3.2-3.6 anal body widths in the female, 1.7 in the male. Rectum slightly longer than anal body width, prerectum in the female 1.5-2.0 x rectum. Sample 17., Published as part of P. A. A. LOOF, 1971, FREELIVING AND PLANT PARASITIC NEMATODES FROM SPITZBERGEN, COLLECTED BY MR. H. VAN ROSSEN, pp. 1-86 in Mededelingen Landbouwhogeschool Wageningen 71 on page 72, DOI: 10.5281/zenodo.8152982

Eudorylaimus maksymovi Altherr, 1963 (Fig. 28; Diagram 7). Two females. Dimensions: L = 1.69-1.83 mm; a = 36 - 40; b = 4.1-4.3; c = 17-19; V = 9 44 - 469. Cuticle thin, 2.5 -3.0 jx; transverse striation very fine. Outer layer thin, sharply demarcated. Lip region offset by a shallow depression; the inner circle of papillae located rather far outward. Length of odontostyle 20 [x or 1.3 x width of lip region, the aperture occupying one-third of its length. Oesophageal characters: The oesophagus begins to widen at 48 % and attains its full width at 58- 60 % of its length from head end. DO lies slightly behind the latter level, the distance DO- DN is 20 fx. The SJM lie a small distance apart; the anterior one is small and indistinct. S2N well developed. Locations: 7 Eudorylaimus maksymovi 9 DO 60- 6 1 %; SiN, 78 -79 %; S2N 89 -91 %; K = 78 -86; D N 65- 66 %; SjN2 81- 82 %; S20 91- 92 %; K' = 83 -89. DO- DN 4.9- 5.0 %; dist. 2.3- 3.5 %; Cardia conoid, 18 (x long. In both specimens there is an elongate organ in the posterior part of the neck, extending to just past the end of the oesophagus; located laterally on the right side. Anteriad the organ soon becomes indistinct; it might be connected with the lateral chord. Vulva depressed, transverse; vagina distinctly sclerotized. Gonads two, opposed, reflexed, with sphincter. No sperm. Tail length equal to 3.7- 3.8 anal body widths; tail conoid the distal half curved to ventral side; in the proximal half there are some saccate bodies in the cuticle ventrally and subventrally. Rectum 1.2-1.3 anal body widths long, prerectum 1.3-1.8 as long as rectum. Sample 69. These specimens correspond well to Altherr's description. The species resembles E. consobrinus (de Man, 1917) but differs from it by the transverse vulva, the longer odontostyle (against 15-16 y.) and the slightly offset lip region (continuous in the type specimen of consobrinus in de Man's collection)., Published as part of P. A. A. LOOF, 1971, FREELIVING AND PLANT PARASITIC NEMATODES FROM SPITZBERGEN, COLLECTED BY MR. H. VAN ROSSEN, pp. 1-86 in Mededelingen Landbouwhogeschool Wageningen 71 on pages 77-79, DOI: 10.5281/zenodo.8152982

Eudorylaimus agilis (de Man, 1880) Loof, 1969. Syn. Dorylaimus lugdunensis apud Steiner, 1916 nee de Man, 1880. Dimensions of four females: L = 1.38-1.56 mm; a = 28 -32; b = 4. 1 -4.6; c = 11-15; V = 12 - 1344 -471 0 -1 3. Lip region offset by a deep constriction, lips well developed with conspicuously protruding papillae. Length of odontostyle 17 [x or 1.2 X width of lip region, the aperture occupying about two-fifths of its length. Distance DO- DN 4.8 - 5.0 % of oesophagus length. Vulva longitudinal. Tail curved to ventral side, its length 3.6-5.0 anal body widths. Rectum 1.0-1.6 xanal body width, prerectum 1.3-2.4 x as long as rectum. This species is easily distinguished from E. lugdunensis (de Man, 1880) by its larger size and stouter body. Samples 1, 29, 37 and 55., Published as part of P. A. A. LOOF, 1971, FREELIVING AND PLANT PARASITIC NEMATODES FROM SPITZBERGEN, COLLECTED BY MR. H. VAN ROSSEN, pp. 1-86 in Mededelingen Landbouwhogeschool Wageningen 71 on page 72, DOI: 10.5281/zenodo.8152982, {"references":["STEINER, G. (1916). Freilebende Nematoden von Nowaja-Semlja. Zool. Anz. 47, 50 - 74."]}

Enchodelus conicaudatus (Ditlevsen, 1927) Thorne, 1939 (Fig. 21; Diagram 1). Dimensions: Females (n = 6): L = 1.80- 2.15 mm: a = 33 -42; b = 6.0-7.8; c = 52 -67; V = 14- 1741_47l5- 20 Fourth—stage juveniles (n = 5): L = 1.33-1.55 mm; a = 33 -35; b = 6.5 - 7.3; c = 43 - 58; V = 43 - 48. One female has V = 53. Lip region offset by depression. Cuticle 4 [x thick, increasing to 6 [x on tail. Outer layer sharply demarcated. Lateral chord one-fourth to one-fifth of body width in mid-body. Length of odontostyle 18 -19 y. in adults; the L - 4 have an odontostyle of 15-17 jx and a spare one of 18 -19 fx. Posterior portion of spear 24 [x long in adults. Oesophagus anteriorly with distinct, somewhat muscular swelling. Oesophageal characters (four females). The oesophagus begins to widen at 59- 61 % and attains its full width at 68 -69 % of its length from head end. DO lies a short distance anterior to the latter level, the distance DO-DN is 12-14 jx. SiN rather indistinct, located about halfway between DN and S2N; the S2N are well developed. Locations: DO 65- 67 %; 8^ 7 8- 80 %; S2N 89 -91 %; D N 70-71 %; SjO 78 - 80 %; S20 90-92 %; DO - D N 4.0 -4.8 %; Vulva transverse, vagina more than one-half body width deep, with distinct sclerotization. Uterus very spacious. Oviduct with distinct sphincter. No sperm. On the ventral side the tail contains 'saccate bodies' which may extend to one anal body width anterior to the anus. Tail 1.1-1.2 anal body widths long. Rectum 1.0-1.2 anal body widths long, prerectum two to three times as long as rectum. Body tapering markedly anteriorly, the diameter at the base of the 1. Enchodelus conicaudatus Ç Oesophagus being almost four times the width of the lip region. Dimensions of three intra-uterine eggs: 85 -90 x 34-38 jx. The specimens agree well with Ditlevsen's description. As he gives a body length of 2.0 mm and a tail length of 33 [x, the value of 'c' is 61, not 30 as stated in the text. Females in samples 1,46 and 68; juveniles in samples 3, 7, 27, 29, 31, 34, 37, 39, 49, 52, 66 and 69., Published as part of P. A. A. LOOF, 1971, FREELIVING AND PLANT PARASITIC NEMATODES FROM SPITZBERGEN, COLLECTED BY MR. H. VAN ROSSEN, pp. 1-86 in Mededelingen Landbouwhogeschool Wageningen 71 on pages 64-65, DOI: 10.5281/zenodo.8152982

As adapter molecules to convert the nucleic acid information into the amino acid sequence, tRNAs play a central role in protein synthesis. To fulfill this function in a reliable way, tRNAs exhibit highly conserved structural features common in all organisms and in all cellular compartments active in translation. However, in mitochondria of metazoans, certain dramatic deviations from the consensus tRNA structure are described, where some tRNAs lack the D- or T-arm without losing their function. In Enoplea, this miniaturization comes to an extreme, and functional mitochondrial tRNAs can lack both arms, leading to a considerable size reduction. Here, we investigate the secondary and tertiary structure of two such armless tRNAs from Romanomermis culicivorax. Despite their high AU content, the transcripts fold into a single and surprisingly stable hairpin structure, deviating from standard tRNAs. The three-dimensional form is boomerang-like and diverges from the standard L-shape. These results indicate that such unconventional miniaturized tRNAs can still fold into a tRNA-like shape, although their length and secondary structure are very unusual. They highlight the remarkable flexibility of the protein synthesis apparatus and suggest that the translational machinery of Enoplea mitochondria may show compensatory adaptations to accommodate these armless tRNAs for efficient translation.

An integrated classification of the free-living and parasitic Nematoda (Subkingdom Aschelmintha) is given in outline, in which three Classes and seven Subclasses are recognized; Class Rhabditea: Subclasses Rhabditia, Diplogasteria and Tylenchia; Class Enoplea: Subclasses Enoplia and Dorylaimia; Class Chromadorea: Subclasses Chromadoria and Monhystena. Twenty-five Orders are recognized and the major changes are explained. The Order Araeolaimida is provisionally retained and classified to the Family level.

The structure of nematode somatic muscles is reviewed. They are obliquely striated and, therefore, supercontractile because they change in length to an exceptional extent by both myofilament interdigitation and shearing. A model is developed which shows that shearing is generated by interdigitation under specified structural conditions. It is concluded that the ability to supercontract is functionally associated with a hydrostatic skeleton, because obliquely striated muscles occur in a wide range of unrelated Phyla and a functionally identical muscle has evolved from cross-striated muscle in other animals with a hydrostatic skeleton, particularly certain insect larvae. Two, possibly 3, morphologically distinct groups of muscles exist in the Nematoda which correspond to the Classes Enoplea, Rhabditea and Chromadorea. Parallel sequences of change occur in the first 2, in which the contractile layer increases in area, the sarcomeres become smaller, and the Z-system more regular. Descriptive terms are redefined, thus: platymyarian, quasi-platymyarian, shallow coelomyarian, and coelomyarian occur in Rhabditea; cubomyarian, regular cubomyarian, and stratimyarian occur in Enoplea; and a characteristic chromadorid-circomyarian is known from 2 Chromadorea. The structure of the muscles corresponds well to the higher nematode classification, except in the Order Spirurida which may have arisen from the Enoplea and not the Rhabditea as generally accepted.

Background Nematodes can be subdivided into basal Enoplea (clades 1 and 2) and more derived Chromadorea (clades 3 to 12). Embryogenesis of Caenorhabditis elegans (clade 9) has been analyzed in most detail. Their establishment of polarity and asymmetric cleavage requires the differential localization of PAR proteins. Earlier studies on selected other nematodes revealed that embryonic development of nematodes is more diverse than the essentially invariant development of C. elegans and the classic study object Ascaris had suggested. To obtain a more detailed picture of variations and evolutionary trends we compared embryonic cell lineages and pattern formation in embryos of all 12 nematode clades. Methods The study was conducted using 4-D microscopy and 3-D modeling of developing embryos. Results We found dramatic differences compared to C. elegans in Enoplea but also considerable variations among Chromadorea. We discovered 'Polarity Organizing Centers' (POCs) that orient cleavage spindles along the anterior-posterior axis in distinct cells over consecutive cell generations. The resulting lineally arranged blastomeres represent a starting point for the establishment of bilateral symmetry within individual lineages. We can discern six different early cleavage types and suggest that these variations are due to modifications in the activity of the POCs in conjunction with changes in the distribution of PAR proteins. In addition, our studies indicate that lineage complexity advanced considerably during evolution, that is we observe trends towards an increase of somatic founder cells, from monoclonal to polyclonal lineages and from a variable (position-dependent) to an invariable (lineage-dependent) way of cell fate specification. In contrast to the early phase of embryogenesis, the second half ('morphogenesis') appears similar in all studied nematodes. Comparison of early cleavage between the basal nematode Tobrilus stefanskii and the tardigrade Hypsibius dujardini revealed surprising similarities indicating that the presence of POCs is not restricted to nematode embryos. Conclusions The pattern of cleavage, spatial arrangement and differentiation of cells diverged dramatically during the history of the phylum Nematoda without corresponding changes in the phenotype. While in all studied representatives the same distinctive developmental steps need to be taken, cell behavior leading to these is not conserved.