Meiofauna in the Gollum Channels and the Whittard Canyon, Celtic Margin—How Local Environmental Conditions Shape Nematode Structure and Function

The Gollum Channels and Whittard Canyon (NE Atlantic) are two areas that receive high input of organic matter and phytodetritus from euphotic layers, but they are typified by different trophic and hydrodynamic conditions. Sediment biogeochemistry was analysed in conjunction with structure and diversity of the nematode community and differences were tested between study areas, water depths (700 m vs 1000 m), stations, and sediment layers. The Gollum Channels and Whittard Canyon harboured high meiofauna abundances (1054–1426 ind. 10 cm−2) and high nematode diversity (total of 181 genera). Next to enhanced meiofauna abundance and nematode biomass, there were signs of high levels of organic matter deposition leading to reduced sedimentary conditions, which in turn structured the nematode community. Striking in this respect was the presence of large numbers of ‘chemosynthetic’ Astomonema nematodes (Astomonema southwardorum, Order Monhysterida, Family Siphonolaimidae). This genus lacks a mouth, buccal cavity and pharynx and possesses a rudimentary gut containing internal, symbiotic prokaryotes which have been recognised as sulphur-oxidising bacteria. Dominance of Astomonema may indicate the presence of reduced environments in the study areas, which is partially confirmed by the local biogeochemical environment. The nematode communities were mostly affected by sediment layer differences and concomitant trophic conditions rather than other spatial gradients related to study area, water depth or station differences, pointing to small-scale heterogeneity as the main source of variation in nematode structure and function. Furthermore, the positive relation between nematode standing stocks, and quantity and quality of the organic matter was stronger when hydrodynamic disturbance was greater. Analogically, this study also suggests that structural diversity can be positively correlated with trophic conditions and that this relation is tighter when hydrodynamic disturbance is greater

Desmodora striatocephala Tchesunov, 2008, sp. nov.

<i>Desmodora striatocephala</i> sp. nov. <p>Figs 10–11</p> <p> <i>Type material</i>: <b>Holotype</b> male. Type specimen deposited in the DIVA nematode collection.</p> <p> <i>Type locality</i>: DIVA I, Meteor 48/1, Station 325/4, Multicorer 8: South­east Atlantic Ocean, 19°58.3'S & 002°59.8'E, depth 5450 m. 14 July 2000.</p> <p> <i>Etymology</i>: The species name reflects fine cross striation of the head.</p> <p> <i>Description.</i> Body cylindrical, of brownish­yellow colouration. Anterior end truncate. Somatic cuticle finely but distinctly annulated (just posterior to the cephalic capsule, nine annules for 10 <i>µ</i> m on convex body side and twelve annules on the opposite concave side; in the midbody, 17–20 annules for 10 <i>µ</i> m), with no lateral differentiation.</p> <p> Body length 1009 <i>µ</i> m, a 34.8, b 7.6, c 7.4. Body diameter at the level of: cephalic setae 16 <i>µ</i> m, amphidial fovea 21 <i>µ</i> m, nerve ring 29 <i>µ</i> m, cardia 29 <i>µ</i> m, midbody 29 <i>µ</i> m, cloaca 24 <i>µ</i> m.</p> <p> Labial region slightly drawn inward and therefore inner and outer labial sensilla not discernible. There are four short cephalic setae 3 <i>µ</i> m long at anterior cephalic capsule. Cephalic capsule 18 <i>µ</i> m long, shaped by thick cuticle with very fine traces of fused annules; the annules of the cephalic capsule by a factor of 1.5–2 wider and much less distinct than postcapsular annules.</p> <p> Amphidial fovea very large and occupies nearly the whole lateral surface of the cephalic capsule. Amphidial fovea loop­shaped, slightly longitudinally oval and narrowed to its anterior end. Exit site of the amphidial nerve is thus unusually situated at the anterior end of the fovea where descending and ascending branches contact with one another. Amphidial fovea width 16 <i>µ</i> m or 76% c.b.d; distance from the cephalic apex to the amphidial fovea 3–4 <i>µ</i> m.</p> <p>Somatic setae arranged in longitudinal rows distinct in the pharyngeal region and becoming irregular in the intestinal region.</p> <p>Cheilostoma indistinctly discernible because of the dense pigmentation. The subsequent part of the buccal cavity narrow, equal to the cephalic capsule. Walls of the buccal cavity and small but distinct dorsal tooth very weakly sclerotized.</p> <p> Pharynx slender, evenly muscular, with sinuous cuticular lining of the internal lumen. Posteriorly, the pharynx widened into a clear roundish bulb. Pharynx width at the level of the nerve ring 13 <i>µ</i> m; posterior bulb 24 <i>µ</i> m wide and 25 <i>µ</i> m long. Nerve ring hardly visible. No indication of a renette cell.</p> <p>Cardia short, trapezium­shaped. Intestine with yellow­brownish inclusion droplets.</p> <p>Testis singular, outstretched, situated ventrally to the intestine. Spermatozoa relatively large, of uncertain shape, with granular content. Vas deferens divided into alternate regions made up of cells with transparent and coarsely granulated content.</p> <p> Spicules arched, distally pointed and proximally widened into shovel­like knobs, Gubernaculum paired, as two curved plates nearly parallel to the distal half of the spicules. Spicules length 29 <i>µ</i> m (chord) and 40 <i>µ</i> m (arch); gubernaculum plate 15 <i>µ</i> m long.</p> <p>Precloacal ventral cuticle thickened and transparent. About five midventral supplementary organs inserted in the precloacal cuticle. Supplementary organ presents an intracuticular canal with a small papilla on the surface of the cuticle. The supplementary organs decrease in size from the cloaca anteriad.</p> <p> Tail elongate conical, relatively slender, with terminal spinnerete tube. Tail length 5.32 anal diameters long. There a few pre­ and postanal subventral setae on the posterior body; their length up to 4.5 <i>µ</i> m, greater than those of the intestinal region.</p> <p> <i>Diagnosis</i>. Body length 1009 <i>µ</i> m, a 34.8, c 7.38. There are four short cephalic setae 3 <i>µ</i> m long at anterior cephalic capsule. Cephalic capsule 18 <i>µ</i> m long, shaped by thick cuticle with traces of fused annules; the annules of the cephalic capsule by a factor of 1.5–2 wider and much less distinct than postcapsular annules. Amphidial fovea very large and occupies nearly the whole lateral surface of the cephalic capsule. Amphidial fovea loop­shaped, slightly longitudinally oval and narrowed to its anterior end. Amphidial fovea width 16 <i>µ</i> m or 76% c.b.d. Precloacal ventral cuticle thickened and transparent. About five midventral supplementary organs inserted in the precloacal cuticle. Supplementary organ present as an intracuticular canal with a small papilla on the surface of the cuticle. Tail elongate conical, relatively slender. Tail length 5.32 anal diameters long.</p> <p> <i>Differential diagnosis</i>: <i>Desmodora striatocephala</i> sp. nov. is characterized by very fine but distinct cross striation of the cephalic capsule. Some related desmodorid genera such as <i>Paradesmodora</i> Stekhoven, 1950, <i>Echinodesmodora</i> Blome, 1982 and <i>Stygodesmodora</i> Blome, 1982 are also characterized by a cross­striated periamphidial cuticle hardly distinguishable from that of the neck region. However, the cephalic region of <i>D. striatocephalata</i> is clearly different in having a thickened cuticle with very fine transversal grooves thus forming a cephalic capsule set off the neck region with thinner cuticle and sharp grooves between annules.</p> <p> <i>Desmodora striatocephala</i> sp. nov. is well characterized by a combination of very large amphidial fovea occupying nearly the entire lateral surface of the cephalic capsule and thickened midventral preanal cuticle with a few supplementary papillae inserted therein in males. The new species shares this set of features with <i>D. cuddlesae</i> Inglis, 1963 and to some lesser degree with <i>D. inflexa</i> Wieser, 1954. <i>D. striatocephala</i> sp. nov. differs from <i>D. cuddlesae</i> by the shorter body (1009 <i>µ</i> m <i>versus</i> 1760–1980 <i>µ</i> m), relatively longer tail (c 7.38 <i>versus</i> 13.5–14.1, c’ 5.32 <i>versus</i> 2.65–2.75), absolutely smaller but relatively bigger amphidial fovea (16 <i>µ</i> m wide and 76% c.b.d. <i>versus</i> 26–37 m and 59% c.b.d.), about five <i>versus</i> twenty­nine preanal supplementary papillae in the ventral thickened transparent cuticle. <i>D. striatocephala</i> differs from <i>D. inflexa</i> with shorter body (1009 <i>µ</i> m <i>versus</i> 2450 <i>µ</i> m), relatively thicker body (a 34.8 <i>versus</i> 53.7), about five <i>versus</i> fourteen preanal supplementary papillae in the ventral thickened transparent cuticle and shorter tail (c 7.38 <i>versus</i> 25.8, c’ 5.32 <i>versus</i> 2.00). Other <i>Desmodora</i> species with ventrally thickened preanal cuticles are much more distinguished from <i>D. striatocephala</i> in other characters.</p>Published as part of <i>Tchesunov, Alexei V., 2008, Three new species of free­living nematodes from the South­East Atlantic Abyss (DIVA I Expedition) *, pp. 151-174 in Zootaxa 1866</i> on pages 169-172, DOI: <a href="http://zenodo.org/record/183775">10.5281/zenodo.183775</a&gt

Paracyatholaimus Micoletzky 1923

Paracyatholaimus Micoletzky, 1923 Wieser, 1954 a: 26, emended Diagnosis Cuticle punctated, lateral differentiation hardly developed. Six outer labial sensilla + four cephalic sensilla setose, in a single circle. Amphidial fovea multispiral. Cheilostoma armoured with twelve rugae; distinct dorsal tooth, often supplemented with smaller subventral teeth and occasionally other denticles in the stegostoma. Precloacal ventromedian supplements as setae­like organs half inserted into the body. Gubernaculum hardly dilated at the distal end and devoid of denticles or serrations. Tail conical or with more or less slender cylindrical distal portion. Type species Cyatholaimus dubiosus Bütschli, 1874. List of valid species 1 Paracyatholaimus arcticus Kreis, 1963. Kreis, 1963: 39 –40, fig. 20 A–C; Iceland. 2 Paracyatholaimus botosaneanui Andrássy, 1973. Andrássy, 1973: 259 –261, Abb. 9 A–C; Cuba. 3 Paracyatholaimus chilensis Gerlach, 1953. Gerlach, 1953 b: 19 –21, Abb. 9 a–e; Chile. 4 Paracyatholaimus diva sp. nov. Present paper. 5 Paracyatholaimus dubiosus (Bütschli, 1874). Bütschli, 1874: 48, fig. 31 a, b (= Cyatholaimus dubiosus); Kiel Bay. Micoletzky, 1922: 377 (to subgenus Paracyatholaimus). Meyl, 1954: 428 –429, Abb. 2 a–f; (Mediterranean). 6 Paracyatholaimus duplicatus Gerlach, 1964. Gerlach, 1964 b: 77 –78, Abb. 5 a–d; Maldive Islands. 7 Paracyatholaimus helicellus Wieser, 1954. Wieser, 1954 a: 27, fig. 107 a–c; Chile. 8 Paracyatholaimus intermedius (de Man, 1880). De Man, 1880: 16 –17 (= Cyatholaimus intermedius); De Man, 1884: 52 –54, fig. 25 – 25 f (= Cyatholaimus intermedius); Kattegat. Gerlach, 1953 a: 21 –22, Abb. 5; Baltic Sea. Gerlach, 1965: 127 –128, Abb. 9 a–c; Spitzbergen. Bussau, 1990: 170 –172, Abb. 3 A–C; North Sea, coastal dunes. 9 Paracyatholaimus lewisi Coomans, Vincx & Decraemer, 1985. Coomans et al., 1985: 268, fig. 2 A–F; Solomon Islands, freshwater pool on a coral island; no males described. 10 Paracyatholaimus occultus Gerlach, 1956. Gerlach, 1956: 91 –92, Abb. 29 a–c; Kiel Bay. 11 Paracyatholaimus paucipapillatus Gerlach, 1955. Gerlach, 1955: 265 –267, Abb. 7 a–e; El Salvador. 12 Paracyatholaimus pentodon Riemann, 1966. Riemann, 1966: 125 –127, Abb. 31 a–e; North Sea. Platt & Warwick, 1988: 282, fig. 128; East and West Scotland. 13 Paracyatholaimus pesavis Wieser & Hopper, 1967: 268 –269, pl. XVI, fig. 32 a–e; Florida. 14 Paracyatholaimus proximus (Bütschli, 1874). Bütschli, 1874: 49, fig. 30 a–b (= Cyatholaimus proximus); Kiel Bay. De Man, 1922: 239 –240, fig. 28 a, b (= Cyatholaimus proximus); North Sea. Micoletzky, 1924: 140 (to subgenus Paracyatholaimus). 15 Paracyatholaimus pugettensis Wieser & Hopper, 1967. Wieser, 1959: 37 –38, fig. 35 a–c (= Longicyatholaimus quadriseta Wieser, 1959, nec L. quadriseta Wieser 1954); Puget Sound, Washington, USA. Wieser & Hopper, 1967: 265. 16 Paracyatholaimus quadriseta (Wieser, 1954). Wieser, 1954 a: 13, fig. 98 a, b (= Longicyatholaimus quadriseta); Chile. Hopper, 1972: 69 (= Marilynia quadriseta). 17 Paracyatholaimus rotundus Gerlach, 1964. Gerlach, 1964 a: 25, Abb. 2 d–e; Red Sea. 18 Paracyatholaimus saradi Gerlach, 1967. Gerlach, 1967: 30 –31, Abb. 15 a–e; Red Sea. 19 Paracyatholaimus separatus Wieser, 1954. Wieser, 1954 b: 194 –196, Abb. 12 a–c; Mediterranean. 20 Paracyatholaimus spinulosus Jensen, 1985. Jensen, 1985: 253 –254, fig. 7 A–F; Gulf of Mexico. 21 Paracyatholaimus ternus Wieser, 1954. Wieser, 1954 a: 27 –28, fig. 108 a–e; Chile. 22 Paracyatholaimus truncatus (Cobb, 1914). Cobb, 1914: 60 –62, fig. 17 (= Cyatholaimus truncatus); Florida, fresh or brackish water. Micoletzky, 1922: 377 (to subgenus Paracyatholaimus). Finding of Riemann (1970) in a similar habitat at the Caribbean coast of Colombia may be doubtful because of the lesser male body length (1050 vs 1600 µ m), strong conical inner labial papillae, other pattern of four preanal supplementary organs (both posteriormost and penultimate organs are situated at the level of spicules while those of the type specimen are separated by much greater distances). 23 Paracyatholaimus vancouverensis Sharma & Vincx, 1982: 276 –278, fig. 15–23; British Columbia. 24 Paracyatholaimus vitraeus Gerlach, 1957. Gerlach, 1957: 140 –141, Abb. 21 l–o; Brazil. Remarks to species composition of the genus Paracyatholaimus Four species originally assigned to Paracyatholaimus, i.e. choanolaimoides Stekhoven, 1942, effilatus Stekhoven, 1946, major Kreis, 1928 and tyrrhenicus Brunetti, 1949, were later transferred to other genera by various authors (Gerlach & Riemann 1973) and are not considered here. Twenty­seven species of Paracyatholaimus are enumerated in the NeMys (Deprez et al. 2005) where P. parasaveljevi Allgén, 1935 is designated species inquirenda. Here four more other species are considered as species inquirendae because of insufficient type material lacking adult stages and/ or incomplete descriptions: Cyatholaimus chungsani Hoeppli et Chu, 1932; China. The species was shifted to Paracyatholaimus by Meyl (1954) and, missing in the NeMys list, is here considered as species inquirenda because of the very poor original description even lacking details actually indicating its affiliation with Paracyatholaimus. This is one of three species ascribed to Paracyatholaimus which were found in fresh­water habitats. Paracyatholaimus exilis (Cobb, 1898) Micoletzky, 1924 (= Cyatholaimus e. Cobb, 1898); Australia. The original description is based on only a female specimen and lacks illustrations. Paracyatholaimus oistospiculoides (Allgén, 1935) Wieser, 1954 (= Paracanthonchus o. Allgén, 1935); Norway Sea. The original description and drawings based on a single male specimen are too poor to determine the genus. Paracyatholaimus parasaveljevi Allgén, 1935; Norway Sea. Wieser (1954 a) qualified the species as species inquirenda. Paracyatholaimus tenuispiculum (Allgén, 1951) Wieser, 1954 (= Paracanthonchus t. Allgén, 1951); Hawaii. The original description and drawings are based on a single male specimen and lacks many details such as amphids and length of anterior setae. Illustrated guide for species of Paracyatholaimus (Figs 1 & 2, Table 1) The guide is a set of simplified images (Figs 1 & 2) constructed in some accordance with the approved practice of Platt (1984) and others (e.g., Platt & Warwick, 1998). Species of Paracyatholaimus differ from one another in rather fine morphological details concerning mainly length of anterior setae, number of turns in the multispiral amphidial fovea, supplementary organs and copulatory apparatus. The species can neither be disposed in a morphological continuum nor grouped in any evident morphological clusters. Therefore, it is not easy to develop a convenient polytomous or dichotomous key. I arrange the images of species in alphabetical order. An important component of the guide is Table 1, where the most important morphometric data are summarized. TABLE 1. Morphometry of valid Paracyatholaimus species (males). Species Characters L a c o.l.s., μ m am.w., m, amphid, c’ spic., m suppl. n. % c.b.d. number of turnsPublished as part of Tchesunov, Alexei V., 2008, Three new species of free­living nematodes from the South­East Atlantic Abyss (DIVA I Expedition) *, pp. 151-174 in Zootaxa 1866 on pages 153-157, DOI: 10.5281/zenodo.18377

Syringolaimus de Man 1888

Identification of <i>Syringolaimus</i> species <p> Species of <i>Syringolaimus</i> 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 <i>et al</i>. (2009) provided a dichotomous key for fourteen <i>Syringolaimus</i> 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).</p>Published as part of <i>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)</i> on page 483, DOI: 10.11646/zootaxa.4306.4.2, <a href="http://zenodo.org/record/845097">http://zenodo.org/record/845097</a&gt

Paracyatholaimus diva Tchesunov, 2008, sp. nov.

<i>Paracyatholaimus diva</i> sp. nov. <p>Figs 3–6</p> <p> <i>Type material</i>: <b>Holotype:</b> male 1, two paratype males 2 & 3 and one paratype female mounted in glycerin on glass slides. Type specimens deposited in the DIVA nematode collection DZMB­Senckenberg, Südstrand 44, 26382 Wilhelmshaven, Germany.</p> <p> <i>Type locality</i>: DIVA I, Meteor 48/1, Station 325/4, multicorer 8: South­east Atlantic Ocean, 19°58.3'S & 002°59.8'E, depth 5450 m. 14 July 2000.</p> <p> <i>Etymology</i>: the species name is derived from the acronym DIVA.</p> <p> <i>Morphometric data</i>: Table 2.</p> <p> <b>TABLE 2</b>. Morphometry of <i>Paracyatholaimus diva</i> sp. nov.</p> <p> <b>Label Specimens & labels</b> <i>Description</i>. Body cylindrical. Cuticle transversally annulated and punctated. The dots (punctations) about the same size along the body and closely arranged in transversal rows. No clear lateral differentiation in size and position of the dots. The dots become a bit more distinct and convex to the amphid and to the anal region.</p> <p>Anterior end truncate. Mouth opening surrounded by unclear conical lips with hardly visible inner labial sensilla. Outer labial and cephalic sensilla constitute a jointed circle of 6+4 short setae. Four cephalic setae slightly smaller than six outer labial setae. Both outer labial and cephalic sensilla seem to be two­jointed, with the proximal joint thicker and at least twice as long as the distal joint. However, the jointed setae are often difficult to recognize in this species. The jointed nature of the outer labial setae is more evident in the female than in the males.</p> <p>Amphidial fovea large, round or slightly transversally oval in outline, multispirally coiled with about six turns in the males and four turns in the female, situated at a distance from the apex. Amphidial fovea of the female notably smaller than that of the male. Cervical setae about four in number, situated laterally posterior to the amphid. There are very few small setae scarcely distributed along the body.</p> <p>Cuticular pores indistinct in the pharyngeal region but become very obviously crater­shaped more posteriorly Cuticular pores arranged in two sublateral rows from the level of the cardia posteriad. There are 21 lateroventral pores and ~37 laterodorsal pores on the left body side of the holotype male.</p> <p>Cheilostoma cup­shaped, its walls reinforced by triangular rugae apparently twelve in number. A big pointed sclerotized tooth on the dorsal side of the pharyngeal portion of the buccal cavity. There are no smaller opposite teeth, but obscure subventral cuticular hardenings in the buccal cavity.</p> <p>Pharynx evenly muscular throughout its length, widening posteriorly but not forming a true bulb. Internal cuticular lining twisted and folded. Cardia poorly visible. Nerve ring hardly discernible in some specimens. Renette cell not found except an oval body just posterior to the cardia ventrally.</p> <p>Didelphic, ovaries antidromously reflected; anterior ovary situated subventrally to the right of the intestine, posterior ovary subventrally to the left of the intestine. Diorchic; anterior testis outstretched, posterior smaller testis reflexed. Anterior testis situated to the right of the intestine, posterior testis to the left of the intestine. Spicules short, weak, sharply angularly bent, distally pointed, proximally with wide knobs. Gubernaculum paired, composed of two slightly sigmoid­curved platelets parallel to the distal portion of the spicules. Six supplementary organs arranged in a midventral preanal row. They look like thick conical setae one third protruded of cuticle and directed aslant anteriad.</p> <p>Tail of moderate length, consists of proximal conical and distal slender cylindrical portions, with delicate terminal spinnerete tube. There are a few short lateroventral setae on the tail.</p> <p> <i>Diagnosis</i>: <i>Paracyatholaimus</i>. Body length 936–1176 <i>µ</i> m. No lateral differentiation in the cuticle. Outer labial and cephalic setae about 3.5–5 <i>µ</i> m. Amphidial fovea multispiral with six turns in males and four turns in females situated at the level of the dorsal tooth. Buccal cavity armoured with a prominent dorsal tooth and no subventral teeth. Tail consists of anterior conical and posterior slender cylindrical half portions. Diorchic, posterior testis reflexed. Spicules sharply bent, distally pointed, proximally knobbed. Gubernaculum distally narrowed and toothless. Six preanal midventral setose supplementary organs.</p> <p> <i>Differential diagnosis</i>: The new species resembles <i>Paracyatholaimus rotundus</i> Gerlach, 1964 closer than other <i>Paracyatholaimus</i> species. <i>P. rotundus</i> is known from only one male specimen from the Red Sea. <i>P. d i v a</i> sp. nov. differs from <i>P. rotundus</i> by a slightly longer body (936–1176 <i>µ</i> m <i>versus</i> 705 <i>µ</i> m), tail shape (with clearly narrowed posterior half <i>versus</i> conical), six <i>versus</i> four supplementary organs of another shape.</p> <p> <i>P. d i v a</i> sp. nov. shares large multispiral amphidial fovea with 5–6 turns with <i>P. botosaneanui</i> Andrássy, 1973, <i>P. duplicatus</i> Gerlach, 1964, <i>P. paucipapillatus</i> Gerlach, 1955, <i>P. pugettensis</i> Wieser & Hopper, 1967, <i>P. quadriseta</i> (Wieser, 1954) and <i>P. vancouverensis</i> Sharma & Vincx, 1982. <i>P. d i v a</i> sp. nov. differs from <i>P. b o t ­ osaneanui</i> by slightly a thicker body (a 23.8–28 <i>versus</i> 31–33), index c (7.45–8.86 <i>versus</i> 13.5–15), smaller cephalic setae (3–4 <i>µ</i> m <i>versus</i> 10–12 <i>µ</i> m), longer spicules (34–36 <i>µ</i> m <i>versus</i> 26–28 <i>µ</i> m) and six <i>versus</i> four supplementary organs of another shape; from <i>P. duplicatus</i> by shorter body (936–1176 <i>µ</i> m <i>versus</i> 1485 <i>µ</i> m), smaller cephalic setae (3–4 <i>µ</i> m <i>versus</i> 7–8 <i>µ</i> m), relatively shorter nearly conical tail (c’ 3.02–3.43 <i>versus</i> 5.5– 6.5) and arrangement of supplementary organs (three distinct pairs in <i>P. duplicatus</i>); from <i>P. paucipapillatus</i> by shorter body (936–1176 <i>µ</i> m <i>versus</i> 1445–1860 <i>µ</i> m), index c (7.45–8.86 <i>versus</i> 13.9–14.1), much smaller cephalic setae (3–4 <i>µ</i> m <i>versus</i> 8–15 <i>µ</i> m) and six <i>versus</i> two supplementary organs; from <i>P. pugettensis</i> by shorter body (936–1176 <i>µ</i> m <i>versus</i> 1310–2230 <i>µ</i> m), smaller cephalic setae (3–4 <i>µ</i> m <i>versus</i> 5–9 <i>µ</i> m), relatively shorter tail (c’ 3.02–3.43 <i>versus</i> 5.5–6.5) and six <i>versus</i> four to five supplementary organs; from <i>P. quadriseta</i> by smaller cephalic setae (3–4 <i>µ</i> m <i>versus</i> 8–9 <i>µ</i> m) and relatively shorter tail (c’3.02–3.43 <i>versus</i> 6.3); from <i>P. vancouverensis</i> by shorter body (936–1176 <i>µ</i> m <i>versus</i> 1890–1960 <i>µ</i> m), relatively thicker body (a 23.8–28 <i>versus</i> 34–35), wider amphidial fovea (53–63% <i>versus</i> 42% c.b.d.) and relatively shorter tail (c 7.45– 8.86 <i>versus</i> 12.1–16, c’ 3.02–3.43 <i>versus</i> 5).</p>Published as part of <i>Tchesunov, Alexei V., 2008, Three new species of free­living nematodes from the South­East Atlantic Abyss (DIVA I Expedition) *, pp. 151-174 in Zootaxa 1866</i> on pages 157-163, DOI: <a href="http://zenodo.org/record/183775">10.5281/zenodo.183775</a&gt

Pomponema Cobb 1917

Pomponema Cobb, 1917 The genus was revised by Lorenzen (1972). An emended generic diagnosis of Pomponema is provided by Platt & Warwick (1988). According to NeMys (Deprez et al. 2005), twenty­nine Pomponema species have been described up until recently.Published as part of Tchesunov, Alexei V., 2008, Three new species of free­living nematodes from the South­East Atlantic Abyss (DIVA I Expedition) *, pp. 151-174 in Zootaxa 1866 on page 163, DOI: 10.5281/zenodo.18377

Syringolaimus smolae Coelho Lima, Lins, Da Silva & Esteves 2009

<i>Syringolaimus smolae</i> Lima, Lins, Da Silva & Esteves, 2009. <p> Lima <i>et al</i>., 2009: p. 128–130, figs 5–6 (South–West Atlantic, off coast of Brazil, Campos Basin, 750 m, siltclay), one male and one female. Cuticle faintly striated; most prominent striation in the middle of the tail ventrally. Ventral pore at the level of the nerve ring. Tail curved dorsally in both males and females. Caudal glands may be visible but no evident spinneret present. Monorchic. One precloacal papilla present.</p>Published as part of <i>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)</i> on page 482, DOI: 10.11646/zootaxa.4306.4.2, <a href="http://zenodo.org/record/845097">http://zenodo.org/record/845097</a&gt

Syringolaimus striatocaudatus De Man 1888

<i>Syringolaimus striatocaudatus</i> de Man, 1888 <p> 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 <i>Enteromorpha</i>, 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 <i>Syringolaimus</i>.</p>Published as part of <i>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)</i> on page 482, DOI: 10.11646/zootaxa.4306.4.2, <a href="http://zenodo.org/record/845097">http://zenodo.org/record/845097</a&gt

Syringolaimus magdae Coelho Lima, Lins, Da Silva & Esteves 2009

<i>Syringolaimus magdae</i> Lima, Lins, Da Silva & Esteves, 2009. <p> Lima <i>et al</i>., 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.</p> <p> <i>Syringolaimus marisalbi</i> Platonova & Mokievsky, 1994 <b>sp. inq.</b></p> <p> 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 <i>S. striatocaudatus</i>.</p> <p> <i>Syringolaimus nitidus</i> Bussau, 1993 <b>nom. nud.</b></p> <p>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 µm 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.</p>Published as part of <i>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)</i> on pages 481-482, DOI: 10.11646/zootaxa.4306.4.2, <a href="http://zenodo.org/record/845097">http://zenodo.org/record/845097</a&gt

Pomponema proximamphidum Tchesunov, 2008, sp. nov.

<i>Pomponema proximamphidum</i> sp. nov. <p>Figs 7–9</p> <p> <i>Type material:</i> <b>Holotype</b> male N1, two paratype males NN2 & 3 mounted in glycerin on glass slides. Type specimens are deposited in the DIVA nematode collection.</p> <p> <i>Type locality</i>: DIVA I, Meteor 48/1, Station 346/2, Multicorer 3: South­east Atlantic Ocean, 16°17.0'S & 005°27.0'E, depth 5389 m. 27 July 2000.</p> <p> <i>Etymology</i>: The species name reflects the position of amphids close to the labial position.</p> <p> <i>Morphometric data</i>: Table 3.</p> <p> <i>Description</i>. Body cylindrical, slender. Cuticle annulated and punctated with dots. Cuticle heterogeneous: thick, light­refracting, brownish in colour cuticle with sharp annules in the anterior body while thinner, lighter in colour cuticle with less sharply defined annules from about 0.4 pharynx length onwards. Anterior end characterized by large, distinct dots arranged in regular transversal rows becoming smaller towards the midpharynx and fusing thereafter into transversal lines. Lateral differentiations of the body cuticle begin just posterior to the amphidial fovea. Lateral differentiation expressed in a pattern of a sequence of paired big light­refractive dots sharply set off other lateromedian dots of the respective transversal row. The big dots in pairs joined by narrow dots. Space between big lateral dots about 7 <i>µ</i> m at the level of the nerve ring and 4 <i>µ</i> m on the midbody.</p> <p> <b>TABLE 3</b>. Morphometry of <i>Pomponema</i> sp. nov.</p> <p> <b>Character Specimens & labels</b></p> <p> <b>1 (holotype)* 2 (paratype) 3 (paratype)</b></p> <p> <b>Box A N3(7) Box A N9(3) Box A N9(4)</b></p> <p> <b>DIVA I, M 48/1, DIVA I, M 48/1, DIVA I, M 48/1,</b></p> <p> <b>346/2, MuC3 346/2, MuC3 346/2, MuC3</b> *The specimen was slightly flattened while being measured. **Anteriormost – posteriormost supplement</p> <p>***lateral + lateromedian sensilla</p> <p>Inner labial sensilla indistinct. Outer labial and cephalic sensilla constitute together a common circle. Six outer labial setae differ notably to one another: lateral setae much shorter than lateromedian outer labial setae. Four cephalic setae a little shorter than the outer labial lateromedian setae. Cervical and somatic setae not found. There are few fuzzy cuticular pores in the pharyngeal region and no visible pores farther posteriad. Amphidial fovea very large multispiral groove, ventrally coiled, with about five turns. It is half shifted to the apical surface of the head.</p> <p>Buccal cavity differentiated into two compartments. Cheilostoma shaped as a truncate cone; its walls armoured with twelve stick­like ternary (three­storyed) rugae. Stegostoma provided with a big and acute dorsal tooth as well as two smaller subventral acute teeth. At the level of each side of the subventral teeth, a lateroventral row of six to eight tiny two­storyed dentlicles.</p> <p>Pharynx evenly muscular throughout its length, slightly widening posteriorly but not forming a well defined bulb. Nerve ring well visible at the midpharynx. Terminal ampulla of the dorsal pharyngeal gland discernible at the base of the dorsal tooth. Cardia indistinct. There are rather large swallowed particles inside the intestine lumen.</p> <p>Renette ampulla transparent and voluminous; ventral pore situated at a distance of about one third pharynx length from the anterior end.</p> <p>Reproductive system diorchic. Both anterior outstretched and posterior reflected testes situated to the left of the intestine in all the specimens. Vas deferens consists of several parts (from anterior end caudad): medium granulated, finely granulated, homogeneous, and coarsely granulated.</p> <p>Spicules short, arched, distally pointed and proximally widened. Gubernaculum as paired slightly curved plate distally adjoined to spicules. There is a small funnel­like structure with an indented sclerotized rim at each lateral side of the spicule distal tip.</p> <p>Thirteen to fourteen midventral preanal supplementary organs. Each organ consists of a stout cylindrical body and a flat cover with a central opening. The supplementary organs may or may not be elevated above the body cuticle depending on the body curvature. There a small midventral sensilla just anterior to the cloacal opening.</p> <p>Tail relatively long, consisting of proximal conical and slender cylindrical parts. A short terminal spinneret tube at the tail end. There are a few small setae laterally on the conical part.</p> <p> <i>Diagnosis</i>. Male body length 911–1203 <i>µ</i> m. Cuticle heterogeneous: anteriormost cuticle thicker, brownish, with sharp annules in the anterior body while more posterior cuticle thinner, light, with less sharply defined annules. Lateral differentiation expressed in a pattern of a sequence of paired light­refractive dots sharply set off other much smaller lateromedian dots. Inner labial sensilla as conical papillae. Six outer labial sensilla differ notably to one another: labial sensilla as minute setae much shorter than lateromedian sensilla looking like true short setae. Four cephalic setae a little shorter than outer labial lateromedian setae. Amphidial fovea very large, multispiral, with about five turns; half shifted to the apical surface of the head. Stegostoma armoured by a big acute dorsal tooth, two smaller subventral acute teeth and two lateroventral rows of denticles at the level of the subventral teeth. Ventral pore situated at a distance of about one third pharynx length from the anterior end. Diorchic, posterior testis reflexed. Spicules short, arched, distally pointed and proximally widened. Gubernaculum as paired slightly curved plate with a small funnel­like structure with an indented sclerotized rim at each lateral side of the spicule distal tip. Thirteen to fourteen midventral preanal supplementary organs. Tail length 7.45–8.12 anal diameters; its distal cylindrical part 52–62% of the entire tail.</p> <p> <i>Differential diagnosis</i>: <i>P. proximamphidum</i> sp. nov. share the subapical position of the amphidial fovea and distinct lateral differentiation of the somatic cuticle with five other species: <i>P. concinnum</i> Wieser, 1954, <i>P. corniculata</i> Gourbault, 1980, <i>P. mirabile</i> Cobb, 1917, <i>P. multipapillatum</i> Filipjev, 1922 and <i>P. stomachor</i> Wieser, 1954.</p> <p> <i>P. proximamphidum</i> sp. nov. differs from <i>P. concinnum</i> (Chile, 70–80 m) with the index c’ (7.45–8.12 <i>versus</i> 6), longer posterior cylindrical part of the tail (52–62% <i>versus</i> 41%), relative width of the amphidial fovea (55–59% c.b.d. <i>versus</i> 40% c.b.d.), lesser number of supplementary organs (13–14 <i>versus</i> 20).</p> <p> <i>P. proximamphidum</i> sp. nov. differs from <i>P. corniculata</i>, a geographically close species (Angola Basin, 2063–3615 m) with much longer tail (index c 4.00–6.03 <i>versus</i> 11.4–13.5 and c’ 7.45–8.12 <i>versus</i> 2.3–2.5) with longer posterior cylindrical part of the tail (52–62% <i>versus</i> 21%), more anterior position of the ventral pore at about half the distance from the cephalic apex to the nerve ring <i>versus</i> just at the nerve ring (54–60 <i>µ</i> m and 105 <i>µ</i> m, respectively), bigger amphidial fovea (width 9–11.5 <i>µ</i> m <i>versus</i> 7 <i>µ</i> m), lesser number of supplementary organs (13–14 <i>versus</i> 20).</p> <p> The original description of <i>P. m i r a b i l e</i> (no locality indicated by Cobb) misses some significant details and any indication on locality, hence the relation of the new species to <i>P. m i r a b i l e</i> remains unclear. However <i>P. proximamphidum</i> sp. nov. is distinctly separated from <i>P. mirabile</i> in the body length (911–1203 <i>µ</i> m <i>versus</i> >1800 <i>µ</i> m), smooth versus jonted setae of the cephalic ring, smaller amphidial fovea (55–59% c.b.d. <i>versus</i> 93% c.b.d.), lesser number of supplementary organs (13–14 <i>versus</i> 20).</p> <p> <i>P. multipapillatum</i> is known from two thorough descriptions of Filipjev (1922, Black Sea, sublittoral silt) and Lorenzen (1972, Helgoland in the North Sea, 30–34 m). <i>P. proximamphidum</i> sp. nov. differs from <i>P. multipapillatum</i> with much longer tail (index c 4.00–6.03 <i>versus</i> 7.3–10 and c’ 7.45–8.12 <i>versus</i> 3.7–4.5) with longer posterior cylindrical part of the tail (52–62% <i>versus</i> 28–44%), position of the ventral pore (respectively 54–60 <i>µ</i> m and 15–38 <i>µ</i> m from the cephalic apex to the ventral pore), shorter setae of the cephalic ring (2–4.5 <i>µ</i> m <i>versus</i> 4–8 <i>µ</i> m), lesser number of supplementary organs (13–14 <i>versus</i> 15–19).</p> <p> <i>P. proximamphidum</i> sp. nov. differs from <i>P. stomachor</i> (Chile, tidal exposed sand) by smaller body (911– 1203 <i>µ</i> m <i>versus</i> 1950–2170 <i>µ</i> m), longer tail (index c 4–6.03 <i>versus</i> 7.1–8, c’ 7.45–8.12 <i>versus</i> 7), much shorter setae of the cephalic crown (2–5.5 <i>µ</i> m <i>versus</i> 3–18 <i>µ</i> m), smaller amphidial fovea (9–11.5 <i>versus</i> 20 <i>µ</i> m), shorter distance from the cephalic apex to the ventral excretory pore (width 54–60 <i>µ</i> m <i>versus</i> 110–150 <i>µ</i> m), smaller spicules (33–44.5 <i>µ</i> m <i>versus</i> 75 <i>µ</i> m), lesser number of supplementary organs (13–14 <i>versus</i> 15– 19).</p>Published as part of <i>Tchesunov, Alexei V., 2008, Three new species of free­living nematodes from the South­East Atlantic Abyss (DIVA I Expedition) *, pp. 151-174 in Zootaxa 1866</i> on pages 163-169, DOI: <a href="http://zenodo.org/record/183775">10.5281/zenodo.183775</a&gt