Paracyatholaimus diva, Tchesunov, Alexei V., 2008

Tchesunov, Alexei V., 2008, Three new species of free­living nematodes from the South­East Atlantic Abyss (DIVA I Expedition) *, Zootaxa 1866, pp. 151-174 : 157-163

Paracyatholaimus diva sp. nov.

Figs 3–6

Type material: Holotype: 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.

Type locality: 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.

Etymology: the species name is derived from the acronym DIVA .

Morphometric data: Table 2.

TABLE 2. Morphometry of Paracyatholaimus diva sp. nov.

Label Specimens & labels Description. 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.

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.

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.

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.

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.

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.

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.

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.

Diagnosis: Paracyatholaimus . Body length 936–1176 µ m. No lateral differentiation in the cuticle. Outer labial and cephalic setae about 3.5–5 µ 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.

Differential diagnosis: The new species resembles Paracyatholaimus rotundus Gerlach, 1964 closer than other Paracyatholaimus species. P. rotundus is known from only one male specimen from the Red Sea. P. d i v a sp. nov. differs from P. rotundus by a slightly longer body (936–1176 µ m versus 705 µ m), tail shape (with clearly narrowed posterior half versus conical), six versus four supplementary organs of another shape.

P. d i v a sp. nov. shares large multispiral amphidial fovea with 5–6 turns with P. botosaneanui Andrássy, 1973 , P. duplicatus Gerlach, 1964 , P. paucipapillatus Gerlach, 1955 , P. pugettensis Wieser & Hopper, 1967 , P. quadriseta (Wieser, 1954) and P. vancouverensis Sharma & Vincx, 1982 . P. d i v a sp. nov. differs from P. b o t ­ osaneanui by slightly a thicker body (a 23.8–28 versus 31–33), index c (7.45–8.86 versus 13.5–15), smaller cephalic setae (3–4 µ m versus 10–12 µ m), longer spicules (34–36 µ m versus 26–28 µ m) and six versus four supplementary organs of another shape; from P. duplicatus by shorter body (936–1176 µ m versus 1485 µ m), smaller cephalic setae (3–4 µ m versus 7–8 µ m), relatively shorter nearly conical tail (c’ 3.02–3.43 versus 5.5– 6.5) and arrangement of supplementary organs (three distinct pairs in P. duplicatus ); from P. paucipapillatus by shorter body (936–1176 µ m versus 1445–1860 µ m), index c (7.45–8.86 versus 13.9–14.1), much smaller cephalic setae (3–4 µ m versus 8–15 µ m) and six versus two supplementary organs; from P. pugettensis by shorter body (936–1176 µ m versus 1310–2230 µ m), smaller cephalic setae (3–4 µ m versus 5–9 µ m), relatively shorter tail (c’ 3.02–3.43 versus 5.5–6.5) and six versus four to five supplementary organs; from P. quadriseta by smaller cephalic setae (3–4 µ m versus 8–9 µ m) and relatively shorter tail (c’3.02–3.43 versus 6.3); from P. vancouverensis by shorter body (936–1176 µ m versus 1890–1960 µ m), relatively thicker body (a 23.8–28 versus 34–35), wider amphidial fovea (53–63% versus 42% c.b.d.) and relatively shorter tail (c 7.45– 8.86 versus 12.1–16, c’ 3.02–3.43 versus 5).

Figures

FIGURE 3. Paracyatholaimus diva sp. nov., entire. A: male N 1 (holotype); B: female (paratype). Scale bars: 100 µ m.

FIGURE 4. Paracyatholaimus diva sp. nov., anterior ends. A: male N 1 (holotype); B: female (paratype). Scale bars: 10 µ m.

FIGURE 5. Paracyatholaimus diva sp. nov., details. A: male N 1 (holotype), anterior body; B: male N 1 (holotype), posterior end; C: female (paratype), posterior end. Scale bars: 50 µ m.

FIGURE 6. Paracyatholaimus diva sp. nov., cloacal region of the male N 1 (holotype). Scale bar: 10 µ m.