Cervonema donghaensis, Hong, Jung-Ho, Tchesunov, Alexei V. & Lee, Wonchoel, 2016

Hong, Jung-Ho, Tchesunov, Alexei V. & Lee, Wonchoel, 2016, Revision of Cervonema Wieser, 1954 and Laimella Cobb, 1920 (Nematoda: Comesomatidae) with descriptions of two species from East Sea, Korea, Zootaxa 4098 (2), pp. 333-357 : 339-340

Cervonema donghaensis sp. nov.

Figs 2–4 , Table 2

Locality. Station ES13: sub-tidal Southern part of East Sea (35˚ 57΄ 25˝ N, 129˚ 37΄ 41˝ E), at a depth of 90 m, in clay sediment.

Material. All the type specimens are deposited in the National Institute of Biological Resources ( Republic of Korea). Holotype: one male NIBRIV0000329853, collected by Kwangsoo Kim at station SE 13 in September 2012, from Research Vessel Hansudan 1. Paratypes: nine males NIBRIV0000329854–NIBRIV0000329862 and nine females NIBRIV0000329863–NIBRIV0000329871 collected by Kwangsoo Kim at station SE 13 in September 2012, from Research Vessel Hansudan 1.

Measurements. See Table 2 for detailed measurements and morphometric ratios.

Description. Males ( Fig. 2 , 4 , Table 2 ). Body elongate, nearly filiform. Cuticle thin, with faint, relatively fine striations throughout body. Punctation in cuticle not visible. Head region distinctly narrowed. Tail conicocylindrical.

Anterior sensilla in three separate crowns. Six inner labial sensilla present as small papillae ( Fig. 4 ). Six outer labial sensilla located about 0.3 head diameter from anterior end, slightly shorter than cephalic setae (80–100% of cephalic setae length). Four cephalic setae located 0.4–0.5 head diameter from anterior end, just after outer labial setae. Somatic setae (about 3.0 µm) scattered randomly on the body, much shorter than cephalic setae. Amphideal fovea large, circular multispiral. Fovea multispiral, coiled ventrally, in about 4.25–5.0 turns.

Buccal cavity very small, conical, its walls not cuticularised and not differentiated, teeth not observed. Pharynx with transverse muscular striation along its entire length. Pharynx slender, cylindrical, expanding to form distinct posterior bulb with very coarse granulation of dorsal pharyngeal gland. Nerve ring at 47–57% of pharynx length from anterior end, surrounded by nerve cell bodies. Opening of secretory-excretory system just posterior to the nerve ring. Cardia round, small, surrounded with intestinal tissue. Ventral gland situated posterior to the cardia.

Reproductive system diorchic, testes opposed. Anterior outstretched testis situated on the left of gut and posterior reflected testis situated on the right of gut. Spermatozoa of ovoid shape with distinct cortical striation. Spicules paired, equal and short, slightly curved, distally pointed, proximally slightly narrowed, cephalated. Gubernaculum paired, with weakly cuticularised pieces, situated laterally to the spicules. Distal cuticularised tips of gubernaculum protrude slightly in cloacal opening along with spicule tips. One short mid-ventral seta located just anterior to the cloaca. Eight minute mid-ventral supplementary papillae observed in precloacal region. Tail consists of proximal conical and distal cylindrical parts (latter 36–55% of tail length). Tail tip slightly swollen, with three long terminal setae (about 5–7 µm long). Other setae (about 3 µm long) arranged irregularly in ventrolateral row on conical parts of the tail. Three caudal glands and spinneret present.

Females ( Fig. 3 , Table 2 ). Similar to male, except body larger and longer than in males. Cylindrical portion of tail slightly longer than in males (49–56% of tail length). Reproductive system didelphic with opposed and outstretched ovaries, anterior ovary situated on the left of gut, posterior on the right of gut. Uteri of both gonads packed with spermatozoa.

Diagnosis and relationships. Cervonema . Body length 1389–1814 µm; a 31–42; b 9.1–11.6; c 9.9–12.2; c’ 4.0–5.2. Outer labial setae 5–7 µm, cephalic setae 6–8 µm. Distance from the apex to amphideal fovea 5–8 µm, less than 1 head diameter. Gubernaculum consisted of lateral pieces and dorsal apophyses 3–8 µm. One precloacal midventral supplementary seta anterior to the cloaca, 3 µm. Eight minute precloacal supplements present.

Cervonema donghaensis sp. nov. can be differentiated from most other species of the genus by having the amphideal fovea less than one head diameter from the anterior end. It is close to C. chilensis , C. hermani , C. proberti and C. proximamphidum in having the amphid at a similar distance from anterior end and having precloacal supplements but differs by the presence of distinct gubernacula. It differs from C. proximamphidum and C. chilensis by having outer labial and cephalic setae of unequal lengths. Cervonema donghaensis sp. nov. also differs from C. proximamphidum in the shape of the posterior widening of the pharynx (oval vs conical) and having distinct muscular striation on the pharynx ( Fig. 2 ). The new species differs from C. chilensis by greater body length in males (1389–1578 µm vs 1192 µm). It can be distinguished from C. proberti by the presence of gubernacula (not observed in C. proberti ), greater body length in males (1389–1578 µm vs 1043–1144 µm), ratio of cephalic setae length to outer labial setae length (1.1–1.3 vs 1.6–2.0) and having jointed outer labial setae (smooth in C. proberti ).

Etymology. The species name donghaensis refers to the sampling location, East Sea, Korea. ‘Donghae’ means ‘East Sea’ in Korean.

Figures

FIGURE 2. Cervonema donghaensis sp. nov., holotype male in lateral view: A, pharynx; B, head; C, anal region; D, tail and precloacal region; E, entire. Scale bars: 20 µm (A, C, D), 10 µm (B) and 50 µm (E).

FIGURE 3. Cervonema donghaensis sp. nov., paratype female in lateral view: A, pharynx; B, head; C, tail; D, vulva; E, entire. Scale bars: 20 µm (A – D) and 50 µm (E).

FIGURE 4. Scanning electron micrographs of Cervonema donghaensis sp. nov. A, male head; B, male mouth and inner labial papillae; C, male cloaca & spicule tip; D, male tail end. Scale bars: 2 µm (B) and 5 µm (A, C, E).