Aponema westindicum, Kovalyev, Shota V. & Miljutina, Maria A., 2009

Kovalyev, Shota V. & Miljutina, Maria A., 2009, A review of the genus Aponema Jensen, 1978 (Nematoda: Microlaimidae) with description of three new species, Zootaxa 2077, pp. 56-68 : 63-68

Aponema westindicum sp. n.

Table 1 , Fig 4 A–F, Fig 5 B, D

Type material. Holotype: male, slide No D-1/1.

Paratypes: male, slide No D-1/2-1 and 2 females, slides Nos D-1/2-2 and D-1/2-3.

Locality. Caribbean Sea, Curacao, West-Point. Depth 2– 3 m. Cruise XX of RV “Dmitry Mendeleyev”, 17.02.1978.

Etymology. The name westindicum refers to “from West India ”.

Description. Body stocky, mainly cylindrical, with conical tail (figs. 4A, 4B; 5B, 5D). Cuticle mainly annulated behind the level of long cephalic seta, smooth in the head region. Brownish granules visible in hypoderm.

Head clearly offset by a constriction in cervical region. Cephalic cuticle hardly thickened in comparison with body cuticle. Stoma quite broad, 20.4–23.0 μm long, 8.0–9.0 μm wide. Cheilostoma possessing longitudinal ribs. Oesophastoma cyathiform, with acute protruding dorsal tooth and two small subventral denticles. Cuticle of buccal cavity weakly sclerotized.

continued.

Morphometric data are summarized from sources cited in the list of valid species.

Cephalic sensilla arranged in three circles: anteriormost formed by inner labial papillae, second by six outer labial papilla, and third by mediolateral setae 11.2–11.9 μm long. In males amphidial fovea rounded, monospiral, 8.3 μm (7.1–8.3 μm) wide, occupying 46 (53 %) of c.b.d. In females amphidial fovea of analogous construction, 5.6–6.0 μm wide (37–38 % of c.b.d). Pharynx mostly cylindrical, muscular, weakly thickened around stoma, posteriorly with marked bulb 42 μm (41.0–43.5 μm) x 34.5 μm (34.0–35.5 μm). Cardia roundish-triangular, 12 μm (10.0–12.0 μm) long (about a quarter of the bulb length), 13.5 μm (11.0–13.5 μm) wide. Renette cell lying ventrally to intestine, posterior to cardia, its ampoule and outlet in front of nerve ring.

Testis single, quite long (a third of total body length in holotype), filled with spermatozoa of irregular shape (to 20 μm in size). Vas deferens consisting of closely packed cylindrical cells. Spicules ventrally curved, proximally cephalated, blade up to 4 μm wide, tapered distally and provided with velum. Gubernaculum curved, corpus midway with crura. Supplements not seen, medioventral cuticle not thickened. Three pairs of short subventral setae at 7, 17, 29 μm posterior to cloacal opening (in holotype).

Female reproductive system didelphic-amphidelphic. Ovaries outstretched. Anterior ovary lying on the left side of the intestine, the posterior on the right side. Two pairs of small rounded vulvar glands (ca 8–10 μm in diameter) in one of females, vulva closed by a plug. Tail conical. Caudal glands restricted to tail, with terminal spinneret.

Diagnosis. Aponema westindicum sp. n. is characterized in both sexes by an amphidial fovea situated very close to the anterior of the body, long cephalic setae and a short tail. Males with dorsal apophysis of gubernaculum.

Discussion. The presence of a single anterior testis in A. westindicum allows us to relate it to the genus Aponema Jensen, 1978 . Aponema westindicum sp. n. belongs to the group of Aponema species with conical tail. It differs from A. nanum ( Blome, 1982) comb. n. by having a longer body and different structure of the buccal cavity (see also identification key). From A. bathyalis sp. n. it differs in the amphid position just posterior to the cephalic constriction, by the size of the amphidial fovea (37–53% of c.b.d vs 50–83%) and by the body length (681–797 μm vs 378–478 μm).

Figures

FIGURE 4. Aponema westindicum sp. n.: A—total view of holotype male, B—total view of paratype female, C—tail region of holotype male, D—anterior body part of paratype female, E—head of holotype, F—copulatory apparatus of holotype. Scale: A, B— 75 μm, C— 10 μm, D— 60 μm, E— 15 μm, F— 20 μm.

FIGURE 5. Photomicrographs: A— A. minutissima sp. n., fragment of the testis of holotype male with large spermatozoa, B— A. westindicum sp. n., holotype male, C— A. bathyalis sp. n., copulatory apparatus of holotype male, D— A. westindicum sp. n., paratype female. Scale: A, C— 20 μm, B, D— 50 μm.