Aponema ninae, Portnova, 2009

Portnova, Daria, 2009, Free-living nematodes from the deep-sea Håkon Mosby Mud Volcano, including the description of two new and three known species *, Zootaxa 2096 (1), pp. 197-213 : 209-212

Aponema ninae sp. n.

Figures 5 , Table 6

Type material: 6 males, 4 females. Holotype: male in glycerin slide No. D–1/14–3. Paratypes: males, Nos. from D-1/14 to D-1/17; females, Nos. from D-1/14 to D-1/15.

Type locality: Norwegian Sea, Håkon Mosby Mud Volcano, southern rim, depth 1288m and 1287m. Sediment from the pogonophoran fields.

Etymology: named in honour of the author’s mother Nina V. Portnova.

Description: Body short, slender. Cuticle thin and finely striated. Striation is easily visible all over the body. Four rows of pores associated with hypodermal glands situated sublateral along the whole body.

Amphidial fovea distinctly sclerotized and circular, with interruption in the posterior part 4–5 µm, in diameter (about 44.4–55.5 % of c.b.d). Distance from cephalic end to anterior border of amphidial fovea 10–12 µm. Head small, offset by a slight constriction, with four cephalic setae, 2.5–3 µm long. Inner and outer labial sensilla not visible using light microscope. Somatic setae 2–4 µm long, scattered along the body.

Stoma small, narrow and weakly sclerotized. The dorsal thickening of cuticle observed in buccal cavity. This thickening resembles the subventral tooth described by other authors. Obvious dorsal and subventral teeth not present. Oesophagus cylindrical and muscular along its entire length. Posteriorly it is enlarged into spherical bulb 18 µm by width and 20 µm by length. Intestine gleam examined. Cardia small, oval. Glandular body of renetta cell sacciform, extended, with granular content.

Single anterior testis to the left side of intestine. Spicules are short, curved, slightly widened and cephalated proximally, 18.3 µm (arch), 12.2 µm (chord). Gubernaculum strongly sclerotized with wide and bevelled top to the apophyses, 6.1 µm long. Sperm cells of irregular form, densely filled testis. Precloacal supplements absent.

The female reproductive system didelphic, posterior and anterior ovaries of equal length, outstretched. The ovaries located to the right of the intestine. The width of the biggest formed eggs in the oviduct was 18–28 µm.

Tail long, slender, narrowed, with drop–shaped tip, 3.2–3.6 a.b.d in males and 3.8–4.4 a.b.d. in females. One caudal seta on the terminal part of the tail, 3–4 µm long.

b, c and c’).

Diagnosis: Body short, cuticle thin and striated. Amphidial fovea circular in outline with interruption in the posterior part. Monorchic, anterior testis to the left side of intestine. Gubernaculum with wide, beveled on the top apophysis. The female reproductive system didelphic, both ovaries similar in length, outstretched. Tail elongated, narrowed and the end of the tail drop–shape, tip thickened with caudal setae.

Discussion: The new species differs from the all known Aponema species by its small length (352–382.5µm). It mostly resembles A. mnazi , A. nympha , A. decramerae and A. torosa . The new species of Aponema differs from A. mnazi Mithumbi & Vincx, 1999 by curved spicules and lack of precloacal supplement. A. ninae sp.n. differs from A. nympha Bussau & Vopel, 1999 and A. decramerae Mithumbi & Vincx, 1999 by the absence of sexual dimorphism in diameter of amphidial fovea. It most resembles A. torosa Lorenzen, 1973 . However, the new species differs by shorter body (352–382.5 µm vs. 740 µm), shorter spicules (18.3 µm vs. 35–37 µm) and slender tail.

Figures

FIGURE 5. Aponema ninae sp.n., sp.n., details. A: Holotype male, total view; B: holotype male, cephalic region; C: holotype male, tail region; D: paratype female, tail region; E: paratype female, vulva. Scale bars: A–C 50 µm; D–E 100 µm.