Trophomera elegantis, Miljutin & Miljutina, 2009

Miljutin, Dmitry M. & Miljutina, Maria A., 2009, Description of Bathynema nodinauti gen. n., sp. n. and four new Trophomera species (Nematoda: Benthimermithidae) from the Clarion-Clipperton Fracture Zone (Eastern Tropic Pacific), supplemented with the keys to genera and species *, Zootaxa 2096 (1), pp. 173-196 : 179

Trophomera elegantis sp. n.

Fig. 3 ; Table 2

Type material: Holotype: one gravid female, collection number MNHN-BN494 .

Type locality: 13°55.63’N, 130°12.20’W, 4900 m depth, 2–5 cm sediment layer, 28.05.2004, submersible “Nautile”, station 1597-5 CL 06.

Etymology: From Latin elegans/ elegantis as adj. (slender, well-proportioned).

Description: Female. Body cylindrical, with fine cuticular transversal striation visible using light microscope; anterior and posterior ends in shape of rounded cone. Cuticle thickness approximately 2 µm along whole body. Amphidial apertures pore-like, 2 µm in diameter, located at 1.3 c.b.d. from anterior end. Amphidial fovea 3.5–4.0 µm in diameter; visible under cuticle. There are four submedian, thick papillae-like, cephalic setae 2.0–2.5 µm long at half the c.b.d. of their insertion from anterior end. Two cervical papilloid sensilla 1 µm long visible laterally before and behind amphid. Mouth opening reduced to a thin apical channel in cuticle. Pharynx a non-muscular, cellular mass devoid of an internal lumen; thin, axial, tube-like structure approximately 10 µm long visible in anterior part of pharynx only. Cardia absent. Midgut, an oligocellular trophosome without internal lumen and consisting of 1 row of cells at most part of body length; borders between cells indistinct. Trophosomal cells filled with large hyaline granules; density of these granules decreasing from anterior and posterior ends towards mid-body region. Rectum vestigial, in shape of hardly distinguishable duct. Anus also vestigial, visible as a thin transverse line/bar in cuticle. Female reproductive system didelphic, amphidelphic, occupying approximately 1/6 of total body length. Ovaries reflected, both about 120 µm long; anterior one lying at right side of body, and posterior one at left side. Oviducts short, with thin walls. Uterus with several mature eggs 24x23 µm in size. Neither morphologically differentiated spermatheca nor spermatozoa observed. Hyaline ring representing a circular vaginal sphincter visible around vagina. Caudal glands absent.

Host unknown.

Male, juveniles: unknown.

Differential diagnosis: T. elegantis sp. n. resembles T. iturupiensis Rubtzov & Platonova, 1974 , T. hureaui (Petter, 1983) ( Petter 1983b) , and T. conicauda ( Petter, 1987) by the shape and tail characteristics (tail in shape of rounded cone; ratio c’ is 1.5; ratio “maximum c.b.d. / anal c.b.d.” is between 1 and 2).

The new species differs from T. iturupiensis by its shorter body length (1.5 mm vs. 26–38 mm), by the size of the cephalic sensilla (2.0–2.5 µm vs. 30–32 µm), by the structure of the trophosome (consisting of one row of cells vs. several cells on the sagittal optical section).

T. elegantis sp. n. differs from T. hureaui by its shorter body length (1.5 mm vs. 2.5–3.8 mm); by the smaller length of the mature, female genital system (occupying 1/6 body length vs. 1/4–1/3 body length); by the relatively bigger size of the eggs (ratio “c.b.d. at the uterus level / maximum egg diameter” = 1.8 vs. 4.0–5.0); by the caudal tip shape (rounded vs. pointed).

T. elegantis sp. n. differs from T. conicauda by its shorter body length (1.5 mm vs. 5.2–6.8 mm); by a thicker body (a = 37.3 vs. 49–58); by the relatively bigger size of the eggs (ratio “c.b.d. at the uterus level / maximum egg diameter” = 1.8 vs. 3.0). Each ovary of T. elegantis contains only 10–20 oocytes, whereas, in T. conicauda , number of oocytes in each ovary reaches hundred or more.

T. elegantis sp. n. resembles T. minutissima sp. n. by parameters of its female genital system (short reflected ovaries, short oviducts, few oocytes, and comparatively large mature eggs (ratio “c.b.d. at the uterus level / maximum egg diameter” is approximately 2 in both species). T. elegantis sp. n. differs from T. minutissima by its tail shape (in shape of rounded cone vs. rounded); and by its longer and thinner tail (c = 36.3 vs. 81.8 and the ratio “tail length / anal body diameter” = 1.5 vs. 0.55).

Figures

FIGURE 3. Trophomera elegantis sp. n., female, holotype. A, total view; B,C, cephalic end, lateral view; D, female genital system; E, posterior end. Abbreviation: t = trophosoma.