Benthimermis pseudominuta, Miljutin, 2004

Miljutin, Dmitrij M., 2004, New findings of deep-sea nematodes of genus Benthimermis Petter, 1980 (Nematoda, Benthimermithidae) with description of seven new species, Zoosystema 26 (1), pp. 21-48 : 40

Benthimermis pseudominuta n. sp. ( Fig. 11 )

TYPE MATERIAL. — Holotype: Western Atlantic , cruise DEMERABY, stn KG 21, 10°24.85’N, 46°46.65’W, 4800 m, 25.IX.1980, 1 ( MNHN 329 BF).

ETYMOLOGY. — The name points to the superficial resemblance with B. minuta Petter, 1987 .

DIAGNOSIS. — Until now the single species B. laubieri was known to possess outstretched ovaries in the genus Benthimermis . B. pseudominuta n. sp. differs from B. laubieri in the shape of the posterior end (rounded vs pointed respectively), body length (2781 vs 5200- 6700 µm respectively), and thicker body (“a” = 23.2 vs 32.0-55.8 respectively).

DESCRIPTION

Measurements: L = 2781 µm; “a” = 23.2; “c” = 86.9; “V” = 66.3%. Maximal body diameter = 120 µm. Diameter at level of: cephalic sensilla = 22 µm; amphids = 86 µm; midbody = 120 µm; anus = 61 µm. Distance from anterior end to amphid = 109 µm. Length of: female reproductive system 606 µm; anterior ovary = 206 µm; posterior ovary = 243 µm; anterior oviduct = 25 µm; posterior oviduct = 140 µm. Maximal size of oocytes inside ovary 50 × 50 µm.

Body stout and sausage-shaped, slightly narrowed at anterior and posterior ends. Anterior and posterior ends rounded. Amphidial apertures pore-like, about 2.5 µm in diameter. Four mediolateral cephalic setae about 3.5 µm long, inserted in small pits. Mouth opening absent. Short pharynx devoid of an internal lumen and looking like a thin string. Midgut resembling a trophosome without visible internal lumen and consisting of two to four rows of cells. Rectum in the form of short tube with thin walls. Anus present. Cuticle width about 4.0 µm at midbody, and slightly decreasing to anterior and posterior ends. Female reproductive system didelphic, amphidelphic, occupying about one fifth of total body length. Ovaries outstretched. Vagina short. Optically dense ring visible around vagina. No distinct uterus. Eggs inside oviducts absent. Neither morphologically differentiated spermatheca nor vulvar glands observed.

REMARKS

Oocytes of the new species are not numerous and very large. The size of the eggs of B. pseudominuta n. sp. is only comparable with the size of eggs of B. megala Petter, 1987 , the biggest species of genus Benthimermis , which reaches 17 cm long. The hosts of B. pseudominuta n. sp. are unknown. However, the small number of eggs in this species suggests that successful invasion of hosts is only possible in relatively dense host population.

Figures

FIG. 11. — Benthimermis pseudominuta n. sp., holotype (MNHN 329 BF); A, cephalic end; B, tail; C, reproductive system; D, total view. Abbreviations: a, amphid; l.-m.ch, lateromedian hypodermal chord; m, somatic musculature; o, oocytes or eggs; od, oviduct; ov, ovary; ph, vestigial pharynx; r, rectum; t, trophosome; v, vulva. Scale bars: A, B, 50 µm; C, 200 µm; D, 500 µm.