Benthimermis ifremeri, 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 : 29-32

Benthimermis ifremeri n. sp.

( Fig. 5 )

TYPE MATERIAL. — Holotype: Western Atlantic , cruise DEMERABY, stn CP 14, 10°24.32’N, 46°46.02’W, 4800 m depth, 28.IX.1980, immature ( MNHN 335 BF).

ETYMOLOGY. — In honour of the Institut français de Recherche pour l’Exploitation de la Mer (IFREMER). DIAGNOSIS. — The new species has a rounded tail without a terminal process like B. arnaudi Petter, 1983 , B. edouardensis Petter, 1983 , and B. minuta Petter, 1987 . B. ifremeri n. sp. differs from B. arnaudi in a smaller body length (5.3 vs 6.7-6.8 mm); by the absence of caudal terminal knob; by a thinner body (“a” = 32.7 vs 23.9-24.3); by a longer tail (“c” = 70.8 vs 80- 335); by the absence of optically dense ring around the vagina. The new species has a smaller body length than B. edouardensis (5.3 vs 8.6-9.35 mm) and a longer tail (“c”= 70.8 vs 107.5-311.7). The new species possesses a body length twice longer than B. minuta ; a thinner body (“a”= 32.7 vs 17.7-20.0); a longer tail (“c”= 70.8 vs 93.0-162.5). Besides, the trophosome of B. minuta consists of one raw of cells whereas the trophosome of B. ifremeri n. sp. consists of several rows of cells. The three species compared with the new species were described from other regions of the world ocean.

DESCRIPTION

Measurements:L = 5313µm; “a” = 32.7; “c” = 70.8; “V” = 55.3%. Maximal body diameter = 155 µm. Diameter at level of: cephalic sensilla = 27 µm; amphids = 77 µm; midbody = 155 µm; anus = 105 µm. Distance from anterior end to amphid = 58 µm.

Body cylindrical, slightly narrower to anterior end. Anterior and posterior ends rounded. Amphids non-spiral. Amphidial aperture porelike. Amphidial fovea tubiform. Four mediolateral cephalic setae about 4 mm long, thin but sharply thickened basally, i.e. possessing basal cone-form part and thinner setiform distal part. Mouth opening absent, but thin axial string 47 µm length visible in anterior part of the pharynx. Short pharynx devoid of an internal lumen and ending by a glandular thickening. Midgut being a trophosome without visible internal lumen and having two or three big cells in transversal optical section. Rectum looking like a short tube with thin walls. Anus present. Cuticle width in cephalic end about 5 µm, and gradually decreasing to 4 µm at posterior end. Female reproductive system didelphic, amphidelphic, occupying about one fifth of all body length. Ovaries reflected. Vagina short. Neither morphologically differentiated spermatheca nor vulvar glands discovered.

REMARKS

The structure of cephalic setae of the new species (basal cone-form part and thinner setiform distal part, absence of pits around setae) is unique for the genus Benthimermis .

Figures

FIG. 5. — Benthimermis ifremeri n. sp., holotype (MNHN 335 BF); A, cephalic end; B, tail; C, reproductive system; D, total view. Abbreviations: a, amphid; l.-m.ch, lateromedian hypodermal chord; m, somatic musculature; m.ch, median hypodermal chord; ov, ovary; ph, vestigial pharynx; r, rectum; v, vulva. Scale bars: A, B, 50 µm; C, 200 µm; D, 500 µm.