Benthimermis petterae, 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 : 34-37

Benthimermis petterae n. sp.

( Figs 8 ; 9 ; Table 5)

TYPE MATERIAL. — Holotype: Western Atlantic , cruise DEMERABY, stn KG 24, 10°22.7’N, 46°44.7’W, 4800 m, 26.IX.1980, mature ( MNHN 330 BF); allotype: stn KG 04, 8°8.62’N, 49°4.65’W, 4436 m, 12.IX.1980, 1 immature ( MNHN 323 BF); paratype: same station as holotype, 1 immature ( MNHN 330 BF).

ETYMOLOGY. — In honour of Dr Annie Petter (MNHN), who first discovered and described the family Benthimermithidae .

DIAGNOSIS. — Females of B. petterae n. sp. are distinguished from females of B. laubieri , the most resembling species, in the absence of anus and rectum, and in the absence of optically dense ring around the vagina. The amphidial fovea of B. petterae n. sp. is pocket-shaped, while the amphidial fovea of B. laubieri is tubiform. The cuticle of the female of B. petterae n. sp. thickens at the anterior and posterior ends unlike that of B. laubieri . The ovaries of B. petterae n. sp. are reflected, whereas the ovaries of B. laubieri are outstretched.

The male of the new species shows some resemblance to B. diploptera Petter, 1981 , B. leptosoma Petter, 1981 , B. aptera Petter, 1982 , B. australis Petter, 1983 , B. rosaliae Tchesunov, 1988 in shape of tail and construction of the male reproductive system (two testes arranged consecutively). However, the new species differs from those species in number of supplementary organs (10 vs 18-68, 14-38, 19, 15- 24, and 11-15, respectively) and in the morphology of the posterior testis possessing a small caecum in its anterior part. Furthermore, the male of the new species differs from the male of B. diploptera in absence of postamphidial part of cervical alae; from male of B. leptosoma in absence of cervical alae at the apical part of the head. The cervical alae of male of B. australis are less wide than the cervical alae of the new species. The male of B. aptera has no cervical alae at all. The male of B. petterae n. sp. also resembles the male of B. improvisa n. sp. in the shape of the tail and the number of supplementary organs (10). However, the male of B. petterae n. sp. differs from the male of B. improvisa n. sp. in morphology of the male reproductive system (two testes vs one testis); in spicule length (49 vs 28 µm); in absence of the small round gland at the level of the amphids on the ventral side of the body, which is present in the male of B. improvisa n. sp.

DESCRIPTION

Male

Measurements: L = 5812 µm; “a” = 77.5; “c” = 70.0. Maximal body diameter = 75 µm. Diameter at level of: cephalic sensilla = 28 µm; amphids = 63 µm; midbody = 75 µm; anus = 50 µm. Distance from anterior end to amphid = 85 µm.

Body thread-like, cylindrical. Anterior end in shape of a rounded cone. Posterior end conical and acute. Mouth opening absent. Four mediolateral cephalic setae about 5 µm long inserted in tiny pits. Amphids non-spiral. Amphidial aperture resembling a pore of 5 µm in diameter. Amphidial fovea tubiform. Cuticle width 4-5 µm along entire body. Cervical alae of 64 µm length and 8 µm height right ahead amphids. Pharynx looking like a non-muscular string devoid of internal lumen. Midgut being a trophosome without visible internal lumen and at midbody consisting of one or several rows of big cells. Rectum and anus present. Male reproductive system long, its anterior end almost reaching anterior end of trophosome. Two testes placed one after the other and linked together by joint spermaduct. Posterior testis at its anterior part having a small caecum directed forward. Spicules straight, 49 µm long, without a gubernaculum. Ten supplementary organs anterior to anus.

Female

Measurements are presented in the Table 5. Body cylindrical, slightly narrowed to anterior and posterior ends. Anterior end in shape of a rounded cone. Posterior end conical and acute, terminal part of tail elongated, completely cuticular, without any longitudinal or oblique striae. Amphidial aperture in shape of a transversally oriented oval of about 2 µm width. Amphidial fovea funnel-shaped. Four mediolateral cephalic setae about 3 µm long set in small foveae. Mouth opening absent, but tiny apical pit visible at cephalic end. Short pharynx devoid of an internal lumen and looking like a thin string ending by a glandular thickening at posterior end. Midgut resembling a trophosome without visible internal lumen and consisting of about 10 rows of big cells. Neither rectum nor anus found. Cuticle width about 8 µm in apical part of head, from 3 to 5 µm at level of midbody, and from 6 to 8 µm in posterior part of tail. Regular fine annulation observable with an optical microscope. Female reproductive system didelphic, amphidelphic, occupying about one quarter of total body length. Ovaries reflected. Vagina short. Vulvar glands present around vagina. Morphologically differentiated spermatheca not observed.

Figures

FIG. 8. — Benthimermis petterae n. sp., holotype (MNHN 330 BF); A, total view; B, C, cephalic end; D, tail; E, posterior testis; F, anterior testis. Abbreviations: a, amphid; gd, gonoduct; l.a, lateral alae; ph, vestigial pharynx; r, rectum; s, spicule; su.or, supplementary organ; t, trophosome; te, testis. Scale bars: A, 1000 µm; B-F, 50 µm.

FIG. 9. — Benthimermis petterae n. sp.,; A-E, H, allotype (MNHN 323 BF); F, G, paratype (MNHN 330 BF); A, total view; B, tail; C, D, cephalic end; E, reproductive system; F, tail; G, cephalic end; H, body wall at the anterior end, laterally. Abbreviations: a, amphid; c.su, cuticle surface; l.ch, lateral hypodermal chord; I.-m.ch, lateromedian hypodermal chord; m, somatic musculature; od, oviduct; ov, ovary; ph, vestigial pharynx; t, trophosome; v.g, vulvar glands. Scale bars: A, 500 µm; B-D, F-H, 50 µm; E, 200 µm.