Benthimermis filiformis Petter, 1987

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 : 23-29

Benthimermis filiformis Petter, 1987

( Figs 1-3 ; Tables 1; 2)

Benthimermis filiformis Petter, 1987: 571 , 572, fig. 4.

TYPE MATERIAL. — Holotype: Norway Sea , 64°24.3’N, 1°43.9’E, 2615 m, 19.VII.1975, mature ( MNHN 37 BC); paratypes: Norway Sea, 69°29.2’N, 10°11.6’E, 2957 m, 27.VII.1975, 1 juvenile ( MNHN 38 BC); Norway Sea, 73°28.2’N, 10°06.6’W, 2973 m, 7.VIII.1975, 1 mature ( MNHN 54 BC).

MATERIAL EXAMINED. — 7 fertile (see Tables 1 and 2 for details).

DESCRIPTION

Measurements are presented in Table 2. Only females were found. Body cylindrical, long. Anterior end in shape of rounded cone. Posterior end conical, possessing a terminal spine from 60 to 110 µm long. For most of the specimens, terminal caudal spine completely cuticular with a longitudinally or obliquely striated core, but terminal spine of the specimen No. 6 having a cytoplasmic core with some vesicle-like includings. Cuticle about 2.5 µm thick at anterior and posterior body part, and about 1.5 µm thick at midbody. Cuticle of apical cephalic part thinner (about 1 µm) in some specimens. Stratification of cuticle usually visible at anterior part of caudal spine. Mouth opening absent. Four mediolateral papilloid cephalic setae (1.5-2.0 µm long) insert- ed in tiny pits. Amphids non-spiral. Amphidial aperture looking like a transversally oriented ovals of about 2.0 µm width. Amphidial fovea tubiform. Somatic sensilla appearing as pores connected with hypodermal glands in lateral chords. Such sensilla only found in several specimens. Pharynx looking like a non-muscular string devoid of internal lumen. Midgut a multicellular trophosome devoid internal lumen and consisting of four cells at cross-section ( Fig. 3 ). Cell borders of trophosome clearly visible. Rectum looking like a tube with thin walls. Anus appearing as narrow channel inside cuticle or absent. Female reproductive system didelphic, amphidelphic, occupying about one quarter of all body length.

Ovaries reflected. Egg diameter about 10.0 mm. Neither morphologically differentiated spermatheca nor spermatozoa nor vulvar glands observed.

REMARKS

B. filiformis was described on three specimens (two mature and one juvenile females) from the Norwegian Sea (64°- 73°N, 10°W- 10°E, depth 2615-2957 m). The present new specimens were found in very distant regions, but they agree with the original description of B. filiformis in shape of the tail, construction of the gonad and the trophosome, in the body length and “V” index (3700-4700 mm and 46.8-56.8% respectively in the original description). But the new nematodes do not correspond with the original description for “a” and “c” (38.6-53.3 and 36.2-53.9 respectively vs 46.3-58.8 and 49.5-74.0 respectively). Besides, the distance from the anterior end to the amphids varies, and is less then in original description (42-121 vs 100-110 µm). The body length is greater than in the original description in most new specimens (4000-5516 vs 3700- 4700 µm). It seems to the author, in spite of these distinctions, that establishment of a new species is not rational, because there are no gaps between ranges of character measurements of new and earlier described specimens.

Benthimermis hureaui Petter, 1983 ( Fig. 4 ; Tables 3; 4)

Benthimermis hureaui Petter, 1983a: 7 , 8, fig. 4.

TYPE MATERIAL.— Holotype: S Indian Ocean, 46°02.0’S, 49°08.5’E, 980 m, 28.IV.1976, ( MNHN 153 BB); paratypes: same locality, 5 ( MNHN 154 BB).

MATERIAL EXAMINED. — 2 immature (see Tables 3 and 4 for details).

DESCRIPTION

Measurements are presented in Table 4. Body cylindrical, slightly narrower at anterior and posterior ends. Posterior end in shape of a truncated cone. Amphids non-spiral. Amphidial apertures pore-like, about 2 µm in diameter. Four mediolateral papilloid cephalic setae 3-4 µm long inserted in tiny pits. Pharynx looking like a non-muscular string devoid of an internal lumen. Specimen No. 2 possessing slight channel in cuticle instead of mouth, as well as vestigial rectum and anus. Cuticle of this specimen thicker at cephalic apex; borders between trophosomal cells distinct. Borders between trophosomal cells of specimen No. 1 indistinct, rectum and anus absent. Cuticle gradually thickened from 2-3 µm at anterior part of body to 4-5 µm at posterior part. Female reproductive system didelphic, amphidelphic, occupying about one quarter of total body length. Ovaries reflected. Neither morphologically differentiated spermatheca nor spermatozoa nor vulvar glands discovered.

REMARKS

B. hureaui was originally described from six specimens collected in the more western French Southern and Antarctic Islands (southern part of the Indian Ocean, 46°2’S, 49°8.5’E, 980 m depth). The new specimens were found in other regions remote from one another. Nevertheless, there is an evident close similarity between them and type specimens, except an absence of sclerotic ring around the vagina, which is mentioned in the original description. Besides, there are no rectum and anus in one specimen, whereas all specimens described by Petter (1983a) possess it. However, basing on these distinctions, an establishment of a new species is not rational.

Figures

FIG. 1. — Benthimermis filiformis Petter, 1987, (see Tables 1 and 2 for locations and measurements of specimens); A, reproductive system of specimen No. 3; B, total view of specimen No. 3; C-E, cephalic end of specimen No. 4; F, cephalic end of specimen No. 3; G, tail of specimen No. 4; H, tail of specimen No. 3. Abbreviations: a, amphid; m, somatic musculature; o, oocytes or eggs; ov, ovary; t, trophosome. Scale bars: A, 100 µm; B, 500 µm; C-H, 50 µm.

FIG. 2. — Benthimermis filiformis Petter, 1987, (see Tables 1 and 2 for locations and measurements of specimens); A, cephalic end of specimen No. 1; B, tail of specimen No. 1; C, cephalic end of specimen No. 6; D, tail of specimen No. 6; E, F, cephalic end of specimen No. 2; G, tail of specimen No. 7. Abbreviations: a, amphid; l.ch, lateral hypodermal chord; m, somatic musculature; ph, vestigial pharynx; s.s, hypodermal gland connected with somatic sensillum; t, trophosome. Scale bars: 50 µm.

FIG. 3. — Benthimermis filiformis Petter, 1987, (see Tables 1 and 2 for locations and measurements), cross-section at level of trophosome of specimen No. 4 (reconstruction based on TEMphotos). Abbreviations: c, cuticle; l.ch, lateral hypodermal chord; l.-m.ch, lateromedian hypodermal chord; m, somatic musculature; m.ch, median hypodermal chord; t, trophosome. Scale bar: 10 mm.

FIG. 4. — Benthimermis hureaui Petter, 1983, (see Tables 3 and 4 for locations and measurements of specimens); A, total view of specimen No. 2; B, cephalic end of specimen No. 2; C, cephalic end of specimen No. 1; D, reproductive system of specimen No. 2; E, tail of specimen No. 2; F, tail of specimen No. 1; G, region of the vulva of specimen No. 1. Abbreviations: a, amphid; h.c, hypodermal cells; l.ch, lateral hypodermal chord; m, somatic musculature; ov, ovary; ph, vestigial pharynx; t, trophosome; v.g, vulvar glands. Scale bars: A, 500 µm; B-G, 50 µm.