Eucephalobus arcticus A..L O O F 1971, n.sp.

Eucephalobus arcticus n.sp.

(Fig. 4).

Dimensions:

Females (n = 17): L = 0.68 -1. 00 mm; a = 22 -29 (36 in one specimen); b = 3.6-4.5;c = 12-16; V = 6 1- 64; G1 _ 1 = 10-19; G1_2 == 12 -19; G2 = 3 -6.

Males (n = 2): L = 0.76 - 0.91 mm; a = 24 -26; b = 3.7-4.4; c = 16-17; T = 49 + l l - 54 + 10.

Female, holotype: L = 0.93 mm; a = 26; b = 4.2; c = 15; V = 62; G^ = 18;Gi _ 2 = 19; G2 = 4.

Body rather stout, curved slightly to ventral side in death. Cuticle thick, 3 \L on middle of body. Transverse striation shallow, very coarse (2.5 -3 \t). Lateral field one-fifth to one-sixth of body width, with two wings (three lateral lines).

Six lips, each with one large, well offset, forward pointing papilla. Mouth cavity cephaloboid, 1 /15 of neck length. Corpus of oesophagus cylindrical, nearly four times as long as isthmus, from which it is offset by a sharp alteration in tissue. Isthmus slightly thinner than corpus. The nerve ring surrounds the oesophagus just before the base of the corpus. Opposite it is a distinct hemizonid, immediately before which lies the excretory pore. Deirid distinct, located at level of junction of corpus and isthmus, at 71 % of neck length from head end. The terminal bulb occupies three-fifths of the corresponding body width, measuring 23 x 18 (x and possesses a well developed valve.

Female- Gonad cephaloboid, with double flexure behind the vulva; the postvulvar part occupying 37 - 64 % of the vulva-anus distance. The uterus is symmetrical, very spacious; the posterior one does not bear any gonad tissue and measures 26-40 \L or about 1.2 body widths. Dimensions of an intra-uterine egg: 69 x 26 \x. Rectum a little longer than anal body width, slightly widened anteriorly. Postanal pulvillus conspicuous. Tail three anal body widths long (2.6- 3.5; in one specimen 3.9); conoid, tapering regularly to the rounded terminus which bears a large, triangular, slightly ventrally directed, mucro which in some specimens on the dorsal side is not offset. The tail tip is slightly knobbed ventrally.

Male- Posterior end curved about 90 ° to ventral side. Spicules measuring 24 (X,gubernaculum 13 |x;both of normal cephaloboid shape. Two pairs of pre-anal subventral papillae, located 1.2 and 3.2 anal body widths from the anus. Adanal and postanal papillae as in Heterocephalobus elongatus, the anterior subventral caudal papillae lying slightly more anterior (31 %). Testis single, reflexed. Terminus with mucro.

Holotype: Female on slide WT 1132. Paratypes: Sixteen females and two males on slides WT 1133-1141.

Type habitat and locality: Sample 5. Paratypes also in samples 3, 4, 23, 41, 44 and 55. Found furthermore in samples 40, 42, 53 and 54.

This species resembles E. strandi-cornutus (Allgén, 1934), from which it differs by the shallow body annulation and the regularly conoid shape of the female tail. It also resembles Heterocephalobus elongatus. but is much plumper, the uteri are symmetrical and more spacious. From E.paracornutus de Coninck, 1943 it differs by the plump, regularly conoid tail, as well as by larger body size and much coarser annulation.