Parachromagasteriella arctica, Allgén, 1953

Allgén, C. A., 1953, Terrestrial nematodes from Jan Mayen, Annals and Magazine of Natural History 12 (6), pp. 665-688 : 682-683

Parachromagasteriella arctica , sp. n. (Fig. 9.)

Dimensions.- Body -l e n g t h=l.2 2 6 mm., max. width=0.0 3 0 mm., oesophagus= 0.197 mm., t a i l=0.0 8 2 mm., v u l v a=0.6 2 5 mm., α=4 0.8 7, β =6.26, γ,=14.95, V =5 0.9 8 per cent.

I n the sample from L2 was found a single specimen (a female? of a n Araeolaimoid, which seems t o resemble this group o f nematodes not only in its general shape b u t also in the presence o f oeell0e a n d in the shape a n d structure o f the lateral organs. With respect t o the last-named organs it is very similar to the genus Parachromagasteriella , described by the author (1933) from Norway, from which it differs only in the presence o f ocell~e.

The body is, on the whole, o f even thickness and tapers only gradually t o w a r d s the head a n d scarcely noticeably in ti'ont of the anus.

Cuticle smooth. The head is rounded a n d the foremost part slightly demarcated by a constriction from the rest of the head, a n d is j u s t in this constriction provided with four submedian bristles, measuring half the corresponding head-diameter.

Buccal cavity (tube) thin. Lateral organs rather remarkable, of a shape characteristic o f the Araeolaimoidea. They are situated 9tz behind the front end, simply spiral-shaped, with a posterior branch, and, as stated above, very similar to those of the marine genus Parachromagasteriella Allg 6n. T h e y measure in transverse section 3 ~, i.e. exactly 1/3 of the corresponding body-diameter.

Ocell a e situated 36 µ behind the f r ont, end, colourless, cube-shaped. Cephalad and caudad to the oeell a e the cuticle shows some sporadic submedian hairs.

(O esophagus elongated, about evenly thick, without bulb.

Immediately in front of the lateral organs the ventral gland opens, the duct of which is dilated as an ampulla at the level o f the ocell a e. The gland itself is probably situated 0.163 ram. caudad to the (esophagus.

I t is very large, of uniform structure and provided with a nucleus in its posterior part.

The tail is slemler, cylindro-conical, in the posterior part more sharply narrowed, thinned, at the end swollen, with end tip. The anterior half contains three large glands with nuclei.

The vulva is situated almost e x a c t l y in the middle of the body. Femalc organs are strongly developed, with the egg cells arranged in a single row.

This species is closely related to the marine species Parachromagasteriella (~ylindricauda, described from some adult specimens by the author (1933, p. 111, pl. xvii, fig. 72 a-c) from the Trondheimsfiord (litteral region of the biological station a t Trondheim).