Dorylaimus (Subg. Doryllium) groenlandicus, Ditlevsen, Hjalmar, 1927

Ditlevsen, Hjalmar, 1927, XXII. Free-living Nematodes from Greenland, Land and Freshwater., Meddelelser om Gronland 22, pp. 175-189 : 175-177

Dorylaimus (Subg. Doryllium) groenlandicus n. sp.

Locality: Disco. Above the Arctic Station. At a brook . 19. 8. 1926. Steinböck and Reisinger.

Female: Length 2,5 mm. α 25; ß = 6; y = 50.

Vulva 43,3 %.

Only one specimen was secured, a fully developed female. Although this specimen in many respects agrees well with the D. macrodorus of DE MAN, so well that there can be no doubt about its belonging to the subgenus Doryllium , it differs, on the other side, so much from the European form that I have found it natural to establish a new species for the Greenland specimen.

Most important is perhaps the size of the Greenland specimen which remarkably exceeds the dimensions indicated for European specimens, the length of which, according to MICOLETZKY, is between 0,9 and 117 mm. But in other respects too it differs rather considerably.

In the front, end the body begins to taper at about the level of the base of the oesophagus; it then tapers evenly oeso- till the level of the proximal end of the spear, from where it tapers rather quickly unto the front end. The head isrounded, but lips obvious, and papillae were are observed; at its no no base the openings of the large lateral organs are situated; they are seen in profile in the figure 10. The spear is long and, as usual, it is possible to distinguish two parts, which are, in the species under con- sideration, of exactly the same length. According to the figure of DE MAN, the proximal part is in the European form, at any rate in the specimen figured, inconsiderably longer than the distal part. The two parts are very different in structure; the distal half consists of the proper spear, strongly chitinized on and thick-walled, the lumen in its interior is obvious but very narrow, and the apical opening is found GH the side immediately behind the tip. The proximal half is relatively weakly chitinized, and the lumen in its interior is increasing towards the base; it is provided with three projecting wings of a somewhat other shape than in the European species, the difference being easily seen, when comparing my figure with the figure of DE MAN (Pl. XXVI, fig. 110 a) in his great monograph of the Dutch free-living Nematodes (1884). The distal half is, as in the European species too, surrounded by a sort of sheath or gubernaculum, which is presumably able to manage the movements of the long spear.

The oesophagus is relatively short in the specimen from Disco. While DE MAN indicates the value of ß to 4—4 1⁄2 DE, in Dutch specimens, the same proportion is 6 in D. groenlandicus ; its distal part is very narrow, then it suddenly widens at about the beginning of the hindmost third or somewhat more ( fig. 11 ).

The female pore is found somewhat in front of the middle, and the ovaries are symmetrical and reflexed. The tail is very short and rounded, nearly semiglobular in shape ( fig. 12 ).

Finally, I shall add that only the distal part of the spear is replaced during the moult. Already STEINER has stated this fact in 1914 for his D. macrodoroides , and this also holds good of D. groenlandicus and of the following species as well, presumably of all species, belonging to the subgenus Doryllium . Besides, it is a question if D. macrodorides Steiner is to be referred to this subgenus.

Figures

Fig. 11. Dorylaimus groenlandicus. Hind part of the oesophagus.

Fig. 12. Dorylai- mus groenlandicus. Hind part.