Eudorylaimus megodon, A..L O O F, 1971

P. A. A. LOOF, 1971, FREELIVING AND PLANT PARASITIC NEMATODES FROM SPITZBERGEN, COLLECTED BY MR. H. VAN ROSSEN, Mededelingen Landbouwhogeschool Wageningen 71, pp. 1-86 : 73-76

Eudorylaimus megodon n.sp.

( Fig. 25 ; Diagram 5).

Dimensions:

Females (n = 4): L = 2.01-2.64 mm; a = 24- 30; b = 3.9 -4.0; c = 27 -41; V = 6 - 1145 - 51 13 " 1 6.

Female, holotype: L = 2.64 mm; a = 25; b = 4.0; c = 34; V = 64916.

Male not found.

Body very robust, large, curved to ventral side, especially in the posterior part. Cuticle very thick: 7 (x in neck, 8 \L in mid-body, 10-12 jx on base of tail; with thin, sharply demarcated outer layer. About ten ventral and three dorsal pores in oesophageal region; two more ventral ones opposite anterior part of mid-gut. Lateral chords one-sixth of body diameter.

Lip region offset by a shallow constriction, its width about one-quarter of body diameter at base of oesophagus. Lips with amalgamated bases; the papillae of the inner circle protrude distinctly. Amphids nearly two-thirds of corresponding body width.

Odontostyle large and robust, 31-38 |x long; in five fourth-stage juveniles the adult odontostyle measures 28 -39 jx. The length of the odontostyle is 1.2-1.7 x width of lip region. The aperture occupies about one-third of its length. Basal portion linear, 48-63 \x long. Guiding ring 'single'.

Oesophageal characters (one female): The oesophagus begins to widen at 47 % and attains its full width at 59 % of its length from head end. DO lies about the latter level, the distance DO- DN is 30 fx. The SXN lie a small distance apart, distinctly behind the middle of the distance DN - S2N; both are distinct, the anterior one somewhat smaller. S2N well developed. Locations:

DO 59%; 8 ^ 77%; S2N 88 %; K = 85;

DN 63 %; SXN2 79 %; S2O 90 %; K ' = 87.

DO- DN 4.4 %; dist. 2.4 %;

Cardia conoid, 48 jx long, 20 jx wide at base.

Vulva of the transverse type, vagina heavily sclerotized. Gonads two, opposed, reflexed, without sperm; in the holotype the anterior gonad is reflexed to past the vulva. Dimensions of two intra-uterine eggs: 82-93 x 43 jx. Tail ventrally arcuate, with blunt tip, the distal part usually slightly finger-shaped; tail length 1.2-1.8 anal body widths. Cuticle on tail with fine transverse striae. Distinct saccate bodies ventrally in the tail. Papillae: two pre-anal subdorsal pairs; one lateral post-anal pair. Tail in some specimens with distinct terminal core. Rectum as long as anal body width, prerectum twice to thrice as long.

Holotype: Female on slide WT 1225 . Paratypes: Three females on slides WT 1226-1228 .

Type habitat and locality: Sample 1. Paratypes from samples 42 and 62. Juveniles found also in samples 3, 5, 11, 15, 25, 41, 54 and 67.

Discussion. - This is one of the group oflarge Eudorylaimus species recorded chiefly from mountainous or arctic regions, comprising E.uniformis (Thorne, 1929) , E.acuticauda apud Steiner, 1916; E.vestibulifer (Micoletzky, 1922) ; E.vestibulifer apud Thorne & Swanger, 1936 and E.alleni Brzeski, 1962 . See Fig. 26.

E. uniformis was described from the Rocky Mountains and has been repeatedly reported from Northern Europe (Filipjev, vide Thorne & Swanger, 1936; van Rossen & Loof, 1962.) Thirteen type specimens were available for study. Dimensions:

Females (n = 8): L = 2.41- 2.79 mm; a = 23-31; b = 4.3 -5.2; c = 31-46; V = 1 8 -2148 - 52 1 6 - 20; odontostyle = 23 -26 |x; basal portion = 37 -41 fx.

Males (n = 5): L = 2.27 - 2.66 mm; a = 22-28; b = 4.0-4.5; c = 25 -38; spicules = 90-109 [x; odontostyle = 23 -27 [x; supplements = 12-16.

Odontostyle 1.1-1.3 X width of lip region. This species resembles E. megodon , but differs clearly in some details, especially the much thinner cuticle (3 -4;x in neck and mid-body, 6-7 (x on base of tail), the shorter odontostyle and basal portion. Furthermore the labial papillae of the second circle protrude more strongly; the tail never has distinct saccate bodies, at most there are some small ones laterally or subventrally; and the tail is curved regularly to the terminus, the distal part never being offset finger-like.

E. uniformis apud van Rossen & Loof has a thick cuticle, slightly finger-shaped distal part of the tail and an odontostyle of 29 [x and thus must be regarded E. megodon .

E. acuticauda apud Steiner, 1916, described from Novaya Zemlya, was identified with E. uniformis by Thorne & Swanger (1936). As odontostyle length is 26 u,, this may be correct.

E. vestibulifer was described from the Austrian Alps. Two male type specimens were available. Dimensions: L = 2.38 -2.42 mm; a = 27 -29; b = 5.9- 6.2; c = 40 - 46; spicules = 94-99 [x; supplements = 21-22. This species is distinguished clearly by the narrow, cap-like lip region, offset by a deep constriction and narrower than the adjoining neck; by the relatively very short oesophagus; and by the short odontostyle: 15 [x or 0.8 X width of lip region.

E. vestibulifer apud Thorne & Swanger, 1936, described from the Rocky Mountains, U. S.A., clearly differs from E. vestibulifer by the long odontostyle: 24 jx. This species is herewith renamed E. coloradensis nom. nov.

E.alleni was described from Spitzbergen. Distinguished by an odontostyle length of 21 |x (a paratype had 22 (x) or 0.9 lip region widths; the tail is curved very strongly and the vulva appears longitudinal.

These five species can be distinguished as follows:

1. Lip region narrow, cap-like; odontostyle length 15 [x vestibulifer .

Lip region not cap-like, odontostyle longer 2.

2. Length of odontostyle 28 - 39 fx; cuticle very thick megodon .

Length of odontostyle under 27 jx 3.

3. Tail curved to nearly 180°; odontostyle length 21 - 23 [x alleni .

Tail curved only weakly; odontostyle length 23 -27 |x 4.

4. Supplement series begins within reach of spicules uniformis .

Supplement series begins anterior to spicules coloradensis .

In sample 28 a female was found coming close to E. megodon , but differing by larger size, posterior vulva and the presence of sperm in the gonads. Dimensions: L = 3.12 mm; a = 31;b = 4.3; c = 45; V = 155420; odontostyle = 33 [x. Tail with saccate bodies, curved very weakly ( Fig. 26 , G- H).

Figures

FIG. 25. Eudorylaimus megodon n.sp., female. A: head end; B: oesophagus base; C-D: vulva; E: entire specimen; F: tail.

FIG. 26. A-F: Eudorylaimus megodon n.sp., female. A-C: head end; D-F: tail. G-H: E.lmegodon, female. G: head end; H: tail. I-N: E.uniformis (Thome), female type specimens. I-K: head end; L-N: tail. O-P: E.vestibulifer (Micoletzky), male type specimens, head end. Q-R: E.alleni Brzeski, female. Q: head end; R: tail.