Onchocerca jakutensis (Gubanov, 1964)

Bosch, Felix, Manzanell, Ralph & Mathis, Alexander, 2016, First description of Onchocerca jakutensis (Nematoda: Filarioidea) in red deer (Cervus elaphus) in Switzerland, International Journal for Parasitology: Parasites and Wildlife 5 (2), pp. 192-197 : 194

3.2. Morphology of O. jakutensis

The living worms are transparent opalescent, white-yellowish filarioids. Females are much longer than males. Mouth orifice 1.5 M m in diameter. Oesophagus divided in anterior muscular part and slightly longer posterior glandular part.

3.2.1. Male of O. jakutensis ( Fig. 3a ‾ d)

The description is given for the same specimen which was also used for PCR/DNA sequencing and SEM. (In addition measurements of another entire male and of the posterior part of a further male specimen are given in parentheses).

Body length 36 mm (40 mm), tapering gradually within about 6 mm towards anterior end, from a width of 180 M m (160 M m, 170 M m) at midbody to 90 M m (90 M m) at end of oesophagus and more rapidly tapering to 60 M m (50 M m, 50 M m) in diameter at cloaca. Cuticle with thin transverse annulations, 2.5 M m apart at midbody, narrowing towards both ends. Oesophagus length 670 M m (530 M m), glandular posterior part 360 M m (280 M m). Nerve ring close to end of muscular oesophagus at 250 M m (220 M m) from anterior end ( Fig. 3d ). Tail 130 M m (110 M m, 110 M m) long, coiled ventrad, flattened or slightly concave on ventral side ( Fig. 3a ).

Spicules unequal and dissimilar. Left spicule 275 M m (260 M m, 220 M m), right 90 M m (90 M m, 110 M m) long, both with well developed head. Proximal shaft cylindrical, distal part modified in both. Left spicule: distal part slightly longer than shaft, thinned to membrane with margins bent ventrad to form tube, very fine membrane forming pointed tip of spicule. Right spicule: distal half flattening to concave groove with strong knob on dorsal distal end. In protruded position, the right spicule serves as gubernaculum for the left spiculum. No gubernaculum present ( Fig. 3b ‾ c).

Two phasmids ventro-lateral near tip of tail with conspicuously protruding flaps. Five pairs of pericloacal papillae and 2 pairs close to tail tip, in proximity to phasmids ( Fig. 3a ‾ b). No unpaired precloacal papilla present ( Fig. 4a,b ). Considerable individual variation in placement and size of papillae (note in Fig. 3b the two very small papillae in pericloacal group and the distal pair on tail tip). In two of three specimens one pair of papillae set between cloacal group and group on tail tip.

3.2.2. Female of O. jakutensis ( Fig. 3e ‾ f)

Description is given of 4 entire females. In addition measurement of the specimen which was also used for PCR/sequencing is given in parentheses.

Body length 705 ‾ 780 mm (810 mm). Oesophagus 600 ‾ 800 M m (720 M m), glandular part slightly longer than anterior, muscular part. Vulva posterior to oesophagus, 1260 ‾ 1500 M m (870 M m) from anterior end ( Fig. 3e ). Body diameter 310 ‾ 320 M m (310 M m) at midbody, gradually tapering in anterior part to 120 ‾ 130 M m (130 M m) diameter at end of oesophagus, tapering more rapidly posteriad to 65 ‾ 105 M m (110 M m) diameter at anus. Tail nearly cylindrical, 90 ‾ 165 M m (170 M m) long with rounded tip, bearing two flapped phasmids subapically ( Fig 3f ).

Outermost layer of cuticle thickened in intervals to conspicuous transverse annulations, which fade out towards lateral fields. Annulations rough in appearance, forming jagged lines ( Fig. 5 ). Some single annuli bifurcated or interrupted towards lateral fields. Internal medullar part of cuticle forming transversely oriented, cushion-like striae, with the appearance of square cells in transverse sections. External annuli to striae in the ratio 1:4 ( Fig. 6 ). External annulation smoothing out towards head and tail end of body, becoming smaller and narrower as in males ( Fig. 3f ).

3.2.3. Description of micro fi lariae from O. jakutensis from uterus

Microfilaria without sheath. Long and thin, specimens measured in oviduct close to vulva 260 ‾ 270 M m long, 6 M m wide. Cuticle with fine transverse annulation, 0.5 M m apart ( Fig. 7 ). Anterior end unevenly rounded with subapical protrusion, in some microfilariae slightly swollen ( Fig. 3g ). Tail tapering to fine tip. The distribution of terminal nuclei is depicted in Fig. 3g.

Figures

Fig. 3. O. jakutensis male and female (bars: 100 Mm): a. Tail of male with five pairs of pericloacal and two pair of closely spaced terminal papillae. b. Tail of another male with more distantly spaced papillae on tail end.Left spicule protruding. c. Spicules in ventral view.d. Head end of male.e. Head end of female with vulva.f. Posterior end of female with conical tail in ventral view, annulations indicated on sides. g. Microfilaria with terminal distribution of nuclei.

Fig. 4. a and b: Posterior end of O. jakutensis male with 5 pairs of pericloacal papillae without unpaired precloacal papilla.

Fig. 5. External cuticular annulation (A) of O. jakutensis female with interruption over lateral field.

Fig. 6. O. jakutensis female: Ratio of cuticular annulation (A) to medullar striae (S) 1:4.

Fig. 7. Microfilaria showing transverse annulation and irregular shape of swollen anterior end (magnitude of annulation and swelling might be exaggerated by artefact of fixation).