Rhabdochona zacconis Yamaguti, 1935

Description (after Moravec, Margolis & Boyce 1981). With characteristics of the genus. Medium-sized worms with smooth cuticle. Mouth approximately hexagonal, slightly compressed dorso-ventrally, surrounded by two large lateral amphids and four small sub-apical papillae. Prostom thick-walled, funnel-shaped, without basal teeth but with 14 teeth projecting anteriorly. Deirids medium-sized, bifurcate, located posterior to middle of vestibule (Fig. 51 A). Tail of both sexes conical, ending in sharp point (Fig. 51 B,E).

Males: body 6.69–10.06 long, 0.122–0.177 maximum width. Prostom 0.018–0.021, vestibule including prostom 0.135–0.207, muscular oesophagus 0.279–0.390 and glandular oesophagus 2.45–4.90 long. Deirids 0.075–0.090, nerve ring 0.192–0.237 and excretory pore 0.303 from anterior end. Pairs of subventral pre-cloacal papillae variable in number; the following combinations were observed: 7+8, 8+9 and 9+9. Another pair was located laterally at level of 3rd subventral pair. Six pairs of post-cloacal papillae present, the 2nd pair lateral, the rest subventral (Fig. 51 B). Longitudinal ventral cuticular ridges anterior to pre-cloacal papillae well developed. Left spicule 0.435–0.510 long and 0.012–0.015 wide at mid-length, shaft representing its anterior half, with its distal tip moderately extended, provided with wide cuticular membrane forming large ventral process (Fig. 51 C). Right spicule 0.108–0.120 long, boat-shaped, sometimes with dorsal barb on distal tip (Fig. 51 D). Length ratio of right to left spicule 1:3.84 to 1:4.47. Tail conical, 0.354–0.411 long, its tip with sharp point (Fig. 51 B).

Females: body 16.32–18.31 long, 0.245– 0.285 maximum width. Prostom 0.030–0.033, vestibule including prostom 0.177–0.210, muscular oesophagus 0.450–0.525 and glandular oesophagus 4.15–5.98 long. Deirids 0.105–0.123, nerve ring 0.264–0.309 and excretory pore 0.414–0.453 from anterior end. Tail conical, 0.273–0.303 long, its tip with sharp point (Fig. 51 E). Vulva post-equatorial, located 6.94 –8.30 from posterior end. Eggs elongate–oval, 0.036–0.039 x 0.021. Each pole of mature eggs (containing larvae) with one, less frequently two, narrow filaments up to 0.57 long (Fig. 51 F).

Site: intestine

Host: Catostomus macrocheilus Distribution: British Columbia Records: Anon. 1978; Arai & Mudry 1983