Rhabdochona canadensis Moravec & Arai, 1971

Arai, Hisao P. & Smith, John W., 2016, Guide to the Parasites of Fishes of Canada Part V: Nematoda, Zootaxa 4185 (1), pp. 1-274 : 68

Rhabdochona canadensis Moravec & Arai, 1971

Description (after Moravec & Arai 1971). With characteristics of the genus.

Males (holotype measurements in parentheses): 5.74–8.36 (8.32) long, 0.109–0.150 (0.122) maximum width. Pseudolabia rudimentary. Prostom conspicuously wide, funnel-shaped, without basal teeth, 0.015–0.021 (0.021) long, 0.012–0.015 maximum width. Prostom lined internally with 14 longitudinal ridges, forming small teeth at their anterior ends ( Fig. 42 A,B). Vestibule including prostom 0.120–0.165 (0.165), muscular oesophagus 0.186– 0.306 (0.216), and glandular oesophagus 2.18–3.90 (3.90) long. Small, bifurcate deirids 0.051–0.069 (0.069), nerve ring 0.177–0.207 (0.198), and excretory pore 0.237–0.279 (not located in holotype) from anterior end. Subventral pre-cloacal papillae asymmetrical in holotype (nine on one side, and seven on the other); the following combinations were seen in paratypes: 7+7, 7+9, 8+8 and 9+9 ( Fig. 42 C). Additional pair of lateral pre-cloacal papillae at level of 3rd subventral pair (counted from cloaca). Six pairs of post-cloacal papillae: five subventral and one lateral ( Fig. 42 C). Left spicule conspicuously slender, 0.471–0.525 (0.495) long and 0.06–0.09 wide at midlength [the figures for width from Moravec et al. 1981], with blade representing about the posterior half; distal tip lanceolate and thin, with cuticular membrane, bifurcate ( Fig. 42 D). Right spicule 0.102–0.129 (0.126) long, with dorsally reflected barb distally. Length ratio of right to left spicule 1:3.86 to 1:5.14 (1:3.91). Tail conical, 0.270–0.390 (0.390) long, with sharp terminal spike ( Fig. 42 C).

Females (allotype measurements in parentheses): gravid worms 9.88–27.92 (14.84) long, 0.190–0.408 (0.245) maximum width. Prostom wide, 0.021–0.033 (0.030) long. Vestibule including prostom 0.144–0.195 (0.186), muscular oesophagus 0.300–0.510 (0.480), and glandular oesophagus 3.26–5.07 (4.52) long. Deirids 0.063–0.078 (0.072), nerve ring 0.219–0.270 (0.237), and excretory pore 0.351–0.420 (0.369) from anterior end. Tail conical, 0.216–0.309 (0.231) long, terminating in sharp spike. Vulva post-equatorial, 4.27–13.15 (5.90) from posterior end of body. Mature eggs oval, embryonated, 0.036–0.042 x 0.018– 0.021 (0.036–0.042 x 0.018–0.021), with one or two long filaments on each pole. Fully mature eggs usually with two filaments on one pole and only one filament on the other pole ( Fig. 42 E); however, often two filaments on both poles. Filaments very long (ca 0.6) with relatively wide bases and ends sometimes frayed.

Site: intestine

Hosts: Catostomus commersonii (10, 11); Cottus sp. (5); Couesius plumbeus (1, 8); Esox lucius (1); Hiodon

alosoides (10, 11); Margariscus margarita (9); Moxostoma anisurum (10, 11); Noturus flavus (1);

Oncorhynchus mykiss (3, 5); Percopsis omiscomaycus (10, 11); Chrosomus eos (9, 12); Phoxinus neogaeus

(9); Platygobio gracilis (1); Rhinichthys cataractae (1, 6, 7); Salvelinus malma (2, 4); Sander vitreus (1);

Semotilus atromaculatus (9); Semotilus corporalis (9)

Distribution: Alberta, British Columbia, Manitoba, Ontario

Records: 1. Moravec & Arai 1971 (AB); 2. Anon. 1978 (BC); 3. Pybus & Samuel 1978 (AB); 4. Arai & Mudry

1983 (BC); 5. McAllister & Mudry 1983 (AB); 6. Dechtiar & Christie 1988 (ON); 7. Dechtiar & Lawrie 1988

(ON); 8. Dechtiar et al. 1988 (ON); 9. Dechtiar et al. 1989 (ON); 10. Szalai 1989 (MB); 11. Szalai et al. 1992

(MB); 12. Marcogliese et al. 2001 (ON)

Figures

FIGURE 42. Rhabdochona canadensis Moravec & Arai, 1971. A. female, en face view; B. female, anterior end, dorsal view; C. male, posterior end, ventral view; D. distal tip of left spicule; E. mature egg. NB: scale bars were not provided in the original for either A. or D. (Redrawn from Moravec & Arai 1971)