Rhabdochona ovifilamenta Weller, 1938

Arai, Hisao P. & Smith, John W., 2016, Guide to the Parasites of Fishes of Canada Part V: Nematoda, Zootaxa 4185 (1), pp. 1-274 : 77-79

Rhabdochona ovifilamenta Weller, 1938

Synonyms: Rhabdochona laurentiana Lyster, 1940 : Rhabdochona fortunatowi Dinnick, 1931 of Kussat (1969); Rhabdochona sp. of Arai & Kussat (1967)

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

Males (three complete and three fragments): body 6.55–8.02 long, 0.095–0.136 maximum width. Pseudolabia rudimentary. Prostom relatively narrow, funnel-shaped, with indistinct basal teeth, lined internally with ribs forming forwardly projecting teeth (exact number not determined). Vestibule including prostom 0.111–0.138, muscular oesophagus 0.255–0.300, and glandular oesophagus 1.90–3.59 long. Relatively small bifurcate deirids 0.051–0.078, nerve ring 0.156–0.204, and excretory pore 0.237–0.264 from anterior end. Pairs of subventral precloacal papillae variable in number: the following combinations were observed—6+7, 7+9, 8+9 and 9+10. Another pair was located laterally at level of 4th subventral pair. Six pairs of post-cloacal papillae present, the 2nd pair lateral, the rest subventral ( Fig. 49 A). Left spicule 0.390–0.420 long, slender, with lanceolate distal tip, and “slightly

outlined” bifurcation with fine cuticular membrane ( Fig. 49 B). Right spicule scoop-shaped, 0.105–0.117 long with

reflected barb at tip. Length ratio of right to left spicule 1:3.52 to 1:3.78. Tail conical, 0.303–0.372 long, with

distinct cuticular spike.

Females (three complete and two fragments): body 11.75–21.76 long, 0.204–0.258 maximum width.

Pseudolabia rudimentary. Prostom thick–walled with distinct basal teeth, 0.030–0.039 long, and 16 teeth projecting

forwardly ( Fig. 49 C). Vestibule including prostom 0.090–0.135, muscular oesophagus 0.276–0.558, and glandular

oesophagus 1.60–4.42 long. Relatively large, “somewhat bifurcate“ deirids 0.039–0.060 ( Fig. 49 D), nerve ring

0.126–0.210, and excretory pore 0.243 from anterior end. Vulva of younger females slightly pre-equatorial, in

larger females distinctly post-equatorial, 6.23–8.98 from posterior end. Eggs oval, 0.036–0.042 x 0.018–0.021.

Mature eggs embryonated. Entire surface covered with fine protuberances and numerous, short thread-like

filaments ( Fig. 49 E); filaments distributed uniformly over entire surface of most eggs but, in some, filaments

appear restricted to area near poles. Tail conical, 0.294–0.315 long, with short cuticular spike. Comment: as already noted, Moravec & Arai (1971) suggested that R. ovifilamenta and R. milleri might be

conspecific.

Site: intestine

Hosts: Catostomus catostomus (3, 4, 7); Catostomus commersonii (1, 8, 9, 11, 12); Catostomus platyrhynchus (4, 7, 8); Perca flavescens (5, 6, 10); Salvelinus fontinalis (2, 13)

Distribution: Alberta, Ontario, Quebec

Records: 1. Lyster 1940 (QC); 2. Choquette 1948a (QC); 3. Kussat 1966 (AB); 4. Arai & Kussat 1967 (AB); 5. Tedla & Fernando 1969a (ON); 6. Tedla 1969 (ON); 7. Kussat 1969 (AB); 8. Moravec & Arai 1971 (AB); 9. Dechtiar & Christie 1988 (ON); 10. Dechtiar & Lawrie 1988 (ON); 11. Dechtiar & Nepszy 1988 (ON); 12. Dechtiar et al. 1989 (ON); 13. Marcogliese & Cone 1991a (QC)

Figures

FIGURE 49. Rhabdochona ovifilamenta Weller, 1938. A. male, posterior end, lateral view; B. left spicule, distal tip; C. female, en face view; D. female, anterior end, dorsal view; E. mature eggs. NB: scale bars were not provided in the original for either B. or C. (Redrawn from Moravec & Arai 1971)