Spinitectus gracilis Ward & Magath 1917

** Spinitectus gracilis Ward & Magath, 1917

Description (after Mueller & Van Cleave 1932, and Jilek & Crites 1982b). With characteristics of the genus. “Head” region without spines. Four cephalic papillae, and two amphids each with two pore-like openings situated on pseudolabia. Deirids between 1st and 2nd rows of spines. 35 to 45 short sharp spines present per row. Spines absent over lateral lines, and decreasing in number and size posteriorly. Spines <0.015 long. Buccal cavity short, with sharp bend. Width of muscular oesophagus about half that of glandular oesophagus (Fig. 67 A).

Males: body slender, 4.150 (3.852–4.390) long, 0.117 (0.102–0.130) wide. Nerve ring 0.150 (0.142–0.155) from anterior end. Excretory pore between the 4th and 5th spine rows (Fig. 67 A). Muscular oesophagus 0.257 (0.203–0.303), and glandular oesophagus 1.805 (1.607–1.895) long. Alae narrow. Four pairs pre-cloacal and five pairs post-cloacal pedunculate papillae. Right spicule short and thick with 90º bend and thickened proximal portion, distal end pointed, lacks barb [length not reported]. Left spicule long, slender [length not reported]. Tail tip rounded (Fig. 67 B). Area rugosa present.

Females: body slender 6.250 (5.648–7.390) long, 0.155 (0.147–0.163) wide. Nerve ring 0.160 (0.153–0.167) and excretory pore 0.228 (0.203–0.235) from anterior end. Muscular oesophagus 0.229 (0.184–0.243) and glandular oesophagus 1.903 (1.784–2.075) long. Vulva immediately posterior to middle of body. Ovijector well developed. Vagina directed anteriorly (Fig. 67 C). Amphidelphic. Eggs thick-shelled. Tail with spine (Fig. 67 D).

Comment: Choudhury & Dick (1992) discussed discrepancies in the four published descriptions of S. gracilis so the foregoing description should be interpreted with caution.

Site: intestinal lumen

Hosts: Acipenser fulvescens (16, 19, 22); Ambloplites rupestris (16, 19, 27); Ameiurus nebulosus (2, 4); Aplodinotus grunniens (1); Catostomus commersonii (14); Coregonus artedi (7, 10, 12, 14, 20, 24); Coregonus clupeaformis (2, 3, 4, 5, 9, 10, 12, 14); Cottus cognatus (21); Cyprinus carpio (4, 5, 19); Esox americanus vermiculatus (1, 6); Esox lucius (1, 10, 13, 14, 20, 24); Ictalurus punctatus (1); Lepomis gibbosus (2, 3); Lota lota (4, 5, 7, 19); Luxilus cornutus (20, 24); Micropterus dolomieu (4, 5, 27); Moxostoma anisurum (7); Notropis hudsonius (4, 5); Noturus flavus (1); Oncorhynchus nerka (9, 19); Osmerus mordax (4, 5, 16); Perca flavescens (3, 4, 5, 7, 8, 9, 14, 15, 16, 20, 23, 24, 25, 26); Percina caprodes (24); Percopsis omiscomaycus (5, 7, 9, 16, 17, 20, 24); Pomoxis nigromaculatus (4, 5, 7, 19); Prosopium cylindraceum (3, 17); Salvelinus fontinalis x Salvelinus namaycush (9, 11, 19); Sander vitreus (14, 18)

Distribution: Manitoba, Ontario, Saskatchewan

Records: 1. Bangham & Hunter 1939 (ON); 2. Bangham 1941 (ON); 3. Bangham & Venard 1946 (ON); 4. Bangham 1951 (ON); 5. Bangham 1955 (ON); 6. Crossman 1962 (ON); 7. Dechtiar 1972a (ON); 8. Cannon 1973 (ON); 9. Collins & Dechtiar 1974 (ON); 10. Watson 1977 (MB); 11. Dechtiar & Berst 1978 (ON); 12. Watson & Dick 1979 (MB); 13. Watson & Dick 1980 (MB); 14. Poole 1983 (MB); 15. Poole & Dick 1985 (MB); 16. Dechtiar & Christie 1988 (ON); 17. Dechtiar & Lawrie (ON); 18. Dechtiar & Nepszy 1988 (ON); 19. Dechtiar et al. 1988 (ON); 20. Szalai 1989 (MB); 21. Dechtiar et al. 1989 (ON); 22. Choudhury et al. 1990 ((MB, SK); 23. Szalai & Dick 1991 (MB); 24. Szalai et al. 1992a (MB); 25. Carney & Dick 1999 (MB); 26. Carney & Dick 2000 (MB); 27. Choudhury & Perryman 2003 (MB)