Hysterothylacium brachyurum Ward & Magath 1917

** Hysterothylacium brachyurum Ward & Magath, 1917

Synonyms: Contracaecum brachyurum (Ward & Magath, 1917) Van Cleave & Mueller, 1934; Thynnascaris brachyura (Ward & Magath, 1917) Margolis & Arthur, 1979

Description (after Van Cleave & Mueller 1934, and Rye & Baker 1984). With characteristics of the genus. Lips large and prominent with well developed interlabia. Lateral alae arise from the interlabia between the subventral and dorsal lips and extend posteriorly to about the level of the posterior end of the preventriculus. A pair of minute, blind-ending deirids are located within the alae at nerve ring level. Nerve ring about 0.5 behind anterior end (Fig. 79 A). Preventriculus 6.0–7.0 long, with “a clearly defined ventriculus”. Intestinal caecum 5.6 long, ventricular appendix relatively short, about 1.0 long. Tail tip of both sexes with few relatively large spines, sharply pointed (Fig. 79 B).

Males: about 60 long and 0.9 wide. Spicules equal, about 0.84 long. Arrangement of male caudal papillae not clear.

Females: about 80 to 90 long and 1.0 wide. Vulva “some distance” anterior to middle of body. Eggs in utero 0.060 x 0.050.

Comments: Hysterothylacium brachyurum should be redescribed, especially as it is the type species of the genus. Moreover, an account of the life-history of H. brachyurum —like that provided by Rye & Baker (1992) for H. analarum —does not appear to be available. In view of the possibility that larvae of H. brachyurum occur in the organs and tissues of Canadian fishes the taxon is adorned with a double asterisk. H. brachyurum has been reported frequently from a variety of fresh-water hosts throughout North America but, as Rye & Baker (1984) pointed out, in most surveys no voucher specimens were deposited in permanent collections so identifications cannot be confirmed; there is evidence that H. brachyurum has been confused in the past with H. analarum and Raphidascaris acus (Rye & Baker 1984).

Sites: intestinal lumen, liver, mesenteries, pyloric caeca

Hosts: Ambloplites rupestris (4, 7, 8, 18, 19); Anguilla rostrata (3); Coregonus artedi (10, 14); Culaea inconstans (22); Esox lucius (4, 5, 7, 8, 10, 15, 16, 18, 19, 20, 21); Esox masquinongy (4, 7, 8, 18); Etheostoma exile (4, 7); Lepomis gibbosus (2, 18); Lota lota (3, 6, 8, 9, 11, 17, 19, 21); Micropterus dolomieu (2, 4, 7, 18, 20, 21); Micropterus salmoides (1, 2, 4, 7); Moxostoma anisurum (8); Notemigonus crysoleucas (4, 7); Notropis atherinoides (4, 8); Noturus flavus (21); Perca flavescens (12, 18, 19, 20, 22); Percopsis omiscomaycus (4, 7, 8, 21); Salvelinus fontinalis (3, 19, 22); Salvelinus fontinalis x Salvelinus namaycush (9, 13, 21, 22); Salvelinus malma (9, 11, 17); Salvelinus namaycush (9); Sander canadensis (8); Sander vitreus (4, 7, 8, 12, 18, 21) Distribution: Alberta, British Columbia, Manitoba, Ontario, Quebec

Records: Bangham & Hunter 1939 (ON); 2. Bangham 1941 (ON); 3. Bangham &Venard 1946 (ON); 4. Bangham 1951 (ON); 5. Worley & Bangham 1952 (QC); 6. Bangham & Adams 1954 (BC); 7. Bangham 1955 (ON); 8. Dechtiar 1972a (ON); 9. Mudry & Anderson 1977 (AB); 10. Watson 1977 (MB); 11. Anon. 1978 (BC); 12. Anthony 1978b (ON); 13. Dechtiar & Berst 1978 (ON); 14. Watson & Dick 1979 (MB); 15. Watson & Dick 1980 (MB); 16. Anthony 1983 (ON); 17. Arai & Mudry 1983 (BC); 18. Dechtiar & Christie 1988 (ON); 19. Dechtiar & Lawrie 1988 (ON); 20. Dechtiar & Nepszy 1988 (ON); 21. Dechtiar et al. 1988 (ON); 22. Dechtiar et al. 1989 (ON)