Philonema oncorhynchi Kuitunen-Ekbaum, 1933

Arai, Hisao P. & Smith, John W., 2016, Guide to the Parasites of Fishes of Canada Part V: Nematoda, Zootaxa 4185 (1), pp. 1-274 : 57

** Philonema oncorhynchi Kuitunen-Ekbaum, 1933

Description (after Moravec & Nagasawa 1999a). With characteristics of the genus. Body filiform, whitish in

colour, cuticle smooth. Head end rounded, bearing two rings of small papillae: outer ring of four pairs of papillae,

inner ring with four single papillae. Small lateral bifid amphids present ( Fig. 37 A). Mouth opening circular.

Oesophagus comprises short and narrow anterior muscular portion, and longer and wider posterior glandular

portion. Oesophagus enters intestine through valve. Intestine light coloured, relatively wide anterior end. Tail

conical ending in sharp point.

Males: body 13.91–30.16 long, and 0.206–0.412 wide. Muscular oesophagus 0.444–0.762, and glandular

portion 1.218–2.162 long. Nerve ring 0.261–0.391 from anterior end ( Fig. 37 B). Excretory pore not seen. Caudal

end ventrally curved. Tail 0.331–0.566 long. Spicules equal, simple, needle-like, well sclerotized, 0.188–0.396

long. Pre-cloacal papillae: nine pairs small sessile subventral papillae, plus two subventral horn-like outgrowths or

papillae separated by one unpaired median papilla on anterior cloacal lip. Post-cloacal papillae: nine pairs of small

subventral papillae, distance between 2nd and 3rd greater than that between 3rd and 4th pairs ( Fig. 37 C). Females (gravid worms with larvae): body 102.8–185.0 long, and 0.948–1.483 wide. Head end rounded,

cephalic papillae indistinct in lateral view. Muscular oesophagus 0.433–1.092, and glandular portion 1.277–2.019

long. Nerve ring 0.252–0.453 from anterior end ( Fig. 37 D). Excretory pore not seen. Anal opening absent. Vulva

and vagina atrophied. Uterus amphidelphic, occupying most of body space, containing many 1st -stage larvae; it

extends anteriorly to oesophagus level ( Fig. 37 D), and posteriorly a little behind end of intestine ( Fig. 37 E).

Anterior and posterior ovaries reflexed, relatively short ( Fig. 37 D,E).

Larvae from uterus variable in shape and size, 0.392–0.580 long, 0.020–0.028 wide. Head end with small

dorsal tooth. Tail sharply pointed ( Fig. 37 E).

Sites: body cavity, mesenteries, swim bladder

Hosts: Carassius auratus (25); Oncorhynchus clarkii (6); Oncorhynchus gorbuscha (9, 31); Oncorhynchus kisutch (6); Oncorhynchus mykiss (6, 16, 25); Oncorhynchus nerka (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 17, 18, 19, 20, 21, 22, 25, 26, 27, 28, 29, 30, 32, 33, 34, 35); Oncorhynchus tshawytscha (5, 23, 24); Salvelinus malma (6)

Distribution: British Columbia, Ontario, Pacific

Records: 1. Kuitunen-Ekbaum 1933a (PA); 2. Kuitunen-Ekbaum 1933b (PA); 3. Smedley 1933 (BC); 4. Kuitunen- Ekbaum 1937a (BC); 5. Margolis 1952b (PA); 6. Bangham & Adams 1954 (BC); 7. Dombrowski 1955 (BC); 8. Margolis 1956 (BC, PA); 9. Margolis 1957 (BC, PA); 10. Margolis 1963 (BC, PA); 11. Bashirullah & Adams 1966 (BC); 12. Platzer 1966 (BC); 13. Platzer & Adams 1967 (BC); 14. Ko & Adams 1969 (BC); 15. Adams 1969 (EX, BC); 16. Bell & Hoskins 1971 (BC); 17. Lewis 1973 (BC); 18. H. D. Smith 1973 (BC); 19. Adams 1974 (BC); 20. Lewis et al. 1974 (BC); 21. Bell & Margolis 1976 (BC); 22. Boyce & Yamada 1977 (BC); 23. Anon. 1978 (BC); 24. Arai & Mudry 1983 (BC); 25. Bashirullah 1983 (EX, BC); 26. Bashirullah & Adams 1983 (BC); 27. Groot et al. 1984 (BC); 28. Bailey & Margolis 1987 ((BC); 29. Wood et al. 1987 (BC); 30. Bailey et al. 1988 (BC); 31. Dechtiar & Lawrie 1988 (ON); 32. Groot et al. 1989 (BC); 33. Garnick & Margolis 1990 (BC); 34. Adamson et al. 1992 (BC); 35. Després et al. 1995 (BC)

Figures

FIGURE 37. Philonema oncorhynchi Kuitunen-Ekbaum, 1933. A. female, en face view; B. male, anterior end, lateral view; C. male, posterior end, lateral view; D. gravid female, anterior end, with larvae in uterus; E. subgravid female, posterior end, with eggs in uterus. (Redrawn from Moravec & Nagasawa 1999 a)