Sites: intestinal lumen, stomach
Hosts: Coregonus nasus (8); Cottus aleuticus (5); Gadus macrocephalus (5); Gadus morhua (9); Hexagrammos decagrammus (1, 5); Mallotus villosus (6); Nautichthys oculofasciatus (5); Oncorhynchus gorbuscha (2, 4); Reinhardtius hippoglossoides (7)
Distribution: Atlantic, British Columbia, Newfoundland, Northwest Territories, Pacific
Records: 1. Margolis 1977 (PA); 2. Anon. 1981 (BC); 3. Sankurathri et al. 1983 (PA); 4. Anon. 1984 (BC); 5. Ko 1986 (BC, PA); 6. Arthur et al. 1995 (AT); 7. Boje et al. 1997 (AT); 8. Choudhury & Dick 1997 (NT): 9. Khan et al. 2011 (NF)
Comments: Five Ascarophis species are known currently from Canadian fishes. Appy (1981) provided good
descriptions and illustrations for A. arctica, A. extalicola and A. filiformis; the original descriptions of A. morrhuae
and A. sebastodis are relatively poor. Taxonomic problems concern morphology of the head of both sexes, and the
tails of males. Regarding the head, the pseudolabia of A. extalicola have a blunt knob rather than the prominent conical apex of A. arctica and A. filiformis, so Appy (op. cit.) and Ko (1986) suggested that A. extalicola might be related to “ Cystidicoloides ” [species of which have been transferred to Salmonema; see page 100]. Regarding male tails, an area rugosa, narrow caudal alae, six pairs of post-cloacal papillae, and paired phasmids behind the 6th pair of papillae appear to be diagnostic. Appy (op. cit.) pointed out that papillae of the 5th pair are relatively small and ventral to the 6th pair, so earlier workers might have overlooked them. Indeed, Figure 55 B illustrates an A. morrhuae male, redrawn from Berland (1961), apparently with only five pairs of post-cloacal papillae, and structures that are [sic] “possibly the phasmids”. The description of neither A. morrhuae nor A. sebastodis mentions an area rugosa; there is no reference to paired phasmids for A. sebastodis; and caudal alae are not mentioned in the descriptions for either species, although Figure 55 B illustrates them for A. morrhuae. Both A. morrhuae and A. sebastodis should be redescribed and illustrated with special attention to the morphology of heads and tails.