Abstract / Introduction / Summary:
In Japan, Argulus coregoni Thorell, 1864 is usually regarded as a parasite of salmoniform fishes, such as those belonging to two families (Salmonidae and Plecoglossidae), but this parasite has also been reported from several fish species of other taxonomic groups. In this study, A. coregoni is briefly described based on specimens collected from the body surface of a dark chub Nipponocypris temminckii (Temminck and Schlegel, 1846) (Cypriniformes: Xenocyprididae) at 47 m elevation in the lower reaches of the Iwaki River, a tributary of the Chikusa River, at Iwaki in Kamigori, Hyogo Prefecture, central Japan, on 30 June 2012. In particular, one female specimen of A. coregoni is examined in detail for its morphology and characterized by six plumose setae on the posterior margin of each coxa of the fist legs and 62 and 63 supporting rods in the marginal membranes of the first maxillae. The second leg coxa of this specimen does not bear any protuberance but has one plumose seta on the posterior margin. Dark chub has been reported as a host of A. coregoni in two other prefectures, central Japan, where this fish species commonly occurs in the upper and middle reaches of rivers. It is likely that dark chub serves as a significant host for A. coregoni in these reaches in central Japan.
