Abstract / Introduction / Summary:
Two specimens of Argulus japonicus Theile, 1900 were collected from a silver crucian carp Carassius sp. (Cypriniformes: Cyprinidae) in the middle reaches of the Kurose River at Misono-u (34°23′56″N, 132°44′23″E) in Higashi-Hiroshima, Hiroshima Prefecture, western Honshu, Japan, on 10 May 2006. These specimens, comprising one female and one male, were found on the body surface of one of the seven silver crucian carp examined. Previously, a crustacean parasite was recorded as A. japonicus from farmed carp in Hiroshima Prefecture without any information on its morphology, locality, and attachment site. Thus, the present collection represents the first specimen-based record of A. japonicus from Hiroshima Prefecture. The specimens are briefly described: they are characterized by a single plumose seta on the posterior margin of the coxa of each of the first legs and 47–51 supporting rods in the marginal membranes of the first maxillae. These numbers differ from those ones (4–9 plumose setae and more than 60 supporting rods) reported from a morphologically similar species, Argulus coregoni Thorell, 1864, which also occurs in Hiroshima Prefecture.
