Abstract / Introduction / Summary:
Two adult females of Argulus japonicus Thiele, 1900 were previously reported from a rosy bitterling Rhodeus ocellatus (Kner, 1866) (Cypriniformes: Cyprinidae: Acheilognathinae) in Kumamoto City, Kyushu, western Japan, but no morphological information was given. In this study, the two females are re-examined for their morphology. They are identical to the descriptions of A. japonicus from Japan and characterized by a single plumose seta on the posterior margin of the coxa of the first leg and 50–52 supporting rods per first maxilla. These characters can be used to distinguish A. japonicus from a morphologically similar congeneric species Argulus coregoni Thorell, 1864, which is known to infect various freshwater fishes including bitterlings in Japan.
