Abstract / Introduction / Summary:
Morphological characters of female and male Argulus japonicus Theile, 1900 are reported using three specimens (one female and two males) collected from a common carp Cyprinus carpio Linnaeus, 1758 (Cypriniformes: Cyprinidae) in Lake Izunuma (38º43’09″N, 141º06’09″E), Miyagi Prefecture, northern Honshu, Japan. The specimens are particularly characterized by the first pair of legs each with a single plumose seta on the posterior margin of the coxa and 46–51 supporting rods per first maxilla. These characters are useful to differentiate A. japonicus from a morphologically similar species Argulus coregoni Thorell, 1864, that also occurs in the inland waters of the same prefecture. This paper compiles the records of fish disease-causing argulid branchiurans from northern Honshu published between 1982 and 2017. These branchiurans were mostly found on common carp, but they have not been identified based on morphological and/or molecular features.
