Abstract
The dactylogyrid monogenean Bivaginogyrus obscurus (Gussev, 1955) is redescribed from the gills of two cyprinids, Pseudorasbora pumila pumila Miyadi, 1930 in Nagano Prefecture and P. parva (Temminck and Schlegel, 1846) in Ibaraki Prefecture. These are the first records of this parasite in Japan. Pseudorasbora p. pumila, which is endemic to central Japan, represents a new host record for B. obscurus. This monogenean is the first helminth and the second parasite discovered from wild P.p. pumila.