<i>Runcinida valentinae </i>Chernyshev, 2006 (Opisthobranchia: Runcinacea), a new opisthobranch species for the Sea of Japan
Runcinida valentinae, an opisthobranch mollusk previously known from waters off Iturup Island (Kuril Islands), has been found off Rudnaya Bay and in Oprichnik Bay, Sea of Japan. New data on radula morphology in this species are presented. Partial sequences of nuclear 28S rRNA and mitochondrial COI genes of the genus Runcinida have been obtained for the first time. Their analysis shows the distinctiveness of R. valentinae, which is morphologically close to R. marisae Chernyshev, 1998 from Peter the Great Bay. The strong nucleotide differences between these species confirm importance of body coloration patterns as species-specific traits in runcinid systematics.