Rhopalobdella japonica n. gen., n. sp (Hirudinea, Piscicolidae) from Dasyatis akajei (Chondrichthyes : Dasyatididae) in the northwestern Pacific

A new genus and species of piscicolid leech in the Platybdellinae inhabits the oral cavity of Dasyatis akajei in the northwestern Pacific Ocean near T anabe, Japan. The genus Rhopalobdella n. gen. is characterized externally b y very small oral and caudal suckers and a smooth body that is widest just posterior to the clitellum. Eyespots and ocelli are lacking. The coelom is spacious with large segmental connecting sinuses between dorsal and ventral sinuses. There are 5 pairs of testisacs, an unusually extensive epididymis , and a very large bursa. Conducting tissue is absent. There are 2 pairs of esophageal diverticula and very well developed nephridia. Rhopalobdella ja ponica n. gen. n. sp. is characterized by a urosome that tapers strongly to the caudal sucker and by a single gonopore; the common oviduct opens into the posterior portion of the bursa. The coelomic and excretory systems rese mble Aestabdella, but in other respects the genera are quite different. Thi s is the first marine leech reported from rays in the northwestern Pacific.