Benedenia akajin n. sp. (Monogenea: Capsalidae) from Leopard Coral Grouper Plectropomus leopardus Reared in Okinawa Prefecture, Japan

― The grow-out stage of leopard coral grouper Plectropomus leopardus reared in land-based tanks in Okinawa Prefecture, Japan, were often heavily infected with capsalid monogeneans, up to a few millimeters in size, on the fins and skin. Morphological investigation revealed that the parasite belongs to Benedenia (Monogenea: Capsalidae). Benedenia akajin n. sp. is proposed here and described morphologically, based on the unique structures in the vaginal duct with a thick-walled distal one-third, the penis with a teat-shaped tip and the testes smaller than the germarium. A positive relationship between the lengths of three haptoral sclerites (anterior sclerites and anterior and posterior hamuli) and body length indicates that these taxonomically important structures keep growing as the parasite ages. Molecular analyses showed that the present species is most closely related to B. epinepheli and B. sargocentron , with the highest 28S rDNA identity of 98.1%, but no identical sequences were found in the database. Both morphological and molecular evidences suggest Benedenia akajin n. sp. as an undescribed species, and this new skin fluke deserves further investigations for the stable aquaculture of P. leopardus .