Description of Gnathia maculosa and a new record of Gnathia trimaculata (Crustacea, Isopoda, Gnathiidae), ectoparasites of elasmobranchs from Okinawan coastal waters

Abstract

Gnathia maculosa sp. nov. is described from males reared in a laboratory from larvae that were collected as ectoparasites on elasmobranchs, caught off Okinawa Island in the Ryukyu Archipelago, southwestern Japan. The species is most similar to G. trimaculata but it is distinguished from G. trimaculata by deeper and narrower dorsal sulcus, a narrower body, and the wider pylopod. Gnathia trimaculata, previously recorded from Great Barrier Reef, Australia, was also collected from elasmobranchs caught off Okinawa Island. The record of G. trimaculata from Okinawa indicates a wide range of the distribution of the gnathiids inhabiting elasmobranchs.