Morphological and Molecular Study of the Fish Parasitic Crustaceans Cymothoa indica and Mothocya collettei (Isopoda: Cymothoidae), with New Distribution Records

Cymothoidae are parasitic isopods that infest fishes inhabiting marine, brackish, and fresh-water environments. The systematics, distribution, host specificity of cymothoids is often unknown. In this study, morphological observations molecular analysis using the COI 16S rRNA genes were conducted on a juvenile individual Cymothoa indica infesting wide-banded hardyhead silverside, Atherinomorus lacunosus, an ovigerous female Mothocya collettei hound needlefish, Tylosurus crocodilus, both collected from Okinawa Island, Japan. This first time these two species cymothoid have been in Ryukyu Islands, C. particular represents new northern range limit for its species. That specimen was identified showed almost identical morphology to previously reported juveniles, but it differed numbers robust setae pereopods 6 7. M. high similarity had some traits consistent with affinis. DNA indicated nominal very closely related, studies larger populations needed.