A metamorphosed adult female of Lernaea cyprinacea Linnaeus, 1758 was found to parasitize a rock flagtail, Kuhlia rupestris (Lacepède, 1802), in the Miyara River on Ishigaki-jima Island, one of the Ryukyu Islands, southern Japan. This represents the first record of L. cyprinacea from Ishigaki-jima Island. Kuhlia rupestris is a new host record for L. cyprinacea.

Lernaea cyprinacea (Copepoda: Lernaeidae) infecting a rock flagtail, Kuhlia rupestris (Kuhliidae), in a subtropical river, southern Japan (Kazuya Nagasawa and Hirotaka Katahira)