沖縄諸島の久米島から得られたヘビギンポ科Ceratobregma helenaeミカンヘビギンポ（新称）の北限記録および本種の日本国内における分布状況

抄録

The triplefin genus Ceratobregma Holleman, 1987 includes two valid species, the Spotted Spiny-eye Triplefin C. acanthops (Whitley, 1964) and Helen’s Triplefin C. helenae Holleman, 1987. Both are characterized by the first dorsal fin having 3 spines, the anal fin 2 spines, and the pelvic fin with one spine and 2 rays, in addition to discontinuous lateral lines (upper series of tubular pored scales and lower series of notched scales), well developed lateral ethmoids, 3 or 4 spines on the anterior margin of the orbit in males, and a scaleless opercle and pectoral-fin base. Ceratobregma acanthops is known only from the Coral Sea, whereas C. helenae is widely distributed in the eastern Indian and western Pacific oceans. A single specimen (KAUM–I. 146836, 24.3 mm standard length) of C. helenae collected from Kume-jima Island, Okinawa Islands, Ryukyu Archipelago, Japan in October 2020 possessed the following characters: first spine of 1st dorsal-fin shorter than that of 2nd dorsal-fin; caudal peduncle narrow; sides of body with orange vertical bands; and 2nd dorsal fin with a basal series of orange spots. Previous records of the species from Japan include a single specimen (BPBM 8723, 29.6 mm standard length) collected from Taketomi-jima Island, Yaeyama Islands in 1968, and underwater photographs (as Ceratobregma sp.) taken at Irabu-jima and Miyako-jima Islands, Miyako Islands, in 2002 and 2004, respectively. The two Japanese specimens were examined, that from Kume-jima Island (described in detail) representing the northenmost record for the species. The new standard Japanese name “Mikan-hebigimpo” is proposed for C. helenae on the basis of the Kume-jima specimen, “Mikan-hebigimpo-zoku” serving for the genus Ceratobregma.