南鳥島北東方海域から得られたヤセムツ科魚類Epigonus fragilisイブシギンヤセムツ（新称）

抄録

In an on-going study of the taxonomy of the genus Epigonus (Perciformes: Epigonidae), the author found two specimens of E. fragilis (Jordan and Jordan, 1922) collected off northeast Marcus Island (Minami Torishima), western North Pacific, were found in the Fish Collection of Kyoto University, Maizuru Fisheries Research Station, Kyoto (FAKU). The species having been previously reported from Johnston Atoll, the Hawaiian Islands, and the Colahan Seamount, and Milwaukee Bank (Emperor Seamount chain), the specimens represent the first report of the species from waters adjacent to Japan. The new standard Japanese name “Ibushigin-yasemutsu” is proposed for the species, which belongs to the E. pandionis group, defined by Okamoto and Motomura (2013), and is characterized by the following combination of characters: dorsal fin rays VII-I, 10; pectoral fin rays 17 or 18; gill rakers 25–27; vertebrae 10 + 15; pyloric caeca 7 or 8; pored lateral-line scales 46–49 + 3 or 4; pungent opercular spine absent; maxillary mustache-like process absent; lingual teeth absent; small conical teeth on lower jaw; pair of ribs present on last abdominal vertebra; tubercle on inner symphysis of lower jaw absent; orbital diameter 13.5–15.2% SL; and pectoral-fin length 22.8–26.1% SL. Besides E. fragilis, four species of Epigonus have been recorded from Japan, viz., E. atherinoides (Gilbert, 1905); E. ctenolepis Mochizuki and Shirakihara, 1983; E. denticulatus Dieuzeide, 1950; and E. pectinifer Mayer, 1974. A key to the Japanese species of Epigonus and list of Japanese standard names of Epigonus species worldwide is included.