The records of the chiasmdontid fish Pseudoscopelus obtusifrons from Japan

Abstract

A live chiasmodontid fish, regurgitated from Thunnus albacares individual immediately after its capture by angling off Hachijo Island, Izu Islands, Japan, had the following diagnostic characters: snout convex; a row of maxillary photophores extending almost to the anterior margin of preopercle; a single row of transverse pelvic-fin photophores; suprapectoral-fin photophores present; 36 vertebrae; mesial series of premaxillary teeth arranged in a single row; hooked teeth in lateral series on both premaxilla and dentary. Accordingly, the specimen was identified as Pseudoscopelus obtusifrons (Fowler, 1934). The species listed by Nakabo and Doiuchi (2013) as Pseudoscopelus sp. (Japanese name Tomaru-kurobozugisu) from off Okinotorishima Island is also confirmed as P. obtusifrons, having hooked teeth on the upper jaw and a single row of transverse pelvic-fin photophores. Although P. obtusifrons has already been recorded from well east of Hokkaido Island (Prokofiev and Kukuev, 2006) and off Iwate Prefecture (Prokofiev, 2011), it has received little recognition as a Japanese species. The present report firmly supports the inclusion of P. obtusifrons in the checklist of Japanese marine fishes.