First reliable Japanese record of Dasyscopelus brachygnathos from the Kii-oshima Is., Wakayama and new distributional records of Dasyscopelus

Abstract

A single specimen of the myctophid species Dasyscopelus brachygnathos, collected from Kii-oshima Is., Wakayama Prefecture, Japan, represents the first specimensupported Japanese record, and northernmost of the species. The specimen was characterized by the following characters: opercle with a smooth dorsoposterior margin; eye diameter almost equal to the distance between the orbit extreme posterior margin and opercle dorsoposterior margin; a suprapectoral luminous organ just above the pectoral-fin base; a slightly angled supralateral luminous organ series; and two precaudal luminous organs well below the lateral line. The body scales of the specimen had 2–4 protrusions, being feebly ctenoid and therefore referable to the genus Dasyscopelus [diagnosed by variably developed ctenoid scales, and thereby distinguished from the closely related genus Myctophum (usually cycloid scales)]. A detailed description of the specimen is provided, with comments on scale shape being diagnostic for the genus. In addition, the northernmost Pacific records of D. obtusirostris (previous northernmost record ca. 39˚N) and D. selenops (previous northernmost record ca. 30˚N) off the Tohoku District, northern Japan are reported, with short species descriptions. DNA barcoding of the above and comparative specimens suggested that several cryptic species may also be included in the genus.