大隅諸島黒島沖から得られた日本初記録のアナゴ科Congriscus maldivensisナンヨウオキアナゴ（新称）の葉形仔魚

抄録

A single specimen (153.7 mm total length) of large congrid leptocephalus, collected at a depth of 400 m off Kuro-shima Island, Osumi Islands, Kagoshima Prefecture, Japan, was subsequently identified as Congriscus maldivensis (Norman, 1939), having the following combination of characters: 46 lateral-line pores before anus; 149 total vertebrae, including 46 abdominal vertebrae; maximum body depth 27.2% of total length (TL); pectoral fin length 40.6% of head length; highest margin of head profile anterior to pectoralfin base; snout rounded, its tip anterior to tip of lower jaw; maxilla and mandibular teeth conical, uniserial; anterior nostril with short membranous tube, below snout margin; posterior nostril rounded, anterior to eye; posterior end of mouth posterior to vertical through middle of eye; cephalic sensory pores and lateral line developed; anus slightly anterior to middle of body; dorsal, anal, pectoral, and caudal fins present (dorsal-, anal-, and caudal-fin membranes fused); and dorsal fin origin slightly posterior to ventral through pectoral-fin base. A neighbor joining tree based on mtDNA cytochrome c oxidase subunit I (COI) gene sequences placed the specimen within a clade of C. maldivensis, based on previously published sequences, thereby supporting its conspecificity with C. maldivensis. The specimen was tentatively determined as a metamorphic larva, based on the following features: 153.7 mm TL, head length 12.7% of TL, and body opaque, with melanophores around the midline. An Indo-West Pacific species, C. maldivensis has previously been recorded from Tanzania to the Philippines, Wallis and Futuna Islands, and Australia, the present specimen therefore representing the first Japanese record and northernmost record of the species. The new standard Japanese name “Nan’you-okianago” is proposed for the species.