日本初記録のセキトリイワシ科魚類ヤジリイワシ（新称）Conocara kreffti

抄録

The family Alepocephalidae, comprising about 23 genera and at least 90 species of benthic and pelagic deep-sea fishes, includes 10 species of the genus Conocara, known from about 800 to more than 5000 m depth in the Indo-Pacific and Atlantic oceans. Conocara is characterized by the dorsal-fin origin located posterior to the anal-fin origin, the dorsal-fin base length shorter than the anal-fin base length, the body covered with small scales (>80 in longitudinal row above lateral line), tubular scales in lateral line, maxilla toothless, upper jaw length equal to or longer than snout length and photophores absent on body. A single specimen of Conocara kreffti Sazonov, 1997 [NSMT-P (National Museum of Nature and Science, Tsukuba) 104036, 329 mm in standard length] was collected from the continental slope of the Ryukyu Trench, Japan in a depth of 1338–1396 m, on 24 May 2005. Conocara kreffti is distinguished from all congeners by the following combination of characters: dorsal-fin rays 21–28, anal-fin rays 35–43, number of scales in a longitudinal series above lateral line 190–270, palatine teeth present and premaxilla with a single bony ridge. The species has been previously recorded from tropical and subtropical zones of the Indian Ocean and western central Pacific Ocean, but not from Japanese waters. The present specimen represents the first records of the genus from Japanese waters and the northernmost record of Conocara kreffti. The new Japanese names “Yajiri-iwashi-zoku” and “Yajiri-iwashi” are proposed for the genus and species, respectively.