First Japanese record of the snailfish Osteodiscus andriashevi (Liparidae), collected off Iwate, Japan

Abstract

Snailfishes (Cottoidei: Liparidae) are a large, morphologically diverse group of marine fishes, comprising about 32 genera with over 430 species worldwide. Among them, Osteodiscus Stein, 1978 is primarily distinguished from other genera in having a unique skeletal pelvic disk covered only by thin skin. Three species of the genus are currently known: Osteodiscus cascadiae Stein, 1978 from the eastern North Pacific; Osteodiscus andriashevi Pitruk and Fedorov, 1990 from southern Sea of Okhotsk; and Osteodiscus rhepostomias Stein, 2012 from southeast of New Zealand. During a taxonomic study of snailfishes, a single female specimen of Osteodiscus (150.3 mm in standard length) collected off Iwate in a depth of 1,997–2,108 m, was discovered in the fish collection of the National Museum of Nature and Science, Japan (NSMT). The specimen, characterized by 60 vertebrae (total), 54 dorsal- and 49 anal-fin rays, a horizontal mouth, simple blunt teeth on both jaws, some teeth with lateral cusps on the tip, an unnotched pectoral fin, and the presence of epipleural ribs and a reduced epural, was identified as O. andriashevi, previously known only from the holotype and three paratypes. The present specimen represents the first record of Osteodiscus from Japanese waters and the southernmost record of O. andriashevi. The new standard Japanese names “Hariban-kusauo-zoku” and “Choja-hariban-kusauo” are proposed for the genus and species, respectively. Based on the present specimen, the species diagnosis was partly revised.