Range expansion and redescription of the hagfish Eptatretus walkeri (Myxiniformes: Myxinidae) from Northeast Asia and its distinction from E. atami

Abstract

Eptatretus walkeri was originally described based on 25 specimens from several coasts of Japan by McMillan and Wisner in 2004. We report the first collection of this species since its first description, based on 80 specimens caught at several localities along the southern Korean coast. Eptatretus walkeri is distinguished from its congeners by six gill pouches and gill apertures arranged in a closely spaced, linear pattern or a slightly crowded, irregular pattern; absence of branchial slime pores; 3/2 fused cusps; 36–44 total cusps; 68–79 total slime pores; faint or absent eyespots; poorly developed ventral fin-fold; and gill aperture surrounded by a pale margin. Based on molecular data (mtDNA), Eptatretus walkeri differs from other congeners by 0.9–4.5% in 16S ribosomal RNA gene, and 5.2–12.6% in cytochrome c oxidase subunit I. Because Eptatretus walkeri is poorly known, we redescribe the species based on additional voucher specimens, report its range expansion, and discuss its past taxonomic confusion with E. atami (Dean 1904)