Description of a New Species of Pelagic Eelpouts Melanostigma japonicum sp. nova (Zoarcidae) from the Pacific Coast of South Japan with a Key for the Species of the Genus Melanostigma from the Pacific Ocean and the Adjacent Waters of the Indian and Southern Oceans

A new species of Melanostigma japonicum sp. n. is described from the Tosa Bay (Southern Japan). The holotype of the species, previously identified as M. orientale, differs from the latter and other Melanostigma species by a unique structure of jaws with very large anteriorly protruding front teeth, an original combination of a number of meristic characters, coloration, and body proportions. M. flaccidum, previously placed in the synonymy of M. gelatinosum, is restored as the valid species. The issues of origin and historical dispersal of Melanostigma species are discussed. A key for identifying the species of this genus in the Pacific Ocean and in the adjacent waters of the Indian and Southern Oceans is provided.