Redescription of Melibe japonica (Nudibranchia: Dendronotoidea: Tethydidae) and its phylogenetic relationship in the genus

Abstract

ABSTRACT Melibe japonica is a species of gastropod mollusc originally described as a large (up to 70 cm), translucent yellow-white nudibranch with a strong reddish tinge in parts. Subsequent studies reported that it has reddish tubercles all over its translucent pinkish body and cerata. However, it has recently been suggested that M. japonica is a synonym of Melibe viridis without any discussion or explanation. This study aims to show that M. japonica is a valid species. Due to the state of preservation of the type material of M. japonica, neither morphological nor genetic studies were possible, so a neotype for the species was provisionally designated. We provide a detailed description of its external morphology, internal anatomy and phylogenetic relationship, using fresh and preserved specimens collected in Japan. We also extend and update its geographic distribution.