A new species of the genus <i>Eubranchus</i> (Gastropoda: Nudibranchia) from Vietnamese coastal waters

Abstract

A new species belonging to the Fionidae ( sensu Cella et al ., 2016), Eubranchus flexus sp. nov. is described based on specimens collected in Nha Trang, Vietnam, South China Sea, Indo-West Pacific, from the upper sublittoral depth. An integrative analysis was conducted, including a molecular phylogenetic analysis based on three markers (COI, 16S, H3), and an analysis of the external and internal morphology using light and scanning electron microscopy. The distinctiveness of Eubranchus flexus sp. nov. is well established both morphologically and genetically. Phylogenetically Eubranchus flexus sp. nov. represents a derived branch in the phylogeny of Eubranchus , but its relationships with other Eubranchus species are unresolved likely due to low taxon sampling. Eubranchus flexus sp. nov. is the first representative of the genus Eubranchus for the nudibranch fauna of Vietnam and for now its range is restricted only to the type locality.