Species description and phylogenetics of Oerstedia fuscosparsa sp. nov. (Nemertea: Monostilifera: Oerstediidae) from Japan

Abstract

We provide a morphological and molecular-based description of the eumonostiliferous hoplonemertean Oerstedia fuscosparsa sp. nov. based on two specimens dredged from a depth between 11 and 18 m off Kouyatsu, Tateyama, Chiba, Japan. This Oerstedia differs from its congeners by having a deep brownish pigmentation in the head, four orange ocelli, and imprecise dorsal and ventral transverse bands composed of numerous small brown spots. One of the specimens, herein designated as the holotype, has deep brown spots situated mid-dorsally onto the transverse bands running throughout the body. These dorsal markings are absent in the other specimen designated as a paratype. Internally, the species has accessory lateral nerves, and the proboscis nerves are not distinct. Molecular phylogenetic analyses based on partial sequences of the 16S, 18S, 28S rRNA, cytochrome c oxidase subunit I, and histone H3 gene markers along with the sequences from 22 Oerstedia species available in public databases confirmed that our species is sister to Oerstedia phoresiae (Kulikova, 1987) and belongs to the recently established Paroerstediella clade within the genus Oerstedia.