The taxonomic status of the headshield slug genus Nakamigawaia Kuroda and Habe, 1961 (Gastropoda: Cephalaspidea: Aglajidae), with the description of a new species from the Western Pacific
Journal article, Peer reviewed
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Original versionJournal of Natural History. 2021, 55 (35-36), 2231-2244. https://doi.org/10.1080/00222933.2021.1986165
Nakamigawaia is a poorly understood genus of Aglajidae sea slugs with only two species formally ascribed. In this paper we explore new morpho-anatomical characters using stereo and scanning electron microscopy and employ different molecular approaches (a cytochrome c oxidase sub-unit I gene phylogeny, the Automatic Barcode Gap Discovery species delimitation method, and genetic distances) to compare specimens across the geographical span of the genus and from two distinct chromatic morphotypes occurring in the Western Pacific (blackish morph and white-dotted morph). Our results support the conspecificity of these two morphs and show they belong to an undescribed species here named Nakamigawaia nakanoae sp. nov. The species differs from the type species of the genus, N. spiralis, by the presence of a distinct open-dilated shell and differs from its Western Atlantic congener N. felis by subtle differences in the shell, male reproductive system and caudal lobes. Genetically (COI uncorrected p-distance) the two species (N. nakanoae and N. felis) are 18.8–20.1% distinct. The definition of the genus Nakamigawaia is discussed and the current assignment to the latter of lineages other than the type species is questioned.