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| Live images of Nakamigawaia nakanoae sp. nov. (A, C, D) and Nakamigawaia felis (B). A, black morph, Taiwan (paratype). B, the Bahamas, C–D, white dotted morph, Taiwan (paratype). Hellem & Malaquias, 2021 |
ABSTRACT
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.
KEYWORDS: biodiversity, DNA barcoding, Mollusca, morphology, phylogeny, Western Pacific
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| Figure 3. Shells of Nakamigawaia species. A, N. spiralis, holotype, NSMT-39805, ventral (upper) and dorsal (lower) views (macrophotograph), Japan. B, N. nakanoae sp. nov., micrograph of dorsal view; arrow pointing to protoconch, ZMBN 132073, animal length (L) = 7 mm (fixed length), Japan. C, N. nakanoae sp. nov., micrograph of ventral view, ZMBN 132073, L = 7 mm (fixed length), Japan. D, N. nakanoae sp. nov., micrograph of protoconch observed from ventral side of shell, ZMBN 116778, L = 10 mm, Taiwan. E, N. felis, micrograph of dorsal view, ZMBN 91108, L = 13 mm, the Bahamas. F, N. felis, micrograph of ventral view, ZMBN 91108, L = 12 mm, the Bahamas. Scale bars: a = 200 μm; b, c, e, f = 500 μm; d = 100 μm. |
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| Figure 1. Live images of Nakamigawaia nakanoae sp. nov. (A, C, D) and Nakamigawaia felis (B). A, black morph, Taiwan, ZMBN 116778, animal length (L) = 10 mm (paratype). B, the Bahamas, ZMBN 91108, L = 13 mm. C–D, white dotted morph, Taiwan, ZMBN 116777, L = 8 mm (paratype). |
Nakamigawaia nakanoae Hellem and Malaquias sp. nov.
Diagnosis: External colouration plain black or brownish dotted in white. Internal shell dilated with an open whorl extending half a turn, protoconch dorsally visible near transition to teleoconch, otherwise covered by teleoconch layer; ventrally a funnel-like structure can be present near protoconch. Right caudal lobe nearly half length of left lobe. Male reproductive system with pyriform penial chamber and tubular, long, folded prostate. Prostate about 5 times longer than penial chamber.
Type locality: Taiwan, Pingtung County, Kenting National Park, Shadao.
Etymology: The species is named after Dr Rie Nakano, for her passion and contributions to the study of the sea slug molluscs of Japan and for her continuous support throughout the years of our research work.
Emma Hellem and Manuel António E. Malaquias. 2021. 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 of Natural History. 55(35-36); 2231-2244. DOI: 10.1080/00222933.2021.1986165
