Journal of the Marine Biological Association of the United Kingdom

Molecular evidence for synonymy of the genera Moroteuthis and Onykia and identification of their paralarvae from northern Hawaiian waters

Toshie  Wakabayashi a1, Tsunemi  Kubodera a2, Mitsuo  Sakai a1, Taro  Ichii a1 and Seinen  Chow a3c1
a1 National Research Institute of Far Seas Fisheries, 2-12-4 Fukuura, Kanazawa-ku, Yokohama, Kanagawa 236-8648, Japan
a2 National Science Museum, Tokyo, 3-23-1 Hyakunin-cho, Shinjuku-ku, Tokyo 169-0073, Japan
a3 National Research Institute of Fisheries Science, 6-31-1 Nagai, Yokosuka, Kanagawa 283-0316, Japan

Article author query
wakabayashi t   [PubMed][Google Scholar] 
kubodera t   [PubMed][Google Scholar] 
sakai m   [PubMed][Google Scholar] 
ichii t   [PubMed][Google Scholar] 
chow s   [PubMed][Google Scholar] 


It has been claimed that most squid species in the genus Onykia may be immature stages of species in the genus Moroteuthis. To evaluate the generic status of Moroteuthis and Onykia and to identify paralarvae collected in northern Hawaiian waters, we performed morphological investigation and nucleotide sequence analysis of the mitochondrial cytochrome oxidase I (COI) gene. Of 42 Onykia paralarvae (1.8–8.5 mm dorsal mantle length, DML) examined, 41 had a nucleotide sequence identical to that of M. robusta and one (designated Onykia sp. A) could not be assigned to any known Moroteuthis species. Nucleotide sequence diversity estimates based on Kimura's two-parameter distances between Onykia sp. A and Moroteuthis spp. (0.109–0.150) fell well within the range of congeneric species, suggesting that Onykia sp. A is a member of the genus Moroteuthis. Molecular data supported the conclusion that the genus Moroteuthis is a junior synonym of the genus Onykia. Morphological investigation revealed that paralarvae of O. robusta (= M. robusta) <4.0 mm DML were distinct from other Onykia paralarvae in the chromatophore pattern on the mantle. The key characters for distinguishing O. robusta paralarvae from Onykia sp. A were the number and arrangement of chromatophores on the funnel.

(Published Online July 30 2007)
(Received October 25 2006)
(Accepted July 12 2007)

c1 Corresponding author, e-mail: