Hypselodoris cf. bertschi from Kerama Is

Dear Atsushi,
I think this is a particularly interesting find. I may be wrong but I think this is a species which Terry Gosliner & Rebecca Johnson have recently described as Hypselodoris bertschi, a species only known from the Hawaiian Islands.

The only colour differences I can find in their description is that they say there is an orange band around the mantle margin and the white gills have an orange rachis. However Kay & Young's description (1967) of the Hawaiian species [as Hypselodoris lineata (Pease)] states that the 'margin is sometimes edged with white, sometimes with a narrow band of blue, and at other times margined with orange-yellow' and that the gills are 'transparent white with splashes of orange at the tips.'

A photo in Bertsch & Johnson's Hawaiian Nudibranchs (1981; p.65) is almost identical to your animals. If they are the same this is the first record outside of Hawaii. Hawaiian animals grow to about 35mm long. Mike Miller has recently posted a picture from Hawaii on his Slug Site Nudi of the week 171.

Have you seen any colour variation in Kerama Island animals? It would be interesting to know if they ever have an orange margin to the mantle.

Best wishes,
Bill Rudman.

Reference:
Gosliner, T.M. & Johnson, R.F. (1999) Phylogeny of Hypselodoris (Nudibranchia: Chromodorididae) with a review of the monophyletic clade of Indo-Pacific species, including descriptions of twelve new species. Zoological Journal of the Linnean Society, 125: 1-114.

Kay, E.A. & Young, D.K. (1969) The Doridacea (Opisthobranchia: Mollusca) of the Hawaiian Islands. Pacific Science, 23(2): 172-231.