Re: which is Eubranchus misakiensis?

July 15, 2003
From: Jeff Goddard

Dear Bill,
Marli Wakeling's photos identified as Eubranchus misakiensis? and posted on June 25, match exactly what I have until recently called the outer coast form of Eubranchus olivaceus (O'Donoghue, 1922) (as opposed to the more greenish colored form found on Obelia in the inland water ways of Washington, British Columbia and Alaska). The outer coast form is usually found on the hydroid Plumularia, which is visible in one of Marli's photos.

Sandra Millen, who has been examining the northeastern Pacific species of Eubranchus recently confirmed that my specimens of E. olivaceus from the outer coast of Oregon and Washington are the same as the specimens found in the inland waterways. Sandra also agrees with Alexander Martynov (Martynov, 1998) that E. olivaceus is a synonym of E. rupium (Moller, 1842) from the north Atlantic, and a look at the photo of E. rupium on Bernard Picton's British nudibranchs website shows that externally there is indeed no difference. Lemche, as described in Just & Edmunds (1985:114), also considered E. olivaceus the same as E. rupium.

Eubranchus rupium is therefore circumboreal in distribution.

References:
• Goddard, J.H.R. & N.R. Foster (2002) Range extensions of sacoglossan and nudibranch mollusks (Gastropoda: Opisthobranchia) to Alaska. The Veliger, 45(4): 331-336.
• Just, H. & M. Edmunds (1985) North Atlantic Nudibranchs (Mollusca) Seen by Henning Lemche. Ophelia Publications: Marine Biological Laboratory, Helsingor, Denmark. 170 pp.
• Martynov, A.V. (1998) Opisthobranch mollusks (Gastropoda: Opisthobranchia) of the family Eubranchidae: Taxonomy and two new species from the Sea Of Japan. Zoologicheskii Zhurnal, 77: 763-777.

Best wishes,
Jeff

goddard@lifesci.ucsb.edu

Goddard, J., 2003 (Jul 15) Re: which is Eubranchus misakiensis?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/10325

Dear Jeff,
Thanks for this interesting complication to the story. I thought we had at last sorted out what was E. misakiensis on the west coast of North America. Following Bernard Picton and others work on food specificity in species of Eubranchus, I hesitate to accept that different looking animals on different food hydroids [your outer coast and inland water forms] are the same species. For example Yoshi and Yayoi Hirano have shown that E. misakiensis in Japan feeds exclusively on hydroids of the genus Obelia, while another species, E. horii, which is found abundantly with E. misakiensis feeds only on Plumularia filicaulis. So I think I'll leave Marli's animal as possible E. misakiensis at present, although it is apparently on a species of Plumularia. The only photo I have seen of the greenish form of E. olivaceus is in Behrens (1991). It certainly could be the same as E. rupium. I would think the animal from the east coast of Nth America, Eubranchus cf. olivaceus, is certainly Eubranchus rupium.
Best wishes,
Bill Rudman

Rudman, W.B., 2003 (Jul 15). Comment on Re: which is Eubranchus misakiensis? by Jeff Goddard. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/10325

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Eubranchus misakiensis

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