The first known nudibranch extinction?

April 28, 2001
From: Bill Rudman

One of the first photos of tropical nudibranchs I remember seeing was in an article by Paul Zahl published in the National Geographic Magazine (1959) on Hawaiian Marine Life. I can't say that it attracted me to a life of studying nudibranchs, but I still have the copy of that issue of the magazine. Years later when I began to study chromodorids, one photo in that article, of two red-spotted animals, became quite tantalising. It was clearly of a species which had never been seen, or at least photographed this century. The only record I could find of it was Gould's description of Chromodoris petechialis from the US Exploring Expedition of 1838-42.

Scott Johnson & I mentioned this species in his message about Hypselodoris paulinae and I promised then to approach the National Geographic Society for permission to reproduce Paul Zahl's photo in the hope that someone would recognise the species. It is known only from Hawaii on the basis of these two records, the original in the late 1830s and the second in 1959 by Paul Zahl. After some time I am happy to announce that the National Geographic Society has given me permission to use the photo on the website. As you will see it is quite different from any other described species. In shape it is almost certainly a species of Chromodoris, but in colour it is quite distinct from any named species.

Has anyone a photo of this species from Hawaii? - or from anywhere else for that matter. If not, it does raise the intriguing possibility that this species no longer exists. If so it would be, to my knowledge, the first case of a nudibranch extinction. It is not a 'first' I would be particularly happy to be associated with, so if any of you have photos from Hawaii, or have contacts in Hawaii who could do some searching, let's see if we can bring this species back from the dead.

• Gould, A.A. (1852) United States Exploring Expedition during the years 1838-1842. Under the command of Charles Wilkes, U.S.N. Vol 12. Mollusca and Shells. 510pp, with Atlas of Plates, 1856. [296-7, Pl.22, figs 391,391a].
• Rudman, W.B. (1983) The Chromodorididae (Opisthobranchia: Mollusca) of the Indo-West Pacific: Chromodoris splendida, C. aspersa and Hypselodoris placida colour groups. Zoological Journal of the Linnean Society, 78: 105-173.
• Zahl, P.A. (1959) Unsung beauties of Hawaii's Coral Reefs. National Geographic Magazine, 116(4) October: 510-525

Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Apr 28) The first known nudibranch extinction?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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