Cadlina but which one?

February 13, 2002
From: Alan Shepard

The nudibranchs here in New England and particularly Cape Ann, Massachusetts are quite abundant right now. I don't know why - maybe the fact that the waters got colder earlier and drove the fish to deeper water allowed the nudibranchs to go unmolested. I'm hoping to photograph many of them this winter.

Anyway I know the attached photo is of a Cadlina but is it C. laevis or C. luteomarginata? Most of our local ID books, and there are few of them, seem to result in a match with C. laevis. But when I look over your site I lean towards C. luteomarginata. Any help would be appreciated.

Alan Shepard

Shepard, A., 2002 (Feb 13) Cadlina but which one?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Alan,
The jury is still out on this one. Have a look at the Cadlina cf. luteomarginata and the attached messages there. Your common east coast Cadlina has been identified with the west coast C. luteomarginata but it has consistent colour differences and feeds on a quiet different group of sponges. I have included a part of your photo (lower right) showing a small colony of the slime sponge, Halisarca which seems to be the food of your east coast animal.

This food choice is the same as Cadlina laevis from Europe but there are colour differences with that species. Until its anatomy is looked at there is not much more to say. What would be worth looking out for is an animal in the process of laying eggs. a photo of the egg ribbon, including a close-up showing how large the individual eggs are, would be a very valuable piece of information, as the size of the eggs can give us clues to the type of larval development the slug has.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Feb 13). Comment on Cadlina but which one? by Alan Shepard. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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