Nudibranchs on Sargassum

May 20, 2010
From: David M. Knott

Here is a nudibranch that we've photographed for a poster we are preparing on the faunal associates of Sargassum. I think I've come close to getting and ID on it, but I find it impossible to track down the latest taxonomic word on synonymies. Can someone (Bill?) tell me what the currently accepted name is for this species? It was collected in late April/early May while dipnetting Sargassum off the coast of South Carolina.

on surface, off South Carolina, South Atlantic Bight, USA, May 2010, on Sargassum fluitans or S. natans. Length: 2-3 mm. Photographer: Susan DeVictor, SERTC.

David M. Knott

Knott, D.M., 2010 (May 20) Nudibranchs on Sargassum. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear David,

Your animal is clearly a species of Doto. I am afraid the species of the genus Doto are difficult to identify even in regions such as NW Europe where they are relatively well known. Although some species seem to be easy to distinguish and morphology and colour from others, it seems there are quite a few with very similar colour patterns and shape to other species, and seem to differ on choice of hydroid they feed on. The other problem, is well illustrated by where you found your animal - some species seem to have global distributions - perhaps through misidentifications around the world - or because they are well adapted for 'rafting' on flotsam and floating algae such as Sargassum.

On top of this the nudibranch fauna of the Atlantic coast of Nth America is not well known. You say you are close to an ID. Perhaps if you let us know what you are thinking we could give an opinion on your choice. It has similarities to the tropical west Atlantic Doto pita but it just as well could be a north Atlantic species at the sthn extreme of its range. Hopefully someone closer to the Atlantic can give an opinion

Best wishes,
Bill Rudman

Rudman, W.B., 2010 (May 20). Comment on Nudibranchs on Sargassum by David M. Knott. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Doto spp.

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