Ancula gibbosa from Massachusetts, USA

January 13, 2003
From: Alan Shepard

Bill -
Here's another species of nudibranch that appears in New England when the waters turn colder. It is Ancula gibbosa. We don't see a great many of these but they are common enough that every few dives in the winter one or two will turn up.

I actually have a question that finding this nudibranch raised. I was actually photographing the Doto sp., I just sent in a separate message, when out of the corner of my eye I saw a small nudibranch floating by. Quite often you see Palio dubia floating around so this wasn't a surprise. Anyway something told me this was not Palio dubia so I gently guided it down to the boulder where the Doto was and was happy to see it was an Ancula.

The question seeing it floating raised is do any nudibranchs detach themselves purposefully and drift to areas for more food or is detachment just accidental? The reason I ask is it is very common to see Palio dubia floating around, almost too common to just be accidental.

Alan Shepard
Tolland, CT, USA

Shepard, A., 2003 (Jan 13) Ancula gibbosa from Massachusetts, USA. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Thanks Alan,
Concerning 'drifting' as a means of dispersal. I did start up a page on the topic but have not had many comments. One which seems very relevant was from Jussi Evertsen and concerned Polycera floating, much as you describe, in northern Europe in Autumn and Winter. It is also that another polycerid, the tropical Kalinga ornata, is also reported to float [see messages from Hawaii and eastern Australia].

Rudman, W.B., 2003 (Jan 13). Comment on Ancula gibbosa from Massachusetts, USA by Alan Shepard. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Ancula gibbosa

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