Guernsey opisthobranch

November 20, 2003
From: Richard Lord

Dear Bill:
I would appreciate an identification on this little fellow. I found this 10 mm long sea slug looking like a drop of jelly on the bottom of a cobble on the lower shore at La Valette on Guernsey's east coast (Western English Channel, about 49 degrees north, 2 degrees west) on October 28, 2003.

I placed the rock underwater for photography. On development of the film I saw in a sequence of photos the nudibranch attacking the anemone, which produced acontia in defence.

I sent an email to Bernard Picton who sent the following email:
"I think this is Aeolidiella alderi, but I'm not certain. We had a pair of juveniles from Mulroy Bay in Donegal which had similar colouring. If it had small papillae on the back of the rhinophores I'd wonder if it might be the Mediterranean species Berghia coerulescens!! Try and get an adult - they are typically shore animals feeding on anemones."

He recommended that I contact the sea slug forum for help.
Richard Lord

Lord, R., 2003 (Nov 20) Guernsey opisthobranch. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Richard,
If you had sent the message directly to f anyone else has an idea please let us know. I have enlarged the head end of one of your photos as it seems to show that the digestive gland duct (brown) is much shorter in the anterior row of cerata than it is in the others. This is a characteristic feature of Aeoldiella alderi, so unless it just a trick of the light in this photo I would guess that Bernard's identification is correct
Best wishes
Bill Rudman

Rudman, W.B., 2003 (Nov 20). Comment on Guernsey opisthobranch by Richard Lord. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


Aeolidiella alderi

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