Question on the genus Embletonia

September 16, 2002
From: Alicia Hermosillo

Dear Dr. Rudman,
I was browsing through my books, again, to see if I caughtr a glimpse of any of my unidentified species ... I was looking at Hawaiian Nudibranchs (Bertsch & Johnson, 1981), a book out of print. On page 94 there is a picture of a very unusual Aeolid identified as Embletonia gracile. It is very long compared to the width... I have seen a few animals under rocks that look like that while surveying Bahia de Banderas. Very difficult to collect since they stick to the rock and you can not collect them without hurting them. I managed to collect one and take some tub shots but the animal contracted and the specimen in the pictures does not look like the animal under water at all.

I would like to know if that genus and species has changed or been synonymised with anything because I have not seen the genus mentioned in more recent literature or other pictures of them (again, I am not all that familiar with Indopacific or Hawaiian species). If you look at the picture of Pteraeolidia ianthina, page 115 in ColemanĀ“s book that is the general shape of the animal, mine have been brown cerata on white body or all white, both times I have seen them there were about 10 or so together.

Any comments or ideas?

Hermosillo, A., 2002 (Sep 16) Question on the genus Embletonia. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Ali,
No Embletonia hasn't disappeared. It is one of many things I still have to add to the Forum so since you have brought the subject up I have prepared a page on Embletonia gracilis. It is intersting because there is some debate about whether it is belongs in the Aeolidina or the Dendronotina. As you will see in my discussion, I am in favour of the aeolid relationship.

The only sure way of knowing what you have is seeing a photo or an animal. Even if it not looking too natural in your 'tub shots' I should be able to get a clue to its identity. Things you could look for are the number of cerata in each row - in Embletonia the cerata are single and there are four bumps or tips to ech ceras.
Best wishes,
Bill Rudman

Rudman, W.B., 2002 (Sep 16). Comment on Question on the genus Embletonia by Alicia Hermosillo. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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