Thuridilla bayeri & T. gracilis ?

February 6, 2009
From: Linda Ianniello

Concerning message #3077:

Dr. Bill,
attached is an image that I have not been able to identify. I believe it is a Thuridilla, and the closest I can find is an image of a T. gracilis on page 89 of "Indo-Pacific Nudibranchs and Sea Slugs". But the rhinophores don't match. And it seemed long compared to the few other Thuridilla species I've seen.

Locality: Kadavu Island, 8 feet, Fiji, Pacific Ocean, 15 May 2008, Off the beach. Length: approximately 2 inches. Photographer: Linda Ianniello.

Can you ID this one?

As usual, thanks a lot for your great forum and all the help.

Linda I.

Ianniello, L.M., 2009 (Feb 6) Thuridilla bayeri & T. gracilis ?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Linda,

I wish I could give you a definitive answer, but your beautiful animal seems to have bits of a number of 'species'.  It is probably the same as in message #2398 which I tentatively identified as Thuridilla splendens, but it also has similarities to T. bayeri which Terry Gosliner considers a good species but I suspect is a variant of T. gracilis - but the colour of the rhinophores is different to them all. It is also similar to Thuridilla sp. 3 , but I suspect all that that tells us is that we haven't quite got this group sorted out at present.

I think I will put is with T. splendens - but only because I think it would be even more confusing to have a Thuridilla sp. 5 page at present. I would welcome any thoughts?

Best wishes,
Bill Rudman

Rudman, W.B., 2009 (Feb 6). Comment on Thuridilla bayeri & T. gracilis ? by Linda Ianniello. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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