Coriocella nigra

May 5, 1999
From: Jacquie Sheils

I work as a tour guide at Hardy Reef, on the Great Barrier Reef, about 80km NE of the Whitsunday Islands.
For several years we have regularly observed specimens of Coriocella nigra on the reef we visit. I wish I there was more information available on their biology! Having found out that they feed on ascidians I'll take more notice of where I see them in future. I seem to see them more frequently in the cooler months of the year, rarely in the summer, could this have something to do with food availability or life cycle?

What I'd really like to know is, what are the knobs on their backs for?!

Jacquie Sheils.

Sheils, J., 1999 (May 5) Coriocella nigra. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Jacquie,
I bet there are a lot of people who would like your job! As you will see from the Lamellariid or rather, as they should be called, the Velutinid page, these animals are not really 'Sea Slugs'. Though as I made the rules I guess I can stretch them a bit. You are right about the lack of information on these animals. What would be great would be somebody like you who is on the spot to 'adopt' a species and keep regular records of when they are around, what size they are, what they appear to be eating, and any other interesting natural history observations. Photos are a good way to record such information if you have access to a camera. It is possible that they are around all year but only big enough to be noticed in the winter. Until you know what they actually eat, and many animals only feed on one or a very few prey species, it is not possible to say whether food availability restricts their numbers.

Concerning the large tubercles on their backs. To me they look like a soft coral that has retracted its polyps so one guess I would make is that the tubercles are a form of camouflage, but I might be quite wrong.

Best wishes,
Bill Rudman.

Rudman, W.B., 1999 (May 5). Comment on Coriocella nigra by Jacquie Sheils . [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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