Colour variations of Ceratosoma trilobatum?

December 22, 2006
From: Mike Krampf

I thought I'd share these pics showing three different colour variations of Ceratosoma trilobatum. All these pics were taken in Lembeh Strait.

Locality: Lembeh Strait, 45 ft, Indonesia, Celebes Sea, 28 October 2006, Sandy bottom. Length: 8 mm. Photographer: Mike Krampf.


Krampf, M., 2006 (Dec 22) Colour variations of Ceratosoma trilobatum?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Mike,
Thanks for these photos which show not only colour variation but species differences as well. The upper two animals are Ceratosoma gracillimum which can be distinguished externally by the complete absence of the mantle edge between the head and the well-developed lateral lobes on each side. The animal in the lower photo is indeed C. trilobatum. In it you can see the mantle edge, edged in purple, between the head and the lateral lobes. Both species have a similar range of colour variations, as does C. tenue, but they differ from each other externally by the lack of a mantle edge in C. gracillimum and the extra pair of small lateral lobes in C. tenue.

One other point which might be of interest. In the middle photo there is a bit of a grey sponge visible in the top of the photo. You wouldn't by chance have a photo of Ceratosoma, on or eating that sponge would you? It looks as though it could belong to a family of sponges which I think Ceratosoma feeds on. For that matter, if you haven't already been harassed by me for photos of slugs 'doing things', if you have any photos of Ceratosoma  feeding or taking what looks like more than a passing interest on a possible food item, please send them in. I consider one success out of 20 'possibles' to be reasonable odds so don't worry if you are not sure.

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (Dec 22). Comment on Colour variations of Ceratosoma trilobatum? by Mike Krampf. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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