Ceratosoma gracillimum? from Komodo Ids

December 11, 2003
From: Teresa Zubi

I found a pair of Ceratosoma nudibranchs in the Komodo islands, Indonesia. I know this kind of nudibranch from other dive sites in Indonesia such as Lembeh, but this one is a light pink with no visible spots. Is it a Ceratosoma gracillimum?
Teresa Zubi


Zubi, T., 2003 (Dec 11) Ceratosoma gracillimum? from Komodo Ids. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11578

Dear Teresa,
Colour is not a good character in species of Ceratosoma most species being very variable in colour. Shape is very important. In the upper and lower right photos you can see that there is no mantle ridge between the head and the lateral mantle lobes alongside the gills. This is unique to this species. If you look at photos of C. trilobatum you will see a distinctive ridge on each side from the lateral lobes to the head.

The animal in your lower left photo has obviously been damaged. It has lost the medio-dorsal horn behind the gills, and there is a prominent ridge on each side running back from the gills. I suspect something has eaten off the horn. In species of Ceratosoma, the horn stores noxious chemicals the animal obtains from the sponges it feeds on. I have suggested elsewhere that this horn is a defensive lure attracting predators to bite the most distasteful, and otherwise useless, part of its body so deterring them from eating a more vital part of the body.
Best wishes
Bill Rudman

Rudman, W.B., 2003 (Dec 11). Comment on Ceratosoma gracillimum? from Komodo Ids by Teresa Zubi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/11578

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