The soft coral mimic - Ceratosoma alleni

May 18, 2006
From: Tristan Green


Hi,

I'm new to the Forum so don't know the form, but I hope someone can help me identify this little creature.

Spotted in Anilao, Philippines at about 10 m moving across some sand between flower soft coral (Probably Xenia sp.) from memory which was almost the same colour as the nudibranch.

Locality: Anilao, 10 m, Luzon, Philippines, South China Sea, 30 April 2006, Coral reef. Length: 100 mm. Photographer: Tristan Green

I've not been able to find a photo of anything similar in any of my books.

Regards,
Tristan Green

tag2000@pacific.net.hk

Green, T.A., 2006 (May 18) The soft coral mimic - Ceratosoma alleni . [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16620

Dear Tristan,
Welcome to the Forum and thanks for a spectacular first contribution. This is Ceratosoma alleni. When it was first described, the author, Terry Gosliner,  mentioned its similarity to a xeniid soft coral and suggested it was probably a defensive camouflage strategy to protect it from predators. Your photos show the similarity to a soft coral with polyps retracted, very well. This animal is a member of the family Chromodorididae which contains some of the most brightly coloured nudibranchs. Most store distasteful chemicals they obtain from their sponge prey in their skin and the brightly coloured ones seem to be 'shouting loudly' to potential predators that they should be avoided. Ceratosoma alleni on the other hand, is one of the few that has decided that discretion is the better strategy, but they still store distasteful chemicals in their skin - just in case their camouflage fails.

Best wishes,
Bill Rudman

Rudman, W.B., 2006 (May 18). Comment on The soft coral mimic - Ceratosoma alleni by Tristan Green. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/16620

Factsheet

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