Ceratosoma amoena and ? from Nelson Bay, NSW

April 25, 2001
From: David Harasti

Hi Bill,
These 2 pics were taken at Halifax Park at Nelson Bay, New South Wales, Australia in April 2001. Depth was about 15 metres and water temp was 23 degrees. Obviously 1 animal is Ceratosoma amoena but I am not sure what the other species is. Is it a colour variation of Ceratosoma amoena?

Thanks,
David
http://www2.dynamite.com.au/davidh/index.htm

davidh@dynamite.com.au

Harasti, D., 2001 (Apr 25) Ceratosoma amoena and ? from Nelson Bay, NSW. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4229

Dear Dave,
The one on the right in the upper photo is C. amoena, and the other one is another species of Ceratosoma, Ceratosoma brevicaudatum. Both these species are found around southern Australia and are a pair of temperate representatives of what is otherwise a tropical genus. In the bottom photo you can see a bright orange-red knob at the rear of the mantle (left side of photo). This is the very short 'tail' which gives this species its name: brevi = short; caudatum = tail.

If you look at the top of the page you will see a photo of two juveniles with very prominent 'short tails'. This is where species of Certaosoma store distasteful chemicals which they use to deter predators. I think the brightly coloured patch is a 'lure' to attract potential predators to this most distasteful part of their body. If the predator bights off a bit of this tissue, it does not really hurt the nudibranch and ensures the predator gets a very nasty mouthful.

The other species on your photo, Ceratosoma amoena, is a primitive member of the genus and has no tail. Look at Ceratosoma trilobatum and Ceratosoma tenue for two tropical species in which the 'tail' has developed into a large dorsal horn.
Best wishes,
Bill Rudman

Rudman, W.B., 2001 (Apr 25). Comment on Ceratosoma amoena and ? from Nelson Bay, NSW by David Harasti. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/4229

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Ceratosoma brevicaudatum

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