Hypselodoris bennetti & Ceratosoma amoena

February 12, 2007
From: Lynda Clarke

Dear Bill,
We found these two nudibranchs on Friday, both species are common at Julian Rocks. The blue Hypselodoris bennetti, is usually found either alone or mating, which they seem to do a lot of. Even when there are several on the same sponge they are usually quite separate. Ceratosoma amoena is also quite common, but usually alone. I thought the close proximity of these two was interesting.

Locality: Julian Rocks, 10 to 15 metres, New South Wales, Australia, Pacific, 9 February 2007, rocky reef. Length: less than 3cms. Photographer: Andrew Green.

Kind regards
Lynda

polymath@bigpond.com

Clarke, L, 2007 (Feb 12) Hypselodoris bennetti & Ceratosoma amoena. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19437

Dear Lynda (& Andrew),

Thanks for the photo. The sponge these animals are on is an irciniid of the genus Psammocinia, which gets its name from psammo the ancient Greek word for sand. You will note in the photo how there are sand grains embedded in the tissue of the sponge, and this is a characteristic of species of this genus.  From earlier records I am pretty sure that species of Psammocinia are the preferred food of Hypselodoris bennetti, and in your photo the oral tube seems to be partially everted suggesting it may be feeding. However from most preious records I am pretty sure that Ceratosoma amoena feeds on sponges of the family Thorectidae. You seem to suggest in your message that you often find it on Psammocinia. If so I would like some other photos to confirm this - especially if they show signs of feeding. There is an earlier message from Sue Newson [# 9843] showing C. amoena on a colony of Psammocinia, but the close-up showing feeding seems to be of a thorectid sponge. It's possible they could feed on both, but it would be nice to have some conclusive evidence. So any photos you think might help, would be very welcome

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Feb 12). Comment on Hypselodoris bennetti & Ceratosoma amoena by Lynda Clarke. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/19437

Factsheet

Hypselodoris bennetti

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