Ceratosoma gracillimum feeding?

April 2, 2008
From: Kamal El Tawil

Following on from my last message [#20945], here is another of Ceratosoma tenue. The animals were also slowly moving on black sandy bottom and rubble. They don't seem to be feeding and I couldn't spot any sponges. Maybe you can?

Locality: Lembeh Straight, N.E. Sulawesi, 10 metres, Indonesia, Celebes sea, 12 August 2007, Sandy bottom. Length: 100 mms. Photographer: Kamal El Tawil.

Kind regards,
Kamal El Tawil


El Tawil, K., 2008 (Apr 2) Ceratosoma gracillimum feeding?. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20946

Dear Kamal,

Firstly, this is Ceratosoma gracillimum. In this species there is no mantle edge along the sides between the head and the large gill lobes. In C. tenue there is a small lobe on each side between the head and the gills. As in your last message, the lumpy mass is definitely sponge. In the photo alongside you can see a large hole [or siphon] which sponges use to suck fresh seawater into the colony. It is possible there is more than one sponge present. I have also added a close-up - not very clear I'm afraid - showing a purplish pink patch which is almost certainly the dysideid sponge Euryspongia. Interestingly, Ken Tucker's message [#20282] gives good evidence that this species feeds on a species of Euryspongia. Before this the only information we had on feeding in this species was indirect evidence from the presence of sesquiterpenoid molecules in chemical assays (Rudman & Bergquist, 2007).

  • Rudman, W.B. & Bergquist, P.R. (2007) A Review of feeding specificity in the sponge-feeding Chromodorididae (Nudibranchia: Mollusca). Molluscan Research, 27(2): 60-88

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Apr 2). Comment on Ceratosoma gracillimum feeding? by Kamal El Tawil. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/20946

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