Re: Ceratosoma gracillimum feeding? from Lembeh

July 23, 2007
From: Ken Tucker

Concerning message #20164:

I thought perhaps someone might be able to glean some info from this photo of Ceratosoma tenue.

Locality: North Sulawesi, Lembeh Strait, 10 metres, Indonesia, Celebes Sea, 9 Nov 2005. Length: 7 cm. Photographer: Ken Tucker.

Ken Tucker

Tucker, K. C., 2007 (Jul 23) Re: Ceratosoma gracillimum feeding? from Lembeh. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Ken,
This is an very useful find. Although even in the high resolution copy of your photo, I can't make out enough detail in the blue sponge to make a positive identification of the sponge, the presence of Mexichromis multituberculata on the sponge as well is a very large clue. If you look at Richard Swann's recent message [#20194], and my comments, you will see that Mexichromis multituberculata feeds on a species of the dysideid genus Euryspongia, and it is very similar in shape and morphology to the blue sponge in your photo, so I think we can be fairly sure that this Ceratosoma feeds on Euryspongia.

As to the identity of the Ceratosoma, the lack of secondary mantle lobes on eacxh side between the gills and the rhinophores suggest this is C. gracillimum rather than C. tenue. This is a valuable bit of information, as it confirms the only information we have on this species, which is from the sponge metabolites found in its mantle glands which suggest it feeds on a dysideid sponge. It's certainly possible the sponge C. tenue is feeding on in the message you refer to above [# 20164], is also Euryspongia, but I'm afraid we don't have a Mexichromis on hand to give us a clue.

Best wishes,
Bill Rudman

Rudman, W.B., 2007 (Jul 23). Comment on Re: Ceratosoma gracillimum feeding? from Lembeh by Ken Tucker. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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