Re: Diaulula sandiegensis from British Columbia

April 7, 2003
From: Brian Penney

Dear Bill,
Concerning Jackie & Glen's message about the food of Diaulula sandiegensis. Haliclona cf. permollis is one of its major food items in the intertidal from what I've seen in Bamfield, British Columbia. This is also what Bloom (1974) found from his work in Washington State. In the intertidal Haliclona typically occurs in crevice microhabitats, presumably to reduce dessication risk, and seems to co-occur with prosobranch eggs quite frequently.

There is a purplish sponge in the lower left of their photo which looks like this species but I am not sure if it lives at the depth mentioned by Jackie & Glen. I am curious if they are sure about the depth? As you might know, D. sandiegensis has two coloration patterns: either the leopard spotted form in Jackie and Glen's photo, or the ring form on your Fact Sheet. Typically, I don't find the leopard spot form deeper than about 25' (8m) or larger than approximately 4cm; I find the ring form from about 20' to 60', and almost always larger than 4cm. Several of us are curious just how different the two forms are in distribution, habits, size, etc. Julia Kubanek once told me the two forms seem to have different secondary chemicals as well.

Reference:
• Bloom, S. A. 1981. Specialization and noncompetitive resource partitioning among sponge-eating nudibranchs. Oecologia, 49: 305-315.

Cheers
Brian

bpenney@ualberta.ca

Thanks Brian,
I wonder if this is the 'Doris echinata O'Donoghue, 1922' that Dave Behrens discusses in his earlier message? It would be interesting to know if the colour forms are depth related, or for that matter separated by some other parameter. It would be interesting to hear of other observations on these two colour forms
Cheers,
Bill Rudman

Rudman, W.B., 2003 (Apr 7). Comment on Re: Diaulula sandiegensis from British Columbia by Brian Penney. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/9576

Factsheet

Diaulula sandiegensis

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