Pleurobranch acid secretions

May 6, 1999
From: Rhanor Gillette

Hi, Bill.
We in this lab greatly enjoy your sea-slug forum. Thank you for maintaining it. I was interested in yours and others' observations on Pleurobranchus forskalii. Is this the species that can grow up to a foot?

I wonder how easily available this species is, were I to find myself on the Barrier Reef in Oz? I work on pleurobranchs (Pleurobranchaea californica mostly), and have a comparative study I do when possible (rarely). I once looked at acid secretion and how it is integrated into the animals' behavior in Pleurobranchaea, Berthella, Berthellina and Pleurobranchus sp. -- J. Exp. Biol. 156, 335-347 (1991) -- the skin pH drops to 1.5 pretty fast. Never could bring myself to taste the animals, ought to, I guess but I'll put it off. Weirdly, taurine at 0.1-10 mM concentrations in SW triggers it in Pleurobranchaea, and I've been wondering if it does it for all the pleurobranchomorphs (there is some kind of selective receptor), but its hard to get any other species here in the american midwest.


Rhanor Gillette
University of Illinois at Urbana-Champaign

Gillette, R., 1999 (May 6) Pleurobranch acid secretions. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Rhanor,
Glad you like the Forum. Pleurobranchus forskalii is usually found growing to about 10cm in length, but a few years ago in northern New Caledonia I was on a French Expedition where a couple of divers proudly returned with a couple of animals they had found in 12m which were 31cm long! So they definitely reach a foot in length. I must say I find animals growing that big a bit of a problem - too big to photograph, too big to dissect, too big to fit in any container etc. Those two, thanks to the insistence of Philippe Bouchet are now safely stored in a large polydrum in the bowels of the Paris Museum.

Concerning finding them if you are lucky enough to come to Oz. Well I have discussed this with a couple of experienced Great Barrier Reef collectors and their experiences are much the same as mine from East Africa. At times they can be very common (up to 10cm long) in shallow water back-reef - reef-flat regions, but there is no guaranteed time of year that you will find them. Sorry I can't be more deinite than that.

I would be interested in hearing of your work on Pleurobranchaea. Perhaps you could write an account for the Forum - even a review you've used for university report etc would be great. How do you work with these animals so far from the sea? Do you keep a breeding colony going or do you have to buy them from a commercial supplier?

Best wishes,
Bill Rudman.

Rudman, W.B., 1999 (May 6). Comment on Pleurobranch acid secretions by Rhanor Gillette. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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