Pleurobranchus forskalii, P. peroni

April 29, 1999
From: K. Koyanagi

ID: Pleurobranchus forskali, Pleurobranchus peroni
Location: Hawaii(North Shore of Oahu)

I am interested in more background information on these two organisms. Where else can they be found? What do they eat? How can you tell what sex thay are? Are they toxic? Any information
Any help ASSP would be much appreciated.

K. Koyanagi


Koyanagi, K., 1999 (Apr 29) Pleurobranchus forskalii, P. peroni. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear K. Koyanagi,
I'm afraid we don't know much about the biology of any species of Pleurobranchus. The two species your are interested in, Pleurobranchus forskalii and Pleurobranchus peroni are found throughout the tropical Indo-West Pacific and are sometimes found in large numbers on shallow reef flats.

All Sea Slugs are hermaphrodite, with a full complement of male and female organs. In Pleurobranchus they open on the right side of the body just in front of the gill. You can see the partly extended penis in the photo at the Top of this Page.

It is thought that all species of Pleurobranchus feed on ascidians (Sea Squirts), eating both solitary and compound species. However the European species, P. membranaceous, is the only species we have direct observations on.

Concerning their toxicity. Many Sea Slugs, including pleurobranchs, have secretory glands in their skin which are used for defence. The milky secretions of pleurobranchs are said to be quite acidic.

Any information you can collect on the basic natural history of these two species would be of interest. For example, What do they actually feed on? What do their egg masses look like? etc.

Best wishes,
Bill Rudman.

Rudman, W.B., 1999 (Apr 29). Comment on Pleurobranchus forskalii, P. peroni by K. Koyanagi. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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