Two colors for Bosellia mimetica

March 25, 2008
From: Miquel Pontes

Dear Bill,

We found three Bosellia mimetica specimens in our last dive. One of them was curious because it was not colored green as they are normally found here, but instead it was colored brown.

I could not found color variability documented in the bibliography for this species, despite I have seen in the Forum that these variations do exist.

These animals were found on Halimeda tuna, but curiously these algae were almost white in color and showing their calcified structure. Maybe the Halimeda algae were dying because of some other reasons, but could the Bosellias be the reason for the "bleaching" ?

Locality: Platja de Caials, Cadaqués, Costa Brava, 15 metres, Spain, Mediterranean Sea, 27 october 2007, Precoraligen rocky bottom. Length: 6-7 mm.. Photographer: Miquel Pontes.

Best regards,
Miquel Pontes

Pontes, M., 2008 (Mar 25) Two colors for Bosellia mimetica. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Miquel,

It is certainly interesting to find a brown colour form in the Mediterranean. It certainly accords with Colin Redfern's find of similarly coloured animals in the Caribbean. [see message #6121]

Concerning white patches on the Halimeda - I had always presumed they were from the activities of the sacoglossans, and as you can see in the close-up, the white regions are often patches on the green background, much like the scrape marks left by a grazing limpet. However these animals don't feed by scraping or grazing, they pierce a hole through the skin and suck out the cell contents. Perhaps in this example each patch represents an area of the plant that has had its cell contents sucked out.

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Mar 25). Comment on Two colors for Bosellia mimetica by Miquel Pontes. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from


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