Chromodoris leopardus from Sipadan

June 28, 2005
From: Sergey Parinov

This picture of Chromodoris leopardus almost cost me missing the famous giant school of Chevron barracuda.

Locality: Sipadan Island, Malaysia. Celebes Sea. Depth: 15 m. Length: 4 cm. April 2003. Vertical reef wall. Photographer: Sergey Parinov

Sergey Parinov

Sergey Parinov, 2005 (Jun 28) Chromodoris leopardus from Sipadan. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Sergey,
I'm glad you didn't miss the barracuda experience. I know it sounds a bit strange to be excited by a photo of an anus, but your photo shows very clearly the anal papilla surrounded by the circle of gills. I am often asked why the animal's waste products are released amongst its gills, which need clean oxygenated water. This phenomenon is best explained as an historical legacy, much like we have tail bones of no functional use. In the snail-like ancestors of opisthobranchs, the flap of specialised skin [the mantle], which produces the shell, forms a cavity, protected by the shell, which we call the mantle cavity. This cavity protects the gills and is a place into which the anus, kidney opening and reproductive openings are situated. In nudibranchs the shell and mantle cavity have been lost during evolution, but the ancient link between gills and anus has remained. Have a look at the Torsion Fact Sheet for more background information.
Best wishes,
Bill Rudman

Rudman, W.B., 2005 (Jun 28). Comment on Chromodoris leopardus from Sipadan by Sergey Parinov. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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