Re: Pleurobranchus from the French Mediterranean

July 14, 2008
From: Dominique Horst

Concerning message #21071:

Hello Bill,

Still at the same site, we've met a specimen of Pleurobranchus testudinarius. It seems that this species has strong colour variation. Is it accordingly to their food variation? I wonder what can be the significance of the name testudinarius? Have you an idea about the name root ?

Locality: Cagnes, 8 m, France, Mediterranean sea, 09 July 2008, muddy. Length: 200 mm. Photographer: Dominique Horst.

Many thanks in advance,
Kind regards,

Horst, D., 2008 (Jul 14) Re: Pleurobranchus from the French Mediterranean. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

Dear Dom,

Many species of Pleurobranchus show quite a variation in background colour, from pale yellow to dark brown and even reddish purple. I don't know of any work that has been done on colour variability. More importantly we have very little information on what any species of Pleurobranchus feeds on. There are a few records of species feeding on ascidians but not enough to even hazard a guess as to whether body colour is relted to food colour.

I can help you with the origin of testudinarius. I am not a Latin scholar but I remember once reading that Roman soldiers had a defensive formation in which they all got into a tight group and the soldiers in the middle held their shields above their heads and the one around the edge held their shields out sideways so they were all protected from their enemies' arrows, spears and swords. They looked like a tortoise which in latin was testudo - which was also the name given to the defensive formation. If you look at your Pleurobranchus photos you can see the 'shields', outlined in pink, and imagine the Roman soldiers underneath.

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Jul 14). Comment on Re: Pleurobranchus from the French Mediterranean by Dominique Horst. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from

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