Platydoris argo from southern France

July 28, 2008
From: Dominique Horst


Hello Bill,

I've a couple of Platydoris argo with their eggs ribbon. As you can see their colour is dark red. If the general colour (included eggs) depends on their food, I'm puzzled about what can be this food. I did not see any red orange sponge around, as they are living on mud .... This colour was only on the gorgonian Lophogorgia ceratophyta... Could this be their food?

Locality: Cagnes, 8 m, France, Mediterranean sea, 1 July 2008, muddy. Length: 60 mm. Photographer: Dominique Horst.

Kind regards,
Dom.

dominique.horst@wanadoo.fr

Horst, D., 2008 (Jul 28) Platydoris argo from southern France. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21673

Dear Dom,

Only some sea slugs make use of colour pigments from their food. Some transparent or semi-transparent species with very branching digestive glands take on the colour of their food because we can see it in their digestive system. A few others actually remove colour pigments from their food and incorporate the pigments into their skin. However many of them produce their skin colour genetically. Some have evolved colour patterns to match the colour of their food, but many others have colours which make the animals blatantly obvious. Have a look at the Fact Sheet on colour in sea slugs and the pages on Defence - Colour patterns, and Camouflage.

I am sure P. argo is not eating gorgonians. Concerning the whereabouts of the sponge it is eating.  Many sponges are able to survive being covered with a fine layer of silt and debris which can completely hide the presence of the sponge colony. Many can also survive being overgrown by algae. I suspect from your photos that their sponge food is nearby but it is either hidden in a crevice or under a rock, or is covered in a layer of silt or algae. I know the last thing you want to do when diving is to disturb the bottom and make the water murky, but that might be the way to find their food.

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Jul 28). Comment on Platydoris argo from southern France by Dominique Horst. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21673

Factsheet

Platydoris argo

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