Re: Caloria elegans from the French Mediterranean

July 31, 2008
From: Dominique Horst


Concerning message #20021:

Hello Bill,

These Caloria elegans have a great variation in colour. It's probably, as in many other cases, a result of their food colour. The last two were found at the same place, which means that two individuals, quite the same size and at the same place, are feeding so differently?

Locality: Antibes, 12 m, France, Mediterranean sea, 06 April 2008. Length: 12 mm. Photographer: Dominique Horst.

Kind regards,
Dom.

dominique.horst@wanadoo.fr

Horst, D., 2008 (Jul 31) Re: Caloria elegans from the French Mediterranean. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21502

Dear Dom,

In aeolids, the colour in the cerata is certainly related to the colour of their food but I don't know if it is always a direct relationship. In egg-eating aolids [species of Favorinus] the colour in the ceratal digestive gland is definitely the same as the colour of the eggs they are eating, but in small hydroids it may be more difficult to show as it is often difficult to see the polyp colour. Interestingly in your two lower photos of animals which were found together, the 'yellow' one in the middle photo has traces of the orange brown colour of the lower photo, which would suggest the middle one has changed its food source.

In the upper photo, the digestive gland duct in each ceras seems to be almost empty and colourless suggesting the animal has not fed for a while. The orange layer in the body is not part of the digestive gland but is the gonad - the organ which produces the eggs and sperm. I don't know if the colour of the eggs is related to food colour in this example, but I guess it is possible.

Best wishes,
Bill Rudman

Rudman, W.B., 2008 (Jul 31). Comment on Re: Caloria elegans from the French Mediterranean by Dominique Horst. [Message in] Sea Slug Forum. Australian Museum, Sydney. Available from http://www.seaslugforum.net/find/21502

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