Re: Caloria elegans from the French Mediterranean

Dear Dom,

One of the biggest problems in studying the biology of nudibranchs is the difficulty in accurately identifying their prey. Almost all their food items -sponges, hydroids, bryozoans, soft corals etc - are groups which need expert assistance in identification. Unfortunately such experts are very scarce on the ground. Looking at your photos they appear to me to be a sequence showing this Caloria 'eating' two stalks of a small hydroid colony. Some aeolids feed by delicately biting off individual polyps as they crawl along the hydroid colony. In other cases, such as here, the aeolid ingests a stalk or branch, stripping or breaking off all the polyps in their individual cases, and then moves on to another branch. This happens in hydroids with small stalks or branches, and small polyps which retract back into their cases. What is left after feeding are the stalks minus the polyps. Once they have fed there is no way to easily identify the hydroid.

Best wishes,
Bill Rudman