THE INVASIVE ALGA CAULERPA-TAXIFOLIA IS NOT A SUITABLE DIET FOR THE SEA-URCHIN PARACENTROTUS-LIVIDUS

Food intake by the sea urchin Paracentrotus lividus (Lamarck, 1816) wa s investigated when sea urchins were given a diet exclusively composed of Caulerpa taxifolia (Vahl) C. Agardh, an invasive alga recently int roduced into the Mediterranean. Experiments were carried out under aqu arium conditions over two periods of 3 months. In the first experiment (summer/autumn), P. lividus consumed C. taxifolia 3-30 times less tha n control algae. In the second experiment (winter/spring), consumption of C. taxifolia by urchins was low at the beginning, but increased du ring the following weeks to achieve levels similar to those of control s. Whatever the period of year, urchins with C. taxifolia diet showed marked loss of spines, long righting times and small gonosomatic ratio s compared with the controls. This may result either from the action o f toxic substances in the alga, and/or from a too small food intake (p articularly in summer).