FEEDING AND PHARMACOLOGICAL PROPERTIES OF ANISODORIS NOBILIS INDIVIDUALS (MOLLUSCA; NUDIBRANCHIA) SELECTING DIFFERENT NOXIOUS SPONGES PLUS DETRITUS

Individual differences in Anisodoris nobilis food selection were sought in the natural environment, to determine why their digestive glands differed pharmacologically. Of 73 stationary A. nobilis specimens turned over in the initial survey, 84% of those on sponges and 65% of those on detritus had their mouths everted; no others were feeding. Microacoustic observations showed that an individual stops on a sponge, everts its proboscis for a long period, then rasps the sponge. Field studies of individual diets were made without disturbing the animals, by tabulating the foods on which each nudibranch was found to be stationary.Twelve individual nudibranchs observed subtidally about three times daily for 8 days differed significantly in the sponge species they selected. Each individual was found stopped on detritus during roughly 50% of the observations, remaining there for 1 day at a time. Each nudibranch stopped for <2 days on a sponge, sometimes returning to that spot during subsequent days. Among individua...