OBSERVATIONS ON THE FEEDING ACTIVITY OF THE ISOPOD, IDOTHEA BALTICA (PALLAS)

Abstract

Observations both in the laboratory and in the field were made on food preference, feeding behavior, rate and amount of feeding in the isopod, Idothea baltica (PALLAS), These observations demonstrated that I. baltica is an omnivore that feeds readily on both the Fucus that harbors it and on both living and dead animals. Values obtained from several experiments showed that, on the average, an individual consumed about one-fifth of its body weight in half an hour when feeding on Fucus. When preying on a member of its own species, it consumed approximately more than one-third of its body weight in four hours. It was demonstrated that the animals fed preferentially on the filiform processes on the surface of the Fucus thallus and on the younger a{ld more tender portions of the plant. When feeding on other crustaceans, including individuals of their own species, they attacked living animals of up to one-half of their own length and dead or molting animals of almost their own size. They grasped their prey with the pereiopods and usually feeding was initiated on the soft ventral parts. Eventually, the prey, including the exoskeleton, was totally consumed.