PREY SELECTION BY THE SOUTH-AFRICAN CAPE ROCK LOBSTER JASUS-LALANDII - ECOLOGICAL AND PHYSIOLOGICAL APPROACHES

Certain aspects of the foraging behavior of the Cape Rock Lobster, Jas us lalandii, were investigated to determine whether this animal select s prey or merely feeds randomly on a variety of prey items in proporti on to their abundance. We also investigated the lobsters' ability to d igest unusual food items, e.g., sponges and seaweeds, which are someti mes found in large quantities in their gut. The study combined field o bservations with analyses of gut contents and digestive enzyme activit y. The results suggest that Jasus lalandii is primarily a carnivore wi th limited ability to digest plant tissue. Preferred foods are black a nd ribbed mussels (Choromytilus meridionalis and Aulacomya ater corres pondingly), and a large variety of marine arthropods; activities of pr otease and chitinase are strong. Seaweeds are probably only incidental ly caught by lobsters. They are only sporadically found in lobster gut s. Moreover, neither laminarinase nor alginase activity, which is esse ntial for the digestion of plant tissue, was detected. It is possible, however, that Jasus lalandii extracts some starches from marine plant s as amylase activity in their gut is strong. The most significant fin ding of this study is the ability of lobsters to feed on and digest sp onges. This is evidenced by large quantities of sponge in certain lobs ter guts and strong activity of the protease gelatinase (which breaks down the sponge collagen skeleton).