Feeding and Digestion
The molluscan gut has a separate mouthand anus. Digestion involves salivary
anddigestive glands(Fig. 7.19) that releasedigestive enzymes,
which break downfood into simpler molecules. Other as-pects of the digestive system differ amonggroups and according to diet.Chitons and many snails are grazers. They have a rasping radula that removesminute algae from surfaces or cuts throughlarge seaweeds. Their relatively simple di-gestive system can efficiently process largeamounts of hard-to-digest plant material.Digestion is partly extracellular in the gutcavity and partly intracellular in the diges-tive glands. Some shell-less gastropodsthat feed on seaweeds keep the seaweeds’chloroplasts
intact. The chloroplasts arekept in the digestive gland and continue tocarry out photosynthesis, providing nour-ishment for the gastropod.Carnivorous snails have a radulamodified to drill, cut, or even capture prey