Molluscs

Abstract

Most molluscs are not herbivores. Apart from the many clearly obligate carnivores, the myriad of aquatic filter and detritus feeders eat bacteria and algae as phyto- and zooplankton, or growing on the surface of rocks, aquatic plants, or organic and mineral particles in sediments. There are few apparently true herbivores, those that eat only the tissues of vascular plants. Of these the terrestrial gastropods, snails and slugs, are probably the best known. They eat two sorts of tissues. When it is available they selectively eat flush new growth, especially seedlings (with devastating effect as any gardener knows), but for most of the time such food is not available. Then they select senescing or dead parts of plants (Grime and Blythe 1969). Others eat rotting wood, fungi, soil detritus, or carrion (Mason 1970). All are saprophagous to a greater or lesser degree, and as such their diet is variably supplemented by microbial or animal protein.