Mollusca: Bivalvia

This chapter introduces general biology, morphology, ecology, physiology, life histories, evolution, and classification of bivalve molluscs found in freshwaters of North America. The freshwater bivalves of North America are represented by two native groups, the freshwater mussels (Unionoidea) and the pill, fingernail, and pea clams (Sphaeriidae), as well as two widely publicized invasive genera, Corbicula and Dreissena. The North American fauna of freshwater bivalves is the richest in the world, with about 350 species of mussels and clams, nine or so of which are exotic. The latter includes Asian clams and zebra mussels. Molluscs, are major deposit and suspension feeders within permanent lakes, streams, and large rivers, where they are often the largest invertebrates in body mass. Freshwater mussels are considered to be part of a guild of freshwater, sedentary filter feeders. These molluscs have interesting and important ecological interactions with their environments. Given the processes they perform and their high biomass in rivers where they are abundant, freshwater mussels have the potential to have strong effects by modifying the habitat and controlling the availability of resources to other organisms.