GILL STRUCTURE IN ZEBRA MUSSELS - BACTERIAL-SIZED PARTICLE FILTRATION

The filtration mechanics of the gill of the zebra mussel, Dreissena po lymorpha, allow this organism to capture particles less than 1 mu m. T he organization of gill cirri and the architecture of the cirri appear to be important in providing the organism with the ability to filter small particles. Bacteria may provide a useful nutrient source for the se animals as bacterial proteins can be digested and assimilated into mussel proteins. Laboratory experiments indicate that D. polymorpha is capable of filtering and assimilating a wide range of bacteria rangin g in size from 1-4 mu m. Unionid species appear to be at least an orde r of magnitude less efficient at filtering bacteria than D. polymorpha . Because of its relatively smaller gill size, C. fluminea also filter s bacteria less efficiently than D. polymorpha. We suggest that bacter ial utilization by freshwater mussel species has important population and evolutionary implications.