The bivalve pump

A filter feeding bivalve, represented by the mussel Mytilus edulis, is modelled as a pump, consisting of the bands of lateral cilia along the gdl filaments, and a system of afferent and efferent canals. The relation between pump pressure a H p and pumping rate V was approached through studies of the relations between system resistances and V. The most important resistances distinguished were the frictional resistance m the canal system nHl, the exit loss 'H,,, and the back pressure a H l 2 , imposed on the pump as a means to study the performance characteristics of the gill system. Removal of the laterofrontal cini from the flow path by treatment with serotonin did not measurably affect the frictional resistance, but the cirri presumably constituted a flow-rate-independent resistance nH1,, arising from their beating against the flow. Thus, in steady state, a H p = AH, + AH,, + L H , ~ -t &H1,.