Some mechanisms for the control of pumping activity in bivalves

Abstract

1) Filtration rates of a number of bivalves are compared on a basis of the porosity of their gills. There is no obvious difference in the performance of infaunal, siphonate bivalves and epifaunal, non‐siphonate bivalves. 2) The exhalant aperture may control water flow in three ways : periodic closure of the exhalant aperture; restriction of the exhalant aperture to a small size; rapid and repeated expansion and contraction of the exhalant aperture. 3) In high concentrations of suspension of Phaeodactylum, a reduction in the time spent pumping accounted for reduced filtration rates up to concentrations of 1 million cells/ml in the cases of Mytlius edulis and Mya arenaria, and up to concentrations of ½ million cells/ml in the cases of Cerastoderma edule and Venerupis pullastra. 4) Water flow in a bivalve has been examined from a theoretical standpoint and suggests that an 80 % reduction in the size of the exhalant aperture is required before greatly affecting the total resistance to flow through the system.