The effect of concentration of suspension on the filtration rates and pseudofaecal production for Mytilus edulis L. , Cerastoderma edule (L. ) and Venerupis pullastra (Montagu)

Abstract Filtration rates for Mytilus edulis L., Cerastoderma edule (L.) and Venerupis pullastra (Montagu), using concentrations of Phaeodactylum that were found to give optimum results, were compared with rates of water transport recorded for other species. When expressed in terms of soft body wet weight there seems to be no clear distinction between epifaunal, non-siphonate bivalves and infaunal, siphonate species. There is a close correlation between the nitration rates of the three species when compared on a basis of the porosity of the gill. Filtration rates and pseudofaecal production for the three species have been determined for increasing concentrations of various types of suspension to arrive at some indication of the efficiency and the methods which these bivalves show in controlling ingestion. Two methods are apparent; 1. 1) by increasing the proportions of material rejected as pseudofaeces ( e.g., Mytilus edulis ), and 2. 2) by reducing the amount of material filtered by reducing filtration rates ( e.g., Cerastoderma edule and Venerupis pullastra ). As determined from the ability to maintain rates of ingestion at a constant level after a ‘satiation point’ is reached, Mytilus edulis is more efficient in controlling rates of ingestion with increasing concentration of suspension than the other two species. The rates of ingestion of particles at any one concentration was roughly proportional to the size of the particles, with the exception of Isochrysis and Platymonas which were ingested in smaller amounts than accounted for by their size alone; potential sources of food (algae) were not ingested in larger amounts than were inorganic particles.