Suspension feeding on phytoplankton by Solemya velum, a symbiont-containing clam

Abstract

Solemya velum Say, a bivalve found in coastal sediments along eastern North America, is known to harbor chemoautotrophic symbionts in its gill tissue These lntracellular bacteria are thought to contribute significantly to the nutrition of the host S. velum's behavlor, however, suggests that it inay feed on suspended particles. The ingestion of 14C-labeled phytoplankton (Isochq~sis galbana, Dunaliella tertiolecta, and Synecl~ococcus sp.) by S. velum was compared to Mya arenaria, a suspension-feeding bivalve that is not assoc~ated with symbionts. S. veluni Ingested only the smallest food particles (Synechococcus sp.) in detectable amounts. The number of cells ingested, however, averaged only about half that taken up by M. arenana under identical experimental conditions. It is hypothesized that the symbiotic clam S velum does not ingest particles for bulk nutrition, but may depend on a small amount of phytoplankton for essent~al nutrients available only from exogenous sources.