Suspension feeding: Basic mechanisms controlling recognition and ingestion of larvae

Oysters (Crassostrea virginica) are valuable subjects for investigations of basic mechanisms regulating suspension feeding on invertebrate larvae. In separate laboratory experiments, we introduced inert particles or larvae to the oyster mantle cavity. Small inert particles (<40-mu m diam) equal to phytoplankton cells in size were eaten, whereas large inert particles (>100-mu m diam) equal to larvae in size were rejected. Neither particle specific gravity nor phytoplankton in the seawater medium affected ingestion of inert particles or larvae. Oysters consumed a wide range of invertebrate larval forms, including conspecific veligers. Nearly all larvae (>75%): delivered to the oyster mantle cavity, except those of Bugula neritina, were eaten and digested. Feeding stimulants in the larvae were a mixture of polar and nonpolar compounds that were insoluble in seawater. Although contrasting mechanisms regulated feeding on different-sized particles, ingestion of larvae was strictly controlled by particle surface chemistry (=flavor).