A threshold feeding behavior in Calanus pacificus1

Abstract

Adult females of a marine planktonic copepod, Calanus pacificus , were fed the diatom Thalassiosira fluviatilis at several densities of cells well below the critical concentration. As food concentration decreased, copepods filtered at a constant maximal rate until their ingestion rate fell below about 15% of the maximal hourly ration; then the copepods fed at a significantly depressed rate. The concentration of food at which this threshold feeding behavior occurs apparently depends on the size of the food particles.