EFFECTS OF SIZE AND CONCENTRATION OF FOOD PARTICLES ON THE FEEDING BEHAVIOR OF THE MARINE PLANKTONIC COPEPOD CALANUS PACIFICUS 1

When adult females of Calanus pacificus are fed on monospecific cultures of centric diatoms which grow as single cells, a predictive relationship is found between feeding behavior of the copepods and size and concentration of food particles. Ingestion rate of copepods increases linearly with cell concentration up to a maximal rate. This maximal ingestion rate, expressed as carbon, is the same for copepods feeding on diatoms ranging in diameter from 11–87 µ . As the size of food particles increases, the carbon concentration at which this ingestion rate is achieved decreases. Thus females of C. pacificus can obtain their maximal daily ration at relatively low carbon concentrations of large cells.