Modes of cell capture in calanoid copepods1

Abstract

High‐speed cinematography was used to observe adult female copepods feeding in pure cultures of roughly spherical algal cells ranging from 4.5 to 22.0 µ m in diameter. Eucalanus pileatus and Paracalanus parvus detect and handle individual cells as small as 12 µ m. Continuous low amplitude movement of the second maxillae and combing of the appendages is used by E. pileatus to capture cells smaller than the 12‐ µ m sensitivity threshold. Different energetic costs are probably associated with capturing small and large cells, and the probability of copepods encountering large cells should be greatly increased due to remote detection. The above suggests that descriptions of selective feeding in grazing trials using Coulter Counter data are influenced by the size above which the copepods can detect individual cells and by the proportions of the pregrazing particle spectrum larger and smaller than this threshold.