Copepod feeding currents: Food capture at low Reynolds number1

High‐speed motion pictures of dye streams around feeding calanoid copepods revealed that these important planktonic herbivores do not strain algae out of the water as previously described. Rather, a copepod flaps four pairs of feeding appendages to propel water past itself and uses its second maxillae to actively capture parcels of that water containing food particles. The feeding appendages of Eucalanus pileatus operate at Reynolds numbers of only 10 −2 to 10 −1 . In the viscous world of a feeding copepod, water flow is laminar, bristled appendages behave as solid paddles rather then open rakes, particles can neither be scooped up nor left behind because appendages have thick layers of water adhering to them, and water and particle movement stops immediately when an animal stops beating its appendages.