Particle capture by Daphnia carinata

Abstract

The morphology of limbs I, II and III of D. carinata was examined to ascertain whether they could act as filters for food particles. The dimensions of limb III setules (0.29 µm), the intersetular distances (0.23 µm), the associated Reynolds number (=10^-3) and boundary layers (5-9µm) suggest that the filtering function attributed to the limb is unlikely. Photographic data and the distribution of Ankistrodesmus falcatus on the feeding limbs show that limb II is the limb most closely associated with particle capture. The structural complexity of limb II suggests a functional diversity that includes particle capture and the redirection of feeding currents produced by limbs III and IV. Analysis of feeding rates and the size selection of algal particles shows that capture is not a simple mechanical process.