Feeding by an omnivorous planktonic copepod aetideus divergens Bradford

Abstract

Aetideus divergens Bradford is representative of a large group of marine planktonic calanoid copepods which are omnivores or mixed feeders. Because very little quantitative information is available on the feeding behavior of these copepods, laboratory feeding experiments have been carried out with adult female A. divergens presented with various sizes and concentrations of diatoms and freshly hatched nauplii of Artemia. The copepod fed most efficiently on the largest size of diatom and on Artemia nauplii, but was peculiarly inefficient at feeding on small diatoms, even when they were available at very high concentrations. In this respect, the copepod differs from filterfeeding copepods, such as Calanus pacificus Brodsky. A possible explanation of this difference depends upon Aetideus being less capable of handling very small food particles than Calanus. Aetideus divergens and its congeners usually occur at subsurface depths not far below the mixed layer and seem to be adapted for feeding on large particles, possibly large phytoplanktonic organisms and fecal pellets, which sink out of the mixed layer.