Detection and capture of inert particles by calanoid copepods: the role of the feeding current

Although there is a scarcity of supporting empirical evidence, it has long been suspected that calanoid copepods use mechanoreception to detect the presence and location of potential prey items entrained in the feeding current. In this study, we document the first observations showing a freely, swimming calanoid copepod, Skistodiaptomus oregonensis, attacking prey-sized, non-motile, inert particles entrained in the feeding current before the particles contact the copepods sensory, appendages. Feeding current geometry, fluid velocities and associated behaviours that characterize these interactions are described. The results of this study show how copepod swimming behaviour coupled with a low-velocity feeding current, not only increases copepod encounter rates with inert pray by increasing direct contact rates, but also increases the probability, of detecting and capturing remotely, located prey that have well-developed escape responses. In turbulent regimes, a far-reaching, low-velocity feeding current should increase encounter rates, but only if coupled with behaviours that quickly, minimize separation distances once prey is detected.