Meeting Abstract
As one of the most numerous animal groups and a key link in aquatic food webs, copepods have developed numerous anti-predator strategies. One of the most effective is the escape response. Copepods are capable of reaching speeds over 500 body lengths per second and can respond to a hydrodynamic disturbance is as little as 2-3 ms. The pereiopods or ‘swimming legs’ generate propulsive thrust for escape swimming but compared to other animals, the force per gram of muscle controlling the pereiopods, is exceptionally powerful and fast. How copepods achieve such force has remained undetermined. In this study we employ a new approach to micro-scale particle image velocimetry (µPIV) to visualize fluid motion created by free-swimming copepods. Our results show that the both the antennae and telson contribute significantly to thrust generation during escape swimming. Antennae motion acts both to re-orient the animal as well as provide initial thrust prior to initiation of the swimming legs. The telson creates a substantial jet of fluid which can even overwhelm the one produced by the pereiopods. During the recovery stroke the telson can create secondary positive thrust which coincides with the resetting the pereiopods for the next stroke. This appears to aid in offsetting any negative thrust from the recovery stroke and prevents copepods from moving backwards. These results help to address the uncertainty of copepod force production during swimming and aid our understanding small-scale fluid dynamics that govern efficient animal locomotion and aquatic predator-prey interactions.
