Meeting Abstract
The response of precise three-dimensional trail following by the aquatic microcrustacean copepod is a consequence of viscosity-induced attenuation of mixing that enables the persistence of small-scale chemical and hydrodynamic cues. Temora longicornis , a coastal marine copepod, and Hesperodiaptomus shoshone , a high-alpine freshwater lake copepod, exhibit tracking of laminar trails. High-speed videography coupled with high-magnification Schlieren optics enabled us to visualize both the deformation of the trail signal and the propulsive movements of the male copepod, providing the opportunity to examine a guidance system at an intermediate Reynolds number. Males happily followed the trails we made and our observations show clear differences between the marine and freshwater species. Comparative analyses of these two species reveal tracking mechanisms that differ in sensor location with respect to the trail and locomotory kinematics. Copepods perform directed motions that lead them to a stimulus source in the absence of other collimating stimuli. Tracking by the copepod around the trail allows it to have one or numerous sensors inside and outside the trail to facilitate edge detection using spatial sampling. The advantage of this remarkable behavior of following trails fast and accurately is to encounter mates or food patches more frequently, thus contributing to recruitment into the population and transfer of energy up the trophic food web. Precise mate and food finding strategies found for pelagic copepods may be a key adaptation, promoting survival in these open-ocean planktonic populations.
