A lightning stab in the dark: fluid dynamics of attack jumps of ambush feeding copepods

A large class of marine zooplankton, in particular among copepods, are ``ambush feeders'', who wait for their prey and capture them by surprise attacks. The successful attack must happen so rapidly and unexpectedly that the prey cannot escape and the fluid disturbances created by the attack must be so small that the prey is not pushed away by the flow created by the much larger approaching copepod. Detailed high speed video\textit{ in vivo} reveals that the nearly blind copepod manages to perform the attack by precision maneuvering during a rapid jump of a few milliseconds moving approximately one body length. The prey is pushed only by around 10{\%} of this distance, and thus the bulk flow must be close to potential with small boundary layers. From this, we argue that the smallest ambush feeding copepod, \textit{Oithona davisae}, is close to the size limit for the ambush feeding strategy. REF: T. Ki{\o}rboe, A. Andersen, V. J. Langlois, H. H. Jakobsen and T. Bohr, PNAS (2009)