Meeting Abstract

107.5  Saturday, Jan. 7  Copepod Escape Jumps: Tomo-PIV Measurements of the Eliciting Hydromechanical Signal and Subsequent Flow Disturbance MURPHY, DW*; WEBSTER, DR; YEN, J; Georgia Institute of Technology; Georgia Institute of Technology; Georgia Institute of Technology

We present time-resolved tomographic particle image velocimetry (Tomo-PIV) measurements of freshwater (Hesperos) and marine (Calanus) copepod escape sequences initiated by an impulsive siphon flow that mimics the aquatic suction feeding of a piscine predator. Copepods perform dramatic escape jumps reaching speeds up to 500 body lengths per second in response to hydromechanical signals that are perceived as threats. Copepods sense the flow disturbance via their long, highly enervated, setae-bearing antennules, and the behavior response is believed to result from the structure of the velocity gradient field. Volumetric velocity measurements around the copepod allow determination of the threshold of both the magnitude and orientation of the hydromechanical disturbance along the antennules to which the animal responds. Further, the flow field resulting from a copepod escape jump, which may carry sensory information to a predator, consists of a wake vortex and a body vortex. These two counter-rotating viscous vortex rings of similar intensity can be modeled as an impulsive stresslet for comparison.