Meeting Abstract

P3.135  Friday, Jan. 6  Three-dimensional escape trajectories in larval fish RYAN, D S*; BERG, O; FEITL, K E; MCHENRY, M J; MULLER, U K; Wageningen University; California State University Fresno; University of California Irvine; University of California Irvine; California State University Fresno david.ryan@wur.nl

Fish execute C starts when they escape from a threat. The neural control, body kinematics and hydrodynamics of escape responses have been studied extensively in adult and larval fish. However, due to experimental constraints, biomechanical studies have focused on mapping the body movements and the center-of-mass trajectories from a dorsal view, neglecting the vertical dimension. These 2-dimensional studies suggest that prey randomize their escape trajectories, but bias the response away from the stimulus. This study explored the escape response of larval fish to a horizontal startle stimulus by recording the trajectories in three dimensions. We used a piston to generate a brief suction event simulating a predator attack. Consistent with published findings, our pilot data show that escape responses occurred either away or toward the stimulus in a horizontal plane, there seemed to be also no preference for left or right. However, zebrafish larvae consistently responded to a horizontal stimulus with a downward escape trajectory. We developed several hypotheses: (1) Demersal lifestyle: zebrafish larvae are demersal and might therefore always escape towards the substrate; (2) Insufficient pitch control: fish larvae are more dorso-ventrally asymmetric and have smaller pitch control surfaces than adults and therefore experience a stronger downward pitch; (3) Directional response: fish larvae process the direction of the stimulus and select a trajectory biased away from the stimulus. To test whether larvae use the stimulus direction to bias their escape response or default to a downward trajectory due to behavioral or mechanical constraints, we vary the direction of the stimulus.