Figure 3

Figure 3

Free-swimming open-loop behavior. Individual freely-swimming zebrafish larva were presented with virtual open-loop visual stimuli while multiple behavioral metrics were recorded (332 Hz). The curvature along 14 tail segments, from the most rostral portion of the tail at the tail base to the most caudal portion of the tail at the tail tip, were calculated and averaged into 4 consecutive bins (cyan to magenta). The angle of the left (red) and right eye (green), the cumulative heading angle (yellow), the visual stimulus angle (black), tail beat frequency (orange), peak amplitudes (navy blue), and bout detection (gray) are displayed. (A) A looming dot stimulus (predator avoidance) produced a rapid escape turn followed by a burst swim and a marked divergence of the eyes (arrow). The location of the looming stimulus was fixed with respect to the heading direction and centroid position of the larvae such that the visual angle of the stimulus increased exponentially to a fixed size of the visual field. (B) During optomotor swimming, the direction of the OMR stimulus was fixed to the heading direction of the larvae and the point at which the OMR stimulus pivoted was fixed to the larva’s centroid. In this example, the OMR stimulus traversed 90° to the left of the heading direction of the fish, which consistently drove the fish to produce routine turns. (C) A small white dot on a black background was presented to larvae from below to create virtual prey stimuli. In this example, the prey stimulus moved along an arc with a fixed radius from the centroid. The velocity of the dot along the arc was defined by a sinusoidal function which reached a maximum of 100°/s directly in front of the larvae and reached a minimum of 0°/s at 60° to the left and to the right of the heading direction. Larvae displayed characteristic hunting behavior towards this stimulus by producing J-turns when the stimulus was presented to the lateral parts of the visual field and slow, approach swims when the stimulus was presented in the frontal field. These hunting episodes were also characterized by convergence of the eyes throughout the hunting episode (arrow). Images of larvae in (A–C) were adjusted so they stand out against the stimulus background.