Fig. 4. Kinematics of archer fish predictive starts. Comparison of two responses (imaged at 500 frames s^-1) in which the fish had to execute a small turn (filled circles; response of Fig. 3) and a larger turn (open circles; frames shown in Fig. 11A). Color coding of the two kinematic stages is as in Fig. 3 with dark blue highlighting the initial bending phase and light blue indicating subsequent straightening. Time is set to zero at the start of stage 2. (A) Time course of chord length (CL) shows initial bending and later straightening. Inset illustrates how CL is defined as the minimal distance between mouth and caudal peduncle, normalized to body length. The amount of bending (i.e. the minimum CL) was larger for the larger turn. The courses shown are smoothed using a 5-point moving average. (B) The course of turning (accumulated angle ). The inset illustrates how the angular increment was derived by lines (dotted) drawn through the anterior body portion of the fish in successive frames. The lesser turn (filled circles) already aligned the fish to the point of impact by the end of stage 1 and the angle was then kept to. In the large turn (open circles) turning continued and alignment was achieved during stage 2. (C) The accumulated displacement (s). The inset illustrates how the increment s between successive frames was derived. The distances (a, b) between the mouth and the point of intersection (red) of the stippled lines through the anterior body part were taken and s taken as their difference. For each frame, the mouth position was independently digitized 3 times and the average position was taken. In the two responses shown, speed values acquired in the first 20 ms after the end of stage 2 were 1.225 m s^-1 for the lesser turn (filled circles) and 1.015 m s^-1 for the wide-angle turn (open circles).