Fig. 3. Body wavelength, body wave speed, and lateral amplitude along the body for all treatments, where L is the total length of the fish. The x axis (from left to right): experiments in the light with lateral line intact for the first day of cylinder exposure (V+L+₁); the same experiments with fish exposed to the cylinder on two consecutive days (V+L+₂, see Materials and methods); experiments in the dark (gray fill) with lateral line intact on the first day (V–L+₁); experiments in the light with lateral line blocked on the second day (red box, V+L–₂); and experiments in the dark with lateral line blocked on the second day (gray fill and red box, V–L–₂). Gray lines connect treatments that are statistically significant at P<0.05. Values for control fish that were exposed to the cylinder for one (V+L+₁) and two consecutive days (V+L+₂) are statistically the same, illustrating that fish do not alter swimming kinematics as a result of previous exposure to the experimental setup. (A) Body wavelength and (B) speed of propagation down the body are statistically higher when the lateral line is blocked and tend to increase in magnitude and variance in the dark. (C) Lateral body amplitudes were measured relative to the midline at three locations. Circles represent the tail tip, squares represent the center of mass (COM), and triangles represent the snout. The tail tip and COM amplitudes for fish in the dark with a blocked lateral line (V–L–₂) are significantly lower than control fish on day 1 (V+L+₁) and 2 (V+L+₂), as well as for fish in the dark with an intact lateral line (V–L+₁). All values are mean ± s.e.m., N=16 tail-beats for four fish.