Fig. 3. Corrective roll turn performed by an intact animal. (A,B) The side and top views for 18 consecutive frames. (C–E) Curvature plots for frames 2 (red), 13 (blue) and 17 (green) are analogous to those in Fig. 2. In frame 2, the animal is positioned with its right side up and starts rolling to the right. In frame 13, the animal has almost reached the dorsal-side-up position. In frame 18, the animal is positioned with its dorsal side up and its body is straightened in the sagittal plane; this shape is similar to that during normal swimming. Note that in E all data points for frame 2 are situated in right ventral and left dorsal quadrants and that most of the data points for frame 13 are located in left ventral and right dorsal quadrants. On the other hand most of the data points for frame 18 are located close to the abscissa, as seen during undisturbed swimming. R, right; L, left; D, dorsal; V, ventral sides of the body. White dots in frames 13-18 are the white markers attached to the skin along the dorsal midline.