Fig. 1. C-start of a zebrafish larva (age 5 d.p.f., body length L=4.2 mm). Swimming kinematics. (A) During the preparatory stroke the body, represented by its midlines, adopts a C shape. Silhouettes (left, time step 10 ms) and midlines (right, time step 1 ms) of a fish larva. Black arrow, path of the centre of mass (dark red dot); blue arrow, path of head; red arrow, path of tail. (B) During the propulsive stroke the body straightens and the tail completes the first tail-beat cycle. Silhouettes (right, time step 10 ms) and path of the centre of mass are shown for preparatory plus propulsive stroke; midlines (left, time step 1 ms) are shown for the propulsive stroke only. White arrow, path of the centre of mass (dark red dot); blue arrow, path of head; red arrow, path of tail. (C) Curvature of the larval midline during a C-start. Body curvature increases steadily during the preparatory stroke; the propulsive stroke commences when the total concave curvature (red) reaches its maximum and the first body wave begins to form, visible as a convex curvature (blue) band that travels down the full length of the body. (Same sequence as Fig. 2.)