Fig. 3. Tail beat kinematics of zebrafish larvae (age 2, 3, 5 and 7 days post-fertilisation) during cyclic swimming and a slow start (age 2 days). Lateral position of tail tip (h; black), swimming speed (U; thin red line), lateral speed of tail tip (v; thick red line), angle of incidence (_i; thick blue line) and angle of attack (_a; thin blue line) of the tail over one tail beat cycle. All values are means based on two (age 7 days) or three tail beat cycles of one swimming sequence. The grey bars indicate roughly when swimming speed reaches a maximum during the tail beat cycle. U is expressed as % deviation from the specific swimming speed averaged over one complete tail beat (U): U=(U–U)/U.