Figure 1.

Rhythmic pectoral fin movements in 3 dpf larvae. A, A typical slow swimming of larval zebrafish. The fins alternate rhythmically in conjunction with the body undulation. B, Histogram of swimming frequency (143 cycles from 11 fish). C, Example body shape at the time point when the right fin started to abduct. The red line shows the regression line for the rostral half of the body. The midline of the body is indicated by the thick white line. The red circle shows the farthest protruding point from the regression line. D, Midlines of the body in six swim cycles are aligned. E, Plots of the farthest protruding point in the larva at the time point when the right fin started to abduct (15 swim cycles). F, Same as in E, but the averaged values obtained from seven fish are plotted.