Fig. 3

Measurement of contraction force in a larva. A A larva was hooked at the head and tail. The extension and tensile force of the larva were measured by a tensile tester. B A sample trace of spontaneous contraction force of a larva. C Optogenetic stimulation to a larva during measurement with the tensile tester. D A sample trace of larval force with optogenetic activation (shown in blue bars above the trace). E The tensile force of larvae generated by spontaneous contraction (“Spt”; n = 11 contraction events from three larvae) and optogenetic activation (“Opt”; n = 44 activations from seven larvae)