Fig. 5

Reproduction of larval crawling by a neuromechanical model. A Kinematics parameters in segmental boundary dynamics (left, same as Fig. 1D) and segmental length change (right, same as Fig. 1G). B A schematic of our neuromechanical model for larval crawling. The neural circuit was referred to Pehlevan et al. [10], although the parameter values in the model were different. Since we assumed w_ES = w_IS as stated in Pehlevan et al. [10], the total number of the free parameters (written in magenta) was 15. Two segments in a larva (corresponding to the dotted box below) are drawn. Circles are populations of neurons: E_i is an excitatory neuron group, I_i is an inhibitory neuron group, and S_i is a sensory neuron group in the ith segment. Excitatory and inhibitory connections are labelled by red and blue arrows, respectively. The body of the ith segment is modelled by two springs (k₁ and k₂), one damper (c), and one muscle whose force is M_i. Segment boundaries have masses (m) that feel friction with the substrate (F_f in forward motion and μ_bfF_f in backward motion). The position of the ith segment is denoted as y_i. C A kymograph of segmental boundaries during larval crawling (same as Fig. 1C). D Change in segmental length during larval crawling (same data shown in Fig. 1G). E A simulation result of kymograph of segmental boundaries. F Simulation result of segmental length. Segment labels and line colours in C and E correspond to those in Fig. 1B, C. G–L Comparison of seven kinematics between parameters obtained from larval crawling (black dots, n = 9 larvae) and simulation (red dots). G Stride length. H Stride duration. I Intersegmental delay. J Crawling speed. K Maximum segment length. L Minimum segment length. M Contraction duration of single segments