Movie 7.

Simulation of Hydra tissue mechanics during global activation of fiber contraction in a spheroid with a large disordered domain. The movie depicts the results of simulations of a transient activation of global fiber contraction in a Hydra tissue spheroid with a nematic configuration containing a large disordered domain of net charge +2 surrounded by a fully ordered region, emulating the nematic pattern at the early stages of regeneration (Fig. 5B). The tissue spheroid is modeled as a deformable shell that contains an embedded nematic field that experiences a time-dependent global activation of contraction (bottom inset). The images show cell segmentation maps depicting cells colored according to the cell area strain defined as ε_c = ln(A_c/A_c^ref), where A_c is the cell area and A_c^ref is the initial cell area, overlaid with lines indicating the orientation of the embedded nematic field in each cell (blackordered region; gray-disordered regions). The spheroid is shown from a top view centered on one of the actin foci and a side view. The active stress generated within each cell is aligned with the nematic field in that cell, and global activation leads to mechanical strain focusing around the two foci.