Movie 2.

Mechanical strain focusing at the future head region. High-resolution time-lapse, spinning-disk confocal movie acquired every 20 seconds of a regenerating tissue fragment expressing Lifeact-GFP in the ectoderm. The tissue spheroid is oriented with its future head region facing the objective. The images show computationally generated projected views of the fiber organization at the ectodermal basal surface (left) and the cellular organization at the ectodermal apical surface (right). Deformation events involving mechanical strain focusing at the future head site are indicated by green frames, and are slowed down to better demonstrate the tissue deformations. The elapsed time from excision is displayed (hh:mm:ss), and the scale bar is 100 μm.