Fig. 1.

Cartoon of D. japonica fission. (A) Unperturbed planarian before fission. The pharynx is marked by the blue arrowhead. To increase the fission rate (3), we amputate as indicated by the gray line. (B) Waist formation. Tissue movement causes local narrowing (orange arrowhead) and formation of wide contact regions at the head and tail (green arrowheads). The waist is not in contact with the surface. (C) The head lifts off the substrate during pulsation and then readheres and slides back against the surface. (D) Rupture.