Behavior of contractile rings severed by laser microsurgery during constriction. (A) End-on view stills from time-lapse imaging series of constricting contractile rings in ABp cells expressing myosin^NMY-2::GFP. The contractile ring snaps open after the laser cut (cyan arrow, frame 4), the gap is repaired (frame 25), and ring constriction resumes to completion. (B–D) Kymographs of ring regions cut by laser microsurgery built as depicted in Fig. S1 E. The time interval between frames is 2.32 s in B, 1 s in C, and 3.2 s in D. Rings were subjected to a single cut (B), or to two sequential cuts with the second cut either hitting the same region (C) or a neighboring region (D). Time-lapse acquisition in D resumed after both cuts were executed (missing frames are indicated by a black box). (E) Stills of a constricting ring with a persistent gap, which was maintained by iteratively cutting the same site. Time is in seconds, and time zero denotes the frame before the laser cut. Bars, 5 µm.