Actomyosin pulses in one- and two-cell–stage embryos. (A) Schematic view of the P0 during early interphase. Open circles represent the two pronuclei. (B) Micrograph of the P0 in early interphase expressing GFP::UTR and NMY-2::RFP. The white arrowheads (in B only) indicate individual pulses, and magenta arrows indicate membrane invaginations (ruffles). (C) Time evolution of a single pulse in the P0. The time delay between frames is 6 s for the first six frames and 8 s thereafter. (D) Schematic of an embryo at the early two-cell stage, showing the AB and the posterior blastomere P1. Open circles represent the interphase nuclei. (E) Micrograph of an early two-cell–stage embryo expressing GFP::UTR and NMY-2::RFP. White arrowheads indicate individual pulses. (F) Time evolution of a single pulse. The time delay between frames is 2 s for the first five frames and 4 s thereafter. Bars, 5 µm.