Fig. 6. Localization of non-muscle myosin II during zebrafish cytokinesis. (A-F) Wild-type embryos labeled with an anti-non-muscle myosin II antibody during the early cellular cleavages. B,D,F are higher magnification images of the boxed regions of the embryos shown in A,C,E, respectively. During furrow initiation (A,B), myosin appears to be present at the cortex of the embryo but does not show a significant enrichment at the forming furrow (arrowheads in A,B). At the four-cell stage (C,D), when the first furrow is undergoing furrow maturation, myosin accumulates at this furrow (arrowheads in C,D) but is not yet observable at the initiating first furrow (arrow in C). At the eight-cell stage (E,F), myosin remains at the site of the first furrow (arrowheads in E,F) and has become localized to the now mature second furrow (arrow in E). (H,I) Blebbistatin-treated embryos at the late four-cell stage (65 minutes p.f.). I is a higher magnification of the first furrow in the embryo shown in H. Myosin does not accumulate at the first furrow at this late stage of furrow maturation, when it is normally accumulated at the furrow in control embryos. Images are animal views. In panels with the lower magnification images arrowheads, arrows and asterisks indicate the first, second and third cleavage furrows, respectively. Bar, 50 µm (A,C,E,H); 16 µm (B,D,F,I).