Spot AJs integrate actomyosin fibers to form a supracellular meshwork. (A) Apical myosin II (green) and subapical E-cadherin, ∼2 µm below the apical cortex (purple), in fixed embryos. Schematics indicating the stage of furrow formation are shown above each image pair. (B) Magnified view of supracellular actomyosin fibers. Apical myosin II (green), subapical E-cadherin (purple), and apical actin filaments (cyan) were imaged in fixed embryos. Supracellular actomyosin fibers are often oriented perpendicular to cell interfaces (i, arrows), but can also be seen running parallel to cell interfaces (ii, arrows). Actomyosin fibers often radiated from a central myosin II spot or ring (red asterisks). The bottom-middle images of i and ii were thresholded to facilitate visualization of myosin II fibers. (C) Apical E-cadherin (purple) and myosin II (green) in fixed embryos. Subapical E-cadherin staining is used to illustrate cell outlines. Myosin II fibers connect to apical E-cadherin puncta, or spot AJs (arrows). In late stages, spot AJs can appear stretched along the fiber (yellow asterisks). Bars, 5 µm.