Anisotropic actin accumulation in epithelial trails drives collective epithelial movement. Secondary palate sagittal section of E15.5 control (Myh9f/+; Myh10f/+; CrectTg/0; R26mTmG/+) embryos were stained with SiR-actin and then live imaged for GFP expressing MES cells (green) and F-actin (magenta). Arrowheads indicate anisotropic contracting F-actin during peristaltic MES cell movement. A contractile actin filament (arrowhead) can be seen adjacent to an MES cell of the trail. Scale bar, 5μm. Images were captured every 15 minutes. Frames shown in movie represent a 1-hour subset of a 20-hour time lapse shown in Figure 8A at a higher time-resolution.