Fig. 8. Schematic representation of zebrafish epiboly and Drosophila dorsal closure movements. (A,B) EVL/YSL epiboly in zebrafish. At the onset of gastrulation (50% epiboly), marginal cells of the EVL (green) are oval shaped and loosely aligned at the interface between the EVL and the YSL. Actin (red) appears evenly distributed within the YSL (A). At 75% epiboly, marginal EVL cells have become increasingly elongated and aligned into a taut row. Actin has accumulated at the interface between EVL and YSL, forming an `actin ring' within the YSL along the circumference of the embryo (B). (C,D) Drosophila dorsal closure. At the onset of dorsal closure, marginal cells of the lateral epidermis cells (green) are loosely aligned and are in contact with the amnioserosa cells (blue, C). Actin (red) is beginning to accumulate at the leading edges of marginal cells at this stage. With dorsal closure proceeding, marginal cells become clearly elongated and aligned as actin strongly accumulates at the leading edge of these cells (D).