Endodermal cells exhibit changes in migratory behavior and cell shape as embryos progress through gastrulation. (A–C) Representative migration tracks over a 1-h period of endodermal cells at shield (6 h after fertilization; A), 75% epiboly (8 h after fertilization; B), and 90% epiboly (9 h after fertilization; C). Dorsal is to the right. Bars, 25 µm. (D and E) Quantification of migration persistence (D) and instantaneous velocity (E) shows that migration persistence and speed increase as gastrulation proceeds. Shield, n = 49 cells; 75% epiboly, n = 74 cells; 90% epiboly, n = 95 cells. (F and G) Representative images of endodermal cells from Tg(sox17:GFP-UTRN) embryos at 70% epiboly (F) and 90% epiboly (G). (H) Quantification of circularity shows that cells are significantly more rounded at 70% epiboly. a.u., arbitrary units. 70% epiboly, n = 63 cells; 90% epiboly, n = 66 cells. All error bars represent SEM. *, P < 0.05.