Fig. 1

Three patterns of calcium transients that appear between 50% and 75% epiboly are ventral marginal signal (A-F), yolk flash (G), and marginal hot spots (H). (A-F) The persistent ventral signal is shown in f-aequorin-loaded zebrafish embryos at approximately 50% epiboly. (A-C) Sixty seconds of accumulated luminescence. (D-F) Same data superimposed on corresponding bright-field images. In A and D, the embryo is viewed from the vegetal pole, in B and C it is viewed from the left side, and in E and F it is viewed from the ventral side. (G) A rapid increase in calcium in the exposed portion of the yolk cell appears as a brief "yolk flash," shown in a 30-sec integration at the late shield stage. This image corresponds to the large spike at 100 min in Fig. 2A. A time-lapse imaging sequence of the yolk flash is shown in the supplementary material on the PNAS web site. (H) Multiple loci of persistent elevated calcium levels, or marginal hot spots, are shown in a 30-sec integration of photons from minute 135 in Fig. 2B. (I) Schematic showing orientation of G and H. D, dorsal; V, ventral; L, left; R, right; HS, hot spots. The color code indicates luminescent flux in the same units as in Figs. 2 and 3. The scale bar applies to all frames.