Representative (A) facial, (B) axial, and (C) top views of three f-aequorin-loaded zebrafish embryos demonstrating the changes in intracellular free calcium during the first and second cell division cycles. The photon images (colored panels) represent 30 s of accumulated luminescence with a 30-s gap between each image. Corresponding bright-field images were grabbed just after the preceding photon image. In the case of (A and B), this was every 3 min, while in the case of (C), every 9 min. In (C), for the sake of clarity, the outline of the blastodisc and locations of the furrows are outlined in red. Scale bar is 200 μm.

Representative patterns of luminescence and corresponding bright-field images, from aequorin-loaded zebrafish eggs during the first 60 min after the onset of first cell division. Fertilized eggs were (A) raised under normal conditions, (B) bathed in Ca²⁺-free medium, or (C) injected with 5,5′-dibromo-BAPTA 1 min after the appearance of the positioning signal during the first cell division. (D) An example of a parthenogenetically activated egg. Each photon image represents 60 s of accumulated light. 1–5 indicate images obtained at the following time intervals: just prior to the first localized rise in intracellular calcium which accompanies the first appearance of the furrow arc (1), during this rise (2), and then 15 (3), 30 (4), and 60 (5) min following this initial rise, respectively. The maximum photon index was maintained at 20 for the N′ photon images, but was increased to 130 in the N′ panels to show that although the overall amount of calcium is elevated significantly, a relative localized elevation of calcium is still maintained. Scale bar is 200 μm.

DIC images indicating the ‘‘stress lines’’ (arrowheads) during the first (A) and second (B) meroblastic divisions of zebrafish. Scale bar is 80 μm.