Fig. 3

Fig. 3 Representative sequence of images from an aequorin-loaded egg illustrating changes in intracellular free calcium during activation in the absence of sperm. A is a bright-field image of the unactivated egg just prior to the initiation of the signal and shows no separation between the chorion and the egg plasma membrane, whereas K shows the egg after the passage of the calcium wave, clearly indicating (arrowhead) a raised chorion. Each photon image (B to J) represents 60 s of accumulated light, with a 20-s step separating each successive image. The schematic image (L) shows subsequent blastodisc (in white) formation and thus the location of the animal pole during wave propagation. The egg developed only as far as a few abortive cleavages. Color scale indicates luminescent flux in photons per pixel. Scale bar is 200 μm.