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Fig. 4
Dorsal enveloping layer cells ingress to form forerunner cells. Selected frames from a multi‐plane video time‐lapse recording of the dorsal margin using DIC bright field optics showing (A) focal plane at the surface and (A′) focal plane 5 µm deeper at the same X, Y location. Individual cells are identified by numbers and elapsed time is indicated in h:min past 30% epiboly (4.7 h). As cells in the enveloping layer (pseudo‐colored blue) round up and loose contact with neighbors, they ingressed (color shift to green) and became forerunner cells, often visible in both planes of focus. Black arrowheads indicate ruffling on enveloping layer cells, white arrows indicate filopodia on forerunner cells, and white arrowheads indicate protrusions on deep domain cells beginning to ingress. Forerunner cells that were not followed are indicated with asterisks (see Supplementary Movie S3). B: Illustration of forerunner cell formation in side view. From left to right are shown the same four cells, as enveloping layer cells at the margin round up, ingress and transform into deep‐like forerunner cells (colored as in A). Data analysis and presentation were performed as described in Kane et al. (2005).