a view of the enveloping layer, cellular mechanics of blastopore closure
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Movie#2855. Zebrafish embryo at 80% epiboly.
The initial frame shows the junction of the enveloping layer with the yolk cell. The next frame is at a focal plane deeper within the embryo. The blastoderm margin is visible. Dark nuclei within the yolk syncytial layer are also apparent.
As the sequence progresses, one sees closure of the blastopore. The ending sequence shows a small opening--the remnant of the yolk syncytial layer--and a constricted germ ring.
Taken with a 20X lens. Zoom of 1.0