The permeability barrier is located between the trilaminar shell and the embryo surface. Montage of DIC (top), fluorescence (middle), and merged (bottom) images of an embryo expressing mCherry::CPG-2 (red inmerge). mCherry::CPG-2 is soluble in the perivitelline space, but the permeability barrier located between the embryo and eggshell restricts its diffusion. The permeability barrier is malleable but does not always conform to the surface of the embryo. For example, when the embryo changes shape during cytokinesis, the furrow pulls away from the permeability barrier, which behaves like a tightly drawn blanket that encases the embryo. The second polar body resides beneath the permeability barrier. Single-plane wide-field images were acquired every 20 s on an upright microscope (Eclipse E800). Playback rate is 120× real time.
