The video sequence below provides an overview of the behavior of the dorsal involuting marginal zone (DIMZ) during Xenopus gastrulation. The sequence can be divided into several steps, which can be seen more easily as you play back single frames of the movie: (1) Rolling of the vegetal edge of the DIMZ, which corresponds to the "dirty frown" visible on the surface of the embryo (see the preceding sections). (2) The DIMZ then undergoes massive convergence and extension to extend dramatically on the dorsal side. It is the asymmetric extension of this tissue that transforms the torus of DIMZ tissue into a tube with anterior-posterior polarity.
