[Variation and asymmetry of axial rudiments of Xenopus laevis embryos in response to a disturbance of cell movements and tension fields in the marginal gastrula].

We studied changes of volume, disturbances of mutual volumetric proportions, and asymmetry of axial rudiments in the embryo of Xenopus laevis after partial separation of the dorsal blastopore lip with P-shaped incisions from the remaining part of the marginal zone. This was conducted at the stage of early gastrula. The incision was directed either towards the lip (series 1) or away from the lip (series 2). Gastrulation movements were inhibited in both series of experiments. In series 1, the dorsal zone acquired isotropic structure, and in series 2, it quickly restored the initial longitudinal tensions. Sometimes and pairwise (but strongly asymmetric) notochord rudiments were formed in the lateral lips of the unclosed blastopore. In both experimental series, we have noted a high (exceeding the control by an order of magnitude) variation in the volume and mutual proportions of axial rudiments, their high asymmetry, and low volume correlations. Asymmetry of chordal rudiments in the lateral lips was higher in series 1, and the occurrence of the notochord in the dorsal region was higher in series 2. The results are discussed from the point of view of a possible role of gastrulation movements and the associated tension fields in the marking of axial rudiments.