Artificially Applied Tensions Normalize Development of Relaxed
Xenopus laevis Embryos

L. V. Beloussov and A. S. Ermakov

Biological Faculty, Moscow State University, Vorob’evy gory, Moscow, 119899 Russia

Received February 14, 2000; in final form, April 3, 2000

Abstract—Relaxation of tensions of the surface of Xenopus laevis embryos at the late blastula stage leads to
deep and diverse developmental defects and increased variability in mutual position and volume ratios of the
axial rudiments. Here, we demonstrate that the development of such embryos was markedly normalized if the
relaxed tensions were restored in one of two ways: (1) isotropic stretching of the blastocoel roof induced by the
incubation of relaxed embryos in a hypotonic medium or (2) anisotropic stretching of embryos on two needles.
In the latter case, we succeeded in restoring the morphological axis not only after longitudinal stretching but
also after transverse stretching, and the new axis had signs of anteroposterior polarity. The role of isotropic and
anisotropic tensions in organization of the early amphibian development is discussed.

Key words: morphogenesis, axial rudiments, mechanical tensions

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