FURROWING SURFACE CONTRACTION WAVE COINCIDENT WITH PRIMARY NEURAL INDUCTION IN AMPHIBIAN EMBRYOS

We predicted, and have now observed, a surface contraction wave in axo lotl (Ambystoma mexicanum) embryos that appears to coincide temporally and spatially with primary neural induction and homoiogenetic inducti on, and with involution of the chordomesoderm The wave starts from a f ocus anterior to the dorsal lip of the blastopore and spreads as an el lipse, until part of it encounters the rim of the blastopore and vanis hes there. The remaining are then continues over the dorsal hemisphere until it reforms an ellipse that decreases in size. About 9 to 12 hou rs after it begins, the wave vanishes at a focus diametrically opposit e its point of origin. The wave involves both local contraction and fu rrowing in the monolayer ectoderm. To a good approximation, the hemisp herical portion of the ectoderm traversed by the wave becomes neuroepi thelium, while the ectoderm not transversed by the wave becomes epider mis. The wave might provide a mechanism to determine the time and loca tion at which neuroepithelial differentiation occurs. (C) 1994 Wiley-L iss, Inc.