Axial structure development in ultraviolet-irradiated (notochord-defective) amphibian embryos

Fertile Xenopus eggs were irradiated with low doses of ultraviolet irradiation (254 nm) and permitted to develop through neural morphogenesis. They were then examined with the scanning electron microscope. The effects of irradiation on the development of the notochord, neural tube, and somites were observed. Embryos which displayed defects in notochord structure frequently exhibited normal development of both neural tube and somites. Those embryos were examined in detail. The apparent normal character of axial structures in “notochord-defective” embryos prompted a discussion of the role of the notochord in normal axial structure morphogenesis.