Introductory class exercises in experimental embryology using Xenopus laevis

Abstract

This paper describes classical experiments of experimental embryology which may be repeated at class level using the early embryos of Xenopus laevis. The experiments demonstrate the effects of lithium on the early development of the nervous system, and the use of hypertonic salt solutions to produce exogastrulation. Both experiments involve the removal of the jelly coats around the embryo, and for this purpose a rapid chemical method using a cysteine hydrochloride/papain solution is described. Both experiments are theoretically important: the effects of lithium are used as evidence for the existence of an anterior-posterior gradient in the early embryo, while exogastrulation provides a convenient system for interfering with the primary inductive effect of the chordo-mesoderm, necessary for ectodermal neuralization.

The procedure for obtaining fertile eggs from mature Xenopus specimens by injection of mammalian chorionic gonadotrophin is described.