[Fertilization and development of axolotl oocytes with already grey crescent experimentally formed during their maturation].

Pigmented axolotl coelomic oocytes were induced to form a gray crescent by simultaneous action of a gravity vector and of a heat-shock (36 +/- 0.5 degree C during 10-15 min), according to a previously described method. Those oocytes were subsequently reintroduced into the coelomic cavity of an albino recipient female, which had been previously inseminated. Among fertilized treated oocytes, more than 75% developed into embryos whose dorsal side corresponded to the gray crescent-forming area of the oocyte. It is known that in normally fertilized control eggs, a gray crescent forms just prior to the first cleavage and corresponds in most cases to the dorsal side of the future embryo. Therefore, our results strongly suggest that fertilization is not a primary compulsory step towards effective determination of the future dorsal area in an Amphibian egg, since the required cytoplasmic rearrangements can be elicited much earlier in a maturing oocyte and remain effective during subsequent development.