La gynogenèse chez les vertébrés

International audienceAfter a rapid description of five gynogenetic unisexual species, this paper reviews themethods used for inducing gynogenesis in bisexual species.1) The frequency of male genome extrusion, very low after intraspecific mating, canbe appreciably increased in some particular interspecific combinations ; cold-shocking theeggs at the time of fertilization can also result in gynogenetic development. In the case, ofmammals, the male pronucleus can be microsurgically removed, but in most cases(amphibians, fish), haploid gynogenesis is induced by mutagenic treatment of the sperm(gamma, X, UV irradiation ; chemicals) before fertilization.2) Viable gynogenesis depends on the possibility of diploidizing the female geneticset ; several factors (oocyte aging, genetic factors, induction of ovulation) may beresponsible for the high frequency of « spontaneous » diploidization reported in somestudies. But diploid gynogenesis is generally obtained by induced retention of the secondpolar body or by induced suppression of the first cleavage, achieved by heat or pressuretreatment of eggs (fish and amphibins) or by the use of antimitotic chemicals (mammals).Diploid gynegenesis results in high inbreeding levels and original sex ratios. In thediscussion, we have tried to show that the objectives which stimulated its induction inamphibians have been frequently unattained or reached in other ways. In commercial fishspecies, gynogenesis may in the future contribute to the solution of major problems suchas genetic improvement and control of reproduction