Vertebrates employ varied strategies, both chromosomal and nonchromosomal, to determine the sex of the developing embryo. Among reptiles, temperature-dependent sex determination (TSD) is common. The temperature of incubation during a critical period preceding sexual differentiation determines the future sex of the embryo, presumably by altering the activity or expression of a temperature-depend...

Single interstitial stem cells of male polyps of Hydra magnipapillata give rise to clones that differentiate either male or female gametes. To test the sexual stability of these clones, stem cells were recloned. The results indicate that stem cells from female clones are stable in their sexual differentiation capacity; male stem cells, by comparison, switch sexual phenotype at the rate of 10(-2...

Differentiation of mouse embryonic germ cells as male or female is dependent on the somatic environment of the gonad rather than the sex chromosome constitution of the germ cell. However, little is known about the initiation of germ cell sexual differentiation. Here, we traced the initiation of germ cell sexual differentiation in XX gonads using the Stra8 gene, which we demonstrate is an early ...

During the intrauterine period the fetal brain develops in the male direction through a direct action of testosterone on the developing nerve cells, or in the female direction through the absence of this hormone surge. In this way, our gender identity (the conviction of belonging to the male or female gender) and sexual orientation are programmed into our brain structures when we are still in t...

Theory predicts that sexual selection can promote the evolution of reproductive isolation and speciation. Those cases in which sexual selection has led to speciation should be characterized by significant differentiation in male display traits and correlated female preferences in the absence of post-zygotic isolation, accompanied by little genetic or other morphological differentiation. Previou...

Sexual reproduction in an environmental pathogen helps maximize its lineage fitness to changing environment and the host. For the fungal pathogen Cryptococcus neoformans, sexual reproduction is proposed to have yielded hyper virulent and drug resistant variants. The life cycle of this pathogen commences with mating, followed by the yeast-hypha transition and hyphal growth, and it concludes with...

Ecological speciation is the evolution of reproductive isolation as a consequence of direct divergent natural selection or ecologically mediated divergent sexual selection. While the genomic signature of the former has been extensively studied in recent years, only few examples exist for genomic differentiation where environment-dependent sexual selection has played an important role. Here, we ...

In Xenopus laevis the basic mechanisms underlying sexual differentiation were investigated by determining time courses of sexual steroids and their corresponding receptors during complete larval development from egg to juveniles. Androgens as well as estradiol (E2) are derived from maternal origin and accumulate in hatching tadpoles. Sexual steroid contents decreased rapidly after hatching and ...

1. The widespread occurrence of sexual reproduction indicates that the benefits of sex can overcome its costs relative to asexual reproduction. Many closely related sexual and asexual taxa have different geographic distributions suggesting that their relative fitness may depend on the environment. However, support for such ecological differentiation is mainly based on correlative evidence, with...

Sexual differentiation is essential for the transmission of Plasmodium to mosquitoes and therefore, for the spread of malaria. The molecular mechanisms underlying sexual differentiation are poorly understood but may be elucidated by a detailed study of the regulation of expression of sexual stage specific genes. In the present work we describe the differential expression of the gene encoding th...