Intersex, Hermaphroditism, and Gonadal Plasticity in Vertebrates: Evolution of the Müllerian Duct and Amh/Amhr2 Signaling

In vertebrates, sex organs are generally specialized to perform a male or female reproductive role. Acquisition of the Müllerian duct, which gives rise to the oviduct, together with emergence of the Amh/Amhr2 system favored evolution of viviparity in jawed vertebrates. Species with high sex-specific reproductive adaptations have less potential to sex reverse, making intersex a nonfunctional condition. Teleosts, the only vertebrate group in which...