Sexual versus individual differentiation: the controversial role of avian maternal hormones.
Avian embryos are exposed not only to endogenous sex steroids, which are produced by their gonads and have a key role in sexual differentiation, but also to maternal steroids transferred into the egg yolk, which can modulate the development of individual differences in behavior. Studies of maternal hormones have primarily focused on ultimate questions (evolutionary trade-offs, functional significance), whereas proximate mechanistic questions have been largely ignored. A central problem that must be addressed is how exposure to maternal hormones affects the individual phenotype without interfering with sexual differentiation. Separate effects could result from the action of different hormones, at different doses or at different times, on different targets.
Carere
Claudio
C
Section of Behavioural Neurosciences, Department of Cell Biology and Neuroscience, Istituto Superiore di Sanità, Rome, Italy.
Balthazart
Jacques
J
D000818:Animals; D001717:Birds / Q000196:embryology*; D004625:Embryo, Nonmammalian; D004627:Embryonic Induction / Q000502:physiology*; D012739:Gonadal Steroid Hormones / Q000502:physiology*; D008954:Models, Biological; D052287:Oviparity / Q000502:physiology; D012733:Sex Differentiation / Q000502:physiology*
D012739:Gonadal Steroid Hormones