MATERNAL TRANSFER OF ESTRADIOL TO EGG-YOLKS ALTERS SEXUAL-DIFFERENTIATION OF AVIAN OFFSPRING

Three experiments were conducted to determine whether avian egg yolks contain the sex steroid 17 beta-estradiol and whether experimentally produced elevations in maternal estradiol alter yolk estradiol and influence sexual differentiation of the offspring. The yolks of eggs laid by Japanese quail (Coturnix japonica) were found to contain significant amounts of estradiol comparable to those in the maternal circulation. Treatment of laying females with estradiol benzoate (EB) resulted in elevated yolk estradiol and a permanent morphological alteration of female offspring in the form of an increased incidence of right oviducts in adulthood. Such maternal transfer of a sex steroid to the egg yolk constitutes a potentially significant source of maternal influence over embryonic development and adult phenotype in oviparous species. (C) 1995 Wiley-Liss, Inc.