y, J

of G ité l.pi y r tost ina va s ob te her dependent but unrelated to genetic sex determination and the type of gonadogenesis. We also found that the onset of sex steroid exposure influences gonad differentiation and the meiotic status of the germ cells depends on their location within the gonad. Our findings reveal lity in mice and humans (Piprek 2009b), sex steroid such as herbicides act as hormone disruptors and may observed in gonadal culture in vitro (Miyata & Kubo synthesis, action, and metabolism must be strictlyDOI: 10.1530/REP-12-0048controlled during development. q 2012 Society for Reproduction and Fertility2000). Early studies suggested that the heterogametic sex is impervious to steroid hormones (Witschi et al. 1958a,et al. 1990, Warner & Shine 2008). In vertebrates, the differentiated gonads produce steroid hormones that orchestrate the development of secondary (genitals) and tertiary (body shape and larynx) sexual features. Further, exogenous sex steroids may exert an impact on gonad development in some animals. This effect was first described by Lillie (1917) in freemartin cattle, where female infertility, due to partial sex reversal, was caused by steroid hormones produced by the opposite-sex twin in the womb. Because abnormalities in hormone levels can have broad effects on sexual development including sex reversal usually accompanied by inferti-be involved in global decline of amphibian population in recent years (Collins & Storfer 2003, Murphy et al. 2006). In amphibians, steroid hormones (testosterone and 17b-estradiol (E2)) added to water during tadpole development can, depending on the dose and species, alter gonadal sex (Wallace et al. 1999). Complete sex reversal observable as a one-sex progeny can be interpreted as a major effect caused by high dose of sex steroids; however, weak hormonal effects include partial sex reversal manifested by hermaphroditic (intersex) gonads termed ovotestes (Wallace et al. 1999). Impairment of sexual differentiation was alsodifferential sensitivity of amphibians to testosterone and E2, establishing a hierarchy of sensitivity to these hormones among different anuran species