The Relative Effectiveness of Estrone, Estradiol-17β, and Estriol in Sex Reversal in the Red-Eared Slider (Trachemys scripta), a Turtle with Temperature-Dependent Sex Determination (original) (raw)

1996, General and Comparative Endocrinology

triol treatment also resulted in cranially hypertrophied In many turtles the temperature during the middle of oviducts at all incubation temperatures in a dose-depenincubation determines the gonadal sex of the hatchling. dent manner, whereas animals treated with estradiol-Sex steroid hormones have been implicated in tempera-17b and estrone had normal oviducts. These results supture-dependent sex determination in the red-eared slider port the hypothesis that estrogens are involved in the turtle, Trachemys scripta; nonaromatizable androgens final common pathway of female sex determination in are involved in male sex determination and estrogens this species. ᭧ 1996 Academic Press, Inc. and aromatizable androgens in female sex determination. Administration of exogenous estradiol-17b to eggs incubating at a temperature that normally produces only In many reptiles gonadal sex is determined by the males can overcome the effect of temperature and result temperature of the incubating egg, a process known as in all offspring being female. Further, estradiol-17b and temperature-dependent sex determination (TSD). In the incubation temperature synergize to produce a greater red-eared slider turtle (Trachemys scripta), incubation of feminizing effect at intermediate incubation temperaeggs at relatively low temperatures (e.g., 20-28.6Њ) retures that produce mixed sex ratios. This study demonsults in only male hatchlings, whereas relatively high strates that, in the red-eared slider, there is a complex temperatures (e.g., 29.6-35Њ) results in only female interaction between incubation temperature, different hatchlings; when eggs are incubated at temperatures estrogens, and the dosage effect of each hormone. There intermediate to these, varying sex ratios are produced are changes in potency of different estrogens with incu-(Crews et al., 1994). Sex steroid hormones appear to be bation temperature such that estriol is more potent than the physiological equivalent of incubation temperature estrone and estradiol-17b at 26Њ (an all-male producing and both male-and female-producing incubation temincubation temperature), estrone and estriol are equipoperatures and exogenous steroids exert their effects tent to each other and more potent than estradiol-17b at during the mid-trimester of development (Crews et al., 28.8Њ (an incubation temperature that produced a male-1996; Wibbels et al., 1991a). Estrogens and aromatizable biased sex ratio), and estradiol-17b is more potent than androgens induce female sex determination, whereas estrone and estriol at 29Њ (an incubation temperature nonaromatizable androgens induce male sex determithat produced equal numbers of males and females).