Printer-friendly version PDF version. Temperature-Dependent Sex Determination in Reptiles The sex of a reptile embryo partly results from the production of sex hormones during development, and one such process to produce those hormones depends on temperature of the embryo's environment.
PLOS Biology. Other work centers on a theoretical model the Charnov — Bull model  predicted that selection should favour TSD over chromosome -based systems when "the developmental environment differentially influences male versus female fitness";  this theoretical model was empirically validated thirty years later temperature dependent sex determination is seen in in Chesapeake but the generality of this hypothesis in reptiles is questioned.
Next article. Consequently, the adaptive significance of TSD in all but the most recent origins of TSD may have been obscured by the passage of deep time, with TSD potentially being maintained in many amniote clades simply because it works 'well enough' i. Like many turtles, loggerheads have temperature-dependent sex determination, meaning that the sex of the hatchlings is determined by egg temperature during incubation.
Access through your institution. The temperature of the developing eggs is what decides whether the offspring will be male or female. Statistical confidence for likelihood-based paternity inference in natural populations. Accepted : 26 November The scope of the model for other reptiles, however, requires further research.
Temperature-Dependent Sex Determination in Reptiles The sex of a reptile embryo partly results from the production of sex hormones during development, and one such process to produce those hormones depends on temperature of the embryo's environment.
For instance, polychlorinated biphenyls PCBs are pollutants whose molecules are structurally similar to some estrogens. Making males from females: the effects of aromatase inhibitors on a parthenogenetic species of whiptail lizards. Theoretical models predict that selection should favour ESD over genotypic sex determination when the developmental environment differentially influences male versus female fitness that is, the Charnov—Bull model 4but empirical evidence for this hypothesis remains elusive in amniote vertebrates—the clade in which ESD is most prevalent 5.
Reprints and Permissions. Current research suggests that warming trends due to climate change may result in more female turtles being born! Studying the spotted skink, they observed that the highland population was not affected by temperature, yet, there was a negative correlation between annual temperature and cohort sex ratios in the lowlands.
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However, in the bipotential gonads of those turtles raised at male-promoting temperatures, Sox9 expression was retained in the medullary sex cords destined to become Sertoli cells Spotila et al. Spencer and Janzen found further support for the Charnov-Bull model by incubating painted turtles Chrysemys picta at different temperatures and measuring various characteristics indicative of fitness.
Journal of Heredity.