Corticosterone exposure during embryonic development affects offspring growth and sex ratios in opposing directions in two lizard species with environmental sex determination.

Stress experienced by a reproducing female can substantially affect the morphology, behavior, and physiology (and hence fitness) of her offspring. In addition, recent studies demonstrate that stress hormones (corticosterone) influence sex determination of embryos. To explore these issues, we manipulated corticosterone levels in eggs of two Australian lizard species (Amphibolurus muricatus and Bassiana duperreyi) that exhibit temperature-dependent sex determination (TSD). Elevated corticosterone levels during embryonic development affected body size, growth rates, and sex ratios of the resultant offspring, but the direction and magnitude of these effects differed between the species. Corticosterone enhanced growth rates of hatchling B. duperreyi but inhibited growth of A. muricatus. Eggs with elevated levels of corticosterone produced more daughters in A. muricatus and more sons in B. duperreyi. The sex-ratio effect in A. muricatus may have been due to sex-specific embryonic mortality, but it may represent a direct effect on sex determination in B. duperreyi (because embryonic mortality was not affected by corticosterone manipulation in this species). These results demonstrate the complexity of proximate mechanisms for sex determination among reptiles with TSD and illustrate the potential role of corticosterone in sex-determining systems.