Conditions experienced by individuals during prenatal development can have long-term effects on their phenotype. Maternally-transmitted resources are important mediators of such prenatal effects but the potential interactive effects among them in shaping offspring phenotype have never been studied. Maternally-derived testosterone is known to stimulate growth, but these benefits may be counterbalanced by an increase in the production of reactive oxygen species (ROS). Maternally-transmitted carotenoids might have the capacity to scavenge ROS and thereby buffer an increase in oxidative stress caused by prenatal exposure to high testosterone levels. Here, we experimentally tested for such interactive effects between maternal yolk testosterone and carotenoid in Japanese quail (Coturnix japonica). We found that hatching mass was reduced and reactive oxygen metabolites (ROMs) levels at the end of the period of maximal growth increased in chicks from eggs injected with either testosterone or carotenoid (only a tendency in chicks from testosterone injected eggs). However, when both egg compounds were manipulated simultaneously, hatching mass and ROMs levels were not affected, showing that both carotenoid and testosterone lose their detrimental effects when the ratio between the two compounds is balanced. Our study provides the first experimental evidence for interactive effects of two maternally-derived egg compounds on offspring phenotype and suggests that developmental cues are tightly co-adjusted within an egg.
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