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Embryonic growth and antioxidant provision in avian eggs

Avian embryos undergo extremely rapid development over a relatively short period of time, and so are likely to suffer high levels of oxidative damage unless this is mitigated by sufficient maternal allocation of appropriate antioxidants. At a species level, it is therefore predicted that antioxidants should be allocated to eggs according to the rate of embryonic growth, such that eggs containing embryos that grow faster are furnished with higher antioxidant levels, independent of egg size. We tested this prediction for three potentially important classes of dietary-derived yolk antioxidants: carotenoids, vitamin E and vitamin A. Across species, we found positive relationships between embryonic growth rate and total yolk levels of each of the three antioxidant classes. Moreover, there were consistent differences in antioxidant provision between pairs of species that share a common initial egg mass yet have differing rates of embryonic growth, such that the eggs of the faster-developing species have higher levels of carotenoids and vitamin E. These results may explain the marked interspecific variation in antioxidant provision and provide evidence for the role that these antioxidants play during embryonic development.