Data from: Oxidative damage increases with reproductive energy expenditure and is reduced by food-supplementation

A central principle in life-history theory is that reproductive effort negatively affects survival. Costs of reproduction are thought to be physiologically-based, but the underlying mechanisms remain poorly understood. Using female North American red squirrels (Tamiasciurus hudsonicus), we test the hypothesis that energetic investment in reproduction overwhelms investment in antioxidant protection, leading to oxidative damage. In support of this hypothesis we found that the highest levels of plasma protein oxidative damage in squirrels occurred during the energetically-demanding period of lactation. Moreover, plasma protein oxidative damage was also elevated in squirrels that expended the most energy and had the lowest antioxidant protection. Finally, we found that squirrels that were food-supplemented during lactation and winter had increased antioxidant protection and reduced plasma protein oxidative damage providing the first experimental evidence in the wild that access to abundant resources can reduce this physiological cost.

生命史理论（life-history theory）的核心原则之一是繁殖投入对存活具有负向影响。繁殖成本被认为具有生理基础，但其背后的调控机制仍未得到充分阐释。本研究以雌性北美红松鼠（Tamiasciurus hudsonicus）为实验对象，验证了“繁殖过程中的能量投入会挤占抗氧化保护（antioxidant protection）的资源分配，进而引发氧化损伤（oxidative damage）”这一假说。研究结果支持该假说：松鼠血浆蛋白氧化损伤的最高水平出现在泌乳期这一高能量需求阶段。此外，能量消耗最高、抗氧化保护水平最低的松鼠，其血浆蛋白氧化损伤程度也显著升高。最后我们发现，在泌乳期与冬季进行食物补给的松鼠，其抗氧化保护能力得以提升，血浆蛋白氧化损伤程度显著降低——这是野外环境中首次通过实验证实，充足的资源获取可降低该生理繁殖成本。