Data from: The oxidative cost of reproduction depends on early development oxidative stress and sex in a bird species

In the early 2000’s, a new component of the cost of reproduction was proposed: oxidative stress. Since then the oxidative cost of reproduction hypothesis has, however, received mixed support. Different arguments have been provided to explain this. Among them, the lack of a life history perspective on most experimental tests was suggested. We manipulated the levels of a key intracellular antioxidant (glutathione) in captive zebra finches (Taeniopygia guttata) during a short period of early life and subsequently tested the oxidative cost of reproduction. Birds were allowed to mate freely in an outdoor aviary during several months. We repeatedly enlarged or reduced their broods to increase or reduce, respectively, breeding effort. Birds whose glutathione levels were reduced during growth showed higher erythrocyte resistance to free radical-induced hemolysis when forced to rear enlarged broods. This supports the hypothesis predicting the occurrence of developing programs matching early and adult environmental conditions to improve fitness. Moreover, adult males rearing enlarged broods endured higher plasma levels of lipid oxidative damage than control males, whereas adult females showed the opposite trend. Since most previous studies reporting non-significant or opposite results used females only, we also discuss some sex-related particularities that may contribute to explain unexpected results.

21世纪初，学界提出了繁殖成本的一个全新组成部分：氧化应激（oxidative stress）。自此之后，繁殖氧化成本假说（oxidative cost of reproduction hypothesis）却并未获得一致的支持证据。对此，学界提出了多种解释，其中一种观点指出，多数相关实验研究均未纳入生活史视角。本研究在圈养斑胸草雀（Taeniopygia guttata）幼年时期的短时段内，对其体内关键细胞内抗氧化剂——谷胱甘肽（glutathione）的水平进行了操控，并随后对其繁殖的氧化成本展开了检验。研究期间，受试雀鸟可在室外大型鸟舍内自由交配，时长达数月之久。我们通过反复调整其窝卵数，分别提升或降低了亲鸟的繁殖投入。在幼年期谷胱甘肽水平被降低的个体，在被迫抚育更大窝卵数时，其红细胞对抗自由基诱导溶血的能力显著更强。这一结果支持了相关假说：生物体可发育出匹配早期与成年期环境条件的适应性程序，以提升自身适合度。此外，抚育大窝卵数的成年雄性个体，其血浆脂质氧化损伤水平显著高于对照组雄性；而成年雌性个体则呈现出相反的趋势。鉴于既往多数报告得到非显著结果或相反结果的研究仅以雌性为受试对象，本研究还探讨了可能有助于解释异常结果的性别相关特异性特征。