Differences in oxidative status explain variation in thermal acclimation capacity between individual mosquitofish (Gambusia holbrooki)

1. Evolutionary theory predicts that the capacity to acclimate should be favoured in variable environments. However, perfect compensation for thermal variation is rare and the capacity for thermal acclimation can vary considerably between individuals within natural populations. This variation may be explained by costs associated with acclimation, but it is not clear what these costs are. 2. We tested the hypothesis that oxidative stress is a cost of acclimation that could explain the variation between individuals in acclimation capacity. We acclimated individual mosquitofish (Gambusia holbrooki, n = 416) to 18oC and 28oC sequentially, and determined swimming performance at each temperature to evaluate their acclimation capacity. Fish were then acclimated to either cold (18oC) or warm (28oC) conditions, and we increased antioxidant capacities of a subset of fish experimentally by administering N-acetyl cysteine (NAC). We measured H2O2 production, catalase antioxidant activities, and oxid...1. 进化理论预测，在环境多变的生境中，驯化能力应当受到自然选择的青睐。然而，对温度变化的完全补偿现象十分罕见，且自然种群内不同个体间的热驯化（thermal acclimation）能力差异显著。这种个体间差异或许可通过与驯化相关的代谢成本加以解释，但目前学界尚未明确此类成本的具体构成。 2. 本研究检验了“氧化应激是驯化成本之一，可解释个体间驯化能力差异”这一假说。我们将416尾霍氏食蚊鱼（Gambusia holbrooki）依次驯化于18℃与28℃环境，并通过测定其在对应温度下的游泳表现，评估个体的热驯化能力。随后将实验鱼分别驯化至低温（18℃）或高温（28℃）环境，并通过饲喂N-乙酰半胱氨酸（N-acetyl cysteine, NAC）对其中一部分个体的抗氧化能力进行实验性提升。本研究检测了过氧化氢（H₂O₂）生成量、过氧化氢酶（catalase）抗氧化活性，以及氧化...