Seawater carbonate chemistry and activity, escape response, and muscle physiology of marine threespine stickleback (Gasterosteus aculeatus)

We exposed threespine stickleback (Gasterosteus aculeatus) to pCO2 of ~ 700 µatm (pH 7.9 representing current levels), ~ 1400 µatm (pH 7.6 representing upwelling events) and ~ 3500 µatm (pH 7.3 representing a future predicted scenario for coastal areas) for 2 weeks. We evaluated the baseline activity, interindividual distance as a proxy for group sociality, and escape response. Then, we measured whole-body routine metabolic rate and maximum metabolic rate to determine if changes in locomotory traits might be due to changes in metabolism. We also assessed lactate dehydrogenase (LDH; EC 1.1.1.27), which is a glycolytic enzyme that interconverts pyruvate and NADH to lactate and NAD+ as well as citrate synthase (CS; EC 2.3.3.1), which is a mitochondrial enzyme that catalyzes the first step of TCA cycle to synthesize citrate from acetyl-CoA and oxaloacetate. Additionally, we also measured muscle fiber size and succinate dehydrogenase staining as a measure of muscular metabolism.

我们将三刺棘鱼（Gasterosteus aculeatus）分别暴露于约700 µatm的二氧化碳分压环境（pH 7.9，代表当前大气水平）、约1400 µatm的二氧化碳分压环境（pH 7.6，代表上升流事件情景）以及约3500 µatm的二氧化碳分压环境（pH 7.3，代表沿海区域未来预测情景），暴露时长为2周。我们评估了受试个体的基础活动水平、以个体间距离作为群体社会性替代指标的性状，以及逃逸反应。随后，我们测定了全身体静代谢率与最大代谢率，以探究运动性状的变化是否由代谢水平改变所介导。我们还检测了乳酸脱氢酶（LDH；EC 1.1.1.27）——一种可催化丙酮酸与NADH相互转化为乳酸与NAD+的糖酵解酶——以及柠檬酸合酶（CS；EC 2.3.3.1）——一种定位于线粒体、可催化三羧酸循环（TCA cycle）第一步反应，将乙酰辅酶A与草酰乙酸合成为柠檬酸的酶类。此外，我们还测定了肌纤维尺寸，并通过琥珀酸脱氢酶染色来评估肌肉代谢水平。