Department of Biological Sciences, University of New Orleans, New Orleans, LA 70148, USA.
Department of Biology, McGill University, Montreal, QC, CanadaH3A 1B1.
J Exp Biol. 2022 Jun 15;225(12). doi: 10.1242/jeb.243680. Epub 2022 Jun 22.
This study asked whether interindividual variation in maximum and standard aerobic metabolic rates of the Gulf killifish, Fundulus grandis, correlates with gill morphology and cardiac mitochondrial bioenergetics, traits reflecting critical steps in the O2 transport cascade from the environment to the tissues. Maximum metabolic rate (MMR) was positively related to body mass, total gill filament length and myocardial oxygen consumption during maximum oxidative phosphorylation (multiple R2=0.836). Standard metabolic rate (SMR) was positively related to body mass, total gill filament length and myocardial oxygen consumption during maximum electron transport system activity (multiple R2=0.717). After controlling for body mass, individuals with longer gill filaments, summed over all gill arches, or greater cardiac respiratory capacity had higher whole-animal metabolic rates. The overall model fit and the explanatory power of individual predictor variables were better for MMR than for SMR, suggesting that gill morphology and myocardial bioenergetics are more important in determining active rather than resting metabolism. After accounting for body mass, heart ventricle mass was not related to variation in MMR or SMR, indicating that the quality of the heart (i.e. the capacity for mitochondrial metabolism) was more influential than heart size. Finally, the myocardial oxygen consumption required to offset the dissipation of the transmembrane proton gradient in the absence of ATP synthesis was not correlated with either MMR or SMR. The results support the idea that interindividual variation in aerobic metabolism, particularly MMR, is associated with variation in specific steps in the O2 transport cascade.
本研究探讨了海湾鲦鱼（Fundulus grandis）最大和标准需氧代谢率的个体间变异是否与鳃形态和心脏线粒体生物能学相关，这些特征反映了氧气从环境到组织的运输级联中的关键步骤。最大代谢率（MMR）与体重、总鳃丝长度和最大氧化磷酸化期间的心肌耗氧量呈正相关（多重 R2=0.836）。标准代谢率（SMR）与体重、总鳃丝长度和最大电子传递系统活性期间的心肌耗氧量呈正相关（多重 R2=0.717）。在控制体重后，具有较长鳃丝、所有鳃弓总和或更大心脏呼吸能力的个体具有更高的整体代谢率。整体模型拟合度和个体预测变量的解释力对于 MMR 比 SMR 更好，这表明鳃形态和心肌生物能学在决定主动代谢而不是静息代谢方面更为重要。在考虑体重后，心室质量与 MMR 或 SMR 的变化无关，这表明心脏的质量（即线粒体代谢能力）比心脏大小更为重要。最后，在没有 ATP 合成的情况下抵消跨膜质子梯度耗散所需的心肌耗氧量与 MMR 或 SMR 均不相关。结果支持这样一种观点，即有氧代谢的个体间变异，特别是 MMR，与氧气运输级联中特定步骤的变异有关。
