Data from: Metabolic rate is canalized in the face of variable life history and nutritional environment

Despite its central importance in organismal physiology, we have poor understanding of how metabolic rate is influenced by two key factors – food nutritional content and an organism's physiological characteristics. We examined how variation in nutrients and physiological aspects of life history affect standard metabolic rate in Gryllus firmus cricket morphs that differ dramatically in flight capability and early-age fecundity. Newly moulted female morphs were fed one of 13 diets that differed in concentrations of protein and carbohydrate. Carbon dioxide production, respiratory exchange ratios (RERs), nutrient intake and mass and lipid levels were measured. CO2 production and RERs increased to a similar degree in both morphs as food macronutrient content increased. In contrast, no difference in whole-organism O2 consumption was observed across the protein–carbohydrate landscape or between morphs. Both morphs similarly increased food intake as nutrient concentration – particularly protein – decreased, but differed in mass and lipid gains, across the diets. Modulation of the substrate used for respiration coupled with compensating aspects of morph-specific metabolism appears to buffer the effects of variable nutrient intake and life history on standard metabolic rate. That is, respiration rate can be highly canalized in the face of dramatic variation in both the external nutritional environment and internal aspects of intermediary metabolism.

尽管代谢速率在个体生理学中占据核心地位，但目前我们对两大关键因素如何影响代谢速率仍缺乏深入认知——即食物营养成分与生物体自身的生理特征。本研究针对飞行能力与早期繁殖力存在显著差异的南方田蟋蟀（Gryllus firmus）不同表型个体，探究了营养成分差异与生活史生理特征如何影响其标准代谢速率。将刚蜕皮的雌性蟋蟀表型个体分别饲喂于13种不同蛋白质与碳水化合物浓度的日粮中，测定了二氧化碳产生量、呼吸交换率（RERs）、营养摄入情况，以及个体体重与脂质水平。随着日粮宏营养成分含量升高，两种表型蟋蟀的二氧化碳产生量与呼吸交换率均以相似幅度上升。与之相反，无论蛋白-碳水化合物配比梯度如何，抑或是不同表型个体之间，整体机体的耗氧量均未出现显著差异。在所有日粮处理中，两种表型个体均随着营养浓度（尤其是蛋白质浓度）降低而增加摄食量，但在体重与脂质积累量上存在差异。对呼吸底物的调控结合表型特异性代谢的补偿机制，似乎能够抵消营养摄入变化与生活史特征对标准代谢速率的影响。换言之，即便外部营养环境与中间代谢的内部特征均发生剧烈变化，呼吸速率仍可保持高度稳定。