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

1. 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. 2. 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. 3. Newly molted female morphs were fed one of 13 diets that differed in concentrations of protein and carbohydrate. Carbon dioxide production, respiratory exchange ratios, nutrient intake, and mass and lipid levels were measured. 4. CO2 production and respiratory exchange ratios 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. 5. Modulation of the substrate used for respiration coupled with compensating aspects of morph-specific metabolism appear 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.

1. 尽管代谢率在机体生理学中处于核心地位，但目前我们对两大关键因素如何影响代谢率仍知之甚少——即食物营养成分与机体自身的生理学特征。2. 本研究探讨了营养物质变异与生活史生理学特征，如何影响两种飞行能力及早期繁殖力差异显著的田野蟋蟀（Gryllus firmus）形态型的标准代谢率（standard metabolic rate）。3. 将刚蜕皮的雌性形态型个体投喂于13种不同蛋白质与碳水化合物浓度的饲料中，随后测定其二氧化碳产生量、呼吸交换率（respiratory exchange ratio）、营养摄入情况，以及体重与脂质水平。4. 随着饲料宏量营养素（macronutrient）含量升高，两种形态型的二氧化碳产生量与呼吸交换率均以相近幅度上升。与之相反，无论在何种蛋白质-碳水化合物配比梯度下，或是两种形态型之间，整体机体耗氧量均未出现显著差异。随着营养浓度（尤其是蛋白质浓度）降低，两种形态型的饲料摄入量均会同步上升，但在不同饲料条件下，二者的体重与脂质积累量存在差异。5. 呼吸底物的调控结合形态型特异性代谢的补偿机制，似乎能够缓冲可变营养摄入与生活史对标准代谢率的影响。换言之，即便外界营养环境与机体内部中间代谢均存在剧烈波动，呼吸速率仍可维持高度稳态化（canalized）。