黑线仓鼠繁殖输出与基础代谢率的关系

为了解黑线仓鼠繁殖输出与基础代谢率(BMR)的关系,阐明最大持续能量收支(SusMR)的限制水平, 揭示哺乳期能量收支对策,本文测定了哺乳期黑线仓鼠的体重、摄食量、BMR 和身体组成,以及哺乳期的胎仔数、胎仔重和泌乳能量支出(MEO)。结果显示,黑线仓鼠哺乳期体重降低了15.0 ± 0.8% , 摄食量显著增加, 哺乳高峰期平均摄食量为13.9 ± 0.3 g /d, 摄入能为222.1 ± 5.3 kJ/ d, 比哺乳初期增加121% , 比对照组高288% ;哺乳高峰期MEO 为62.4 ± 2.3 kJ/ d, 哺乳末期BMR 为49.7 ± 1.1 kJ/ d; 断乳时平均胎仔数4.7 ± 0.2、窝胎仔重50.5 ±1.6 g; 哺乳末期BMR 比对照组增加48% ,BMR 与消化系统各器官的相关性高于对照组; BMR 与胎仔数、胎仔重、乳腺重量和MEO 显著正相关。结果表明:初次繁殖的黑线仓鼠哺乳期SusMR 限制为4.47 ×BMR, 在自身维持和繁殖输出之间采取了“权衡分配”的原则,通过体重降低以减少BMR 的增加幅度, 从而有利于繁殖输出。     

Intraspecies variation in avian energy expenditure: correlates and constraints

Data on energy expenditure by 553 individuals of 28 species of small bird (10–150 g) are presented. All estimates of energy expenditure were obtained using the doubly-labelled water technique. Intraspecies variation in daily energy expenditure was found to be positively correlated with brood provisioning rates, percentage of time flying and the frequency of non-resting activity. Correlations were also shown with body-mass, body-size and several environmental factors. Published data on basal metabolic rates (BMR) sometimes differed substantially from estimates either made specifically as part of the studies considered here or calculated from allometric equations. For the purpose of interspecific comparisons, specific estimates of BMR are to be preferred. When expressed as a function of BMR, energy expenditures of free-living birds ranged from 1 + to 7 + times BMR with a mode at 3 +. Values of daily energy expenditure exceeding 4 times BMR were found in up to 48% of species and 30% of individuals, so that, contrary to earlier suggestions, 4 times BMR is not a universal upper limit to the sustained work rate of small birds. Observed upper limits tended to be higher in species with energy-expensive foraging habits. Energy expended by breeding birds is likely to involve a balance between the benefits a greater expenditure has for offspring production and any fitness penalty associated with the high level of energy expediture which nest provisioning involves.     

Comparative analyses of basal rate of metabolism in mammals: data selection does matter

Basal rate of metabolism (BMR) is a physiological parameter that should be measured under strictly defined experimental conditions. In comparative analyses among mammals BMR is widely used as an index of the intensity of the metabolic machinery or as a proxy for energy expenditure. Many databases with BMR values for mammals are available, but the criteria used to select metabolic data as BMR estimates have often varied and the potential effect of this variability has rarely been questioned. We provide a new, expanded BMR database reflecting compliance with standard criteria (resting, postabsorptive state; thermal neutrality; adult, non‐reproductive status for females) and examine potential effects of differential selectivity on the results of comparative analyses. The database includes 1739 different entries for 817 species of mammals, compiled from the original sources. It provides information permitting assessment of the validity of each estimate and presents the value closest to a proper BMR for each entry. Using different selection criteria, several alternative data sets were extracted and used in comparative analyses of (i) the scaling of BMR to body mass and (ii) the relationship between brain mass and BMR. It was expected that results would be especially dependent on selection criteria with small sample sizes and with relatively weak relationships. Phylogenetically informed regression (phylogenetic generalized least squares, PGLS) was applied to the alternative data sets for several different clades (Mammalia, Eutheria, Metatheria, or individual orders). For Mammalia, a ‘subsampling procedure’ was also applied, in which random subsamples of different sample sizes were taken from each original data set and successively analysed. In each case, two data sets with identical sample size and species, but comprising BMR data with different degrees of reliability, were compared. Selection criteria had minor effects on scaling equations computed for large clades (Mammalia, Eutheria, Metatheria), although less‐reliable estimates of BMR were generally about 12–20% larger than more‐reliable ones. Larger effects were found with more‐limited clades, such as sciuromorph rodents. For the relationship between BMR and brain mass the results of comparative analyses were found to depend strongly on the data set used, especially with more‐limited, order‐level clades. In fact, with small sample sizes (e.g. <100) results often appeared erratic. Subsampling revealed that sample size has a non‐linear effect on the probability of a zero slope for a given relationship. Depending on the species included, results could differ dramatically, especially with small sample sizes. Overall, our findings indicate a need for due diligence when selecting BMR estimates and caution regarding results (even if seemingly significant) with small sample sizes.     

小鼠基础代谢率与繁殖输出和繁殖期末器官的关系

以封闭式流体压力呼吸计测定KM小鼠(Mus musculus)的基础代谢率(BMR);采用残差分析和Pearson相关分析检验BMR与繁殖输出、内脏器官的相关性。哺乳末期BMR显著高于繁殖前,繁殖前BMR与繁殖输出不相关,但哺乳末期BMR与体重、摄食量、胎仔数和胎仔重、内脏器官和消化道显著正相关;与消化道器官的相关性高于其他内脏器官。研究结果支持"哺乳期较高的BMR有利于消化系统增强消化和吸收能力,以增加能量摄入用于繁殖输出"的假设。     

树麻雀代谢率和器官重量在季节驯化中表型的可塑性变化

动物能量代谢的生理生态特征与物种的分布和丰富度密切相关,基础代谢率(BMR)是内温动物能量预算的重要组成部分。北温带的小型鸟类,通过增加产热来适应低温环境。增加BMR的基础之一是中心器官(代谢机器)发生明显的变化。本研究中我们测定了树麻雀(Passermontanus)的BMR、体重和各器官的重量,分析了麻雀各器官的季节性变化及与BMR的关系。方差分析表明:麻雀的BMR存在明显的季节性变化,在冬季和秋季较高。麻雀内部器官的变化同样有明显的季节性,冬季和秋季麻雀的肝脏、心脏、肌胃、小肠、直肠和整体消化道的重量,都有明显的增加。相关分析表明:麻雀的BMR与肝脏、心脏和消化道等内部器官存在明显的相关性。我们的结果验证了“中心限制假说”,即麻雀体内存在着与BMR相关的“代谢机器”,中心器官是提高麻雀BMR的基础之一。     

Metabolic consequences of hard work

When an animal has to meet increased demands on its working capacity, for example, for thermoregulation or parental care, two strategies are available. The animal can reallocate energy from costly maintenance processes - such as immunological defence or DNA repair systems (compensation hypothesis) - or it may try to increase the rate of energy intake or efficiency of digestion by increasing the size of the alimentary tract (increased-intake hypothesis). By manipulating brood size, I affected parental effort among marsh tits (Parus palustris) as demonstrated by a significant increase in parental feeding rate with experimental brood size. Basal metabolic rate (BMR) increased both with manipulated brood size and individual feeding rate, supporting the predictions from the increased-intake hypothesis. Furthermore, I found a direct positive relation between BMR and energy expenditure, measured with the help of the doubly labelled water technique. The cost of achieving a higher working capacity is substantial since BMR increases more quickly than the surplus energy available for work. Since the cost of a high sustained workload was not primarily dependent on a reallocation of energy away from maintenance, such a cost should be searched for among the detrimental effects of a high metabolic rate per se, for example, an increased oxidative damage to DNA, proteins and lipids.     

Life in the unthinking depths: energetic constraints on encephalization in marine fishes

Several hypotheses have been proposed to explain the limitation of brain size in vertebrates. Here, we test three hypotheses of brain size evolution using marine teleost fishes: the direct metabolic constraints hypothesis (DMCH), the expensive tissue hypothesis and the temperature‐dependent hypothesis. Our analyses indicate that there is a robust positive correlation between encephalization and basal metabolic rate (BMR) that spans the full range of depths occupied by teleosts from the epipelagic (< 200 m), mesopelagic (200–1000 m) and bathypelagic (> 4000 m). Our results disentangle the effects of temperature and metabolic rate on teleost brain size evolution, supporting the DMCH. Our results agree with previous findings that teleost brain size decreases with depth; however, we also recover a negative correlation between trophic level and encephalization within the mesopelagic zone, a result that runs counter to the expectations of the expensive tissue hypothesis. We hypothesize that mesopelagic fishes at lower trophic levels may be investing more in neural tissue related to the detection of small prey items in a low‐light environment. We recommend that comparative encephalization studies control for BMR in addition to controlling for body size and phylogeny.     

Functional implication of the basal metabolic rate in homeothermic animals

Data on energetic profile of many species Passeriformes and Non-Passeriformes show that the basal metabolic rate (BMR) is strongly correlated with potential energy (MPE) and potential productive energy (PPE) (MPE is about 4BMR in all homeothermic animals). BMR is the minimal power of animal and strongly correlated with the daily work output, which may be determined by measuring total animal activity. Hence, BMR is the fundamental scale of power which determines the intensity of the actual interaction of an individual with the environment. The increase in BMR of a particular animal should rise the potential energy (MPE), potential productive energy (PPE), and the level of daily work output. BMR in Passerines birds is 1.3-1.5 fold higher than that in Non-Passerines and Mammals. Origin ofendothermy in the course of evolution should be associated with needs of general activity rather than with the requirements of thermoregulation.     

内蒙古草原布氏田鼠代谢率与身体器官的关系

动物代谢率存在差异的原因及其意义是进化生理学的一个核心问题。为了解代谢率的影响因素和功能意义, 我们测定了不同驯化条件下布氏田鼠(Microtus brandti) 的基础代谢率(basal metabolic rate , BMR) 、日能量消耗(daily energy expenditure , DEE) 和冷诱导的最大代谢率(maximum metabolic rate , MMR) , 分析了动物体内11 种器官、组织的重量与代谢率的关系。结果显示, 排除温度、光照、食物质量和体重的影响后, BMR 与心脏、肝脏、肾脏、胃和盲肠相关; DEE与心脏、肾脏、胃和盲肠相关; MMR 与脑重显著负相关。这表明: 在布氏田鼠体内存在着代谢活性器官, 主要包括心脏、肝脏、肾脏、胃和盲肠, 这些器官对BMR 有较大的贡献。动物的能量周转水平与体内“代谢机器” (metabolic machinery) 的大小相关连, 主要受到心脏、肾脏、胃和盲肠的影响。最大代谢率受脑重的影响。BMR 与MMR 的相关性不显著, 而BMR 与DEE 的相关性显著, 说明较高的BMR 有助于维持较高的DEE , 但不能维持较高的MMR。     

Is BMR repeatable in deer mice? Organ mass correlates and the effects of cold acclimation and natal altitude

Basal metabolic rate (BMR) is probably the most studied aspect of energy metabolism in vertebrate endotherms. Numerous papers have explored its mass allometry, phylogenetic and ecological relationships, and ontogeny. Implicit in many of these studies (and explicit in some) is the view that BMR responds to selection, which requires repeatability and heritability. However, BMR is highly plastic in response to numerous behavioral and environmental factors and there are surprisingly few data on its repeatability. Moreover, the mechanistic underpinnings of variation in BMR are unclear, despite considerable research. We studied BMR repeatability in deer mice (Peromyscus maniculatus) across intervals of 30–60 days, and also examined the influence of birth altitude (3,800 m versus 340 m) and temperature acclimation (to ∼5 or ∼20°C) on BMR, and the relationship between BMR and organ size. Neither acclimation temperature nor natal altitude alone influenced BMR, but the combination of birth at high altitude and cold acclimation significantly increased BMR. Few visceral organ masses were correlated to BMR and most were inconsistent across natal altitudes and acclimation temperatures, indicating that no single organ ‘controls’ variation in BMR. In several treatment groups, the mass of the ‘running motor’ (combined musculoskeletal mass) was negatively correlated to BMR and the summed mass of visceral organs was positively correlated to BMR. We found no repeatability of BMR in any treatment group. That finding—in sharp contrast to high repeatability of BMR in several other small endotherms—suggests little potential for direct selection to drive BMR evolution in deer mice.     

The allometry of parrot BMR: seasonal data for the Greater Vasa Parrot, <Emphasis Type="Italic">Coracopsis vasa</Emphasis>, from Madagascar

In this study we examined the allometry of basal metabolic rate (BMR) of 31 parrot species. Unlike previous reports, we show that parrots per se do not display BMRs that are any different to other captive-raised birds of their body size. An ordinary least squares regression fitted the data best and body mass explained 95% of the variation in BMR. There was no phylogenetic signal in the BMR data. We also provide new data for the Greater Vasa Parrot (Coracopsis vasa) of Madagascar. We tested the hypotheses that C. vasa may, because of its insular existence, display conservative energetic traits (low BMR, use of adaptive heterothermy) similar to those observed in several Malagasy mammals. However, this was not the case. C. vasa had a higher BMR than other parrots, especially during summer, when BMR was up-regulated by 50.5% and was 95.7% higher than predicted from an ordinary least squares (OLS) allometry of parrots (BMR = 0.042M _b^0.649, BMR in Watts, M _b in grammes). Compared with BMR data for 94 captive-raised bird species, the winter and summer BMRs were, respectively, 45.5 and 117.8% higher than predicted by a phylogenetic generalised least squares (PGLS) allometry (BMR = 0.030M _b^0.687, BMR in Watts, M _b in grammes). The summer up-regulation of BMR is the highest recorded for a bird of any size to date. We suggest that the costs of a high summer BMR may be met by the unusual cooperative breeding system of C. vasa in which groups of males feed the female and share paternity. The potential breeding benefits of a high summer BMR are unknown.     

Changes in body temperature influence the scaling of VO2max and aerobic scope in mammals

Debate on the mechanism(s) responsible for the scaling of metabolic rate with body size in mammals has focused on why the maximum metabolic rate (VO2max ) appears to scale more steeply with body size than the basal metabolic rate (BMR). Consequently, metabolic scope, defined as VO2max/BMR, systematically increases with body size. These observations have led some to suggest that VO2max, and BMR are controlled by fundamentally different processes, and to discount the generality of models that predict a single power-law scaling exponent for the size dependence of the metabolic rate. We present a model that predicts a steeper size dependence for VO2max than BMR based on the observation that changes in muscle temperature from rest to maximal activity are greater in larger mammals. Empirical data support the model's prediction. This model thus provides a potential theoretical and mechanistic link between BMR and VO2 max.     

Basal metabolic rate in carnivores is associated with diet after controlling for phylogeny

Studies of basal metabolic rate (BMR), the minimum metabolic rate of postabsorptive, inactive endotherms while in their rest phase and thermal neutral zone, have contributed significantly to our understanding of animal energetics. Besides body mass, the main determinant of BMR, researchers have invoked diet and phylogenetic history as important factors that influence BMR, although their relative importance has been controversial. For 58 species within the Carnivora, we tested the hypothesis that BMR is correlated with home range size, a proxy for level of activity, and diet, using conventional least squares regression (CLSR) and regression based on phylogenetic independent contrasts (PIC). Results showed that BMR of Carnivora was positively correlated with home range size after controlling for body mass, regardless of the statistical method employed. We also found that diet and mass-adjusted home range size were correlated. When we simultaneously tested the effect of diet and mass-adjusted home range on mass-adjusted BMR, home range size was insignificant because of its colinearity with diet. Then we eliminated home range size from our model, and diet proved to be significant with both CLSR and PIC. We concluded that species that eat meat have larger home ranges and higher BMR than species that eat vegetable matter. To advance our understanding of the potential mechanisms that might explain our results, we propose the "muscle performance hypothesis," which suggests that selection for different muscle fiber types can account for the differences in BMR observed between meat eaters and vegetarian species within the Carnivora.     

The energy economy of the arctic-breeding Kittiwake (Rissa tridactyla): a review

The present paper reviews recent studies on changes in body mass, body composition and rates of energy expenditure during the breeding season in the black-legged Kittiwake (Rissa tridactyla) on Svalbard (79 degrees N). The main characteristic of the energy budget is a pronounced decrease in body mass as well as basal metabolic rate (BMR) after the eggs have hatched. While most internal organs lose mass in direct proportion to the general decrease in body mass, the liver and kidney masses decrease to a disproportionately greater extent. Since both the liver and the kidney have high intrinsic metabolic rates, these results support an earlier notion that the reduction in body mass is an adaptation to reduce maintenance costs. Alternatively, the reduced BMR is due to a decrease in energy uptake from the gastrointestinal tract, thereby ensuring that undigested food is ready to be regurgitated to the chicks. At the end of the chick-rearing period, the field metabolic rate (FMR) reaches its highest level, probably due to an increased workload associated with chick feeding. This occurs at a time of low body mass and BMR. A pronounced increase in the metabolic scope (FMR/BMR) during the latter part of the chick-rearing period demonstrates that BMR and FMR may change independently of each other and that the ratio FMR/BMR may not be a good measure of energy stress.     

Evolutionary dynamics of intron size, genome size, and physiological correlates in archosaurs

It has been proposed that intron and genome sizes in birds are reduced in comparison with mammals because of the metabolic demands of flight. To test this hypothesis, we examined the sizes of 14 introns in a nonflying relative of birds, the American alligator (Alligator mississippiensis), and in 19 flighted and flightless birds in 12 taxonomic orders. Our results indicate that a substantial fraction (66%) of the reduction in intron size as well as in genome size had already occurred in nonflying archosaurs. Using phylogenetically independent contrasts, we found that the proposed inverse correlation of genome size and basal metabolic rate (BMR) is significant among amniotes and archosaurs, whereas intron and genome size variation within birds showed no significant correlation with BMR. We show statistically that the distribution of genome sizes in birds and mammals is underdispersed compared with the Brownian motion model and consistent with strong stabilizing selection; that genome size differences between vertebrate clades are overdispersed and punctuational; and that evolution of BMR and avian intron size is consistent with Brownian motion. These results suggest that the contrast between genome size/BMR and intron size/BMR correlations may be a consequence of different intensities of selection for these traits and that we should not expect changes in intron size to be significantly associated with metabolically costly behaviors such as flight.     

Dominant black-capped chickadees pay no maintenance energy costs for their wintering status and are not better at enduring cold than subordinate individuals

Winter requires physiological adjustments in northern resident passerines. Cold acclimatization is generally associated with an increase in physiological maintenance costs, measured as basal metabolic rate (BMR), and cold endurance, reflected by summit metabolic rate (M _sum). However, several northern species also form social groups in winter and a bird’s hierarchical position may influence the size of its metabolically active organs as well as its BMR. Winter metabolic performance in these species may therefore reflect a complex set of adjustments to both seasonal climatic variations and social environment. We studied the effect of social status on parameters of cold acclimatization (body mass, size of fat reserves and pectoral muscles, BMR and M _sum) in free-living black-capped chickadees (Poecile atricapillus). Birds that were structurally large and heavy for their body size, mostly dominant individuals, carried more fat reserves and had larger pectoral muscles. However, social status had little effect on metabolic performance in the cold. Indeed, M _sum was independent of social rank while mass-corrected BMR was slightly lower in dominant individuals, likely due to a statistical dilution effect caused by large metabolically inactive fat reserves. BMR and M _sum, whether considered in terms of whole-animal values, corrected for body mass or body size were nevertheless correlated, suggesting a functional link between these metabolic components. Our results therefore indicate that the energy cost of social dominance is not a generalized phenomenon in small wintering birds.     

Basal metabolic rate and risk‐taking behaviour in birds

Basal metabolic rate (BMR) constitutes the minimal metabolic rate in the zone of thermo‐neutrality, where heat production is not elevated for temperature regulation. BMR thus constitutes the minimum metabolic rate that is required for maintenance. Interspecific variation in BMR in birds is correlated with food habits, climate, habitat, flight activity, torpor, altitude, and migration, although the selective forces involved in the evolution of these presumed adaptations are not always obvious. I suggest that BMR constitutes the minimum level required for maintenance, and that variation in this minimum level reflects the fitness costs and benefits in terms of ability to respond to selective agents like predators, implying that an elevated level of BMR is a cost of wariness towards predators. This hypothesis predicts a positive relationship between BMR and measures of risk taking such as flight initiation distance (FID) of individuals approached by a potential predator. Consistent with this suggestion, I show in a comparative analysis of 76 bird species that species with higher BMR for their body mass have longer FID when approached by a potential predator. This effect was independent of potentially confounding variables and similarity among species due to common phylogenetic descent. These results imply that BMR is positively related to risk‐taking behaviour, and that predation constitutes a neglected factor in the evolution of BMR.     

Endocranial volumes of primate species: scaling analyses using a comprehensive and reliable data set

We present a compilation of endocranial volumes (ECV) for 176 non-human primate species based on individual data collected from 3813 museum specimens, at least 88% being wild-caught. In combination with body mass data from wild individuals, strong correlations between endocranial volume and body mass within taxonomic groups were found. Errors attributable to different techniques for measuring cranial capacity were negligible and unbiased. The overall slopes for regressions of log ECV on log body mass in primates are 0.773 for least-squares regression and 0.793 for reduced major axis regression. The least-squares slope is reduced to 0.565 when independent contrasts are substituted for species means (branch lengths from molecular studies). A common slope of 0.646 is obtained with logged species means when grade shifts between major groups are taken into account using ANCOVA. In addition to providing a comprehensive and reliable database for comparative analyses of primate brain size, we show that the scaling relationship between brain mass and ECV does not differ significantly from isometry in primates. We also demonstrate that ECV does not differ substantially between captive and wild samples of the same species. ECV may be a more reliable indicator of brain size than brain mass, because considerably larger samples can be collected to better represent the full range of intraspecific variation. We also provide support for the maternal energy hypothesis by showing that basal metabolic rate (BMR) and gestation period are both positively correlated with brain size in primates, after controlling for the influence of body mass and potential effects of phylogenetic relatedness.     

黑线仓鼠的BMR个体差异及其应对高脂食物的能量学对策

为探讨高脂食物对小型哺乳动物能量代谢的影响及其与基础代谢率(Basal metabolic rate, BMR)的关系,将成年雌性黑线仓鼠(Cricetulus barabensis)分为高、低BMR组,每组再随机分为低脂、高脂食物组,驯化6周后,测定体重、摄入能和代谢率,以及消化酶活力、褐色脂肪组织(Brown adipose tissue, BAT)和主要内脏器官与肌肉的细胞色素c氧化酶(Cytochrome c oxidase, COX)活性、解偶联蛋白(Uncoupling protein, UCP) mRNA表达等。结果显示,高脂食物对高、低BMR组动物体重均无显著影响。与低脂食物组相比,高脂食物组的摄食量、摄入能和消化能显著下降,小肠脂肪酶活力显著增强,消化率明显增加,但高、低BMR组的组间差异不显著。夜间代谢水平显著高于昼间,高脂食物使高BMR组的夜间代谢率显著升高。BAT、肌肉和内脏器官COX活性不受高脂食物的影响,高、低BMR组的组间差异也不显著。高脂食物组仅肝脏UCP2表达显著上调。结果表明,能量摄入和消化系统形态及功能的可塑性调节是黑线仓鼠应对高脂食物的主要策略;黑线仓鼠的代谢率具有显著的昼夜节律,既受高脂食物的影响,也与动物自身的BMR水平有关,但UCP表达具有组织特异性,这可能不是导致BMR个体差异的因素。