Search

Aging coincides with the progressive loss of muscle mass and strength, increased adiposity, and diminished physical function. Accordingly, interventions aimed at improving muscle, metabolic, and/or physical health are of interest to mitigate the adverse effects of aging. In this study, we tested a stem cell secretome product, which contains extracellular vesicles and growth, cytoskeletal remodeling, and immunomodulatory factors. We examined the effects of 4 weeks of 2×/week unilateral intramuscular secretome injections (quadriceps) in ambulatory aged male C57BL/6 mice (22-24 months) compared to saline-injected aged-matched controls. Secretome delivery substantially increased whole-body lean mass and decreased fat mass, corresponding to higher myofiber cross-sectional area and smaller adipocyte size, respectively. Secretome-treated mice also had greater whole-body physical function (grip strength and rotarod performance) and had higher energy expenditure and physical activity levels compared to control mice. Furthermore, secretome-treated mice had greater skeletal muscle Pax7+ cell abundance, capillary density, collagen IV turnover, reduced intramuscular lipids, and greater Akt and hormone sensitive lipase phosphorylation in adipose tissue. Finally, secretome treatment in vitro directly enhanced muscle cell growth and IL-6 production, and in adipocytes, it reduced lipid content and improved insulin sensitivity. Moreover, indirect treatment with secretome-treated myotube culture media also enhanced muscle cell growth and adipocyte size reduction. Together, these data suggest that intramuscular treatment with a stem cell secretome improves whole-body metabolism, physical function, and remodels skeletal muscle and adipose tissue in aged mice.

Globally, large mammals are in decline. Biological traits including low population densities and longer generation times make them particularly susceptible. Their losses can have wide-ranging ecological consequences, including dramatic reductions in total heterotrophic energy use. To determine the key drivers of variation in energy use, we calculated daily rates of energy flow across the globe for 241 ecological communities, encompassing 441 large mammal species, using camera trap inventories. These were scaled up from individual metabolic rates and compared with various climate, anthropogenic, geographic, and species richness variables using three analytical methods: model selection, spatial autoregression, and a multiple regression method that completely removes multicollinearity known as least-squares orthogonalization. Community energy use is significantly lower in the Neotropics and Australasia than in the Afrotropics and Eurasia. This pattern mirrors the spatial distribution of megafaunal extinction intensity during the Late Pleistocene. Rates not being greatly reduced in the Nearctic is a notable exception to this pattern, and is likely due to the high abundances of certain species not present in the other highly-impacted realms. There are also strong negative correlations between community per-gram rates of energy flow and species richness, indicating that megafauna persist mainly in more speciose communities. The strong geographic differences that dominate energy use patterns indicate that past mammal extinctions are the ultimate cause of modern energetic variation in large mammal communities. If so, then ongoing losses of large mammals will greatly impact community and ecosystem functioning.

Cancer is a leading cause of death in domestic dogs. Deaths due to cancer vary widely among breeds, providing an opportunity for testing the multi-stage model of carcinogenesis. This model underpins evolutionary and basic studies of cancer suppression and predicts a linear increase in cancer with breed size, an expectation complicated by bigger breeds having a shorter lifespan (decreasing risk). Using three independent datasets, the weight and lifespan of breeds provided a good fit of lifetime cancer mortality to the multi-stage model, the fit suggesting many canine cancers are initiated by four driver mutations. Of 85 breeds in more than one dataset, only flat-coated retriever showed significantly elevated cancer mortality, with Scottish terrier, Bernese mountain dog and bullmastiff also showing notable risk (greater than 50% over expected). Analysis of breed clades suggested terriers experience elevated cancer mortality. There was no evidence that the lower mass-specific metabolic rate of larger breeds reduced cancer risk. Residuals indicated increased breed inbreeding shortened expected lifespan, but had no overall effect on cancer mortality. The results provide a baseline for identifying increased breed risk for specific cancers and demonstrate that, unless selection promotes increased cancer suppression, the evolution of larger longer-lived animals leads to a predictable increased cancer risk.

The mechanistic link between metabolic rate and foraging behaviour is a crucial aspect of several energy‐based ecological theories. Despite its importance to ecology however, it remains unclear whether and how energy requirements and behavioural patterns are mechanistically connected. Here we aimed to assess how modes of behaviour, including cumulative space use, patch selection and time spent in an experimental resource‐patchy environment, are related to a forager's standard metabolic rate (SMR) and its main determinants, i.e. body mass and temperature. We tested the individual behavioural patterns and metabolic rates of a model organism, the amphipod Gammarus insensibilis, across a range of body masses and temperatures. We demonstrated quantitatively that body mass and temperature exert a major influence on foraging decisions and space use behaviour via their effects on metabolic rates and the marginal value of energy. Individual cumulative space use was found to scale allometrically with body mass and exponentially with temperature, with patch giving‐up time falling as body mass and temperature increased. In response to warmer temperatures, the specimens adaptively intensified their foraging effort and explored larger spaces to offset the elevated SMR. Our results showed that SMR explained more variation than body mass and temperature combined, and had greater predictive power for behavioural patterns. Furthermore, foraging decisions regarding patch choice and partitioning were strongly related to mass‐and‐temperature‐adjusted SMR (residual), which is a component of metabolic phenotype. Individuals with higher M–T adjusted SMR initially preferred the most profitable patch and, as time progressed, abandoned the patch earlier and explored more space than the others. These results demonstrate that foraging decisions are intimately associated with variations in standard metabolic rate, whether phenotypic or due to size and temperature combined. This, in turn, sheds light on higher‐order energy‐based ecological processes. [ABSTRACT FROM AUTHOR]

There is growing evidence that the body's energy expenditures constitute a significant risk factor for the development of most deadly diseases, including cancer. Our aim was to investigate the impact of basal metabolic rate (BMR) on the growth and progression of colorectal cancer (CRC). To do so, we used a unique model consisting of three lines of laboratory mice (Mus musculus) artificially selected for high (HBMR) and low (LBMR) basal metabolic rate and randomly bred individuals (non-selected, NSBMR). The experimental individuals were implanted with human colorectal cancer cells DLD-1. The variation in BMR between the lines allowed for testing the impact of whole-body metabolism on oxidative and antioxidant parameters in the liver throughout the cancerogenesis process. We investigated the dependence between metabolic values, reactive oxygen species (ROS) levels, and Kelch-like ECH-associated protein 1-based E3 ligase complexes (Keap1) gene activity in these animals. We found that the HBMR strain had a higher concentration of oxidative enzymes compared to the LBMR and NSBMR. Furthermore, the growth rate of CRC tumors was associated with alterations in the levels of oxidative stress enzymes and Keap1 expression in animals with a high metabolic rate. Our results indicate that a faster growth and development of CRC line DLD-1 is associated with enzymatic redox imbalance in animals with a high BMR. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Hydrobiology is the property of Editorial Department of Journal of Hydrobiology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The metabolic rate of a freely moving fish (routine metabolic rate) is tightly coupled with volitional movement (spontaneous activity), both of which commonly show strong daily cycles linked to the species‐specific diel activity pattern. Mummichog (Fundulus heteroclitus), an important estuarine fish in the north western Atlantic Ocean, are historically reported as diurnal (i.e., more active during daylight). Our recent laboratory studies on a Bay of Fundy population, however, showed a free‐running (i.e., similarly active daytime and night‐time) or even nocturnal (i.e., more active at night‐time) diel activity pattern. In the laboratory, near‐infrared (NIR) illumination is commonly used with a NIR‐sensitive camera to visualize fish activity across the light–dark periods of the day. Because NIR light is close to the visible light spectrum and certain fishes show sensitivity to NIR, the use of NIR with mummichog possibly could disturb the animals and obscure the identification of their true diel activity pattern. We aimed to determine if NIR illumination (940 nm wavelength) influences the diel activity pattern of mummichog. We used measurements of routine metabolic rate (oxygen consumption rate, MO2) as a proxy for activity, as evaluating the effect of NIR requires treatments where NIR lights are off, which precludes visualization and direct assessment of fish activity at night‐time. We measured routine MO2 of mummichogs over 6 days, exposed to either NIR off–on–off (2 days for each off or on period) or the opposite sequence of NIR on–off–on (to control for time‐dependent effects). NIR lights did not influence the diel cycle of routine MO2, and activity by proxy, in mummichog. Thus, NIR illumination is a suitable method to visualize mummichog during light–dark diel cycles. Routine MO2, and presumably activity, was similar or higher during night‐time periods compared to daytime periods, confirming a free‐running or nocturnal activity pattern for at least certain populations of mummichog. [ABSTRACT FROM AUTHOR]

Bioenergetics models are powerful tools used to address a range of questions in fish biology. However, these models are rarely informed by free‐swimming activity data, introducing error. To quantify the costs of activity in free‐swimming fish, calibrations produced from standardized laboratory trials can be applied to estimate energy expenditure from sensor data for specific tags and species. Using swim tunnel respirometry, we calibrated acceleration sensor‐equipped transmitting tags to estimate the aerobic metabolic rates (ṀO2) of lake trout (Salvelinus namaycush) at three environmentally relevant temperatures. Aerobic and swim performance were also assessed. Like other calibrations, we found strong relationships between ṀO2 and acceleration or swimming speed, and jackknife validations and data simulations suggest that our models accurately predict metabolic costs of activity in adult lake trout (~5% algebraic error and ~20% absolute error). Aerobic and swim performance metrics were similar to those reported in other studies, but their critical swimming speed was lower than expected. Additionally, lake trout exhibited a wide aerobic scope, suggesting that the avoidance of waters ≥15°C may be related to selection for optimal growing temperatures. The ability to quantify the free‐swimming energetic costs of activity will advance our understanding of lake trout ecology and may yield improvements to bioenergetics model. [ABSTRACT FROM AUTHOR]

Catch and release has become a very popular fish conservation strategy and fisheries management tool. The physiological and behavioral changes in individuals who experience catch and release may be adaptive. These individuals may exhibit more cautious bait use or hook avoidance behavior when faced with lures again. Here, our study was conducted on crucian carp (Carassius auratus) to compare energy metabolism and personality (e.g. activity) before and after angling for three bouts of repeated angling. Our study showed that the standard metabolic rate, maximum metabolic rate, aerobic scope and factorial aerobic scope were all lower after three bouts of repeated angling, and the metabolic rates were greater before angling than after angling in the first two bouts of angling. In addition, the total magnitude of excess postexercise oxygen consumption after repeated angling also showed a decreasing trend as the number of angled bouts increased. The percentage of time spent moving increased after three bouts of repeated angling, but there were no changes in either individual swimming speed or total distance traveled. Our results suggest that repeated angling causes a high death rate and decreases the aerobic/anaerobic metabolic capacity of crucian carp, which may reduce their metabolic potential for other physiological functions, such as locomotion, growth and digestion. Future studies should continue to focus on the effects of fishing on the physiology, behavior, and population dynamics of fish. [ABSTRACT FROM AUTHOR]

Coffee is one of the three most consumed beverages in the world. It is made by first roasting coffee beans, and then grinding and boiling or steeping the roasted beans in water (brewing). The process of roasting and brewing produces a complex mix of bioactive compounds, including methylxanthines (caffeine, theobromine, theophylline), diterpenes, chlorogenic acid, trigonelline, flavonoids, and hydroxycinnamic acid. In the body, these compounds may be metabolized to produce other bioactive compounds. For example, caffeine is primarily (80%) broken down by demethylation to produce paraxanthine. In the post-ingestion period, levels of paraxanthine may be higher than caffeine due to its slower elimination. Hence, while paraxanthine is not found in coffee itself, it has many of the same properties as caffeine and may be a major contributor to its metabolic effects. The impacts of caffeine and paraxanthine on metabolism relate to their impact on adenosine receptors (notably the A2A receptor). It has been known for almost 100 years that intake of coffee stimulates metabolism by between 5% and 20% for at least 3 h. About half of the increase in metabolic rate after drinking coffee is due to caffeine and derivatives, but the source of the other half is unclear. There are large differences in the response to the same amount of coffee in different individuals, which may be related to caffeine clearance rates, effects of other unknown pathways, genetic polymorphism, age, sex, and body composition. [ABSTRACT FROM AUTHOR]

The experiment aims to evaluate the nutritional value of fermented pleurotus eryngii residue in yellow-feather broilers. 45 healthy male yellow-feather broilers (Tuhuang No.6) weighing (2.04±0.14) kg at 60 days old were randomly divided into 3 groups. Control group was fed with basal diet, groups A and B with basal diets + 20% and 30% fermented pleurotus eryngii residue, respectively. At the end of the experiment, the average daily feed intake (ADFI), energy metabolism and nutrient metabolism were measured. The experiment lasted for 13 days. The results showed as follows: the ADFI was significantly increased in groups A and B (P<0.05). The groups A and B with different substitution ratios of fermented fungus residue had a significant difference in the metabolic rates of calcium, phosphorus, and crude fiber calculated by the substitution method (P<0.05), while no significant differences were found in the metabolizable energy and nutrient metabolizable rates (P>0.05). The AME (TME) and AMEN (TMEN) of fermented fungus residue in groups A and B were 4.87, 5.21 MJ/kg (5.01, 5.39 MJ/kg) and 4.77, 5.14 MJ/kg (4.92, 5.32 MJ/kg), respectively. The total energy metabolism rate and nitrogen metabolism rate were 32.88%, 33.77% and 22.86%, 18.31%, respectively. The apparent (true) metabolic rates of DM, CP, EE, NDF, and ADF were 24.24%, 22.67% (26.37%, 24.55%), 22.86%, 18.31% (31.91%, 27.45%), 58.39%, 48.92% (59.02%, 49.58%), 19.20%, 25.44% (18.99%, 25.44%), and 62.67%, 58.51% (62.38%, 58.48%), respectively. It is concluded that the substitution ratio of untested raw materials may affect the metabolic rate of calcium, phosphorus, and crude fiber calculated by the substitution method, while metabolizable energy and other nutrient metabolizable rates can be used as a data reference for the application of fermented pleurotus eryngii residue in yellow-feather broilers. [ABSTRACT FROM AUTHOR]

Face masks' wearing for a long duration brings thermal discomfort, especially in hot climate cities. The face masks' thermal insulation and its effect on outdoor thermal comfort have been rarely investigated. In this study, five types of face masks and their thermal insulations have been tested by using a thermal manikin in the climate chamber. Experimental results are assessed by using physiological equivalent temperature (PET) and standard effective temperature (SET*) for thermal comfort with masks at three walking speeds both in summer and winter. Slight differences in thermal insulation are observed among the different masks, the values of PET and SET* rise with increasing mask thermal insulation, and they are generally higher in summer than in winter. Moreover, the variation of SET* is more obvious than PET with same masks at different walking speeds. And the differences of SET* with and without masks appear to rise significantly for fast walking. Results further indicate that the individuals' physical discomfort caused by wearing masks cannot simply be assumed as an additional effect of the clothing thermal insulation. The findings enrich the clothing thermal insulation database, explore the differences in thermal indices if the face mask is used, and provide advice on heat mitigation with masks outdoors. [ABSTRACT FROM AUTHOR]

Revisiting classical experiments on the impact of air resistance on metabolic rate, we aimed to overcome limitations of previous research, notably: low participant numbers (n = 1–3), highly turbulent wind, and confounding effects of rising body temperature. In a custom-built wind tunnel with reduced turbulence, 14 participants (8 males, 6 females) walked (5 km·h−1) and ran on a treadmill (70%V̇ o 2max) at 0, 2, 4, and 6 m·s−1 headwind or tailwind in a counterbalanced design, with rest breaks between each exposure to avoid rises in body core temperature. Oxygen consumption (V̇ o 2) exhibited strong linear relationships versus wind direction, dynamic pressure, and air speed squared (Vwr2), lower in magnitude for headwind than tailwind. A moderate linear relationship was observed between heart rate, wind direction, dynamic pressure, and Vwr2. Below 4 m·s−1, the effect of wind was well within inter- and intraindividual variation and equipment uncertainty, and only at wind speeds ≥4 m·s−1 did the differences in physiological responses reach statistical significance. Our data indicate that at running speeds below 4 m·s−1 (14.4 km/h), indoor treadmills and outdoor running are comparable in terms of the metabolic impact of air movement relative to the person. However, this does not extend to the thermoregulatory effect of wind, with outdoor running providing a higher cooling rate due to the self-generated wind created during running. By removing the confounding impact of core temperature rises, the observed effects of headwind were lower and those of tailwind larger than observed previously. In the context of middle-distance running, the headwind created by running at 21.5 km·h−1 would result in a 2.2% increase of V̇ o 2. A relative tailwind of the same speed would lead to a 3.1% reduction. NEW & NOTEWORTHY: Revisiting classical work by Pugh and Davies on the metabolic effects of air speed and direction, shortcomings in the original studies were addressed. Using more participants, less turbulent wind, and avoiding confounding effects of work-induced core temperature increases, new equations describing the impact of air speed/direction were developed. This study observed a lower impact of headwind and a larger impact of tailwind in the absence of an exercise-induced core temperature increase. [ABSTRACT FROM AUTHOR]

The electricity system and the industrial sector interrelate on the path to decarbonization. The study addresses the drivers and environmental pressure within the industrial sector on the National Electricity System (NES). This article aims to characterize the metabolic pattern of the NES and the industrial sector using the Multiscale Integrated Analysis of Social and Ecological Metabolism (MuSIASEM) from a bioeconomic perspective to identify fields of opportunity in the regulatory policy instruments. A set of extensive and intensive variables (2019) on energy, production factors, and emissions was used at different hierarchical levels based on both subsectors. Our results show that the NES used primary energy sources (PES) and secondary energy carriers to fulfill its functions, of which 72% were domestic sources and 28% were imported. México imported 79.5% of the natural gas (NG) for electricity generation. However, there are favorable conditions for renewable PES to increase the installed capacity of solar plants between 3 and 4 orders of magnitude and 2–3 in wind power from the current capacity. NES's energy consumption per hour of human time is 17,388 MJ/h, with 65% being the heat equivalent to a total energy input consumed of 2139 PJ/y. Public plants contributed 43.7% to the generation, and the independent and self-supply producers the rest. End uses needed the supply of 69.3% of electricity from baseload plants. Sixty-three percent of the metabolic pattern of the industrial sector is based on heat and fuel processes, which depend on NG imports. The NES is reorganizing and recovering its energy autonomy. [ABSTRACT FROM AUTHOR]

The evolutionary patterns of the mitochondrial genome are influenced by both adaptive and nonadaptive forces, with their contributions varying among taxa. There appears to be a correlation linking mutagenesis and latitude, which could be due to differences in metabolic rates. These discrepancies in metabolic rates exhibit a positive connection with mutation pressure. On this basis, we hypothesise that nonadaptive forces play a role in the differences in mutation rates observed along latitudinal gradients. In this study, we selected widely distributed carnivores as representatives of mammals to test our hypothesis. We examined the correlations between the dN/dS ratio (ω), as well as the substitution rates (dS and dN), of 13 PCGs in the mtDNA of 122 carnivores, and the latitude and climatic factors. We found that taxa distributed in higher latitudes tend to have higher substitution rates, but not ω values indicating selective pressure. Notably, dN shows a strong positive correlation with dS, although dS is primarily influenced by mutation pressure, while dN is also influenced by effective population size (Ne). Phylogenetic generalised least squares (PGLS) regression analyses showed that both substitution rates were correlated with climatic factors representing the temperature, precipitation and variability of climate. Based on our findings, we propose that the mutations are primarily influenced by nonadaptive forces (mutation pressure). This forms the fundamental premise for natural selection and speciation. Moreover, the correlation between substitution rates and latitudinal distribution and climate, which are outcomes of nonadaptive factors, can aid in comprehending the global distribution of species diversity. [ABSTRACT FROM AUTHOR]

Djungarian hamsters (Phodopus sungorus) living at constant 15 °C Ta in short photoperiod (8:16 h L:D) showed pronounced ultradian rhythms (URs) of metabolic rate (MR), body temperature (Tb) and locomotor activity. The ultradian patterns differed between individuals and varied over time. The period length of URs for MR, Tb and activity was similar although not identical. Wavelet analysis showed that three different URs are existing in parallel, URs of small amplitude and short duration (URsmall), URs of medium amplitude and medium duration (URmedium) and URs of large amplitude (URlarge), superimposed on each other. URlarge were accompanied by an increase in locomotor activity, whereas URsmall and URmedium were of metabolic origin with lacking or delayed responses of activity. An energetic challenge to cold which raised total energy requirements by about 50% did not accelerate the period length of URs, but extended the amplitude of URsmall and URmedium. URlarge corresponds with the URs of activity, feeding and drinking, sleep and arousal as described in previous studies, which are related to midbrain dopaminergic signalling and hypothalamic ultradian signalling. The cause and control of URmedium and URsmall is unknown. Their periods are similar to periods of central and peripheral endocrine ultradian signalling, suggesting a link with URs of metabolism. [ABSTRACT FROM AUTHOR]

Nutrient foramina are small openings in the periosteal surface of the mid-shaft region of long bones that traverse the cortical layer and reach the medullary cavity. They are important for the delivery of nutrients and oxygen to bone tissue and are crucial for the repair and remodeling of bones over time. The nutrient foramina in the femur's diaphysis are related to the energetic needs of the femur and have been shown to be related to the maximum metabolic rate (MMR) of taxa. Here, we investigate the relationship between nutrient foramen size and body mass as a proxy to the aerobic capacity of taxa in living and extinct xenarthrans, including living sloths, anteaters, and armadillos, as well as extinct xenarthrans such as glyptodonts, pampatheres, and ground sloths. Seventy femora were sampled, including 20 from extant taxa and 50 from extinct taxa. We obtained the blood flow rate (Q̇) based on foramina area and performed PGLS and phylogenetic ANCOVA in order to explore differences among mammalian groups. Our results show that, among mammals, taxa commonly associated with lower metabolism like living xenarthrans showed relatively smaller foramina, while the foramina of giant extinct xenarthrans like ground sloths and glyptodonts overlapped with non-xenarthran placentals. Consequently, Q̇ estimations indicated aerobic capacities comparable to other placental giant taxa like elephants or some ungulates. Furthermore, the estimation of the MMR for fossil giant taxa showed similar results, with almost all taxa showing high values except for those for which strong semi-arboreal or fossorial habits have been proposed. Moreover, the results are compatible with the diets predicted for extinct taxa, which indicate a strong consumption of grass similar to ungulates and in contrast to the folivorous or insectivorous diets of extant xenarthrans. The ancestral reconstruction of the MMR values indicated a lack of a common pattern for all xenarthrans, strongly supporting the occurrence of low metabolic rates in extant forms due to their particular dietary preferences and arboreal or fossorial habits. Our results highlight the importance of considering different evidence beyond the phylogenetic position of extinct taxa, especially when extinct forms are exceptionally different from their extant relatives. Future studies evaluating the energetic needs of giant extinct xenarthrans should not assume lower metabolic rates for these extinct animals based solely on their phylogenetic position and the observations on their extant relatives. [ABSTRACT FROM AUTHOR]

Persistent individual variation in behaviour, or 'personality', is a widespread phenomenon in animals, and understanding the evolution of animal personality is a key task of current biology. Natural selection has been proposed to promote the integration of personality with animal 'intrinsic states', such as metabolic or endocrine traits, and this integration varies with ecological conditions. However, these external ecological modulatory effects have rarely been examined. Here, we investigate the effects of thermal acclimation on between-individual covariations between physiology and behaviour in Asiatic toads (Bufo gargarizans) along an altitudinal gradient. Our results reveal that the thermal modulatory effects on the covariations depend on the altitudinal population. Specifically, at low altitudes, between-individual covariations are highly plastic, with risk-taking behaviour covarying with baseline glucocorticoids (GCs) under warm acclimation, but risk-taking and exploration behaviour covarying with resting metabolic rate (RMR) under cold acclimation. In contrast, between-individual covariations are relatively fixed at high altitudes, with risk-taking behaviour consistently covarying with baseline GCs. Furthermore, at low altitudes, changes in covariations between RMR and personality are associated with adjustment of energy management models. Evidently, animal physiological states that determine or covary with personality can adapt according to the seasonal thermal environment and the thermal evolutionary background of populations. Our findings highlight the importance of a multi-system physiological approach to understand the evolution of animal personality. [ABSTRACT FROM AUTHOR]

The master circadian clock, located in the suprachiasmatic nuclei (SCN), organizes the daily rhythm in minute ventilation (V ̇ E). However, the extent that the daily rhythm in V ̇ E is secondary to SCN-imposed O2 and CO2 cycles (i.e., metabolic rate) or driven by other clock mechanisms remains unknown. Here, we experimentally shifted metabolic rate using time-restricted feeding (without affecting light-induced synchronization of the SCN) to determine the influence of metabolic rate in orchestrating the daily V ̇ E rhythm. Mice eating predominantly at night exhibited robust daily rhythms in O2 consumption (V ̇ O2), CO2 production (V ̇ CO2), and V ̇ E with similar peak times (approximately ZT18) that were consistent with SCN organization. However, feeding mice exclusively during the day separated the relative timing of metabolic and ventilatory rhythms, resulting in an approximately 8.5-h advance in V ̇ CO2 and a disruption of the V ̇ E rhythm, suggesting opposing circadian and metabolic influences on V ̇ E. To determine if the molecular clock of cells involved in the neural control of breathing contributes to the daily V_ E rhythm, we examined V ̇ E in mice lacking BMAL1 in Phox2b-expressing respiratory cells (i.e., BKOP mice). The ventilatory and metabolic rhythms of predominantly night-fed BKOP mice did not differ from wild-type mice. However, in contrast to wild-type mice, exclusive day feeding of BKOP mice led to an unfettered daily V̇ E rhythm with a peak time aligning closely with the daily V ̇ CO2 rhythm. Taken together, these results indicate that both daily V ̇ CO2 changes and intrinsic circadian time-keeping within Phox2b respiratory cells are predominant orchestrators of the daily rhythm in ventilation. [ABSTRACT FROM AUTHOR]

Metabolic rate is a crucial trait shaping organismal physiology, adaptability, and ecological roles, with extensive studies on its allometric relationship with body size. Larger organisms have lower mass-specific metabolic rates, a pattern observed across taxa and ontogeny. Despite numerous hypotheses, no universally accepted theory exists on the biological mechanisms of metabolic allometry, particularly for suborganism-level. We investigated the relationship between body size and metabolic rate as well as mitochondrial characteristics in isolated gill tissue of the marine mussel Mytilus edulis. Results indicated that metabolic allometry patterns observed at the organismal level did not manifest at the tissue level. Our study also revealed that while the density of mitochondria in gill tissue did not differ significantly between large and small individuals, area and perimeter of mitochondrial cross-sections increased significantly with body mass. This finding contrasts with mammalian data, suggesting potential phylogenetic differences. Larger mussels exhibited higher mitochondrial activity, supporting a link between mitochondrial morphology, activity, and growth rates. Our results highlight the importance of mitochondria in mollusk metabolism and growth, warranting further exploration into the mechanisms translating mitochondrial characteristics into growth rates. [ABSTRACT FROM AUTHOR]

We tested whether spontaneous physical activity (SPA) from accelerometers could be used in a whole room calorimeter to estimate thermic effect of food (TEF). Eleven healthy participants (n = 7 females; age: 27 ± 4 yr; body mass index: 22.8 ± 2.6 kg/m2) completed two 23-h visits in randomized order: one "fed" with meals provided and one "fasted" with no food. SPA was measured by ActivPAL and Actigraph accelerometers. Criterion TEF was calculated as the difference in total daily energy expenditure (TDEE) between fed and fasted visits and compared with three methods of estimating TEF: 1) SPA-adjusted TEF (adjTEF)—difference in TDEE without SPA between visits, 2) Wakeful TEF—difference in energy expenditure obtained from linear regression and basal metabolic rate during waking hours, 3) 24-h TEF—increase in TDEE above SPA and sleeping metabolic rate. Criterion TEF was 9.4 ± 4.5% of TDEE. AdjTEF (difference in estimated vs. criterion TEF: activPAL: −0.3 ± 3.3%; Actigraph: −1.8 ± 8.0%) and wakeful TEF (activPAL: −0.9 ± 6.1%; Actigraph: −2.8 ± 7.6%) derived from both accelerometers did not differ from criterion TEF (all P > 0.05). ActivPAL-derived 24-h TEF overestimated TEF (6.8 ± 5.4%, P = 0.002), whereas Actigraph-derived 24-h TEF was not significantly different (4.3 ± 9.4%, P = 0.156). TEF estimations using activPAL tended to show better individual-level agreement (i.e., smaller coefficients of variation). Both accelerometers can be used to estimate TEF in a whole room calorimeter; wakeful TEF using activPAL is the most viable option given strong group-level accuracy and reasonable individual agreement. NEW & NOTEWORTHY: Two research-grade accelerometers can effectively estimate spontaneous physical activity and improve the estimation of thermic effect of food (TEF) in whole room calorimeters. The activPAL demonstrates strong group-level accuracy and reasonable individual-level agreement in estimating wakeful TEF, whereas a hip-worn Actigraph is an acceptable approach for estimating 24-h TEF. These results highlight the promising potential of accelerometers in advancing energy balance research by improving the assessment of TEF within whole room calorimeters. [ABSTRACT FROM AUTHOR]

BACKGROUND: Wheat grain containers or silos can be perfect habitats for insects, which generate large economic losses to grain production. Natural alternatives to synthetic insecticides have grown in popularity because of health, economic and ecological issues. Diatomaceous earth is a natural compound that has an insecticide effect by enhancing an insect's dehydration with no toxicity on mammals including humans. The aim of this study is to confirm the effect of diatomaceous earth as an insecticide for the wheat grain pest, the red flour beetle Tribolium castaneum (Coleoptera: Tenebrionidae) and demonstrate its underlying mechanisms as an insecticide by open‐flow respirometry and scanning electron microscopy. RESULTS: Survival bioassays of T. castaneum revealed a dose‐dependent insecticide effect of diatomaceous earth. Gravimetric measurements showed that 2 days exposure to diatomaceous earth produces a significant increase of mass loss. Open‐flow respirometry measurements showed an increase of total water emission rate on insects due to an increase of both, respiratory and cuticular water loss. Our study revealed that diatomaceous earth produces an increase of insect's cuticle permeability, which is responsible for elevated cuticular water loss. Scanning electron microscopy images provided visual evidence of the lipid absorbent properties of diatomaceous earth particles, and showed a tendency for higher, although not significant, damaged area of the cuticle's surface from diatomaceous earth treated insects compared to control ones. CONCLUSION: With state‐of‐the art techniques like open‐flow respirometry and scanning electron microscopy, we demonstrated the underlying mechanism of diatomaceous earth as an insecticide and provided new cues for understanding the properties of the cuticle and its ecological importance. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

An important goal of environmental and comparative physiology research is to identify species or populations that may be susceptible to environmental change such as heat wave events that are predicted to become more frequent and intense in the future. This study tested the hypothesis that fishes inhabiting alkaline lakes face significant physiological challenges, which results in reduced thermal tolerance. Brook stickleback (Culaea inconstans) were collected from an alkaline lake (pH 9.3) in Alberta, Canada and held under neutral conditions in the laboratory. Subsequently, fish were acutely exposed (4 d) to neutral (pH 7) or alkaline (pH 9.5) waters at 10 or 25°C. Exposure to alkaline water reduced critical thermal maximum (CTmax) in stickleback by approximately 1°C, but thermal acclimation capacity ("thermal plasticity") was unaffected by alkaline exposure. Alkaline conditions resulted in physiological disturbances characteristic of exposure to high pH including elevated whole-body ammonia and lactate concentrations. Acute warming to CTmax in alkaline-exposed fish resulted in reductions in whole-body sodium and chloride concentrations. In addition, alkaline exposure compromised recovery from exercise at elevated temperatures. Overall, these results suggest that the physiological disturbances observed in response to alkaline exposure may render fish more susceptible to acute warming, reducing thermal tolerance. [ABSTRACT FROM AUTHOR]

Maintenance metabolism as the minimum energy expenditure needed to maintain homeothermy (a high and stable body temperature, Tb), reflects the magnitude of metabolic machinery and the associated costs of self‐maintenance in endotherms (organisms able to produce heat endogenously). Therefore, it can interact with most, if not all, organismal functions, including the behavior–fitness linkage. Many endothermic animals can avoid the costs of maintaining homeothermy and temporally reduce Tb and metabolism by entering heterothermic states like torpor, the most effective energy‐saving strategy. Variations in BMR, behavior, and torpor use are considered to be shaped by food resources, but those conclusions are based on research studying these traits in isolation. We tested the effect of ecological contexts (food availability and predation risk) on the interplay between the maintenance costs of homeothermy, heterothermy, and exploration in a wild mammal—the yellow‐necked mouse. We measured maintenance metabolism as basal metabolic rate (BMR) using respirometry, distance moved (exploration) in the open‐field test, and variation in Tb (heterothermy) during short‐term fasting in animals captured at different locations of known natural food availability and predator presence, and with or without supplementary food resources. We found that in winter, heterothermy and exploration (but not BMR) negatively correlated with natural food availability (determined in autumn). Supplementary feeding increased mouse density, predation risk and finally had a positive effect on heterothermy (but not on BMR or exploration). The path analysis testing plausible causal relationships between the studied traits indicated that elevated predation risk increased heterothermy, which in turn negatively affected exploration, which positively correlated with BMR. Our study indicates that adaptive heterothermy is a compensation strategy for balancing the energy budget in endothermic animals experiencing low natural food availability. This study also suggests that under environmental challenges like increased predation risk, the use of an effective energy‐saving strategy predicts behavioral expression better than self‐maintenance costs under homeothermy. [ABSTRACT FROM AUTHOR]

Animals often experience changes in their environment that can be perceived as stressful. Previous evidence indicates that different individuals may have distinct stress responses. The role of serotonin (5-HT) in stress adaptation is well established, but its relationship with different defense strategies and the persistence of physiological and behavioral responses in different individuals during repeated acute stress remain unclear. In this study, using olive flounder (Paralichthys olivaceus) as a model, we analyzed the relationship between boldness and neurotransmitter 5-HT activity. We found that 5-HT suppression with 5-HT synthesis inhibitor p-chlorophenylalanine (pCPA) and 5-HT receptor subtype 1A (5-HT1A) antagonist WAY-100635 increased their oxygen consumption rates and the boldness of shy individuals. We determined the metabolic and behavioral changes in bold and shy individuals to repeated acute stress. The results suggest that bold individuals switch on passive "energy-saving" personality by changing their defense behavior from "fight-flight" to "freeze-hide" during a threat encounter, which manifests high behavioral plasticity. Both behavioral types decreased their spontaneous activity levels, which were also strengthened by limiting metabolic rate. Interestingly, treatment with pCPA and WAY-100635 before stress procedure attenuated stress and increased the boldness across diverse behavioral types. This study provides the initial empirical evidence of how perception of stress impacts both individual defense behavior and personality in this species. These findings can enhance our comprehension of individual variability and behavioral plasticity in animals, thereby improving our ability to develop effective adaptive management strategies. [ABSTRACT FROM AUTHOR]

To determine whether body fat and body mass index (BMI) affect the energy cost of walking (Cw; J/kg/m), ventilation, and gas exchange data from 205 adults (115 females; percent body fat range = 3.0%–52.8%; BMI range = 17.5–43.2 kg/m2) were obtained at rest and during treadmill walking at 1.34 m/s to calculate gross and net Cw. Linear regression was used to assess relationships between body composition indices, Cw, and standing metabolic rate (SMR). Unpaired t‐tests were used to assess differences between sex, and one‐way ANOVA was used to assess differences by BMI categories: normal weight, <25.0 kg/m2; overweight, 25.0–29.9 km/m2; and obese, ≥30 kg/m2. Net Cw was not related to body fat percent, fat mass, or BMI (all R2 ≤ 0.011). Furthermore, mean net Cw was similar by sex (male: 2.19 ± 0.30 J/kg/m; female: 2.24 ± 0.37 J/kg/m, p = 0.35) and across BMI categories (normal weight: 2.23 ± 0.36 J/kg/m; overweight: 2.18 ± 0.33 J/kg/m; obese: 2.26 ± 0.31, p = 0.54). Gross Cw and SMR were inversely associated with percent body fat, fat mass, and BMI (all R2 between 0.033 and 0.270; all p ≤ 0.008). In conclusion, Net Cw is not influenced by body fat percentage, total body fat, and BMI and does not differ by sex. [ABSTRACT FROM AUTHOR]

Drought profoundly affects the morpho-physiological responses of desert plants in dryland. To scrutinize the morpho-physiological responses of nitrogen (N)-fixing legumes (Ammopiptanthus mongolicus, Caragana korshinskii), N-fixing non-legumes (Elaeagnus angustifolia, Hippophae rhamnoides), and non-N-fixing plants (Nitraria tangutorum, Haloxylon ammodendron) under varied drought stress levels (75%, 50%, 25% and 5% of soil water holding capacity), a pot experiment was conducted in greenhouse. Following prolonged water deficit, carbon (C) and N stoichiometry, metabolic rates, plant growth, and biomass distribution of unstressed and stressed plants were recorded. Intensified drought significantly reduced stem, root and whole-plant biomass, with no significant changes observed in leaf dry-fresh mass ratio, specific leaf area, intrinsic water use efficiency and root to shoot ratio. However, other traits were impacted differently, reflecting distinct adaptive strategies to drought among three plant functional types (PFTs). Patterns of trait-soil water content (SWC) relationships varied across different PFTs, with N-fixing non-legumes followed by N-fixing legumes displayed greater sensitivity to SWC variations than non-N-fixing plants. This resulted in a shift from a stronger trait-SWC relationship in N-fixing non-legumes and N-fixing legumes to a less correlated relationship in non-N-fixing plants. The diverse responses to drought among PFTs suggest a shift from N limitation to water limitation as SWC decreases. [ABSTRACT FROM AUTHOR]

Elucidating the underlying mechanisms behind variations of animal space and resource use is crucial to pinpoint relevant ecological phenomena. Organism's traits related to its energy requirements might be central in explaining behavioral variation, as the ultimate goal of a forager is to fulfill its energy requirements. However, it has remained poorly understood how energy requirements and behavioral patterns are functionally connected. Here we aimed to assess how body mass and standard metabolic rate (SMR) influence behavioral patterns in terms of cumulative space use and time spent in an experimental patchy environment, both within species and among individuals irrespective of species identity. We measured the behavioral patterns and SMR of two invertebrate species, that is, amphipod Gammarus insensibilis, and isopod Lekanesphaera monodi, individually across a range of body masses. We found that species of G. insensibilis have higher SMR level, in addition to cumulatively exploring a larger space than L. monodi. Cumulative space use scaled allometrically with body mass, and it scaled isometrically with SMR in both species. While time spent similarly in both species was characterized by negative body mass and SMR dependence, it was observed that L. monodi individuals tended to stay longer in resource patches compared to G. insensibilis individuals. Our results further showed that within species, body mass and metabolic rate explained a similar amount of variation in behavior modes. However, among individuals, regardless of species identity, SMR had stronger predictive power for behavioral modes compared to body mass. This suggests that SMR might offer a more generalized and holistic description of behavioral patterns that extend beyond species identity. Our study on the metabolic and body mass scaling of space and resource use behavior sheds light on higher‐order ecological processes such as species' competitive coexistence along the spatial and trophic dimensions. [ABSTRACT FROM AUTHOR]

Seasonal changes in environmental conditions may induce reversible physiological adjustments in organisms. We studied the acclimatization for multiple stressors in energy expenditure and water balance in Galea leucoblephara, a diurnal hystricognath rodent native to South America that experiences significant changes in temperature, precipitation, and food availability among seasons. We conducted a field study in the Monte Desert of Mendoza, Argentina, where we evaluated adult individuals' physiological status during two contrasting seasons in terms of climate and primary productivity. Reduced temperature, rainfall, and primary productivity during winter were associated with a decrease of 70% in basal metabolic rate (BMR), 30% in total evaporative water loss (TEWL), and 9% in body mass (Mb). In contrast, higher water availability, high temperature, and primary productivity during summer, induced significant increases in energy expenditure and evaporative water loss. As expected, the proportion of dietary items consumed by G. leucoblephara varied seasonally, resulting in a more diverse diet during summer. Our results illustrate how G. leucoblephara can cope with high seasonal contrasts in water availability, temperature, and food availability by modifying its physiological performance. Our data provide support for the hypothesis of physiological flexibility in energetic traits and water balance in response to the environmental challenges of the Monte Desert. [ABSTRACT FROM AUTHOR]

During periods of torpor, hibernators can reduce metabolic rate (MR) and body temperature (T b) substantially. However, to avoid physiological dysfunction at low temperatures, they defend T b at a critical minimum, often between ~0°C and 10°C via an increase in MR. Because thermoregulation during torpor requires extra energy, individuals with lower T b's and thus minimal MR during torpor should be selected in colder climates. Such inter- and intraspecific variations occur in some placental mammals, but for the evolutionary separate marsupials, available information is scarce. Marsupial eastern pygmy possums (Cercartetus nanus ; ~22 g body mass), widely distributed along the Australian southeastern coast including subtropical to alpine areas, were used to test the hypothesis that the defended T b of torpid individuals is related to the climate of their habitat. Possums were captured from five regions, 1,515 km apart, with midwinter (July) minimum environmental temperatures (min T env's) ranging from −3.9°C to 6.6°C. Captive possums in deep torpor were slowly cooled with ambient temperature (T a), while their MR was measured to determine the minimum torpor metabolic rate (TMR), the T a at which their MR increased for thermoregulation (min T a), and the corresponding minimum T b (min T b). Partial least squares regression analysis revealed that T a and T env were the strongest explanatory variables for the min T b. The min T b and T a were also correlated with latitude but not elevation of the capture sites. However, the best correlations were observed between the min T env and the min T b and T a for individuals experiencing min T env > 0 ° C ; these individuals thermoconformed to min T a's between −0.8°C and 3.7°C, and their min T b ranged from 0.5°C to 6.0°C and was 0.5°C–2.6°C below the min T env at the capture site. In contrast, individuals experiencing a min T env of −3.9°C regulated T b at 0.6 ° C ± 0.2 ° C or 4.5°C above the T env. The minimum TMR of all possums did not differ with T a and thus did not differ among populations and was 2.6% of the basal MR. These data provide new evidence that thermal variables of marsupials are subject to regional intraspecific variation. It suggests that min T b is a function of the min T env but only above 0°C, perhaps because the T b − T a differential for torpid possums in the wild, at a min T env of −3.9°C, remains small enough to be compensated by a small increase in MR and does not require the physiological capability for a reduction of T b below 0°C. [ABSTRACT FROM AUTHOR]

Patlak slope (PS) images have the potential to improve lesion conspicuity compared with standardized uptake value (SUV) images but may be more artifact-prone. This study compared PS versus SUV image quality and hepatic tumor-to-background ratios (TBRs) at matched time points. Early and late SUV and PS images were reconstructed from dynamic positron emission tomography (PET) data. Two independent, blinded readers scored image quality metrics (a four-point Likert scale) and counted tracer-avid lesions. Hepatic lesions and parenchyma were segmented and quantitatively analyzed. Differences were assessed via the Wilcoxon signed-rank test (alpha, 0.05). Forty-three subjects were included. For overall quality and lesion detection, early PS images were significantly inferior to other reconstructions. For overall quality, late PS images (reader 1 [R1]: 3.95, reader 2 [R2]: 3.95) were similar (p > 0.05) to early SUV images (R1: 3.88, R2: 3.84) but slightly superior (p ≤ 0.002) to late SUV images (R1: 2.97, R2: 3.44). For lesion detection, late PS images were slightly inferior to late SUV images (R1 only) but slightly superior to early SUV images (both readers). PS-based TBRs were significantly higher than SUV-based TBRs at the early time point, with opposite findings at the late time point. In conclusion, late PS images are similar to early/late SUV images in image quality and lesion detection; the superiority of SUV versus PS hepatic TBRs is time-dependent. [ABSTRACT FROM AUTHOR]

Abstract The evolutionary patterns of the mitochondrial genome are influenced by both adaptive and nonadaptive forces, with their contributions varying among taxa. There appears to be a correlation linking mutagenesis and latitude, which could be due to differences in metabolic rates. These discrepancies in metabolic rates exhibit a positive connection with mutation pressure. On this basis, we hypothesise that nonadaptive forces play a role in the differences in mutation rates observed along latitudinal gradients. In this study, we selected widely distributed carnivores as representatives of mammals to test our hypothesis. We examined the correlations between the dN/dS ratio (ω), as well as the substitution rates (dS and dN), of 13 PCGs in the mtDNA of 122 carnivores, and the latitude and climatic factors. We found that taxa distributed in higher latitudes tend to have higher substitution rates, but not ω values indicating selective pressure. Notably, dN shows a strong positive correlation with dS, although dS is primarily influenced by mutation pressure, while dN is also influenced by effective population size (Ne). Phylogenetic generalised least squares (PGLS) regression analyses showed that both substitution rates were correlated with climatic factors representing the temperature, precipitation and variability of climate. Based on our findings, we propose that the mutations are primarily influenced by nonadaptive forces (mutation pressure). This forms the fundamental premise for natural selection and speciation. Moreover, the correlation between substitution rates and latitudinal distribution and climate, which are outcomes of nonadaptive factors, can aid in comprehending the global distribution of species diversity.

During the Israel-Hamas war, researchers conducted a study on the physiological effects of repeated bombings on reptiles. The study focused on the elegant short-fingered gecko and found that their metabolic rates were 2.3 times higher immediately after explosions compared to before. The increased metabolic costs indicate an acute stress response, which could deplete energy stores and negatively impact fitness. The study highlights the far-reaching effects of armed conflicts on biodiversity conservation and calls for armed forces to consider conservation issues during training. [Extracted from the article]

Purpose: To critically appraise the utility of heart rate (HR) and power output (PO) to predict metabolic rate (MR) and oxygen consumption ( V ˙ O 2 ) during variable-intensity roller skiing and cycling. Methods: National-level cyclists (n = 8) and cross-country skiers (n = 9) completed a preliminary session to determine V ˙ O 2 max , and a variable-intensity protocol with 3 high-intensity stages at 90% V ˙ O 2 max for 3 minutes interspersed with 3 moderate-intensity stages at 70% V ˙ O 2 max for 6 minutes. Cardiorespiratory measures were recorded throughout. Linear HR–MR, HR – V ˙ O 2 , PO–MR, and PO – V ˙ O 2 regressions were computed from the preliminary session, individually, for all athletes and used to predict MR and V ˙ O 2 from both HR and PO, separately, during the variable-intensity protocol. Mean differences with 95% limits of agreement (LOA) between measured and predicted MR and V ˙ O 2 were calculated. Results: MR and V ˙ O 2 estimated from HR displayed a mean bias close to zero but wide LOA. HR overestimated MR and V ˙ O 2 during moderate intensity but underestimated MR and V ˙ O 2 during high intensity, for both roller skiing and cycling. MR and V ˙ O 2 estimated from PO were more consistent across the experimental trial, displaying a mean bias farther from zero but with tighter LOA. Conclusions: This study has demonstrated that HR has limited utility to predict metabolic intensity during variable-intensity roller skiing and cycling because of wide LOA. On the other hand, metabolic intensity predicted from PO had tighter LOA, suggesting better consistency. PO might provide a better prediction of metabolic intensity compared with HR, particularly when longer-duration steps are performed during preliminary testing. [ABSTRACT FROM AUTHOR]

The phenomenon of cuckoos’ brood parasitism is well known and can be investigated using applied mathematical techniques. Among adaptive features of this phenomenon are certain egg parameters that ensure their shortened incubation period (I) and thus the successful survival of their offspring. In particular, the volume of a cuckoo egg is not less than, or exceeds, that of the host species, which should, in theory, increase I. Also, cuckoo eggs have thicker shell than that of nest hosts. Here, we analyzed the available geometric dimensions of eggs in 447 species and found an inverse correlation (−0.585, p

Purpose: We aimed to determine the test–retest repeatability of quantitative metrics based on the Patlak slope (PS) versus the standardized uptake value (SUV) among lesions and normal organs on oncologic [18F]FDG-PET/CT. Procedures: This prospective, single-center study enrolled adults undergoing standard-of-care oncologic [18F]FDG-PET/CTs. Early (35–50 min post-injection) and late (75–90 min post-injection) SUV and PS images were reconstructed from dynamic whole-body PET data. Repeat imaging occurred within 7 days. Relevant quantitative metrics were extracted from lesions and normal organs. Repeatability was assessed via mean test–retest percent changes [T-RT %Δ], within-subject coefficients of variation (wCVs), and intra-class correlation coefficients (ICCs). Results: Nine subjects (mean age, 61.7 ± 6.2 years; 6 females) completed the test–retest protocol. Four subjects collectively had 17 [18F]FDG-avid lesions. Lesion wCVs were higher (i.e., worse repeatability) for PS-early-max (16.2%) and PS-early-peak (15.6%) than for SUV-early-max (8.9%) and SUV-early-peak (8.1%), with similar early metric ICCs (0.95–0.98). Lesion wCVs were similar for PS-late-max (8.5%) and PS-late-peak (6.4%) relative to SUV-late-max (9.7%) and SUV-late-peak (7.2%), with similar late metric ICCs (0.93–0.98). There was a significant bias toward higher retest SUV and PS values in the lesion analysis (T-RT %Δ [95% CI]: SUV-late-max, 10.0% [2.6%, 17.0%]; PS-late-max, 20.4% [14.3%, 26.4%]) but not in the normal organ analysis. Conclusions: Among [18F]FDG-avid lesions, the repeatability of PS-based metrics is similar to equivalent SUV-based metrics at late post-injection time points, indicating that PS-based metrics may be suitable for tracking response to oncologic therapies. However, further validation is required in light of our study's limitations, including small sample size and bias toward higher retest values for some metrics. [ABSTRACT FROM AUTHOR]

Exposure to a pathogen is predicted to lead to increased energy use as hosts attempt to activate a costly immune system and repair damaged tissue. To meet this demand, metabolic rates, which capture the rate at which a host can use, transform and expend energy, are expected to increase. Yet for many host–pathogen systems, metabolic rates after encountering a pathogen are just as likely to decrease as increase, suggesting that increased energy expenditure may not always be best for fighting infection.Diverging metabolic trajectories have been previously attributed to the different pathways that specific pathogen classes, such as bacteria or viruses, induce in a host. Here, we test how the magnitude and direction of metabolic change following pathogen exposure might also depend on whether a host has cleared infection or is instead fighting to reduce pathogen burden, as well as interactions between host and pathogen genotypes of a single host–pathogen system.Using a model system, Daphnia magna and its bacterial pathogen, we quantified changes in mass‐independent metabolic rates over a 30‐day period for multiple host and pathogen genotypes. We found that the metabolic trajectory of an exposed host diverged quickly during the infection process. For hosts that were exposed to a pathogen and resisted infection, their mass‐independent metabolic rates remained suppressed long after exposure, leading to a sustained reduction in total energy use compared to unexposed animals. The reverse was true for hosts in which the pathogen was able to establish an infection.Underlying these changes were differences in the energetic burden that each pathogen genotype imposed on its host, as well as changes in the way host genotype and the outcome of infection shaped underlying scaling relationships between host body mass and metabolic rates. Our results demonstrate how variation in an organism's metabolic rate and overall energy use can arise from within a single host–pathogen encounter and depend on the likelihood of pathogen clearance, as well as the within‐species genetic variability of both hosts and pathogens. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

Introduction: About 10% of all rodent species have evolved a subterranean way of life, although life in subterranean burrows is associated with harsh environmental conditions that would be lethal to most animals living above ground. Two key adaptations for survival in subterranean habitats are low resting metabolic rate (RMR) and core body temperature (Tb). However, the upstream regulation of these traits was unknown thus far. Previously, we have reported exceptionally low concentrations of the thyroid hormone (TH) thyroxine (T4), and peculiarities in TH regulating mechanisms in two African mole-rat species, the naked mole-rat and the Ansell's mole-rat. Methods: In the present study, we treated Ansell's mole-rats with T4 for four weeks and analyzed treatment effects on the tissue and whole organism level with focus on metabolism and thermoregulation. Results: We found RMR to be upregulated by T4 treatment but not to the extent that was expected based on serum T4 concentrations. Our data point towards an extraordinary capability of Ansell's mole-rats to effectively downregulate TH signaling at tissue level despite very high serum TH concentrations, which most likely explains the observed effects on RMR. On the other hand, body weight was decreased in T4-treated animals and Tb was upregulated by T4 treatment. Moreover, we found indications of the hypothalamus-pituitaryadrenal axis potentially influencing the treatment effects. Conclusion: Taken together, we provide the first experimental evidence that the low serum T4 concentrations of Ansell's mole-rats serve as an upstream regulator of low RMR and Tb. Thus, our study contributes to a better understanding of the ecophysiological evolution of the subterranean lifestyle in African mole-rats. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity can improve an organism's fitness when exposed to novel environmental conditions or stress associated with climate change. Our study analyzed spatiotemporal differences in phenotypic plasticity and offspring performance in Olympia oysters Ostrea lurida. This species is an ecosystem engineer and is of great interest for commercial and restoration aquaculture. We used a multidisciplinary approach to examine acute and long-term physiological differences in O. lurida in response to in situ oceanographic conditions in a dynamic inland sea. We outplanted oysters to different areas in Puget Sound, Washington, affixing cages to anchor lines of oceanographic monitoring buoys. This allowed us to couple high-resolution oceanographic data with organism's phenotypic response. To assess spatiotemporal differences in oyster physiological performance, we collected oysters after six-months and one year of acclimatization at four field sites. During each collection period we evaluated changes in shell properties, diet, metabolism, and reproduction. Adult growth, d13C and d15N isotopic signatures, and gametogenesis were affected by both seasonal and environmental conditions. In the winter, oysters from all sites had higher respiration rates when exposed to acute thermal stress, and lower respiration response to acute pH stress. Lipid content, sex ratio and shell strength were unchanged across locations. Offspring growth rates between sites at experimental temperature 20°C closely reflected parental growth rate patterns. Offspring survival was not correlated with growth rates suggesting different energetic trade-offs in oyster offspring. The metabolic response (respiration) of larvae reached its highest point at 20°C but sharply decreased at 25°C. This indicates that larvae are more sensitive to temperature stress, as adults did not exhibit a reduction in metabolic response at 25°C. By deploying genetically similar oysters into distinct environments and employing a wide range of physiological methodologies to examine performance and fitness, our results indicate that Olympia oysters exhibit a high degree of phenotypic plasticity and show evidence of parental carryover. [ABSTRACT FROM AUTHOR]

Heterothermy is considered to be the most effective energy-saving strategy improving survival under natural conditions. Interspecific studies suggest that this strategy is also associated with reduced reproductive output. Yet little is known about the reproductive consequences of heterothermy use at the intraspecific level and thus its repercussions for microevolutionary processes. Moreover, as yet no study has aimed to test if litter size and juvenile mass are affected by torpor use in wild captured animals under undemanding laboratory conditions. Here we tested the hypothesis that intraspecific variation in heterothermy use is associated with different reproductive successes, being the result of the evolution of distinct life histories. We predicted that heterothermy use in winter negatively correlates with litter size and juvenile body mass during the subsequent breeding season. To test this prediction, we used yellow-necked mice from a population in which individuals consistently differ in their use of heterothermy in winter. We measured body size (head width) and body mass, basal metabolic rate, as well as metabolism and body temperature during fasting-induced torpor in wild caught mice in winter. Phenotyped mice were bred in the subsequent summer selectively - males and females with similar heterothermy characteristics were paired, the most to the least heterothermic. Dam body size, but not basal metabolism, was positively correlated with litter size (but not juvenile mass). However, when accounting for this relationship, litter size was negatively while juvenile mass was positively correlated with the average heterothermy use of a given couple. Our study indicates that heterothermy use correlates with specific life-history strategies arising from a fundamental evolutionary trade-off between survival and reproduction. [ABSTRACT FROM AUTHOR]

This experiment aimed at the nutritional value of spirulina powder and its effects on growth performance, apparent metabolic rate and meat quality of broilers. A total of 960 healthy 1-day-old AA broilers (40 g) were selected and randomly divided into 4 treatments by using a single-factor experiment design (control group, test group Ⅰ, test group Ⅱ and test group Ⅲ), with 6 repetitions for each treatment and 40 broilers for each repetition (half male and half female). The 4 treatments were fed with 0, 5, 10, 15 kg/t spirulina powder in the basal diet respectively, and the metabolizable energy and crude protein levels of each treatment group were same. The test period is 42 days, of which the pre-feeding test period is 1-14 days, and the formal test period is 15-42 days. The test results showed that the average daily gain and average daily feed intake of each test group were significantly higher than those of the control group (P<0.05), and there was no significant difference in the feed-to-meat ratio (P>0.05). The apparent metabolic rate of protein in each test group was higher than that in the control group (P<0.05), the apparent metabolic rate of crude fat in the test group Ⅱ and the test group Ⅲ was significantly higher than that in the control group (P<0.05). The apparent metabolic rate of calcium in the test group Ⅰ and Ⅱ was significantly higher than that in the control group (P<0.05). Compared with the control group, the test group showed improvements in slaughter performance and meat quality of broilers. Adding spirulina powder to the diet can significantly increase the growth performance and slaughter performance of broilers, and the optimum adding ratio is 15 kg/t. [ABSTRACT FROM AUTHOR]

Simple Summary: The yellowtail kingfish is a highly active and fast-growing marine fish with promising potential for aquaculture. In this study, we learned about the energy that these fish spend by measuring heart rate and acceleration during both a test where fish had to swim at increasing speeds and a test where fish were subjected to four steps of increasing stress load. Yellowtail kingfish need to swim to provide sufficient water flow over the gills to be able to extract sufficient oxygen. Oxygen consumption, heart rate and acceleration all increased when the fish had to swim faster. The oxygen levels that the fish consumed when swimming were high and heart rate values were even among the highest ever measured for fishes. Oxygen consumption and heart rate were only correlated when fish were swimming steadily near the optimal swimming speed, which is when all of their energy is required for fueling the muscles. With every stress step, the acceleration peak decreased, possibly suggesting that fish knew what was coming, until the fourth step, when fish were also chased, where the acceleration and heart rate showed their highest peaks. Acceleration and heart rate data can be used for modelling the energy flows that are required for steady swimming and unsteady stress movements. Such an energy economy model can then be applied for estimating the energy that the fish spend in field studies and for optimal farming of this species by exercising them. The yellowtail kingfish is a highly active and fast-growing marine fish with promising potential for aquaculture. In this study, essential insights were gained into the energy economy of this species by heart rate and acceleration logging during a swim-fitness test and a subsequent stress challenge test. Oxygen consumption values of the 600–800 g fish, when swimming in the range of 0.2 up to 1 m·s−1, were high—between 550 and 800 mg·kg−1·h−1—and the heart rate values—up to 228 bpm—were even among the highest ever measured for fishes. When swimming at these increasing speeds, their heart rate increased from 126 up to 162 bpm, and acceleration increased from 11 up to 26 milli-g. When exposed to four sequential steps of increasing stress load, the decreasing peaks of acceleration (baseline values of 12 to peaks of 26, 19 and 15 milli-g) indicated anticipatory behavior, but the heart rate increases (110 up to 138–144 bpm) remained similar. During the fourth step, when fish were also chased, peaking values of 186 bpm and 44 milli-g were measured. Oxygen consumption and heart rate increased with swimming speed and was well reflected by increases in tail beat and head width frequencies. Only when swimming steadily near the optimal swimming speed were these parameters strongly correlated. [ABSTRACT FROM AUTHOR]

Temperature varies on multiple timescales and ectotherms must adjust to these changes to survive. These adjustments may lead to energetic trade-offs between self-maintenance and reproductive investment. However, we know little about how diurnal and seasonal temperature changes impact energy allocation. Here we used a combination of empirical data and modeling of both thermoregulatory behaviors and body temperature to examine potential energetic trade-offs in the dung beetle Onthophagus taurus. Beginning in March 2020, universities and laboratories were officially closed due to the COVID-19 pandemic. We thus performed experiments at a private residence near Knoxville, Tennessee, USA, leveraging the heating, ventilation and air conditioning of the home to manipulate temperature and compare beetle responses to stable indoor temperatures versus variable outdoor temperatures. We collected O. taurus beetles in the early-, mid-, and late-breeding seasons to examine energetics and reproductive output in relation to diurnal and seasonal temperature fluctuations. We recorded the mass of field fresh beetles before and after a 24-h fast and used the resulting change in mass as a proxy for energetic costs of self-maintenance across seasons. To understand the impacts of diurnal fluctuations on energy allocation, we held beetles either indoors or outdoors for 14-day acclimation trials, fed them cow dung, and recorded mass change and reproductive output. Utilizing biophysical models, we integrated individual-level biophysical characteristics, microhabitat-specific performance, respirometry data, and thermoregulatory behaviors to predict temperature-induced changes to the allocation of energy toward survival and reproduction. During 24 h of outdoor fasting, we found that beetles experiencing reduced temperature variation lost more mass than those experiencing greater temperature variation, and this was not affected by season. By contrast, during the 14-day acclimation trials, we found that beetles experiencing reduced temperature variation (i.e., indoors) gained more mass than those experiencing greater temperature variation (i.e., outdoors). This effect may have been driven by shifts in the metabolism of the beetles during acclimation to increased temperature variation. Despite the negative relationship between temperature variation and energetic reserves, the only significant predictor of reproductive output was mean temperature. Taken together, we find that diurnal temperature fluctuations are important for driving energetics, but not reproductive output. [ABSTRACT FROM AUTHOR]

Metabolic rate is a key parameter in fish energy budgets that strongly influences the output of bioenergetics models. In this study, we tested the hypothesis that metabolic rate varies with growth history of age-1 largemouth bass Micropterus nigricans Cuvier, 1828. Two groups of fish were fed alternating maintenance or ad libitum rations of fathead minnow Pimephales promelas Rafinesque, 1820, so that over a 9-week period, initial and ending size of fish was similar. After 9 weeks, oxygen consumption was measured using static, closed respirometry. Although final body weight was similar between the two groups (means, 104–108 g), specific oxygen consumption for fish fed maintenance rations (0.094 mg O2 g−2 h−1) was 38% less than that measured for fish fed ad libitum (0.152 mg O2 g−2 h−1). Bioenergetics estimates of food consumption were similar to observed values for fish fed ad libitum (∼7% error), but for fish fed maintenance rations, the model overestimated food consumption by 65%. By accounting for changes in metabolic rate owing to reduced feeding, error in model estimates of food consumption was reduced. These findings shed new insight into factors associated with consumption-dependent error in bioenergetics models and highlight the importance of feeding history on metabolic rate of fish. Incorporating growth-dependent metabolism into bioenergetics models can improve model accuracy and allow fisheries biologists to make more informed decisions regarding fish growth and energetics. [ABSTRACT FROM AUTHOR]

Aim: We evaluate whether the biomass and trait biogeography of cephalopods follow the distribution expected by metabolic theory for ectotherms with rapid growth and high metabolic rate. Location: Continental shelves of the North Atlantic and Northeast Pacific oceans; global marine ecoregions. Time Period: 1968–2020. Major Taxa Studied: Cephalopods and fishes (Chondrichthyes and Osteichthyes). Methods: We map the biomass of cephalopods and their traits across marine shelves using scientific bottom trawl survey data from the North Atlantic and Northeast Pacific. We further map global fisheries catch. We apply statistical methods to evaluate how temperature, zooplankton productivity and depth drive these patterns. Results: Cephalopods represent a small fraction (1%) of the combined fish and cephalopod biomass on continental shelves. However, their distribution displays a high regional heterogeneity, with some areas being virtually absent of cephalopods and other areas accounting for up to 24% of total biomass. Higher temperatures and zooplankton productivity are associated with increased cephalopod biomass and proportional biomass relative to fish. The largest cephalopods are found in the Northeast Pacific. Growth rates are highest in warmer waters with fastest growth rates found in lower latitudes of the North Atlantic. Cephalopods constitute 5% of the combined fish and cephalopod global fisheries catch. This proportion varies across regions. Higher temperature and zooplankton productivity are associated with increased cephalopod catch relative to fish. Main Conclusions: Temperature and productivity shape the large‐scale biogeography of cephalopods and their traits on marine shelves. The relations with temperature suggest that future warming could lead to a proliferation of fast‐growing cephalopods in cold and temperate systems, with implications for ecosystem dynamics and fisheries. Despite a relatively low observed biomass, cephalopods hold substantial potential to change ecosystem structure and functioning given their high energy lifestyle. [ABSTRACT FROM AUTHOR]

Numerous marine invertebrates form symbiotic relationships with single-celled algae, termed "photosymbioses", and the diversity of these interactions is likely underestimated. We examined Phidiana lynceus, a cladobranch sea slug that feeds on photosymbiotic hydrozoans. We assessed its ability to acquire/retain algal symbionts by examining specimens in starvation, finding that P. lynceus is able to incorporate and retain symbionts for up to 20 days. Examining body size during starvation revealed that P. lynceus does not receive enough energy from hosting symbionts to maintain its body mass let alone grow. Intact symbionts were still present in deceased specimens, indicating that P. lynceus does not digest all of its symbionts, even when starving to death. We also examined slug behavior in the field and lab to determine if it seeks light to facilitate photosynthesis, which could provide energetic and oxygenic benefits. In the field, slugs were always observed hiding under stones during the day and they displayed light avoidance in the lab, suggesting this species actively prevents photosynthesis and the benefits it could receive. Lastly, we measured their metabolic rates during the day and night and when treated with and without a photosynthetic inhibitor. Higher metabolic rates at night indicate that this species displays nocturnal tendencies, expending more energy when it emerges at night to forage. Paradoxically, P. lynceus has evolved all of the requisite adaptations to profit from photosymbiosis but it chooses to live in the dark instead, calling into question the nature of this symbiosis and what each partner might receive from their interaction. [ABSTRACT FROM AUTHOR]