Metabolic Rate Research Articles

Testing the hypothesis of a nested block covariance matrix structure with applications to medicine and natural sciences

This paper addresses the challenge of testing the hypothesis of what the authors call a nested block circular‐compound symmetric (NBCCS) covariance structure for the population covariance matrix. This is a covariance structure which has an outer block compound symmetric structure, where the diagonal blocks are themselves block circular matrices, while the off‐diagonal blocks are formed by all equal matrices. The NBCCS null hypothesis is decomposed into sub‐hypotheses, allowing this way for a simpler way to obtain a likelihood ratio test and its associated statistic. The exact moments of this statistic are derived, and its distribution is carefully examined. Given the complicated nature of this distribution, highly precise near‐exact distributions were developed. Numerical studies are conducted to assess the proximity between these near‐exact distributions and the exact distribution, highlighting the performance of these approximations, even in the case of very small sample sizes. Furthermore, three datasets, on bone mineral content, metabolic rates of glucose, and soil moisture are used to exemplify the practical application of the methodology derived in this study.

Snail shell shape, force of attachment, and metabolic rate together cope with the intertidal challenge

Inhabitants of rocky intertidal shores, including gastropods, require specific adaptations to cope with numerous challenges that vary across the intertidal levels. We collected Stramonita biserialis snails from upper (wave-protected and intense predation) and lower (wave-exposed and low predation) intertidal sites to compare the following traits: shell skeleton (ventral and abaxial lateral views of shell shape, thickness, and mass), foot size, energy metabolism, and attachment strength to determine whether the trait values of snails from each zone fit the environmental challenges they face. We used a Principal Component Analysis to reduce the dimensionality of the data. Multivariate Analysis of Covariance (MANCOVA) for comparing characteristics between the two intertidal zones, and Partial Least Squares (PLS) analyses for testing the integration of overall snail characteristics. The traits of the snails of the two intertidal sites matched with the adaptations expected to allow them to cope with their contrasting challenges. The snails from the lower intertidal had more streamlined shells (which reduces drag forces) and a larger aperture and foot extension (which increase the strength of their attachment to the substrate) compared to snails from the upper sites. Snails from the lower intertidal also had a high mass-specific metabolism and soft body proportion, indicating that these snails from the wave-exposed sites have an energetically active musculature that matches their strong substrate attachment. The thin shell walls of the snails of the lower intertidal match the relatively low predatory pressure there.

Ocean weather, biological rates, and unexplained global ecological patterns.

As on land, oceans exhibit high temporal and spatial temperature variation. This "ocean weather" contributes to the physiological and ecological processes that ultimately determine the patterns of species distribution and abundance, yet is often unrecognized, especially in tropical oceans. Here, we tested the paradigm of temperature stability in shallow waters (<12.5 m) across different zones of latitude. We collated hundreds of in situ, high temporal-frequency ocean temperature time series globally to produce an intuitive measure of temperature variability, ranging in scale from quarter-diurnal to annual time spans. To estimate organismal sensitivity of ectotherms (i.e. microbes, algae, and animals whose body temperatures depend upon ocean temperature), we computed the corresponding range of biological rates (such as metabolic rate or photosynthesis) for each time span, assuming an exponential relationship. We found that subtropical regions had the broadest temperature ranges at time spans equal to or shorter than a month, while temperate and tropical systems both exhibited narrow (i.e. stable) short-term temperature range estimates. However, temperature-dependent biological rates in tropical regions displayed greater ranges than in temperate systems. Hence, our results suggest that tropical ectotherms may be relatively more sensitive to short-term thermal variability. We also highlight previously unexplained macroecological patterns that may be underpinned by short-term temperature variability.

Sexual color ornamentation, microhabitat choice, and thermal physiology in the common wall lizard (Podarcis muralis).

Common wall lizards (Podarcis muralis) in Italy show a striking variation in body coloration across the landscape, with highly exaggerated black and green colors in hot and dry climates and brown and white colors in cool and wet climates. Males are more intensely colored than females, and previous work has suggested that the maintenance of variation in coloration across the landscape reflects climatic effects on the strength of male-male competition, and through this sexual selection. However climatic effects on the intensity of male-male competition would need to be exceptionally strong to fully explain the geographic patterns of color variation. Thus, additional processes may contribute to the maintenance of color variation. Here we test the hypothesis that selection for green and black ornamentation in the context of male-male competition is opposed by selection against ornamentation because the genes involved in the regulation of coloration have pleiotropic effects on thermal physiology, such that ornamentation is selected against in cool climates. Field observations revealed no association between body coloration and microhabitat use or field active body temperatures. Consistent with these field data, lizards at the extreme ends of the phenotypic distribution for body coloration did not show any differences in critical minimum temperature, preferred body temperature, temperature-dependent metabolic rate, or evaporative water loss when tested in the laboratory. Combined, these results provide no evidence that genes that underlie sexual ornamentation are selected against in cool climate because of pleiotropic effects on thermal biology.

Energy Cost of Selected Physical Activities of Older Persons Living in Taguig City, the Philippines

The promotion of physical activity is important for fostering healthy aging. However, a substantial proportion of older adults remain sedentary. Current metrics assessing the energy cost of physical activity are primarily designed for the general adult population and inadequately account for distinct physiological changes in older individuals – encompassing variations in muscle mass, bone density, metabolism, and overall functional capacity. This study aimed to determine the energy cost of selected physical activities of Filipino older persons. This cross- sectional study conducted in Taguig City involved 19 older adults aged 60–79 yr using the COSMED Fitmate indirect calorimeter for resting metabolic rate determination, as well as the portable COSMED K5 indirect calorimeter for measuring energy cost of different physical activities – including treadmill walking, self-paced walking, a routine based on the DOST-FNRI manual, and multi-gym equipment. The outcomes of the study were presented in percentages and averages. Participants in the study were categorized based on their muscle strength and mass. Analysis revealed a consistent trend where older adults with lower appendicular skeletal muscle mass index and handgrip strength values demonstrated lower metabolic equivalent values across the different exercise routines. Notably, Routine 2 displayed an exception, with individuals above the 50th percentile of ASMI and HGS exhibiting lower METs than those below the 50th percentile. This study contributes insights into the energy cost of specific activities among older adults emphasizing the importance of physical activity in healthy aging and providing valuable information for tailored interventions and a nuanced understanding of energy expenditure in this age group.

Field investigation on thermal comfort of metro passengers in hot summer and warm winter zone of China: A case study in Guangzhou

In the hot summer and warm winter zone of China, the metro thermal environments and passengers’ thermal comfort were rarely examined, influencing factors such as commuter hours and individual factors were less discussed, and understanding them was beneficial for improving human thermal comfort and saving energy. In this study, a field study was undertaken in Guangzhou located in the region during the summer of 2023. Four metro stations and three metro lines were selected, a total of 1481 valid questionnaires were gathered. The results revealed that the metro thermal environment was highly commendable during the hot summer months, with a thermal acceptability vote (TAV) ranging from 81 % to 89 % across the entrance (ET), concourse (CC), platform (PF), and carriage (CR). Furthermore, the upper limit of the 80 % acceptance range for operative temperature (Top) was 29.11 °C in the ET, 27.82 °C in the CC, 29.13 °C in the PF, and 28.44 °C in the CR. These temperatures exceed the actual mean Top values in these locations, indicating there is a significant potential for energy savings in metro environments. The upper limits of Top values for passengers with low, medium and high metabolic rates are 30.34 °C, 28.92 °C, and 28.25 °C, respectively. Thermal sensation votes (TSVs) fell well within the comfort zone specified in ISO 7730 (−0.7 < PMV < 0.7) during both peak and off-peak hours. No difference was found in TSVs between the two genders and among the different ages.

Multispecies macrozoobenthic seasonal bioturbation effect on sediment erodibility

Bioturbation in estuarine environments describes all sediment reworking processes implied in sediment transport. However, modelling at large spatial and temporal scales remains a challenge because of the need to consider the fauna at the community level, and because animal behaviour is highly seasonal with non-linear effects of macrofauna functional trait interactions. Bioturbation processes can be linked to the activity of organisms, based on the principle of energy ecology, linking the metabolic rate to the erodibility of a sediment colonised by benthic fauna. This study investigates this postulate by evaluating the erodibility parameters of a sediment subjected to: i) the bioturbation under seasonal temperature variations; ii) the synergistic bioturbation of different species. The experimental design consisted of: i) three temperature levels (winter, spring and summer), ii) three types of species duos (Cerastoderma edule and Macoma balthica; Scrobicularia plana and Hediste diversicolor; Corophium volutator and Peringia ulvae) at 4 different relative densities. Two successive experiments were carried out on the same individuals: measurement of oxygen consumption of fauna then measurement of the erodibility of the colonised sediment in a flume. The oxygen consumption confirmed that the metabolic rate is a good model of the fauna respiration, regardless of species. The erosion results indicated that the metabolic rate in the case of the fluff layer resuspension is an interesting descriptor for 1) the assessment of the bioturbation under variable temperatures and 2) the integration of the two different bioturbator species that could co-occur in the same habitat. In contrast, the effect of bioturbation on the mass sediment erosion threshold cannot be easily modelled by using the metabolic rate and the classification in functional groups is required. Bioturbation models of the fluff layer using metabolic rate is a promising tool for modelling the effects of faunal communities on sediment transport at the scale of an estuary and over the long term, even projected in the context of global warming.

Exercise and resting periods: Thermal comfort dynamics in gym environments

Physical exercise spaces emerged as popular facilities due to recognizing the significance of physical well-being. This study investigates the relationship among physiological responses, human body energy transfer modes, and indoor environmental conditions in influencing thermal comfort perception within indoor physical exercise space. Seven male participants engaged in a 30 min constant-work-rate cycling exercise and a 20 min resting period in a climatic chamber. The physiological and environmental responses were recorded during the experiments, and the body’s energy transfer modes were calculated using the collected data. The dataset was prepared using the 2 min averages of the collected data and calculated parameters across the experiment phases, including the features of skin temperature, core temperature, skin relative humidity, heart rate, oxygen consumption, body’s heat transfer rates through convection, radiation, evaporation, and respiration, net metabolic heat production rate (metabolic rate minus external work rate), indoor air temperature, indoor relative humidity, air velocity, and radiant temperature. Gradient boosting regressor (GBR) was selected as the analyzing method to estimate predicted mean vote (PMV) and thermal sensation vote (TSV) indices during exercise and resting periods using features determined in the study. Thus, the four GBR models were defined as PMV-Exercise, PMV-Resting, TSV-Exercise, and TSV-Resting. In order to optimize the models’ performances, the hyperparameter tuning process was executed using the GridSearchCV method. A permutation feature importance analysis was performed, emphasizing the significance of net metabolic heat production rate (24.2%), radiant temperature (17.0%), and evaporative heat transfer rate (13.1%). According to the results, PMV-Exercise, PMV-Resting, and TSV-Resting GBR models performed better, while TSV-Exercise faced challenges in predicting exercise thermal sensations. Critically, this study addresses the need to understanding the interrelationship among physiological responses, environmental conditions, and human body energy transfer modes during both exercise and resting periods to optimize thermal comfort within indoor exercise spaces. The results of this study contribute to the operation of indoor gym environments to refine their indoor environmental parameters to optimize users’ thermal comfort and well-being. The study is limited to a small sample size consisting solely of male participants, which may restrict the generalizability of the findings. Future research could explore personalized thermal comfort control systems and synergies between comfort optimization and energy efficiency in indoor exercise spaces.

Disproportional fraction of inactive components leads to the variation in metabolic scaling

In biological systems, solitary organisms or eusocial groups, the metabolic rate often scales allometrically with systems’ size, when they are inactive, and the scaling becomes nearly isometric when the systems are active. Here I propose a hypothesis attempting to offer a departing point for a general joint understanding of the difference in the scaling powers between inactive and active states. When the system is inactive, there exist inactive components, which consume less energy than the active ones, and the larger the system is, the larger the fraction of the inactive components, which leads to sublinear scaling. When the system is active, most inactive components are activated, which leads to nearly isometric scaling. I hypothesize that the disproportional fraction of the inactive components is caused by the diffusants screening in the complex transportation network. I.e., when metabolites or information diffuses in the system, due to the physical limitation of the network structure and the diffusant’s physical feature, not all the components can equally receive the diffusants so that these components are inactive. Using the mammalian pulmonary system, ant colonies, and other few systems as examples, I discuss how the screening leads to the allometric and isometric metabolic scaling powers in inactive and active states respectively. It is noteworthy that there are a few exceptions, in which the metabolic rate of the system has an isometric scaling relationship with size at rest. I show that these exceptions not only do not disapprove the hypothesis, but actually support it.

MR Assessment of Acute Changes of Cerebral Perfusion, Metabolism, and Blood-Brain Barrier Permeability in Response to Aerobic Exercise.

It remains unclear how a single bout of exercise affects brain perfusion, oxygen metabolism, and blood-brain barrier (BBB) permeability. Addressing this unresolved issue is essential to understand the acute changes in cerebral physiology induced by aerobic exercise. To dynamically monitor the acute changes in cerebral physiology subsequent to a single aerobic exercise training session using noninvasive MRI measurements. Prospective. Twenty-three healthy participants (18-35 years, 10 females/13 males) were enrolled and divided into 10-minute exercising (N = 10) and 20-minute exercising (N = 13) groups. 3.0 T/Phase Contrast (PC) MRI (gradient echo), T2-Relaxation-Under-Spin-Tagging (TRUST) MRI (gradient echo EPI), Water-Extraction-with-Phase-Contrast-Arterial-Spin-Tagging (WEPCAST) MRI (gradient echo EPI) and T1-weighted magnetization-prepared-rapid-acquisition-of-gradient-echo (MPRAGE) (gradient echo). A baseline MR measurement plus four repeated MR measurements immediately after 10 or 20 minutes moderate running exercise. MR measurements included cerebral blood flow (CBF) as measured by PC MRI, venous oxygenation (Yv) and cerebral metabolic rate of oxygen (CMRO2) as assessed by TRUST MRI, water extraction fraction (E), and BBB permeability-surface-area product (PS) as determined by WEPCAST MRI. The time dependence of the physiological parameters was studied with a linear mixed-effect model. Additionally, pairwise t-tests comparison of the physiological parameters at each time point was conducted. A P-value of <0.05 was considered statistically significant. There was an initial drop (8.22 ± 2.60%) followed by a recovery in CBF after exercise, while Yv revealed a significant decrease (6.37 ± 0.92%), i.e., an increased oxygen extraction, and returned to baseline at later time points. CMRO2 showed a trend of increase (5.68 ± 3.04%) and a significant interaction between time and group. In addition, E increased significantly (3.86% ± 0.89) and returned to baseline level at later time points, while PS remained elevated (13.33 ± 4.79%). A single bout of moderate aerobic exercise can induce acute alterations in cerebral perfusion, metabolism, and BBB permeability. 2 TECHNICAL EFFICACY: Stage 2.

In vitro approach to refine bioconcentration and biotransformation predictions of organic persistent pollutants using cell lines

The application of the 3Rs (Replacement, Reduction, and Refinement) in animal experimentation has recently concentrated its efforts on utilizing cellular systems to predict toxicity in organisms. In this context, while refining the data obtained from cell lines, this study assesses their bioaccumulation potential and various methods for extrapolating the in vitro metabolization rate constant to support modelled bioaccumulation assessments for fish and their limitations. For this purpose, the concentrations of the parent compound, phenanthrene, and its major metabolites within the cells and in the medium at various exposure times were quantified. A chemical distribution model (mass balance) was applied to calculate the concentrations of the cell-bioaccessible compounds (Cfree) based on the experimentally determined concentrations. An elevated matching was observed between the in vitro bioconcentration factor (BCF) and the in vivo BCFs reported in the literature for zebrafish liver cells (ZFL). This study demonstrates the importance of further investigating in vitro biotransformation kinetics. The results obtained with the approach developed here provide valuable information to enhance current models. Additionally, it underscores the potential of cell lines as a strategy for rapid, simple, and cost-effective predictions without the need for animal experimentation.

Peripheral insulin resistance attenuates cerebral glucose metabolism and impairs working memory in healthy adults

People with insulin resistance are at increased risk for cognitive decline. Insulin resistance has previously been considered primarily a condition of ageing but it is increasingly seen in younger adults. It is possible that impaired insulin function in early adulthood has both proximal effects and moderates or even accelerates changes in cerebral metabolism in ageing. Thirty-six younger (mean 27.8 years) and 43 older (mean 75.5) participants completed a battery of tests, including blood sampling, cognitive assessment and a simultaneous PET/MR scan. Cortical thickness and cerebral metabolic rates of glucose were derived for 100 regions and 17 functional networks. Older adults had lower rates of regional cerebral glucose metabolism than younger adults across the brain even after adjusting for lower cortical thickness in older adults. Higher fasting blood glucose was also associated with lower regional cerebral glucose metabolism in older adults. In younger adults, higher insulin resistance was associated with lower rates of regional cerebral glucose metabolism but this was not seen in older adults. The largest effects of insulin resistance in younger adults were in prefrontal, parietal and temporal regions; and in the control, salience ventral attention, default and somatomotor networks. Higher rates of network glucose metabolism were associated with lower reaction time and psychomotor speed. Higher levels of insulin resistance were associated with lower working memory. Our results underscore the importance of insulin sensitivity and glycaemic control to brain health and cognitive function across the adult lifespan, even in early adulthood.

The upper limit of thermoneutrality is not indicative of thermotolerance in bats

To assess the vulnerability of birds and mammals to climate change recent studies have used the upper critical limit of thermoneutrality (TUC) as an indicator of thermal tolerance. But, the association between TUC and thermal tolerance is not straightforward and most studies describe TUC based solely on a deviation in metabolism from basal levels, without also considering the onset of evaporative cooling. It was argued recently that certain torpor-using bat species who survived prolonged exposure to high ambient temperatures (i.e. high thermal tolerance) experienced during extreme heat events did so by entering torpor and using facultative heterothermy to thermoconform and save on body water. Assuming that TUC is indicative of thermal tolerance, we expect TUC in torpor-using species to be higher than that of species which are obligate homeotherms, albeit that this distinction is based on confirmation of torpor use at low temperatures. To test this prediction, we performed a phylogenetically informed comparison of bat species known to use torpor (n = 48) and homeothermic (n = 16) bat species using published thermoregulatory datasets to compare the lower critical limit of thermoneutrality (TLC) and TUC in relation to body temperature. The influence of diet, biogeographical region, body mass and basal metabolic rate (BMR) was also considered. Body mass had a positive relationship with BMR, an inverse relationship with TLC and no relationship with TUC. Normothermic body temperature scaled positively with BMR, TLC and TUC. There was no relationship between diet or region and BMR, but both influenced thermal limits. Torpor-using bats had lower body mass and body temperatures than homeothermic bats, but there was no difference in BMR, TLC and TUC between them. Exceptional examples of physiological flexibility were observed in 34 torpor-using species and eight homeothermic species, which included 15 species of bats maintaining BMR-level metabolism at ambient temperatures as high as 40 °C (and corresponding body temperatures ∼39.2 °C). However, we argue that TUC based on metabolism alone is not an appropriate indicator of thermal tolerance as it disregards differences in the ability of animals to tolerate higher levels of hyperthermia, importance of hydration status and capacity for evaporative cooling. Also, the variability in TUC based on diet challenges the idea of evolutionary conservatism and warrants further consideration.

A combination of Citrus aurantifolia fruit rind and Theobroma cacao seed extracts supplementation enhances metabolic rates in overweight subjects: a randomized, placebo-controlled, cross-over study.

LN19183 is a proprietary, synergistic combination of Citrus aurantifolia fruit rind and Theobroma cacao seed extracts that increased resting energy expenditure (REE) in high-fat diet (HFD)-fed obese rats. The objective of this study was to validate the thermogenic potential of LN19183 in obese Sprague Dawley (SD) rats and to assess its clinical efficacy in a proof-of-concept, randomized, placebo-controlled, cross-over human trial. In the rat study, HFD-fed obese rats were supplemented with either HFD alone or with 45, 90, or 180 mg LN19183 per kg body weight (BW) for 28 days. In the human study, 60 overweight adults (male and female, aged 20-39 years) were randomized. Subjects took LN19183 (450 mg) or a matched placebo capsule on two consecutive days in phases one and two of the study, separated by a 10-day washout period. In each phase, on day 1, REE at pre-dose, 60-, 120-, and 180-min post-dose, and on day 2, metabolic rates at pre-dose and post-dose during and 20 min after exercise were measured using indirect calorimetry. In rats, LN19183 significantly increased REE, reduced BW gain and fat masses, and increased fat and carbohydrate metabolism marker proteins including beta 3 adrenergic receptor (β3-AR), phospho-AMP-activated protein kinase (AMPK), glucagon-like peptide-1 receptor (GLP-1R) in the liver, and serum adiponectin levels. Furthermore, LN19183-supplemented human volunteers increased (P < 0.05, vs. placebo) the metabolic rates at rest and with exercise; their fat oxidation was increased (P < 0.05, vs. placebo) at rest and 20 min post-exercise. The groups' systolic and diastolic blood pressure (BP), heart rates (HR), and safety parameters were comparable. These observations suggest that LN19183 is a thermogenic botanical composition with no stimulatory effects on BP and HR.

A Critical Investigation of Sick Euthyroid Syndrome in Chronic Heart Failure Patients: Addressing the Need for Accurate Thyroid Assessment.

Background The body undergoes numerous metabolic changes during severe illness or physiological stress to protect itself by lowering metabolism and reducing overall demands. This evolutionary adaptation dates back to early human development, long before the advent of ICU facilities and advanced treatments. One such protective mechanism is Sick Euthyroid Syndrome (SES), also known as Non-thyroidal Illness Syndrome (NTIS). SES commonly occurs in critically ill patients and is frequently observed in conditions such as heart failure, chronic kidney disease, and severe sepsis. This syndrome is characterized by abnormal thyroid function tests in patients with acute or chronic systemic illnesses who do not have intrinsic thyroid disease. Typically, these patients exhibit low serum levels of triiodothyronine (T3), normal or low levels of thyroxine (T4), and normal or low thyroid-stimulating hormone (TSH) levels. SES is believed to be an adaptive response to illness, aimed at reducing the body's metabolic rate and conserving energy during severe physiological stress. This original article delves into SES's prevalence and clinical impact in these settings. Materials and methods The study aims to determine the prevalence of SES in patients with long-standing heart failure, elucidate the relationship between thyroid function and heart failure severity, and assess its impact on various hematological and clinical parameters. This observational, cross-sectional study was conducted at Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pune, India, a 2011-bed hospital, over one and a half years. This study included 70 patients with chronic heart failure, aged 18 years and above, defined by a left ventricular ejection fraction of 40% or less and a Boston criteria score of 8 or more. Patients were excluded if they had a history of thyroid dysfunction, clinical sepsis, or were taking thyroid-affecting drugs. Results The study provides important insights into the prevalence and impact of SES in long-standing heart failure patients. It found that a significant 44.29% of these patients exhibited low T3 levels, highlighting the substantial occurrence of SES in this population. Additionally, the study revealed a negative correlation between N-terminal pro-b-type natriuretic peptide (NT-proBNP) levels, Boston score, and total T3, suggesting that as indicators of heart failure severity worsen, total T3 levels may decrease further. Another key finding is the high prevalence of anemia among heart failure patients, with a notable gender disparity: 92.11% of male patients were affected compared to 50% of female patients. Conclusion The study concluded that SES is significantly prevalent among long-standing heart failure patients, further indicating that thyroid suppression increases with the severity of heart failure. Recognizing SES can guide tailored treatments, prompting intensive monitoring and optimized heart failure management.Additionally, the study found a high prevalence of anemia, particularly among male patients, highlighting the need for gender-specific considerations in managing heart failure. These findings underscore the importance of routine thyroid function assessments and regular monitoring of anemia in heart failure patients. Future research should focus on improving clinical outcomes through comprehensive management of both thyroid function and anemia in these patients.

The seasonal response of metabolic rate to projected climate change scenarios in aquatic amphipods

The responses of organisms to climate change are mediated primarily by its impact on their metabolic rates, which, in turn, drive various biological and ecological processes. Although there have been numerous seminal studies on the sensitivity of metabolic rate to temperature, little is empirically known about how this rate responds to seasonal temperature ranges and beyond under conservative IPCC climate change scenarios. Here, we measured the SMR of the aquatic amphipod, Gammarus insensibilis, which served as our subject species, with body masses ranging from 0.20 to 7.74 mg ash free weight. We assessed the response of the SMR across nine temperature levels ranging from 12 to 30.2 °C. These temperatures match seasonal temperature norms, with an incremental increase of 0.6–1.2 °C above each seasonal baseline, as projected for the years 2040 and 2100 under the modest climate change scenarios. Overall, our findings showed that the effect of temperature on SMR varies with body mass, as indicated by a negative size-temperature interaction, with larger conspecifics exhibiting less sensitivity to temperature changes than smaller ones. From the cold to warm season, the SMR increased by an average of 14% °C−1, with increases of 18.4% °C−1 in smaller individuals and 11.4% °C−1 in larger ones. The SMR of smaller individuals peaked at a 0.6 °C increase from the current summer baseline (15.08% °C−1, Q10 = 4.2), while in larger ones it peaked with a 1.2 °C increase beyond autumn temperatures (14.9% °C−1, Q10 = 3.9). However, at temperatures reflecting global warming that exceed summer temperatures, the SMR of larger individuals levelled off, while that of smaller ones continued to increase. Overall, our findings suggest that smaller-sized individuals have a broader thermal window for SMR performance, while the SMR of larger-sized ones will become increasingly constrained at summer temperatures as those summer temperatures become hotter.

Offshore windfarm construction elevates metabolic rate and increases predation vulnerability of a key marine invertebrate

A global increase in offshore windfarm development is critical to our renewable energy future. Yet, widespread construction plans have generated substantial concern for impacts to co-occurring organisms and the communities they form. Pile driving construction, prominent in offshore windfarm development, produces among the highest amplitude sounds in the ocean creating widespread concern for a diverse array of taxa. However, studies addressing ecologically key species are generally lacking and most research is disparate, failing to integrate across response types (e.g., behavior, physiology, and ecological interactions), particularly in situ. The lack of integrative field studies presents major challenges to understand or mitigate actual impacts of offshore wind development. Here, we examined critical behavioral, physiological, and antipredator impacts of actual pile driving construction on the giant sea scallop (Placopecten magellanicus). Benthic taxa including bivalves are of particular concern because they are sound-sensitive, cannot move appreciable distances away from the stressor, and support livelihoods as one of the world's most economically and socially important fisheries. Overall, pile driving sound impacted scallops across a series of behavioral and physiological assays. Sound-exposed scallops consistently reduced their valve opening (22%), resulting in lowered mantle water oxygen levels available to the gills. Repeated and rapid valve adductions led to a 56% increase in metabolic rates relative to pre-exposure baselines. Consequently, in response to predator stimuli, sound-exposed scallops displayed a suite of significantly weaker antipredator behaviors including fewer swimming events and shorter time-to-exhaustion. These results show aquatic construction activities can induce metabolic and ecologically relevant changes in a key benthic animal. As offshore windfarm construction accelerates globally, our field-based study highlights that spatial overlap with benthic taxa may cause substantial metabolic changes, alter important fisheries resources, and ultimately could lead to increased predation.

Differential toxic effects of nano-titanium dioxide on clams (Meretrix meretrix) with various individuality

Nano-TiO2 is inevitably released into aquatic environment with increasing of nanotechnology industries. Study pointed that different individuality showed divergent behavioral and physiological response when facing environmental stress. However, the effects of nano-TiO2 on tolerance of bivalves with different individualities remain unknown. In the study, clams were divided into two types of individuality - proactive and reactive by post-stress recovery method. It turned out that proactive individuals had quicker shell opening level, stronger burrowing behavior, faster feeding recovery, higher standard metabolic rate and more rapid ammonia excretion ability than reactive individuals after exposed to air. Then, the survival rate, hemocytes response and oxidase activity of classified clams were evaluated after nano-TiO2 exposure. Results showed that after 30 d exposure, proactive individuals accelerated burrowing behavior with higher survival rate. Moreover, proactive clams had better adaptability and less hemocytes response and oxidative damage than reactive clams. The study highlights the individualities of marine shell fish determine individual capacity to adapt to environmental changes, play important roles in aquaculture and coastal ecosystem health.

Physiologically-informed predictions of climate warming effects on native and non-native populations of blue catfish

Blue catfish Ictalurus furcatus has been widely introduced throughout the United States to enhance recreational fisheries. Its success in both its native and non-native range, especially in the context of climate change, will be influenced by its thermal performance. We conducted a laboratory experiment to investigate the responses of wild-captured, subadult blue catfish to temperatures ranging from 7 °C to 38 °C. Blue catfish had relatively low standard metabolic rates, indicating low energetic demands, and hence an ability to survive well even during low-food conditions. Metabolic scope and food consumption rate increased with temperature, with metabolic scope peaking at 29.1 °C, and consumption rate peaking at 32 °C. Body condition remained high up to 32 °C, but decreased drastically thereafter, suggesting limitations in maintaining metabolism through food consumption at temperatures >32 °C; blue catfish cannot survive in such habitats indefinitely. Yet, many fish were able to survive temperatures as high as 38 °C for 5 days, suggesting that acute and occasionally chronic heat waves will not limit this species. Using these results, we also predicted the performance of blue catfish under prevailing conditions and under climate warming at seven locations throughout their current range in the U.S. We found that some blue catfish populations in southern and southeastern areas will likely experience temperatures above the optimal temperature for extended periods due to climate change, thus limiting potential habitat availability for this species. But, many non-native populations, especially those in northern areas such as Idaho, North Dakota, and northern California, may benefit from the expected warmer temperatures during spring and fall.

Analysis of bamboo fibres and their associated dye on a freshwater fish host-parasite system

With the growth of the fashion and textile industries into the twenty-first century, associated pollution has become pervasive. Fibre-based microplastics are the most common types of plastics recovered from aquatic ecosystems encouraging the move towards organic fibre usage. Often marketed as biodegradable and ‘environmentally friendly’, organic textile fibres are seen as less harmful, but their impacts are understudied. Here, we assess the health effects of reconstituted bamboo-viscose fibres, processed bamboo-elastane fibres (both at 700 fibres/L) and their associated dye (Reactive Black-5, at 1 mg/L) on fish, with an emphasis on disease resistance utilising an established host-parasite system: the freshwater guppy host (Poecilia reticulata) and Gyrodactylus turnbulli (monogenean ectoparasite). Following 3 weeks exposure to the bamboo fibres and associated dye, half the experimental fish were infected with G. turnbulli, after which individual parasite trajectories were monitored for a further 17 days. Overall, exposures to reconstituted bamboo-viscose fibres, processed bamboo-elastane fibres or dye were not associated with any change in host mortality nor any significant changes in parasite infection burdens. When analysing the routine metabolic rate (RMR) of fish, uninfected fish had, on average, significantly impacted RMR when exposed to processed bamboo-elastane (increased RMR) and reconstituted bamboo-viscose (decreased RMR). Hosts exposed to reconstituted bamboo-viscose and the associated dye treatment showed significant changes in RMR pre- and post-infection. This study bolsters the growing and needed assessment of the potential environmental impacts of alternative non-plastic fibres; nevertheless, more research is needed in this field to prevent potential greenwashing.