Journal of thermal biology最新文献

This study investigated the single and combined effects of environmental heat stress and physical exercise on executive function (EF) performance, prefrontal cortex oxygenation, thermoregulatory responses and subjective perceptions. Sixteen subjects participated in four experimental sessions: two under moderate environmental conditions (23 °C), with and without physical exercise (R23, E23), and two under hot environmental conditions (35 °C), with and without physical exercise (R35, E35). In each session, participants completed EF tasks before and after 1 h of passive rest or 45 min of moderate-intensity cycling followed by 15 min of rest. We used Δresponse time (ΔRT) and Δaccuracy (ΔACC) of EF tasks to demonstrate changes from pre to post experiment. Additionally, changes in cerebral oxygenation during EF tasks were illustrated using the Δoxygenation difference. Heat stress alone increased core temperature (T_core), mean skin temperature (T_skin), heart rate (HR), thermal sensation (TS), and rating of perceived exertion (RPE). Exercise in a hot environment further increased physiological indicators and RPE, but TS exhibited a different pattern, with lower TS in R35 compared to E35 during the second battery of executive function tests. Moreover, heat stress alone increased ΔRT for the More-Odd Shifting task and the Stroop task under incongruent conditions, while decreasing the Δoxygenation difference during the More-Odd Shifting task. ΔRT for the 2-back, More-Odd Shifting and Stroop tasks under incongruent conditions were lower in the E35 trial than in the R35 trial, whereas the Δoxygenation difference was higher in the E35 trial compared to the R35 trial. These findings indicate that environmental heat stress alone increases T_core and T_skin, alters TS, and impairs EF performance by decreasing prefrontal cortex oxygenation. A 45-min moderate-intensity exercise combined with environmental heat stress enhances the increases in body temperatures but mitigates the detrimental effects of heat stress alone on EF performance by increasing prefrontal cortex oxygenation.

Environmental temperature impacts the physiological processes of reptiles, determines their hours of activity per day, and may constrain their ability to meet critical ecological requirements. When environmental temperatures reach freezing, a few lizard species exhibit two mechanisms (supercooling and freezing tolerance) to survive freezing, and these two processes depend on cryoprotective molecules, such as glucose. Organisms produce high glucose concentrations to reach lower than normal crystallisation points, and this blood glucose concentration can double after freezing. The viviparous lizard Barisia imbricata lives along a wide elevational gradient (2100-4000 m) at tropical latitudes in temperate and subtropical climates. Populations at extremely high elevations experience environmental temperatures at or below 0 °C. We measured blood glucose concentrations in the lizard B. imbricata in different seasons and compared the values between seasons and between two populations occurring at the elevations of 2200 and 3700 m. In addition, we froze lizards from the two populations and measured their blood glucose concentrations before and after freezing. We did not observe any differences in blood glucose concentrations between different seasons or the two populations. In addition, all lizards survived freezing; their mean crystallisation point was -4.13 °C. Blood glucose concentration in the lizards increased after exposure to freezing temperatures during autumn and winter. Our results indicate that B. imbricata tolerates experimental freezing even in individuals not naturally exposed to subzero temperatures (i.e. populations at 2200 m). Elevated blood glucose concentrations (present year-round) may help B. imbricata individuals survive at low temperatures.

Animals can respond differently to shifting thermal variability versus thermal averages, both of which are changing due to climate warming. How these thermal variables affect parental care behaviors can reveal the ability of parents to modify their behaviors to meet the competing demands of their offspring's thermal needs and self-maintenance, which becomes critical in suboptimal thermal conditions. Further, the time frame used to examine the interplay between temperature and behavioral shifts (e.g., seasonal patterns in care vs. drivers of individual care decisions) can provide different information about the plasticity of parental care behavior. We investigated the relationship between thermal means, thermal variability, and incubation behaviors across multiple timescales in Scaled Quail and Northern Bobwhite. Both species decreased off-bout length during periods of high thermal variability, a novel finding among studies of avian parental behavior. Further relationships between thermal endpoints (mean vs. variation) and behavior differed depending on the temporal scale. For instance, total daily time spent off the nest was not influenced by daily average temperature, yet individual off-bout duration increased with increasing average temperature in the 2 h prior to the off-bout. These results provide evidence that thermal-behavioral relationships differ across scales and likely represent a bird's ability to modify their incubation strategy to rapidly respond to the immediate thermal environment (altering individual off-bout length based on temperature) to meet self-maintenance needs while resulting in a similar outcome for their nest (total daily off-bout time). However, longer off-bout durations during high temperature events can come with reproductive costs, sometimes resulting in acute offspring mortality when eggs or chicks experience lethal temperatures.

Ectotherms are considered more susceptible to global warming. Variations in ambient temperature are especially alarming as the majority of animals are ectothermic, with temperature seen as a crucial determinant of their ecology, biogeography, behaviour, and physiology. Ectotherms, which depend on external ambient temperatures to regulate their body temperature, exhibit various physiological and metabolic responses to variations in temperature. These responses are essential for comprehending how these species will acclimatise to changing water temperatures and the consequent alterations in oxygen availability. This study assessed the acclimation ability, temperature tolerance, and metabolic rate of narrow-clawed crayfish (Pontastacus leptodactylus) to elucidate the crayfish's responses to potential climate change. Our study showed that the narrowed clawed crayfish is a species that exhibits high thermal tolerance, with an extensive dynamic (1114 °C²), static thermal polygon area (966 °C²), resistance zone of 103 °C² and the ability to withstand extreme temperatures (CT_min-CT_max: 1.60-36.8 °C). The acclimation temperature has minimal impact on the thermal tolerance of the crayfish (P < 0.01). The optimal temperature range for SMR of Pontastacus leptodactylus is 20-25 °C, within which a decline in standard metabolic rate (SMR) occurs as temperature rises.

This study examined the impact of curcumin nanomicelles (CNM) supplementation on transitioning ewes and their offspring. Thirty-two crossbred pregnant ewes [Ile-de-France × (Dalagh × Romanov)], confirmed to carry twins, were randomly assigned to a control group (CTRL) or a treatment group receiving 40 mg of CNM per ewe per day. Supplementation began before and continued after delivery. We assessed various parameters, including growth performance, metabolic health, inflammatory markers, hematological profiles, immunoglobulin levels, antioxidant status, and greenhouse gas emissions. CNM supplementation improved growth in both ewes and lambs, consistent with curcumin's known metabolic effects. Significant reductions in inflammatory markers were observed in both ewes and lambs, with decreased neutrophil-to-lymphocyte ratios indicating reduced systemic inflammation. Increased levels of IgG and IgA in both ewes and lambs suggested improved immune competence. Antioxidant biomarkers indicated better management of oxidative stress, with some benefits extended to offspring. CNM had varying effects on methanogen populations and nitrous oxide emissions. It significantly reduced methanogen numbers postpartum, but had no significant effect pre-partum. A slight increase in N2O emissions was observed before delivery, but was not sustained after delivery. These results underscore the complex interactions of metabolic, immunological, and environmental factors influenced by CNM supplementation during the transition period. More research is needed to refine supplementation strategies, evaluate long-term effects, and explore ways to mitigate increased greenhouse gas emissions while preserving health benefits.

Objective: This study aimed to evaluate the effects of different cold acclimation strategies on exercise performance in male mice exposed to low-temperature environments.

Methods: Male mice were subjected to five distinct acclimation regimens over 8 weeks: immersion at 10 °C (10 °CI) or 20 °C (20 °CI), swimming at 10 °C (10 °CS), 20 °C (20 °CS), or 34 °C (34 °CS). During the first 2 weeks, the acclimation time progressively decreased from 30 min to 3 min per day, and the water temperatures were lowered from 34 °C to the target levels, followed by 6 weeks of consistent exposure. Body weight, food intake, and rectal temperature were monitored throughout the study. Post-acclimation assessments included low-temperature exhaustion exercise ability testing; 16 S rDNA sequencing of gut microbiota; and quantification of gene expression related to brown adipose thermogenesis, skeletal muscle synthesis, and degradation.

Results: (1) After 8 weeks of acclimation, neither serum adrenaline nor angiotensin II levels significantly increased in mice exposed to 10 °C or 20 °C water. (2) Cold acclimation extended the endurance time under low-temperature conditions, notably in the 20 °CI, 10 °CS, and 20 °CS groups. (3) Compared with the control (C) group, the 20 °CI and 10 °CS groups showed significantly increased UCP1, IGF-1, AKT, and mTOR gene expression levels (P < 0.05). The expression levels of MAFbx and MuRF1 genes in the 10 °CS and 20 °CS groups significantly decreased compared with those in the C group (P < 0.05). (4) Compared with the C group, the 20 °CI, 10 °CS, and 20 °CS groups demonstrated significant changes in intestinal microbiota diversity. Specifically, the abundance of Akkermansia strains significantly increased in the 20 °CI and 10 °C S groups. The abundance of Ruminococcus and Prevotellaceae_UCG-001 significantly increased in the 20 °C S group.

Conclusion: Exercise in cold environments can activate genes related to heat production and skeletal muscle synthesis and increase the abundance of beneficial bacteria producing short-chain fatty acids, thereby modulating host metabolism, accelerating the formation of cold acclimation, and enhancing exercise capacity in low-temperature environments.

Critical thermal maximum (CT_max) is the most widely used method for quantifying acute upper thermal limits in ectotherms. CT_max protocol exposes animals to a consistent rate of environmental warming until they lose motor function. CT_max has been used to assess intraspecific variation among life stages, populations, or as a function of body size, often with the assumption that it is a durable and heritable trait at the individual level. The existence of within-individual repeatability of CT_max has been used to infer the potential for thermal adaptation via the positive correlation between the repeatability of a trait and its heritability. However, for how widely used CT_max has become, surprisingly few studies have quantified within-individual repeatability in aquatic ectotherms, and none have assessed repeatability across contexts. We examined the cross-context repeatability of CT_max in two freshwater ectotherms (one decapod crustacean and one teleost fish): rusty crayfish Faxonius rusticus (n = 31) and pumpkinseed Lepomis gibbosus (n = 38). Individual repeatability was measured on a weekly basis across multiple trials (n = 5 pumpkinseed CT_max measurements, n = 7 rusty crayfish) that varied in acclimation temperature, oxygen saturation, and salinity. CT_max was most strongly influenced by acclimation temperature. Repeatability varied based on the statistical approach and between the two species. Pumpkinseed repeatability across contexts was moderate (ca. 0.4), similar to previous reports on within-context CT_max repeatability studies in fishes. In rusty crayfish, repeatability was much lower (ca. 0.16). This suggests CT_max repeatability may be both taxon- and context-dependent, thus further investigation into repeatability is needed across species for this important and widely used trait.

The traditional overwintering process of sea cucumbers (Apostichopus japonicus) requires burning a large amount of coal to raise the water temperature. It is useful but costly and not environmentally friendly. Bacillus is proposed as a cheap and green alternative. Therefore, this study intended to achieve cleaner production of A. japonicus by adding Bacillus to their diet at low temperature (7 °C) to achieve the production efficiency of sea cucumbers cultured by heating water to 11 °C. Here, we found that number of crawl steps, relative food intake, relative fecal outputs, amylase and proteinase activities, body weight and weight gain rate significantly reduced, and intestinal morphology and intestinal microbiota were also worse in sea cucumbers at low temperature (7 °C), compared with the sea cucumbers cultured at 11 °C. This suggests that low temperature negatively affect the behaviors, intestinal health, and growth of A. japonicus. However, the adverse effects on the behavioral capacities (such as number of crawl steps, relative food intake and relative fecal outputs), intestinal health (such as digestive enzyme activities and intestinal morphology), and growth (such as body weight and weight gain rate) of sea cucumbers under low temperature conditions were compensated after adding dietary Bacillus (Bacillus methylotrophicus and Bacillus amyloliquefaciens) at 10⁷ CFU/g. These traits reached the level of those in sea cucumbers cultured at 11 °C with no significant difference, and were significantly different from those cultured at 7 °C without adding Bacillus. Importantly, the intestinal microbiota structure of sea cucumbers was greatly improved after the addition of dietary Bacillus, reducing the proportion of Proteobacteria and the consequent probability of diseases. In conclusion, the results suggest that dietary supplementation with Bacillus can reverse the adverse effects caused by 4 °C of temperature difference (between 7 °C and 11 °C) on sea cucumbers. Therefore, we recommend that aquaculture farmers use a combination of burning limited coal to increase water temperature to 7 °C and feeding Bacillus to improve the production efficiency of A. japonicus in winter.

Questionnaires exploring tourists' perceptions of ideal climatic conditions are argued to be a more suitable data source for the development of tourism climate indices than the utilization and integration of expert opinion and pre-established thresholds. This assumes that those tourist respondents can accurately quantify meteorological conditions at a given point in time, and effectively discriminate between meteorological thresholds of suitable and unsuitable conditions. For variables such as rainfall and sunshine hours, this assumption is fairly reasonable. However, where tourists' perceptions, captured through questionnaire responses, are used to set thresholds for air temperature and thermal comfort, it is important to determine whether those perceptions are valid. Previous studies contest this, indicating considerable differences in perceptions of heat thresholds based on terminology, nationality, destination, and time of the year. In this study, a benchmarking exercise is performed comparing perceived temperatures and thermal comfort to measured values, through questionnaires administered to 984 adults in South Africa. Findings indicated that while 19.9% of responses are within 1 °C of measured temperatures, up to 12.8% of respondents perceive temperatures as being at least 6 °C higher or lower than the measured values. There are no clear geographic or demographic variables that effectively discriminate between accurate and inaccurate responses. When asked to classify their level of thermal comfort, as opposed to quantifying temperatures, results aligned more closely with measures and classifications of effective temperature. Based on these results, we argue that greater caution should be applied when using temperature thresholds derived from questionnaire data in developing and calibrating any biometeorological indices, and focus instead should be placed on catergorized levels of self-reported thermal comfort in environments where raw meteorological conditions are measured.

Climate warming and frequent incidents of extreme high temperatures are serious global concerns. Heat stress induced by high temperature has many adverse effects on animal physiology, especially in aquatic poikilotherms. Chinese mitten crab (Eriocheir sinensis) is sensitive to high temperatures, this study evaluated the harmful effects of heat stress on the neurotoxicity, intestinal health, microbial diversity, and metabolite profiles. The results showed that heat stress caused histopathological damages and altered the ultrastructure of lesions in the cranial ganglia. Heat stress significantly upregulated the mRNA expression of apoptosis-related genes, and significantly altered the expression of neurotransmitter receptors. In addition, heat stress induced significant intestinal damages that mainly manifested as a significant increase in the activity of diamine oxidase in the serum and contents of histamine in the intestine. The diversity and abundance of intestinal microbiota altered abnormally in E. sinensis exposed to heat stress, and the bacteria that exhibited significant variations in abundance were closely related to the production of neurotransmitters and neuromodulators. Heat stress caused significant changes in the intestinal metabolite profiles, which mainly involved the amino acid and lipid metabolism pathways. Analysis of the correlation showed that the abnormal changes in metabolites were closely related to differences in the abundance of intestinal microbiota. Therefore, this study showed that heat stress could cause neurophysiological toxic effects, which may be related to intestinal ecological imbalance.