Oxygen Availability Affects Behavioural Thermoregulation of Turtle Embryos

Extending recent findings that reptile embryos seek optimal temperatures inside eggs for thermoregulation,our study demonstrates that this thermoregulatory behaviour can be affected by the amount of oxygen available to an embryo.We exposed embryos of a freshwater turtle(Mauremys reevesii)to two heat sources(an optimal temperature of 30°C and a high temperature of 33°C)under three different oxygen levels–hypoxia(12%O2),normoxia(21%O2)and hyperoxia(30%O2)–and quantified the interactive effects of temperature and oxygen availability on embryonic thermoregulatory behaviour.Our results demonstrated that,in both thermal treatments,embryos exposed to hypoxia did not move as close to the heat source and therefore selected lower temperatures than those exposed to normoxia or hyperoxia.Embryos may select low temperatures under hypoxic conditions to decrease oxygen consumption and therefore alleviate the negative impact of hypoxic stress.

Three-dimensional human thermoregulation model based on pulsatile blood flow and heating mechanism

A three-dimensional thermoregulation mathematical model of temperature fluctuations for the human body is developed based on predecessors＇ thermal models. The following improvements are necessary in real situations： ellipsoids and elliptical cylinders are used to adequately approximate body geometry, divided into 18 segments and five layers; the core layer consists of the organs; the pulsation of the heart cycle, the pulsatile laminar flow, the peripheral resistance, and the thermal effect of food are considered. The model is calculated by adopting computational fluid dynamics（CFD） technology, and the results of the model match with the experimental data. This paper can give a reasonable explanation for the temperature fluctuations.

Modeling on Metabolic Rate and Thermoregulation in Three Layered Human Skin during Carpentering, Swimming and Marathon

Metabolisms play a vital role in thermoregulation in the human body. The metabolic rate varies with the activity levels and has different behaviors in nature depending on the physical activities of the person. During the activity, metabolic rate increases rapidly at the beginning and then increases slowly to become almost constant after a certain time. So, its behavior is as logistics in nature. The high metabolic rate during activity causes the increase of body core temperature up to 39˚C [1] [2]. The logistic model of metabolic rate is used to re-model Pennes’ bioheat equation for the study of temperature distribution in three layered human dermal parts during carpentering, swimming and marathon. The finite element method is used to obtain the solution of the model equation. The results demonstrate that there is a significant change in tissue temperature due to sweating and ambient temperature variations.

Temperature‑Gated Light‑Guiding Hydrogel Fiber for Thermoregulation During Optogenetic Neuromodulation

With the rise of optogenetic manipulation of neurons,the effects of optogenetic heating on temperature-sensitive physi-ological processes,and the damage to surrounding tissues have been neglected.This manuscript reports the fabrication of a highly temperature-sensitive semi-interpenetrating optical hydrogel fiber(TSOHF)using the integrated dynamic wet-spinning technique.TSOHF exhibits a structural tunable diameter,clear core/sheath structure,tunable temperature-sensitivity,excellent light propagation property(0.35 dB cm^(-1),650 nm laser light),and good biocompatibility(including tissue-like Young’s modulus,stable dimensional stability,and low cytotoxicity).Based on these properties,a potential application of optogenetic regulation of neural tissue(hypoglossal nerve),with controllable temperature using TSOHF was designed and performed.Further,this work provides new insight into molecular design and a practical approach to continually manufacture a temperature-sensitive hydrogel optical fiber for applications in intelligent photomedicine.

Gut microbiota intervention attenuates thermogenesis in broilers exposed to high temperature through modulation of the hypothalamic 5‑HT pathway

Background Broilers have a robust metabolism and high body temperature,which make them less tolerant to hightemperature(HT)environments and more susceptible to challenges from elevated temperatures.Gut microbes,functioning as symbionts within the host,possess the capacity to significantly regulate the physiological functions and environmental adaptability of the host.This study aims to investigate the effects of gut microbial intervention on the body temperature and thermogenesis of broilers at different ambient temperatures,as well as the underlying mechanism involving the"gut-brain"axis.Methods Broilers were subjected to gut microbiota interference with or without antibiotics(control or ABX)starting at 1 day of age.At 21 day of age,they were divided into 4 groups and exposed to different environments for 7 d:The control and ABX groups at room temperature(RT,24±1℃,60%relative humidity(RH),24 h/d)and the control-HT and ABX-HT groups at high temperature(HT,32±1℃,60%RH,24 h/d).Results The results demonstrated that the antibiotic-induced gut microbiota intervention increased body weight and improved feed conversion in broiler chickens(P<0.05).Under HT conditions,the microbiota intervention reduced the rectal temperature of broiler chickens(P<0.05),inhibited the expression of avUCP and thermogenesisrelated genes in breast muscle and liver(P<0.05),and thus decreased thermogenesis capacity.Furthermore,the gut microbiota intervention blunted the hypothalamic‒pituitary‒adrenal axis and hypothalamic–pituitary–thyroid axis activation induced by HT conditions.By analyzing the cecal microbiota composition of control and ABX chickens maintained under HT conditions,we found that Alistipes was enriched in control chickens.In contrast,antibioticinduced gut microbiota intervention resulted in a decrease in the relative abundance of Alistipes(P<0.05).Moreover,this difference was accompanied by increased hypothalamic 5-hydroxytryptamine(5-HT)content and TPH2 expression(P<0.05).Conclusions These findings underscore the critical role of the gut microbiota in regulating broiler thermogenesis via the gut-brain axis and suggest that the hypothalamic 5-HT pathway may be a potential mechanism by which the gut microbiota affects thermoregulation in broilers.

Personal Thermal Management by Radiative Cooling and Heating

Maintaining thermal comfort within the human body is crucial for optimal health and overall well-being.By merely broadening the setpoint of indoor temperatures,we could significantly slash energy usage in building heating,ventilation,and air-conditioning systems.In recent years,there has been a surge in advancements in personal thermal management(PTM),aiming to regulate heat and moisture transfer within our immediate surroundings,clothing,and skin.The advent of PTM is driven by the rapid development in nano/micro-materials and energy science and engineering.An emerging research area in PTM is personal radiative thermal management(PRTM),which demonstrates immense potential with its high radiative heat transfer efficiency and ease of regulation.However,it is less taken into account in traditional textiles,and there currently lies a gap in our knowledge and understanding of PRTM.In this review,we aim to present a thorough analysis of advanced textile materials and technologies for PRTM.Specifically,we will introduce and discuss the underlying radiation heat transfer mechanisms,fabrication methods of textiles,and various indoor/outdoor applications in light of their different regulation functionalities,including radiative cooling,radiative heating,and dual-mode thermoregulation.Furthermore,we will shine a light on the current hurdles,propose potential strategies,and delve into future technology trends for PRTM with an emphasis on functionalities and applications.

To eat or get heat： Behavioral trade-offs between thermoregulation and feeding in gregarious necrophagous larvae

The thermoregulation behavior ofLucilia sericata larvae （Diptera： Calliphori- dae）, a necrophagous species that feeds on vertebrate cadavers, was investigated. These larvae require high heat incomes to develop, and can elevate temperatures by forming large aggregates. We hypothesized that L. sericata larvae should continue to feed at temperatures up to 38 ℃, which can be reached inside larval masses. Thermal regulation behavior such as movement between a hot food spot and colder areas was also postulated. The hypotheses were tested by tracking for 1 h the activity of single, starved third instar larvae in a Petri dish containing 1 food spot （FS） that was heated to a constant temperature of 25 ℃, 34 ℃ or 38 ℃ with an ambient temperature of 25 ℃. The influence of previous conspecific activity in the food on larval behavior was also tested. The crops of larvae were dissected to monitor food content in the digestive systems. Based on relative crop measurements, larvae fed at all food temperatures, but temperature strongly affected larval behavior and kinematics. The total time spent by larvae in FS and the duration of each stay decreased at high FS temperature. Previous activity of conspecifics in the food slightly increased the time spent by larvae in FS and also decreased the average distance to FS. Therefore, necrophagous L. sericata larvae likely thermoregulate during normal feeding activities by adjusting to local fluctuations in temperature, particularly inside maggot masses. By maintaining a steady internal body temperature, larvae likely reduce their development time.

Methods for improving thermal tolerance in military personnel prior to deployment

Acute exposure to heat, such as that experienced by people arriving into a hotter or more humid environment, can compromise physical and cognitive performance as well as health. In military contexts heat stress is exacerbated by the combination of protective clothing, carried loads, and unique activity profiles, making them susceptible to heat illnesses. As the operational environment is dynamic and unpredictable, strategies to minimize the effects of heat should be planned and conducted prior to deployment. This review explores how heat acclimation(HA) prior to deployment may attenuate the effects of heat by initiating physiological and behavioural adaptations to more efficiently and effectively protect thermal homeostasis, thereby improving performance and reducing heat illness risk. HA usually requires access to heat chamber facilities and takes weeks to conduct, which can often make it impractical and infeasible, especially if there are other training requirements and expectations. Recent research in athletic populations has produced protocols that are more feasible and accessible by reducing the time taken to induce adaptations, as well as exploring new methods such as passive HA. These protocols use shorter HA periods or minimise additional training requirements respectively, while still invoking key physiological adaptations, such as lowered core temperature, reduced heart rate and increased sweat rate at a given intensity. For deployments of special units at short notice(< 1 day) it might be optimal to use heat re-acclimation to maintain an elevated baseline of heat tolerance for long periods in anticipation of such an event. Methods practical for military groups are yet to be fully understood, therefore further investigation into the effectiveness of HA methods is required to establish the most effective and feasible approach to implement them within military groups.

Comparison of the effects of cold water and ice ingestion on endurance cycling capacity in the heat

Purpose: The purpose of this study was to examine the effects of pre-cooling and fluid replacement with either crushed ice or cold water.Methods: On 2 separate occasions, in a counterbalanced order, 9 recreationally-trained males ingested 1.25 g/kg(80–100 g) of either crushed ice(0.5℃)or cold water(4℃) every 5 min for 30 min before exercise. They also ingested 2.0 g/kg(130–160 g) of the same treatment drink at 15 min, 30 min, and45 min after the commencement of cycling to exhaustion at 60%VO_(2max) until voluntary exhaustion in a hot environment(35℃ and 30% relative humidity).Results: The cycling time to exhaustion in the crushed ice trial(50.0 ± 12.2 min) was longer than the cold water trial(42.2 ± 10.1 min; p = 0.02).Although the rectal temperature fell by 0.37℃± 0.03℃(p = 0.01) at the end of the resting period after the crushed ice ingestion, the rates of rise in rectal temperature during the exercise period were not significantly different between these 2 conditions(crushed ice: 0.23℃± 0.07℃, 5 min;cold water: 0.22℃± 0.07℃, 5 min; p = 0.94).Conclusion: Crushed ice ingestion before and during exercise in a hot environment may be a preferred and effective approach for minimizing thermal strain, and for improving endurance performance as compared with cold water ingestion.

Switchable diurnal radiative cooling by doped VO_(2)

This paper presents design and simulation of a switchable radiative cooler that exploits phase transition in vanadium di-oxide to turn on and off in response to temperature.The cooler consists of an emitter and a solar reflector separated by a spacer.The emitter and the reflector play a role of emitting energy in mid-infrared and blocking incoming solar energy in ultraviolet to near-infrared regime,respectively.Because of the phase transition of doped vanadium dioxide at room tem-perature,the emitter radiates its thermal energy only when the temperature is above the phase transition temperature.The feasibility of cooling is simulated using real outdoor conditions.We confirme that the switchable cooler can keep a desired temperature,despite change in environmental conditions.

Ecology and Behaviour of Burton's Legless Lizard(Lialis burtonis,Pygopodidae) in Tropical Australia

The elongate, functionally limbless flap-footed lizards （family Pygopodidae） are found throughout Australia, ranging into southern New Guinea. Despite their diversity and abundance in most Australian ecosystems, pygopodids have attracted little scientific study. An intensive ecological study of one pygopodid, Burton＇s legless lizard （Lialis burtonis Gray 1835）, was conducted in Australia＇s tropical Northern Territory. L. burtonis eats nothing but other lizards, primarily skinks, and appears to feed relatively infrequently （only 20.8% of stomachs contained prey）. Ovulation and mating occur chiefly in the late dry-season （beginning around September）, and most egg-laying takes place in the early to middle wet-season （November-January）. Females can lay multiple clutches per year, some of which may be fertilised with stored sperm. Free-ranging L. burtonis are sedentary ambush foragers, with radio-tracked lizards moving on average 〈 5 m/day. Most foraging is done diurnally, but lizards may be active at any time of day or night. Radiotracked lizards were usually found in leaf-litter microhabitats, a preference that was also evident in habitat-choice experiments using field enclosures. Lizards typically buried themselves in 6-8 cm of litter; at this depth, they detect potential prey items while staying hidden from predators and prey and avoiding lethally high temperatures.

Heat dissipating upper body compression garment:Thermoregulatory,cardiovascular, and perceptual responses

Purpose:The aim of the present study was to determine the effects of an upper body compression garment(UBCG)on thermoregulatory responses during cycling in a controlled laboratory thermoneutral environment(~23℃).A secondary aim was to determine the cardiovascular and perceptual responses when wearing the garment.Methods:Sixteen untrained participants(age:21.3±5.7 years;peak oxygen consumption(V02 peak):50.88±8.00 mL/min/kg;mean±SD)performed 2 cycling trials in a thermoneutral environment(~23℃)wearing either UBCG or control(Con)garment.Testing consisted of a 5-min rest on a cycle ergometer,followed by 4 bouts of cycling for 14-min at ~50%VO2 peak,with 1-min rest between each bout.At the end of these bouts there was 10-min of passive recovery.During the entire protocol rectal temperature(Trec),skin temperature(Tskin),mean body temperature(Tbody),and heat storage(HS)were measured.Heart rate(HR),VO2,pH,hematocrit(Hct),plasma electrolytes,weight loss(Wloss),and perceptual responses were also measured.Results:There were no significant differences between garments for Tskin,HS,HR,VO2,pH,Hct,plasma electrolyte concentration,Wloss,and perceptual responses during the trial.Trec did not differ between garment conditions during rest,exercise,or recovery although a greater reduction in Trec wearing UBCG(p=0.01)was observed during recovery.Lower Tbody during recovery was found when wearing UBCG(36.82℃±0.30℃ vs.36.99℃±0.24℃).Conclusion:Wearing a UBCG did not benefit thermoregulatory,cardiovascular,and perceptual responses during exercise although it was found to lower Tbody during recovery,which suggests that it could be used as a recovery tool after exercise.

Thermoregulatory function and sexual dimorphism of the throat sack in Helmeted Guineafowl(Numida meleagris)across Africa

The responses of ground-dwelling birds to heat and cold stress encompass a variety of behavioural,physiological and even morphological mechanisms.However,the role of glabrous skin in this respect has been marginally addressed so far.The Helmeted Guineafowl(Numida meleagris)is a landfowl distributed across Sub-Saharan Africa with eight traditionally recognised extant subspecies.Among the most prominent morphological traits underlying intraspecific variability are size and pigmentation of the bare throat skin(or sack),which might be related to the different habitats and environmental conditions across its wide range.In order to explore the Helmeted Guineafowl range-wide sack variation and pigmentation in relation to thermoregulation and sexual signalling,we collected morphometric and environmental information for N.m.coronata integrating field data with the inspection of photographic material encompassing seven subspecies and environmental information from their habitats.Field data evidenced that sack size was significantly correlated with ambient temperature,thus pointing to a likely involvement of the throat sack in thermoregulation.When the pictorial data from all subspecies were pooled,sack size correlated negatively with biomass,rainfall and humidity,while a positive correlation was found with annual solar irradiation.Sack size correlated positively with monthly temperature variation among the bluethroated subspecies from southern Africa as opposed to the black-throated subspecies ranging north to Zambia and Mozambique.Still,in this latter group the sack was often larger during winter months,possibly to maximise solar radiation absorbance.Noteworthy,sack size was related to sex dimorphism in two subspecies.Sack morphology and colour in the Helmeted Guineafowl likely modulate body temperature by evaporative cooling or heating upon needs,but in some subspecies it is also seemingly related to sexual signalling.Additional studies are needed to fully understand the multifunctionality of this important morphological feature in this species.

The allometry of number of feathers in birds changes seasonally

Background: Feathers are a defining feature of birds with multiple functions such as flight, insulation, protection against predation and signaling. Feathers are lost during the annual molt while the rate of such loss at other times of the year and its fitness consequences remain poorly known.Methods: I used information on the number and the mass of feathers for 160 individuals belonging to 85 species of birds in general linear mixed models to analyze allometry of feathers and to investigate possible factors explaining variation in the number of feathers. A phylogenetic effect was assessed by quantifying the random effect of genus.Results: The total mass of feathers increased isometrically with body mass, while the total number of feathers and the mean mass of feathers showed negative allometry. Negative allometry implied that small-sized species had relatively many small feathers. There was a negative association between the number of feathers and migration distance. The total number of feathers initially increased during fall and winter, consistent with individuals growing more feathers later during the year or with individuals with fewer feathers selectively disappearing from the population. In contrast, the number of feathers decreased from winter through spring and summer.Conclusions: These findings suggest that thermoregulation has affected the evolution of the number and the size of feathers, there is selection against feather loss, and that the number of feathers varies across seasons.

The stoichiometric approach in determining total evaporative water loss and the relationship between evaporative and non-evaporative heat loss in two resting bird species: passerine and non-passerine

Background: Evaporation is of significant ecological interest.Evaporation from an animal always results in a decrease in the temperature of the surface from which the evaporation occurs.Therefore,evaporation is a one-way transfer which causes heat loss from the organism.Biological evaporation always involves the loss of water which is a vital resource for nearly all biochemical processes.Evaporation is loss of heat via loss of body mass.Methods: The simultaneous determination of energy expenditure and loss of body mass in resting birds allows us to estimate evaporative heat loss.This method includes direct measurements of the energetic equivalent of the loss of body mass as the ratio between heat production,determined by the rate of oxygen consumption and the loss of body mass at various ambient temperatures.Results: The data indicate that evaporation was minimal at lower critical temperature and that the rate of evaporation increased at lower or higher temperatures.Obtained results indicate that passerine and non-passerine species have the ability to change their non-evaporative heat conductance the same number of times(approximately fourfold),and that their abilities in this respect are similar.Conclusions: The novelty of the study resides in the stoichiometric approach to determination of total evaporative water loss.The analysis shows that determinations by stoichiometric approach of total evaporative water loss yielded the values,which fit into the confidence intervals of all equations from literatures.The basal metabolic rate and nonevaporative thermal conductance are fundamental parameters of energetics and determine the level of physiological organization of an endothermic animal.

Bergmann’s rule and Allen’s rule in two passerine birds in China

Background:Animals that live at higher latitudes/elevations would have a larger body size(Bergmann’s rule)and a smaller appendage size(Allen’s rule)for thermoregulatory reasons.According to the heat conservation hypoth-esis,large body size and small appendage size help animals retain heat in the cold,while small body size and large appendage size help them dissipate heat in the warm.For animals living in seasonal climates,the need for conserving heat in the winter may tradeoff with the need for dissipating heat in the summer.In this study,we tested Bergmann’s rule and Allen’s rule in two widely-distributed passerine birds,the Oriental Magpie(Pica serica)and the Oriental Tit(Parus minor),across geographic and climatic gradients in China.Methods:We measured body size(body mass and wing length)and appendage size(bill length and tarsus length)of 165 Oriental Magpie and 410 Oriental Tit individuals collected from Chinese mainland.We used linear mixed-effect models to assess variation patterns of body size and appendage size along geographic and climatic gradients.Results:Oriental Magpies have a larger appendage size and Oriental Tits have a smaller body size in warmer environ-ments.Appendage size in Oriental Magpies and body size in Oriental Tits of both sexes were more closely related to the climates in winter than in summer.Minimum temperature of coldest month is the most important factor related to bill length and tarsus length of male Oriental Magpies,and wing length of male and female Oriental Tits.Bill length and tarsus length in female Oriental Magpies were related to the annual mean temperature and mean temperature of coldest quarter,respectively.Conclusions:In this study,Oriental Magpies and Oriental Tits followed Allen’s rule and Bergmann’rule respectively.Temperatures in the winter,rather than temperatures in the summer,drove morphological measurements in Oriental Magpies and Oriental Tits in Chinese mainland,demonstrating that the morphological measurements reflect selec-tion for heat conservation rather than for heat dissipation.

An unusual homing behavior found in the Sichuan Partridge during the early brooding period

In this study,we report an unusual homing behavior of the Sichuan Partridge(Arborophila rufipectus)at the Laojunshan National Nature Reserve,Sichuan Province,China.Hen Sichuan Partridges led the chicks back to the nests where they hatched in the evening and roosted there over night.This behavior lasted 6.7±4.3 nights(range=1–15;n=13)after the chicks hatched.At this stage,the hens became very vigilant to predators and human disturbance.If disturbed,they often abandoned the nests immediately and no longer returned thereafter.The ambient temperature at night during the early brooding period of Sichuan Partridge at our study site was^12.4°C.Our findings suggest that hen Sichuan Partridges may make trade-offs between nest predation risks versus the thermoregulatory needs of their young.

Statistical Estimation of Surface Heat Control and Exchange in Endotherms

In this paper, we combine polynomial functions, Generalized Estimating Equations, and bootstrap-based model selection to test for signatures of linear or nonlinear relationships between body surface temperature and ambient temperature in endotherms. Linearity or nonlinearity is associated with the absence or presence of cutaneous vasodilation and vasoconstriction, respectively. We obtained experimental data on body surface temperature variation from a mammalian model organism as a function of ambient temperature using infrared thermal imaging. The statistical framework of model estimation and selection successfully detected linear and nonlinear relationships between body surface temperature and ambient temperature for different body regions of the model organism. These results demonstrate that our statistical approach is instrumental to assess the complexity of thermoregulation in endotherms.

Sweat Rate and Electrolyte Composition in Young Women of Varying Body Mass Indices during Moderate Exercise

Sweat is a hypotonic fluid excreted by sweat glands to cool the body. There are conflicting reports on whether or not body composition has an effect on thermoregulatory responses especially during exercise. This study was aimed at determining and comparing sweat rate and electrolyte composition in underweight (BMI BMI 30 kg/m2) during moderate exercise. Forty women (19 - 25 years) were used during this study after assessing their health status. They were stratified for BMI with each group having a total of ten women. It was ensured that all the women used in the study were euhydrated before commencing the research. Before sweat collection, the treadmill was calibrated according to the Bruce Treadmill Protocol. Sweat samples were obtained with a sweat suction apparatus from a 120 cm2 circular area marked on the skin of the face and neck, after a 15 minute fast walk on a treadmill at an inclination of 15° and at a speed of 4.2 km/h at 27°C room temperature. The time at which sweating commenced in the subjects was recorded. Sweat rate (L/hour) was calculated using the formula: sweat rate (L/hr) = (pre-exercise body weight - Post-exercise body weight)/exercise duration. Each sweat sample was collected and analysed immediately. The results showed that obese women had a significantly (P < 0.05) higher sweat rate and underweight women had a significantly (P < 0.05) lower sweat rate than all the other groups. Furthermore, subjects with a high body surface area showed significantly higher sweat rates compared to subjects with lower body surface area. Sweat electrolyte composition did not change in all BMI groups. In conclusion, obese subjects are more likely to develop fluid imbalances than underweight and normal weight subjects during moderate exercise. Also, underweight women might be at a thermoregulatory disadvantage because of their reduced body fat and body surface area.

Effect of Liquid versus Ice Slurry Ingestion on Core Temperature during Simulated Mining Conditions

Miners in Australia frequently perform physically demanding work under high ambient temperatures and humidity, often whilst wearing personal protective equipment, leading to heat-related illnesses. This study investigated effects of replacing 100% and 50% sweat losses with 5% carbohydrate liquid or ice-slurry solution on core temperature during simulated mining conditions. Five randomized treadmill trials were performed with: no fluid replacement (NF), 100% (100 ICE) and 50% (50 ICE) sweat loss replaced with ice-slurry (~-1°C) solution and 100% (100 LIQ) and 50% (50 LIQ) sweat loss replaced with liquid (~+4°C) solution. Time to exhaustion was longer in 100 ICE followed by 100 LIQ, 50 ICE, 50 LIQ and NF. Change in rectal temperature was least in 100 ICE followed by 100 LIQ, 50 ICE, 50 LIQ and NF. Ingestion of ice-slurry resulted in longer time to exhaustion and slower rates of change in rectal temperature. It is recommended that ice-slurry drinks be provided to personnel to lower heat strain during hot working conditions.