Stable Body Temperature Research Articles

Nestling Growth is Impaired by Heat Stress: an Experimental Study in a Mediterranean Great Tit Population.

Samuel Rodríguez and Emilio Barba (2016) During the nestling stage, nestlings of small altricial birds face energetic limitations due to their rapid development and the need to maintain a stable body temperature once homeothermy is achieved. In Mediterranean habitats, high air temperatures reached during the breeding season could negatively affect the health and condition of the nestlings. The aim of this study was to determine the effect of an experimental increase of nest temperatures during the nestling stage on the growth and survival of Great Tit (Parus major) nestlings. Additionally, changes in parental brooding and feeding behavior as a result of the alteration of the nest microclimate were addressed. Increased nest temperatures affected nestling mass, as heated nestlings were lighter than controls on day 15 in the warmer of the two breeding seasons considered. Moreover, females from the heating treatment reduced their brooding time. Fledging success and parental feeding rates were not altered by the experimental treatment. The results of this study suggest that high nest temperatures may impair nestling development and therefore affect post-fledging survival probability. Negative effects are more likely to occur in warm habitats and/or warmer years, where juveniles are liable to suffer from thermal stress.

Thermal conditions experienced during differentiation affect metabolic and contractile phenotypes of mouse myotubes.

Central pathways regulate metabolic responses to cold in endotherms to maintain relatively stable internal core body temperatures. However, peripheral muscles routinely experience temperatures lower than core body temperature, so that it would be advantageous for peripheral tissues to respond to temperature changes independently from core body temperature regulation. Early developmental conditions can influence offspring phenotypes, and here we tested whether developing muscle can compensate locally for the effects of cold exposure independently from central regulation. Muscle myotubes originate from undifferentiated myoblasts that are laid down during embryogenesis. We show that in a murine myoblast cell line (C2C12), cold exposure (32°C) increased myoblast metabolic flux compared with 37°C control conditions. Importantly, myotubes that differentiated at 32°C compensated for the thermodynamic effects of low temperature by increasing metabolic rates, ATP production, and glycolytic flux. Myotube responses were also modulated by the temperatures experienced by "parent" myoblasts. Myotubes that differentiated under cold exposure increased activity of the AMP-stimulated protein kinase (AMPK), which may mediate metabolic changes in response cold exposure. Moreover, cold exposure shifted myosin heavy chains from slow to fast, presumably to overcome slower contractile speeds resulting from low temperatures. Adjusting thermal sensitivities locally in peripheral tissues complements central thermoregulation and permits animals to maintain function in cold environments. Muscle also plays a major metabolic role in adults, so that developmental responses to cold are likely to influence energy expenditure later in life.

Thermal constraints and the influence of reproduction on thermoregulation in a high‐altitude gecko (Quedenfeldtia trachyblepharus)

AbstractTemperature plays a crucial role for ectotherm performance and thus for fitness. Terrestrial ectotherms, including reptiles, regulate their body temperature mainly by behavioural means. At high altitude, however, thermal constraints make precise thermoregulation costly. The cost–benefit model of lizard thermoregulation predicts that thermally challenging environments should favour the evolution of thermoconformity. Yet, several species maintain high and stable body temperatures even in cool environments. We studied the Atlas Day Gecko, Quedenfeldtia trachyblepharus, a cold‐adapted lizard endemic to the High Atlas Mountains of Morocco. We quantified thermoregulation in gravid females, non‐gravid adult females, and adult males during the active season. Geckos thermoregulated during their active season, and thermoregulated with more effectiveness early in the season than late in the season. In the laboratory, the preferred body temperature ranges of gravid females, non‐gravid females, and males were not significantly different. In the field, however, gravid females had smaller deviations from the preferred body temperature and maintained higher body temperatures than males and non‐gravid females. Our study suggests that cold‐adapted reptiles adjust their thermoregulatory behaviour in response to thermal constraints and reproductive status.

Role of thermo TRPA1 and TRPV1 channels in heat, cold, and mechanical nociception of rats.

A sensitive response of the nervous system to changes in temperature is of predominant importance for homeotherms to maintain a stable body temperature. A number of temperature-sensitive transient receptor potential (TRP) ion channels have been studied as nociceptors that respond to extreme temperatures and harmful chemicals. Recent findings in the field of pain have established a family of six thermo-TRP channels (TRPA1, TRPM8, TRPV1, TRPV2, TRPV3, and TRPV4) that exhibit sensitivity to increases or decreases in temperature, as well as to chemical substances eliciting the respective hot or cold sensations. In this study, we used behavioral methods to investigate whether mustard oil (allyl isothiocyanate) and capsaicin affect the sensitivity to heat, innocuous and noxious cold, and mechanical stimuli in male rats. The results obtained indicate that TRPA1 and TRPV1 channels are clearly involved in pain reactions, and the TRPA1 agonist allyl isothiocyanate enhances the heat pain sensitivity, possibly by indirectly modulating TRPV1 channels coexpressed in nociceptors with TRPA1. Overall, our data support the role of thermosensitive TRPA1 and TRPV1 channels in pain modulation and show that these two thermoreceptor channels are in a synergistic and/or conditional relationship with noxious heat and cold cutaneous stimulation.

What drove the evolution of endothermy?

![Figure][1] Michael Hedrick and Stanley Hillman discuss the impact of Albert Bennett and John Ruben's classic paper ‘Endothermy and activity in vertebrates’, published in Science in 1979. The metabolic production of heat and high, stable body temperatures characteristic of birds

The development of a non-invasive behavioral model of thermal heat stress in laboratory mice (Mus musculus)

BackgroundMany behavioral and physiological studies of laboratory mice employ invasive methods such as radio telemetry to measure key aspects of behavior and physiology. Radio telemetry requires surgical implants, which may impact mouse health and behavior, and thus reduce the reliability of the data collected. New methodWe developed a method to measure key aspects of thermoregulatory behavior without compromising animal welfare. We examined the thermoregulatory response to heat stress in a custom-built arena that permitted the use of simultaneous and continuous infrared thermography (IRT) and video capture. This allowed us to measure changes in surface body temperature and determine total distance traveled using EthoVision XT animal tracking software. ResultsLocomotor activity and surface body temperature differed between heat-stressed mice and mice kept within their thermal comfort zone. The former had an increase in surface body temperature and a decline in locomotor activity, whereas the latter had a stable surface body temperature and showed greater activity levels. MethodsSurface body temperature and locomotor activity are conventionally quantified by measurements taken at regular intervals, which limit the use and accuracy of the data. We obtained data of high resolution (i.e., recorded continuously) and accuracy that allowed for the examination of key physiological measurements such as energy expenditure and peripheral vasomotor tone. ConclusionsThis novel experimental method for studying thermoregulatory behavior in mice using non-invasive tools has advantages over radio-telemetry and represents an improvement in laboratory animal welfare.

Going torpid to pass through hard times

![Graphic][1] Endothermy, the maintenance of a high and relatively stable body temperature via internal heat production, comes at a high energetic price, so some mammals use torpor – a controlled decrease in metabolic rate and body temperature – to decrease metabolic costs during

Muscle satellite cells increase during hibernation in ground squirrels.

Skeletal muscle satellite cells (SCs) are involved in muscle growth and repair. However, clarification of their behavior in hibernating mammals is lacking. The aim of this study was to quantify SCs and total myonuclei in hibernator muscle during different phases of the torpor-arousal cycle. Skeletal muscle was collected from thirteen-lined ground squirrels, Ictidomys tridecemlineatus, at five timepoints during hibernation: control euthermic [CON, stable body temperature (Tb)], early torpor (ET, within 24h), late torpor (LT, 5+ consecutive days), early arousal (EA, increased respiratory rate >60 breaths/min, Tb 9-12°C) and interbout arousal (IA, euthermic Tb). Protein levels of p21, Myf5, Wnt4, and β-catenin were determined by western blotting. SCs (Pax7(+)) and myonuclei were identified using immunohistochemistry. Over the torpor-arousal cycle, myonuclei/fiber remained unchanged. However, the percentage of SCs increased significantly during ET (7.35±1.04% vs. 4.18±0.58%; p<0.05) and returned to control levels during LT. This coincided with a 224% increase in p21 protein during ET. Protein levels of Wnt4 did not change throughout, whereas Myf5 was lower during EA (p<0.08) and IA (p<0.05). Compared to torpor, β-catenin increased by 247% and 279% during EA and IA, respectively (p<0.05). In conclusion, SCs were not dormant during hibernation and increased numbers of SC during ET corresponded with elevated amounts of p21 suggesting that cell cycle control may explain the SC return to baseline levels during late torpor. Despite relatively low Tb during early arousal, active control of quiescence by Myf5 is reduced.

Brain temperature and its fundamental properties: a review for clinical neuroscientists.

Brain temperature, as an independent therapeutic target variable, has received increasingly intense clinical attention. To date, brain hypothermia represents the most potent neuroprotectant in laboratory studies. Although the impact of brain temperature is prevalent in a number of common human diseases including: head trauma, stroke, multiple sclerosis, epilepsy, mood disorders, headaches, and neurodegenerative disorders, it is evident and well recognized that the therapeutic application of induced hypothermia is limited to a few highly selected clinical conditions such as cardiac arrest and hypoxic ischemic neonatal encephalopathy. Efforts to understand the fundamental aspects of brain temperature regulation are therefore critical for the development of safe, effective, and pragmatic clinical treatments for patients with brain injuries. Although centrally-mediated mechanisms to maintain a stable body temperature are relatively well established, very little is clinically known about brain temperature's spatial and temporal distribution, its physiological and pathological fluctuations, and the mechanism underlying brain thermal homeostasis. The human brain, a metabolically “expensive” organ with intense heat production, is sensitive to fluctuations in temperature with regards to its functional activity and energy efficiency. In this review, we discuss several critical aspects concerning the fundamental properties of brain temperature from a clinical perspective.

Low field metabolic rates for geckos of the genus Rhoptropus may not be surprising

Geckos of the genus Rhoptropus are small diurnal lizards occurring in arid regions of Namibia and Angola, and are not well studied relative to other desert lizards. Rhoptropus afer has a field metabolic rate significantly lower than that of other desert lizards, but comparable studies have not been carried out in any other Rhoptropus species. We examined the field metabolic rate, water turnover, foraging behavior, and thermal biology of Bradfield's Namib day gecko, Rhoptropus bradfieldi, in the Namib Desert. This species occupies rocky habitats and feeds on arthropods via a sit-and-wait strategy. We found that it has a field metabolic rate (140 J d−1) that is 26% that of a typical desert lizard of the same size (540 J d−1). We also found that R. bradfieldi had a relatively high water influx rate (0.07 ml d−1) for its low rate of energy turnover, and suggest that a significant proportion of this water was sourced from fog. Active body temperatures varied between summer (32.7 ± 2.4 °C) and autumn (34.4 ± 2.5 °C), but in both seasons R. bradfieldi maintained high and stable body temperatures while active. Our study supports the idea that a minimal energy requirement could be widespread within Rhoptropus geckos.

Neo-Naturphilosophie: A Review of Michael Ruse's Gaia: Science on a Pagan Planet

Neo-<i>Naturphilosophie</i>: A Review of Michael Ruse's <i>Gaia: Science on a Pagan Planet</i>

Social and Environmental Influences on Daily Activity Pattern in Free-Living Subterranean Rodents: The Case of a Eusocial Bathyergid.

Predictable daily activity patterns have been detected repeatedly even in mammals living in stable environments, as is the case for subterranean rodents. Whereas studies on activity of these rodents under laboratory conditions almost exclusively have concerned themselves with the influence of light, many field studies have revealed signs of an association between the activity pattern and daily fluctuations of temperature under the ground. This would assume that behavioral thermoregulation is probably involved. The only exceptions to the relationship between temperature and activity are 2 eusocial mole-rats of the genus Fukomys (Bathyergidae, Rodentia), which indicates that activity patterns could be affected also by social cues. To better understand how social and environmental factors influence the activity pattern in a eusocial mole-rat, we monitored the outside-nest activity in another species of this genus, the Ansell's mole-rat (Fukomys anselli), which has a relatively small body mass, high conductance, and more superficially situated burrows. Its daily activity had 1 prominent peak (around 1400 h), and it was tightly correlated with the temperature measured at depth of foraging burrows. Since F. anselli has high thermoregulatory requirements to maintain stable body temperature below the lower critical temperature, we conclude that the observed pattern is probably the result of minimizing the cost of thermoregulation. There were no significant differences in the daily activity patterns of breeding males and females and nonbreeders. Members of the same family group tended to have more similar activity patterns, but consistent activity synchronization between individuals was not proven. From the comparison of available data on all subterranean rodents, we assume that social cues in communally nesting mole-rats may disrupt (mask) temperature-related daily activity rhythms but probably only if the additional cost of thermoregulation is not too high, as it likely is in the Ansell's mole-rat.

The importance of temporal heterothermy in bats

AbstractAnimals must balance their energy budgets even when confronted with periodic food shortages and/or adverse environmental conditions. Especially, small endothermic animals require large amounts of energy to maintain high and stable body temperatures (Tb) via endogenous heat production. To deal with energetic challenges, many small endotherms are heterothermic, abandon regulation of highTband enter a state of torpor resulting in large energy savings. Torpor is used by many bat species because they are small, have high rates of heat loss and rely on fluctuating food resources (e.g. insects, fruit, nectar). Many bats use torpor all year, but the expression of temporal heterothermy can be strongly seasonal especially for temperate and subtropical species, which may hibernate for long periods. Recent advances in our understanding of torpor expression in bats have been made using temperature telemetry for remote data collection ofTbin free‐ranging wild individuals from all climate zones. This new knowledge on free‐ranging bats has revealed the importance of torpor expression not only for energy conservation but also for other benefits, such as reduction of extrinsic mortality (e.g. predation). On the contrary, dense clustering during hibernation, important for minimizing energy and water loss, may also expose bats to infectious disease. An emerging, cold‐tolerant fungal pathogen of bats causes a new disease called white‐nose syndrome (WNS), which is devastating populations of multiple species in easternNorthAmerica. Given the importance of temporal heterothermy to their biology, and links between torpor expression and mortality fromWNS, it is becoming increasingly important to understand the ecology and physiology of torpor in this largely understudied and cryptic mammalian group. Here, we review past and current literature to summarize the importance and evolution of heterothermy in bats.

Increased homeothermy during reproduction in a basal placental mammal

Homeothermic endothermy, the maintenance of a high and stable body temperature (Tb) using heat produced by elevated metabolism, is energetically expensive. There is increasing evidence that the earliest endotherms were heterotherms that, rather than maintaining strict homeothermy, allowed Tb to fluctuate with large variations between active and rest-phase Tb. The high level of homeothermy observed in modern mammals is therefore likely to have evolved from an ancestral heterothermic state. One of the hypotheses for the evolution of endothermy is that homeothermy allows for greater energetic output during reproduction (parental care model). We tested this hypothesis by measuring metabolic rates over a range of ambient temperatures in both reproductive and non-reproductive greater hedgehog tenrecs (Setifer setosus), a physiologically primitive mammal from Madagascar. Tenrecs have some of the lowest metabolic rates and highest levels of Tb variability of any mammal and are therefore good models of the ancestral eutherian state. During pregnancy and lactation, there was an increase in metabolism and Tb below the thermoneutral zone, accompanied by a decrease in Tb variability. The lower critical limit of the thermoneutral zone was estimated at ~25°C. However, whereas increases in resting metabolism were substantial below 20°C (up to 150% higher during reproduction), daytime rest-phase ambient temperatures at the study site rarely reached equivalent low levels. Thus, S. setosus provide an example for how relatively low-cost increases in homeothermy could have led to substantial increases in fitness by allowing for the faster production of young. The mechanisms necessary for increases in thermogenesis during reproduction would have further benefited the development of homeothermy in mammals.

High versus free humidity incubators: a double blind randomized clinical trial

Recent reports found no difference in embryo quality and pregnancy rate when comparing humidity free incubators against full humidity incubators. Nevertheless, high humidity is maintained in vivo due to the fluid content and stable body temperature at 37 degrees. We hypothesized that full humidity incubators may have better ongoing pregnancy rate over the free humidity incubators.

Dinosaur Energetics: Setting the Bounds on Feasible Physiologies and Ecologies

The metabolic status of dinosaurs has long been debated but remains unresolved as no consistent picture has emerged from a range of anatomical and isotopic evidence. Quantitative analysis of dinosaur energetics, based on general principles applicable to all vertebrates, shows that many features of dinosaur lifestyle are compatible with a physiology similar to that of extant lizards, scaled up to dinosaur body masses and temperatures. The analysis suggests that sufficient metabolic scope would have been available to support observed dinosaur growth rates and allow considerable locomotor activity, perhaps even migration. Since at least one dinosaur lineage evolved true endothermy, this study emphasizes there was no single dinosaur physiology. Many small theropods were insulated with feathers and appear to have been partial or full endotherms. Uninsulated small taxa, and all juveniles, presumably would have been ectothermic, with consequent diurnal and seasonal variations in body temperature. In larger taxa, inertial homeothermy would have resulted in warm and stable body temperatures but with a basal metabolism significantly below that of extant mammals or birds of the same size. It would appear that dinosaurs exhibited a range of metabolic levels to match the broad spectrum of ecological niches they occupied.

Maximal Aerobic and Anaerobic Power Generation in Large Crocodiles versus Mammals: Implications for Dinosaur Gigantothermy

Inertial homeothermy, the maintenance of a relatively constant body temperature that occurs simply because of large size, is often applied to large dinosaurs. Moreover, biophysical modelling and actual measurements show that large crocodiles can behaviourally achieve body temperatures above 30°C. Therefore it is possible that some dinosaurs could achieve high and stable body temperatures without the high energy cost of typical endotherms. However it is not known whether an ectothermic dinosaur could produce the equivalent amount of muscular power as an endothermic one. To address this question, this study analyses maximal power output from measured aerobic and anaerobic metabolism in burst exercising estuarine crocodiles, Crocodylusporosus , weighing up to 200 kg. These results are compared with similar data from endothermic mammals. A 1 kg crocodile at 30°C produces about 16 watts from aerobic and anaerobic energy sources during the first 10% of exhaustive activity, which is 57% of that expected for a similarly sized mammal. A 200 kg crocodile produces about 400 watts, or only 14% of that for a mammal. Phosphocreatine is a minor energy source, used only in the first seconds of exercise and of similar concentrations in reptiles and mammals. Ectothermic crocodiles lack not only the absolute power for exercise, but also the endurance, that are evident in endothermic mammals. Despite the ability to achieve high and fairly constant body temperatures, therefore, large, ectothermic, crocodile-like dinosaurs would have been competitively inferior to endothermic, mammal-like dinosaurs with high aerobic power. Endothermy in dinosaurs is likely to explain their dominance over mammals in terrestrial ecosystems throughout the Mesozoic.

Pregnancy during hibernation in Japanese black bears: effects on body temperature and blood biochemical profiles

Abstract Bears from the family Ursidae are the only terrestrial mammals that go through gestation, parturition, and lactation during hibernation. This is the 1st study to examine the influence of reproductive status (i.e., nonpregnant, pseudopregnant, or pregnant) on body temperature and blood biochemical profiles in hibernating black bears. Pregnant bears appeared to have higher and more stable body temperatures (37–38°C) than nonpregnant ones (34–36°C) during pregnancy, which was followed by a rapid drop to levels comparable to those of nonpregnant individuals after parturition. In midpregnancy (i.e., January), pregnant bears had higher blood glucose and lower triglyceride concentrations than did nonpregnant ones, whereas blood concentrations of free fatty acids, glycerol, and ketone bodies did not differ significantly. Plasma urea, creatinine, and urea/creatinine levels were significantly lower in pregnant bears than in nonpregnant ones. Pseudopregnant bears showed similar changes in body temperature a...

Burrow‐dwelling ecosystem engineers provide thermal refugia throughout the landscape

AbstractEcosystem engineers play fundamental ecological roles by modifying habitats in ways that affect a multitude of other species and by creating refugia with novel microclimates. We hypothesize that burrow‐creating organisms may facilitate climate change adaptation by providing refugia from extreme and fluctuating temperatures found aboveground. We support this hypothesis by showing that large burrow‐dwelling tortoises, Gopherus polyphemus, likely depend upon burrows for thermoregulation. By exploiting the varied thermal conditions within burrows, tortoises avoided lethal temperatures and extreme fluctuations in body temperature, maintained moderate and stable body temperatures on hot days, and maintained relatively warm temperatures overnight. Climate change is predicted to increase maximum air temperatures throughout the geographic range of this species, with impacts most severe in Florida, US, where the range of future conditions could be above that of current maxima. This implies that environmental temperatures will be above lethal thermal limits more often, highlighting the importance of refugia from extreme conditions. Large burrowing animals (e.g. aardvarks, pocket gophers, rabbits, seabirds, tortoises, wombats) are widely distributed globally and could provide similar thermal refugia for countless commensal taxa. Burrows and the animals that create them are in urgent need of conservation, which will help ensure the widespread availability of refugia that offer protection from extreme temperatures under climate change.

A 1950s CLASSIC OF THERMAL ADAPTATION TO COLD

> George Somero discusses Scholander et al.'s classic paper ‘Adaptation to cold in Arctic and tropical mammals and birds in relation to body temperature, insulation and basal metabolic rate’, published in The Biological Bulletin in 1950. It is unusual to re-visit a paper a half-century after