Thermoregulatory Significance Research Articles

Modeling the thermoregulatory significance of differential solar absorptance in American football helmets

Modeling the thermoregulatory significance of differential solar absorptance in American football helmets

Keeping cool with poop: Urohidrosis lowers leg surface temperature by up to 6°C in breeding White storks

AbstractStorks (Ciconiidae) are renowned for defecating on their legs when exposed to high temperatures, a phenomenon known as “urohidrosis.” Previous work suggested that this behavior can cool down the blood supply to the legs and thus prevent hyperthermia in captive storks when overheated. However, no study has quantified the magnitude or duration of its evaporative cooling effect in free‐ranging birds. Here, we combine urohidrosis data with thermal imaging and microclimate data to investigate the thermoregulatory significance of urohidrosis in White storks Ciconia ciconia during the breeding season. We show that urohidrosis can reduce leg surface temperature by up to 6.7°C (4.40 ± 1.04°C). Yet its cooling effect was of short duration (lasting no more than 2.5 min) and decreased with time since defecation. Thus, for urohidrosis to significantly contribute to heat dissipation, storks must perform it repeatedly when overheated. Indeed, an individual can perform up to 11 urohidrosis events per hour; our estimates indicate that repeated urohidrosis could represent a significant amount of heat loss during short time span, equivalent to 4% of daily field metabolic rate for an adult stork. Our results point to an absence of differences in the cooling efficiency of urohidrosis between adults and nestlings, probably because all nestlings were recorded during the last phase of the ontogeny of thermoregulation. Besides, during the hottest days, adult storks delivered water to their nestlings, which might allow them to replenish body water reserves to sustain urohidrosis and other heat dissipation behaviors such as panting or gular fluttering. Our results indicate that urohidrosis might buffer the impact of high temperatures in breeding storks, preventing overheating and lethal hyperthermia. Gaining knowledge about behavioral thermoregulation in the heat is therefore crucial to better predict the future persistence and vulnerability of species under different climate warming scenarios.

Brown adipose tissue thermogenesis among a small sample of reindeer herders from sub-Arctic Finland

IntroductionInterest in human physiological responses to cold stress have seen a resurgence in recent years with a focus on brown adipose tissue (BAT), a mitochondria dense fat specialized for heat production. However, a majority of the work examining BAT has been conducted among temperate climate populations.MethodsTo expand our understanding of BAT thermogenesis in a cold climate population, we measured, using indirect calorimetry and thermal imaging, metabolic rate and body surface temperatures of BAT-positive and BAT-negative regions at room temperature, and mild cold exposure of resting participants from a small sample of reindeer herders (N = 22, 6 females) from sub-Arctic Finland.ResultsWe found that most herders experienced a significant mean 8.7% increase in metabolic rates, preferentially metabolized fatty acids, and maintained relatively warmer body surface temperatures at the supraclavicular region (known BAT location) compared to the sternum, which has no associated BAT. These results indicate that the herders in this sample exhibit active BAT thermogenesis in response to mild cold exposure.ConclusionsThis study adds to the rapidly growing body of work looking at the physiological and thermoregulatory significance of BAT and the important role it may play among cold stressed populations.

Thermoregulatory significance of immobility in the forced swim test

The forced swim test (FST) is a widely used animal model of depression and antidepressant drug screen. Rats are forced to swim on two test days in a restricted space from which there is no escape. On the first test day the rats attempt to escape and then become largely immobile; on the second test day the onset of immobility is more rapid. Immobility is said to reflect a state of lowered mood or “behavioral despair”, but the validity of the FST as a model of depression has been questioned. We show here that whatever psychological states the FST may induce, immobility is water temperature dependent and thermoregulatory. In Experiment 1, separate groups of rats were first tested in water of 15, 20, 22, 25, 30, 35, 37, or 40 °C. When retested at the same temperature, reduced activity was evident only in those groups tested above 20 °C and below 37 °C. On a third test, rats previously tested in 35 °C water failed to show reduced activity in 15 °C water, whereas rats previously tested at 15 °C water did exhibit reduced activity when tested in 35 °C water. Thus, activity was dependent on current water temperature rather than prior experience. In Experiment 2, activity and body temperature were monitored during 30 min swim tests in 27 °C water. The more the animals moved, the greater the loss of body temperature. The results are consistent with a hypothesis that immobility in the FST is an adaptive thermoregulatory response that increases survival by minimizing convective heat loss. This interpretation is also aligned with best practices for survival of humans in water that is below thermoneutral.

Perioperative shivering: physiology and pharmacology.

IN homeothermic species, a thermoregulatory system coordinates defenses against cold and heat to maintain internal body temperature within a narrow range, thus optimizing normal physiologic and metabolic function. The combination of anesthetic-induced thermoregulatory impairment and exposure to a cool environment makes most unwarmed surgical patients hypothermic. Although shivering is but one consequence of perioperative hypothermia, and rarely the most serious, it occurs frequently (i.e., 40–60% after volatile anesthetics), and it remains poorly understood. While coldinduced thermoregulatory shivering remains an obvious etiology, the phenomenon has also been attributed to numerous other causes. Our first goal is to review the organization of the thermoregulatory system, and particularly the physiology of postanesthetic shivering. We then discuss the pharmacology of thermoregulation and review the putative mechanisms and sites of action of various antishivering drugs.

Experimental heating of Macrotermes bellicosus (Isoptera, Macrotermitinae) mounds: what role does microclimate play in influencing mound architecture?

Mounds of the fungus-cultivating termite Macrotermes bellicosus (Smeathman) in the Comoe-National Park (Ivory Coast, West Africa) differ in architecture between habitats. Mounds in the cooler, but thermally more stable gallery forest have been shown to be dome-shaped with thick walls, whereas mounds in the shrub savanna are more complex with many ridges and thin walls. In this investigation, we performed heating experiments to determine the thermal properties of the mounds in both habitats in order to test the hypothesis of a thermoregulatory significance of mound architecture. These experiments revealed that each mound had its characteristic individual heating up behavior that depends on its dimensions (height, surface, volume). In addition, habitat-specific traits were demonstrated: mounds of the gallery forest had higher thermal inertia, measured by the thermal capacity, than mounds of the shrub savanna. Thus, the dome-shaped mounds with thick walls in the gallery forest, with its suboptimal low temperatures, reduce loss of heat to the environment.

Basking Is Not of Thermoregulatory Significance in the "Basking" Freshwater Turtle Emydura signata

We measured body temperatures of free-ranging Brisbane River Turtles, Emydura signata with radiotelemetry. These and other species of freshwater turtle are commonly observed on logs or other elevated sites, a behavior which is usually interpreted as thermoregulatory. However, body temperatures of eight E. signata monitored for more than 112 turtle days in winter, spring, and summer showed a striking thermoconformity with the water and provided no data showing that this species routinely elevates its body temperature above water temperature. The biological significance of basking is obscure in this population of E. signata, and the study highlights the need for direct measurements of body temperature in freeranging individuals of other freshwater turtle species.

Is nest building an important component of thermoregulatory behaviour in the pouched mouse ( Saccostomus campestris)?

The thermoregulatory significance of nest building in Saccostomus campestris was investigated by examining the effect of temperature and photoperiod on the size and thermal conductance of nests built within artificial burrows by pouched mice from four localities in southern Africa that experience contrasting thermal conditions. There was no correlation between the amount of nesting material used and the thermal conductance of nests, which indicates that nest size was not a reliable measure of nest quality. For this reason, the significant interactive effect of sex and locality on the quantity of nesting material used, and the significantly larger nests built by wild-caught animals, appear to be unrelated to differences in nesting ability, particularly as there were no similar differences in the thermal conductance of nests between these groups. Several animals blocked the entrance to their artificial burrows and caused a significant reduction in the rate of heat loss from nests therein. However, heat conservation may not have been the primary function of plugging burrow entrances because this did not occur more frequently at lower temperatures and was not more common among animals from cooler localities. Instead, aminals that sealed the entrance to their burrows were found to hoard significantly more food than animals that left the entrance open, which suggests that burrows may have been blocked to prevent the potential theft of stored food. Despite substantial variability in both the size and thermal conductance of nests built throughout the present study, there was no significant effect of temperature, photoperiod, or locality on these characteristics. It therefore appears that nesting ability is not an important component of thermoregulatory behaviour in the pouched mouse, possibly because this species experiences limited selection for nesting behaviour under the stable thermal conditions prevailing within its burrows.

Thermoregulatory abilities in chicks of the Antarctic Petrel (Thalassoica antarctica)

We studied the thermoregulatory capacity of Antarctic Petrel chicks, Thalassoica antarctica, breeding in a large colony in Queen Maud Land (71°53′S,5°10′E) on the Antarctic continent. Compared to newly hatched chicks of other birds, those of the Antarctic Petrel are characterized by a relatively high standard metabolic rate (SMR) and thermal conductance. Their metabolic scope is limited, however, being only 1.6 times the SMR, and they consequently depend on parental brooding to maintain Tb. At an age of 11 days the chicks become thermally independent and are left alone in the nest. The chicks keep a relatively high body temperature (>36°C) throughout their early development and we found no indication that they normally experience hypothermia. A significant positive relationship between latitude of breeding and SMR of the hatchlings is shown to exist for procellariiform birds. It is suggested that the high SMR found in Antarctic Petrel hatchlings could be a prerequisite for achieving a high growth rate, rather than being of any thermoregulatory significance.

Temporal Patterns of Basking Behaviour in a Mediterranean Lacertid Lizard

Abstract1. I studied the thermoregulatory behaviour of the diurnal basker Psammodromus algirus (Reptilia, Lacertidae) in the mosaic of sunshade patches of a Mediterranean evergreen forest. 48 behavioural sequences associated with measurements of the thermal environment provided data on the percentages of time spent basking by focal animals, the duration of individual basking periods and the frequency of basking. 2. The percentage of time basking decreased linearly from the onset of the activity period until midday. The average duration of basking periods had a pronounced decrease after 0700 h and remained constant throughout the rest of the morning, whereas the basking rates, that were minimal before 0700 h, reached a peak between 0700 and 0800 h followed by a progressive fall that continued until noon. 3. In order to explain these behavioural patterns, I experimentally determined the effects of environmental variables (air and ground temperature and solar angle) on the heating and cooling rates of captive lizards. The resulting regression models were then used to predict the heat exchange rates of the observed free-ranging animals. 4. The moment at which heating rates should equal and then exceed cooling rates, appeared to set off the behavioural shift towards a larger frequency of shorter basking periods. Under these circumstances, the apparently random movement of a shuttling heliotherm with respect to sun and shade might still be of thermoregulatory significance.

A comparison of operative temperature estimated by taxidermic mounts and meteorological data

1. 1.Operative temperatures ( T e) calculated using meteorological data and measured directly from taxidermic mounts are compared for Brewer's Blackbirds ( Euphagus cyanocephalus) and Blue-black Grassquits ( Volatinia jacarina). 2. 2.High correlation coefficients (>0.9 for both species) indicate that taxidermic mount temperatures are comparable to calculated values. Mount T e differed from calculated T e by an average of 0.16°C for blackbirds and 1.20°C for grassquits. The 95% confidence interval for predicted mount T e at the mean calculated T e (=22.66°C for blackbirds and 21.94°C for grassquits) was 0.26 and 0.17°C, respectively. Mount temperatures were sometimes as much as 5°C from the best fit regression line. These errors are similar to those reported for the used of simple sphere thermometers instead of mounts. 3. 3. T e is calculated using four different equations: quartic, second order Taylor approximation, linear and iterative. Differences from the quartic values are smallest with iteration and greatest with the linear values. 4. 4.Partial derivatives for six factors of the T e equation are calculated as a sensitivity analysis. The values show the effects a change in each factor has on the final T e calculation and are used to estimate a standard deviation. 5. 5.Sensitivity analysis may also be used to predict adjustment of T e under field conditions or to assess the thermoregulatory significance of behaviour.

Geographic variation in wing melanism of the butterfly Parnassius phoebus F. (Lepidoptera: Papilionidae)

Butterflies from higher elevations and latitudes are often darker than populations from low elevations and latitudes. This "alpine melanism" may be an adaptation to colder environments and may be correlated with smaller size. I quantified geographic patterns of variation in wing melanism and size for the butterfly Parnassius phoebus to determine if individuals from populations living at higher elevations and latitudes are smaller and more melanic. The ratio of black to white scales in the basal area of the hind wings is well correlated with the elevation, latitude, and mean air temperature of a population. This suggests that variation in that component of wing melanism is the result of adaptation to different thermal environments. The width of the predominantly black patch in the basal area of the hind wings of males is correlated with elevation, latitude, and air temperature, suggesting that variation in this character may also have a thermoregulatory significance. In the distal area of the front wings, wing transparency and the extent of black scaling are correlated with elevation on individual mountains, but are not correlated with elevation when populations from many mountains are considered together. Other environmental factors correlated with elevation, such as predation, may be more important than thermal effects in determining variation in melanism of the distal area of the wings of P. phoebus. The positive correlation between size and mean air temperature during the flight period is significantly weaker than the negative correlation between size and elevation, suggesting that thermoregulatory considerations can not account for variation in size between populations.

Thermoregulatory significance of wing melanization in Pieris butterflies (Lepidoptera: Pieridae): physics, posture, and pattern.

Pieris butterflies use a novel behavioral posture for thermoregulation called reflectance basking, in which the wings are used as solar reflectors to reflect radiation to the body. As a means of exploring the thermoregulatory significance of wing melanization patterns, I examine the relation of basking posture and wing color pattern to body temperature. A mathematical model of the reflectance process predicts certain combinations of dorsal wing melanization pattern and basking posture that maximize body temperature. Laboratory experiments and field observations show that this model correctly predicts qualitative differences in the relation of body temperature to basking posture based on differences in the extent of dorsal melanization on the wing margins, both between species and between sexes within species of Pieris. This is the first demonstration in insects that coloration of the entire wing surface can affect thermoregulation. Model and experimental results suggest that, in certain wing regions, increased melanization can reduce body temperature in Pieris; this effect of melanization is exactly the opposite of that found in other Pierid butterflies that use their wings as solar absorbers. These results are discussed in terms of the evolution of wing melanization pattern and thermoregulatory behavior in butterflies.

The Evolution of Egg Clustering by Butterflies and Other Insects

On met en evidence le fait que la ponte en grappes chez de nombreux lepidopteres (et d'autres insectes) a evolue en reponse a la selection pour une fecondite accrue

The effects of cold exposure on blood-flow distribution in sheep

1. 1.|The effects of acute (12 h) and chronic (10–12 week) cold exposure (3°C) on the distribution of cardiac output and blood flow in adult sheep were measured using radioactive microspheres. 2. 2.|Increased blood flow was observed in the nonrespiratory skeletal muscles and thyroids of both acute and chronic cold-exposed sheep, whereas, a simultaneous reduction in relative blood flow was observed in reticulorumen, diaphgragm and lower-limb hoof and bone tissue. There as no significant treatment difference in blood flow to the heart, kidney or fat tissues. 3. 3.|Compared to acute cold, the chronic cold animals demonstrated an increased blood flow to the nonrespiratory skeletal muscles. Based on these findings, it is suggested that skeletal muscle may be of thermoregulatory significance to cold-adapted sheep.

Non-Random Orientation of Gila Woodpecker Nest Entrances in Saguaro Cacti

1976. An evaluation of heat exchange in small birds. J. Comp. Physiol. 105:153-166. WALSBERG, G. E., AND J. R. KING. 1978a. The heat budget of incubating Mountain White-crowned Sparrows (Zonotrichia leucophrys oriantha) in Oregon. Physiol. Zool. 51:92-103. WALSBERG, G. E., AND J. R. KING. 1978b. The energetic consequences of incubation for two passerine species. Auk 95:644-655. WALSBERG, G. E., AND J. R. KING. 1980. The thermoregulatory significance of the winter roost-sites selected by robins in eastern Washington. Wilson Bull. 92:33-39.

Thermoregulatory Significance of Thoracic Lobes in the Evolution of Insect Wings

The evolution of broadly attached thoracic lobes could have increased the body temperature excess of ancient wingless insects by 55 percent over that of lobeless forms. The subsequent expansion of these thoracic lobes for behavioral thermoregulation could have provided the morphological stage required for the evolution of functional wings.

A two-dimensional operative-temperature model for thermal energy management by animals

1. 1.|The directional nature of sum and wind produces two-dimensional variations in the thermal load on the surface of an animal. 2. 2.|Corresponding distributions of colour and insulation are seen on many animals. 3. 3.|An operative-temperature-based heat-transfer model is presented for analyzing the thermoregulatory significance of such patterns. 4. 4.|A test calculation shows that coordinated patterns of thermal load and surface properties have significant thermoregulatory effects not correctly predicted by one-dimensional models. 5. 5.|Standard isothermal laboratory enclosures may not accurately assess these thermoregulatory effects, especially for combinations of strong wind and solar radiation.

QUANTITATIVE GENETIC ANALYSIS OF TEMPERATURE REGULATION IN MUS MUSCULUS. I. PARTITIONING OF VARIANCE

Heritabilities (from parent-offspring regression) and intraclass correlations of full sibs for a variety of traits were estimated from 225 litters of a heterogeneous stock (HS/Ibg) of laboratory mice. Initial variance partitioning suggested different adaptive functions for physiological, morphological and behavioral adjustments with respect to their thermoregulatory significance. Metabolic heat-production mechanisms appear to have reached their genetic limits, with little additive genetic variance remaining. This study provided no genetic evidence that body size has a close directional association with fitness in cold environments, since heritability estimates for weight gain and adult weight were similar and high, whether or not the animals were exposed to cold. Behavioral heat conservation mechanisms also displayed considerable amounts of genetic variability. However, due to strong evidence from numerous other studies that behavior serves an important adaptive role for temperature regulation in small mammals, we suggest that fluctuating selection pressures may have acted to maintain heritable variation in these traits.

Thermal biology of the common garter snake Thamnophis sirtalis (L.) : II. The effects of melanism.

The thermoregulatory significance of a striped-melanic colour polymorphism in the common garter snake, Thamnophis sirtalis, was assessed through a combination of labortory experimentation and field study. In experiments with living snakes the melanic morph maintained a higher body temperature than the striped morph, when exposed to natural insolation. Experiments with excised skin showed that this thermal advantage is attributable to some integumental difference between the two morphs. Body temperatures of snakes in the field revealed that, during the colder part of the active season, melanics were able to stay warmer than striped snakes by an amount (1.24 C°) approximating the difference observed in the laboratory. Some evidence and argument is presented to suggest that melanism also may confer protection against overheating in warm periods.