Les espèces endothermes amphibies font face à de fortes contraintes durant leurs séjours en mer dont l’augmentation des coûts de thermorégulation. La recherche alimentaire du manchot royal (Aptenodytes patagonicus) s’étend sur plusieurs jours alternant des plongées profondes de chasse et des périodes de repos à la surface de l’eau correspondant à deux stratégies de thermorégulation différentes. Durant les plongées, l’hypothermie des tissus suggère une économie d’énergie visant à augmenter la durée d’apnée. Cependant, l’utilité de la réaugmentation des températures corporelles durant les périodes de repos reste méconnue. Alors que la digestion débute durant les plongées, nous supposons que le stockage des acides gras dans les tissus adipeux périphériques ne peut se faire que par le retour à normothermie de ces tissus. Nous avons testé cette hypothèse en maintenant des individus équipés d’enregistreurs de températures (périphériques et interne) dans une piscine d’eau de mer afin d’étudier les variations de températures en fonction de l’état nutritionnel des manchots. De plus, nous avons mesuré, par respirométrie, les dépenses énergétiques en fonction des températures corporelles. Enfin, nous avons étudié les variations de flux sanguins à l’aide de thermographie infra-rouge afin de comprendre le retour à normothermie des tissus périphériques et les coûts énergétiques associés. / The energetic cost of foraging activities in King Penguin (Aptenodytes patagonicus) consists to reach favourable areas, realizes depth diving to attempt fish patch and resting in high latitude cold water. Several studies have shown that resting in cold water could be represent a more expensive cost than realized depth diving. Indeed, this paradox is probably linked with contrasting thermoregulation processes. During daylight, a general hypothermia occurs and is believed to reduce energy expenditure. At sunrise occurs a re-warming to normothermia, contributing to increase heat-loss during the night. We hypothesise an energetic conflict between thermoregulation and digestive processes. During daylight, the organism may be unable to assimilate the end product of prey digestion (free fatty acids) inside the peripheral subcutaneous adipose tissues (SAT), because skin is no more blood perfused. During the night, re-warming and re-connecting to blood circulation peripheral tissues could be inevitable to end the assimilation of FFA inside the SAT. In a first step, we have reproduced the conditions of a resting night at sea and events of rewarming skin temperature, using a sea water tank in which king penguins equipped with internal temperature loggers were maintained several days. In a second step, we have tested a generalisation of our hypothesis studying body temperature variations on penguins fast and feed. Finally, we have measured the cost to maintain normothermia in cold water with respirometry measures and investigated peripheral vasodilation with body temperature variations and infrared thermography.

Philosophiae Doctor - PhD (Biodiversity and Conservation Biology) / Southern Africa harbours one-third of the world's Testudinid species, many of which inhabit arid or semi-arid areas, but ecological information on these species is scant. I studied the habitat, morphology and ecology of Kalahari tent tortoises over 13 months in semi-arid Savanna at Benfontein farm, Northern Cape Province, South Africa. In order to allow continuous monitoring of individuals, I attached radiotransmitters to males and females, split equally between two habitats, sites E (east) and W (west), with apparent differences in vegetation structure. Results of the study were based on data obtained from 27 telemetered tortoises and 161 individuals encountered opportunistically. Female Kalahari tent tortoises were larger than males and the sex ratio did not differ from 1:1. Based on person-hours to capture tortoises, the population appeared to have a low density, with more time required to capture a juvenile (35 hours) than an adult (10-11 hours). The frequency distribution of body size ranges was indicative of recruitment. Relative age, based on annuli counts, suggested that males were younger than females, perhaps because males as the smaller sex are more predation-prone than females. Linear relationships between annuli counts and shell volume indicated that, after reaching sexual maturity, female body size increased faster in volume than did male body size, possibly because a larger volume may enhance female reproductive success. Body condition differed between sites, sexes and among seasons. The hot and dry summer may account for low summer body condition, whereas vegetation differences and size effects, respectively, may account for the low body condition of tortoises in site W and in males. Site E was sandy with grasses, particularly Schmidtia pappophoroides, being the prevalent growth form. This habitat resembled a Savanna vegetation type Schmidtia pappophoroides – Acacia erioloba described for a neighbouring reserve. Site W was stonier, dominated by shrubs, and was reminiscent of Northern Upper Karoo vegetation (NKu3). Neither site resembled Kimberley Thornveld (SVk4), the designated vegetation type of the area. Differences in substrate and grazing intensity may have contributed to site vegetation differences. Rainfall had an important influence on seasonal vegetation. Short grass abundance correlated with rainfall and annual plants sprouted after spring rain. Refuge use changed according to season and sex. Males selected denser refuges than females did, perhaps because males were smaller and more vulnerable to predation and solar heat. Tortoises selected sparse, short grass as refuges in cool months, probably to maximise basking whilst remaining in protective cover. During hot periods, mammal burrows were preferred to vegetation as refugia. The smaller males spent more time in cover than females, which may be related to predator avoidance or thermoregulation. Females spent more time basking than males, perhaps due to their larger size and to facilitate reproductive processes. Tortoises did not brumate, but through a combination of basking, and orientation relative to the sun in their refuges, managed to attain body temperatures that allowed small bouts of activity. Body temperature for active tortoises was similar among seasons, and was higher for more specialised active behaviours, such as feeding and socialising, than for walking. Increased activity by males in spring could relate to mating behaviour while females were more active in autumn, when they foraged more than males, perhaps due to the high cost of seasonal reproductive requirements. Males displaced further per day than did females, but home range estimates did not differ between sexes. Annual home range estimates varied substantially among individuals: 0.7–306 ha for minimum convex polygons and 0.7–181 ha for 95% fixed kernel estimates. The ability to cover large areas would assist tortoises in finding resources, e.g., food, in an area where resource distribution may be patchy. Differences among seasonal home ranges and movements probably reflect seasonal climatic change; activity areas shrinking when temperatures were extreme. In order to assess the effects of a semi-arid environment on the morphology of P. oculifer, I compared its morphology to that of its ‘cool-adapted’ sister taxon Psammobates geometricus, using live and museum specimens. Both P. oculifer and P. geometricus are sexually dimorphic and differences between the two species could indicate environmental or sexual selection effects, or a combination of the two. The shorter bridge length, which allowed more leg space, and wider front feet in P. oculifer cohorts probably represent traits for manoeuvring in a sandy habitat, while wider heads in P. oculifer possibly relate to interspecific differences in diet. The flatter shell in female P. oculifer, relative to P. geometricus, may represent a trade-off between space for reproductive structures, e.g., eggs, and the need to fit into small refuges, e.g., mammal burrows. Male P. oculifer had wider shells, more space around their hind legs, and wider hind feet than P. geometricus males had, all characteristics which may assist males to fight and mate in a sandy environment. / South Africa

This thesis examined why NCAA Division 1 American football “linemen” experience greater heat strain than “backs” during summer training camps. In study #1, exercise at a heat production of 350 W/m2 in a hot environment (Tdb:32.4±1.0ºC; Twb:26.3±0.6ºC) resulted in greater local sweating on the upper body (head, arm, shoulder and chest; all <0.05) and a greater core temperature (P=0.033) in linemen despite a ~25% lower heat production per unit mass (L:6.0±0.5 W/kg; B:8.2±0.8 W/kg). In study #2, greater convective and evaporative heat transfer coefficients (P<0.05) were found in backs during live summer training camp drills, but these did not lead to a greater dry heat transfer or evaporative capacity. However, the maximum metabolic rate per unit mass was lower in linemen due to differences surface area-to-mass ratio. In conclusion, the greater heat strain previously reported in linemen likely arises, in part, from differences in sweating efficiency and body morphology.

Temperature variation affects most biological parameters from the molecular level to community structure and dynamics. Current studies on thermal biology assess how populations vary in response to environmental temperature, which can help determine how populations differentially respond to climate change. To date, temperature fluctuation effects on endothermic poikilotherms such as the common eastern bumblebee (Bombus impatiens) are unknown even though bumblebees are the most important natural pollinators in North America. A cold-acclimation experiment with B. impatiens colonies revealed individuals acclimated to 5°C or 10°C at night did not differ in resting metabolic rate, flight metabolic rate, wingbeat frequency, or morphological measurements, compared to the control group. Moreover, an infrared camera showed that all colonies maintained maximum nest temperature consistently above 36.8°C. A latitudinal sampling of flight metabolic rate and morphological measurements of B. impatiens from four locations spanning Ontario (N 45°; W 75°) to North Carolina (N 34°; W 77°) indicated no latitudinal trend in the measured variables. This study shows that bumblebees are well equipped to face a wide range of environmental temperatures, both in the short term and long term, and can use a combination of behavioural and physiological mechanisms to regulate body and nest temperatures. These results are reassuring on the direct effects of climate change on bumblebee ecology, but further studies on the indirect effect of temperature variation on North American bumblebees are required to predict future ecosystem dynamics.

Studies show that vasomotor and sudomotor activity is compromised in individuals with Type 1 Diabetes (T1DM) which could lead to altered thermoregulatory function. However, recent work suggests that the impairments may only be evidenced beyond a certain level of heat stress. We therefore examined T1DM-related differences in heat loss responses of sweating and skin blood flow (SkBF) during exercise performed at progressive increases in the requirement for heat loss. Participants were matched for age, sex, body surface area and fitness cycled at fixed rates of metabolic heat production of 200, 250, and 300 W•m-2 of body surface area, each rate being performed sequentially for 30 min. Local sweat rate (LSR), sweat gland activation (SGA), and sweat gland output (SGO) were measured on the upper back, chest and forearm while SkBF (laser-Doppler) was measured on the forearm and upper back only. We found that despite a similar requirement for heat loss, LSR was lower in T1DM on the chest and forearm only, relative to Control and only different at the end of the second and third exercise periods. Differences in chest LSR were due to reduced SGA whereas the decreased forearm LSR was the result of a decrease in SGO. SkBF did not differ between groups. The reduction in the sweating response in the T1DM group was paralleled by a greater increase in core temperature. We show that T1DM impairs heat dissipation as evidenced by reductions in LSR and not SkBF. A compromised thermoregulatory response during and following physical exertion is of considerable concern due to the associated increased risk of post-exertion heat-related injury.

A study of the life history and ecology of Camelobaetidius variabilis was conducted in Honey Creek, OK from February 2003-April 2004. Nymph development was assessed using changes in external morphology. Laboratory reared nymphs were used to calculate number of degree days to complete development (772 degree days at 20.8° C ±.38° C), which was used to determine voltinism. Field collected nymph microhabitat distribution was used in assessing microhabitat distribution. Nymphal thermoregulation was assessed during the winter and spring by comparing nymphal numbers present in shaded and un-shaded habitats. Camelobaetidius variabilis nymphs showed preference for algal microhabitats during the spring and leaf packs in the winter. Nymphs inhabited leaf packs to increase metabolic rate during the winter. Increased temperatures aid in development of nymphs. Camelobaetidius variabilis exhibited a multivoltine life cycle with six overlapping generations.

No description available.

This thesis sought to evaluate whether the increased risk of heat-related illness observed in black-African descendants stems from impairements in local- and whole-body heat loss responses in this ethnic group. To evaluate this, in separate studies local- (study 1) and whole–body (study 2) heat loss responses were compared in young men (18-30 y) of black-African (n=21) and Caucasian (n=21) descent, matched for physical characteristics and fitness and born and raised in the same temperate environment. In study 1, we compared nitric oxide-dependent skin blood flow and sweating responses in young men of black-African (n=10) and Caucasian (n=10) descent during rest, exercise, and recovery in the heat. Both groups rested for 10-min, and then performed 50-min of moderate-intensity exercise at 200 W/m2, followed by 30-min of recovery in hot-dry heat (35°C, 20% RH). Local cutaneous vascular conductance (CVC%max) and sweat rate (SR) were measured at two forearm skin sites treated with a) lactated-Ringer (Control), or b) 10 mM NG-nitro-L-arginine methyl ester (L‐NAME, NO synthase-inhibitor). L-NAME significantly reduced CVC%max throughout rest, exercise, and recovery in both groups (both p<0.001). However, there were no significant main effects for the NO contribution to CVC%max between groups (all p>0.500). L-NAME significantly reduced local SR in both groups (both p<0.050). The NO contribution to SR was similar between groups such that L-NAME reduced SR relative to control at 40 and 50 min into exercise (both p<0.050). In study 2, we assessed whole-body total heat loss (evaporative + dry heat exchange) in black-African (n=11) and Caucasian (n=11) men using direct calorimetry. Participants performed three, 30-min bouts of semi-recumbent cycling at fixed metabolic heat productions (and therefore matched heat loss requirements between groups) of 200 (light), 250 (moderate), and 300 W/m2 (vigorous), each followed by 15-min recovery, in dry heat (40°C, ~13% relative humidity). Across all exercise bouts, dry (p=0.435) and evaporative (p=0.600) heat exchange did not differ significantly between groups. As such, total heat loss during light, moderate and vigorous exercise was similar between groups (p=0.777), averaging ((mean (SD)); 177 (10), 217 (13) and 244 (20) W/m2 in men of black-African descent, and 172 (13), 212 (17) and 244 (17) W/m2 in Caucasian men. Accordingly, body heat storage across all exercise bouts (summation of metabolic heat production and total heat loss) was also similar between the black-African (568 (142) kJ) and Caucasian groups (623 (124) kJ; p=0.356). This thesis demonstrates that ethnicity does not influence NO-dependent cutaneous vasodilation and sweating in healthy, young black-African descent and Caucasian men during exercise in the heat. Furthermore, we extend upon these observations by showing no differences in whole-body dry and evaporative heat exchange and therefore body heat storage.

Heat stress (HS) is one of the consequential important problems facing the swine industry. The negative effects of HS include reduced growth performance, reproductive efficiency, and carcass quality as well as increased morbidity and mortality. Although, the swine industry has developed several abatement strategies (i.e., fans, cooling pads, sprinklers, etc.), these approaches may be ineffective in the future as global temperatures continue to rise and the frequency of more severe heat waves increases in regions where animal agriculture is prevalent. These extreme heat events put pigs (especially those approaching market weight) at risk for acute hyperthermia that can lead to death unless body temperature is rapidly returned to euthermia and thermoregulatory function is restored.Therefore, evaluating mitigation strategies to promote recovery from acute hyperthermia is of utmost importance for improving pigs’ health and well-being and ensuring profitability and food security. In four experiments, the existence of microclimates in grow-finish barns during late summer was ascertained and a rapid cooling technique using cold water dousing and feed removal to promote recovery from acute hyperthermia in pigs was evaluated. In the first study, it was determined that microclimates exist in grow-finish barns and that pigs raised in pens that were not located directly below air inlets and ventilation fans had greater body temperature and reduced feed efficiency despite similarities in the in-barn ambient temperature and relative humidity. These data exemplifythe importance of adequate ventilation systems in swine barns and the impact of microclimates on pigs’ health and productivity during warm summer months. In the second study, grow-finish pigs that did not have feed access were exposed to acute HS and then rapidly or gradually cooled. Following the acute HS and recovery phase, all pigs were maintained under thermoneutral conditions and then euthanized over three days to determine the temporal effects of the cooling treatment on body temperature and intestinal integrity. The results showed that rapid cooling following acute hyperthermia in pigswas effective in returning body temperature to euthermia more rapidly compared to gradual cooling and rapid cooling prevented further intestinal damage. Based on these results, it was hypothesized that feed removal may have played a role in the effectiveness of rapid cooling. Therefore, a third experiment was conducted in which grow-finish pigs with or without access to feed were exposed to an acute HS challenge and then rapidly cooled. This study concluded that feed access was a determinant factor in the cooling outcome, as the gastrointestinal temperature returned to euthermia during the rapid cooling period more rapidly when feed was removed. Finally, a fourth study was conducted to evaluate the effects of feed removal in the absence of rapid cooling on the systemic inflammatory response and short-term growth performance of grow-finish pigs. However, it was determined that feed removal alone did not reduce the inflammatory response as expected. Overall, these studies demonstrate the risk forgrow-finish pigs during summer heat events and the potential use of rapid cooling in combination with feed removal for promoting recovery from acute hyperthermia in pigs.

Indiana University-Purdue University Indianapolis (IUPUI) / Thermoregulation system in mammal keeps their body temperature in a vital and yet narrow range of temperature by adjusting two main activities, heat generation, and heat loss. Also, these activities get triggered by other causes such as exercise or certain drugs. As a result, thermoregulation system will respond and try to bring back the body temperature to the normal range. Although these responses are very well experimentally explored, they often can be unpredictable and clinically deadly. Therefore, this thesis aims to analytically characterize the neural circuitry components of the system that control the heat generation and heat loss. This modeling approach can help us to analyze the relationship between different components of the thermoregulation system without directly measuring them and explain its complex responses in mathematical form. The first chapter of the thesis is dedicated to introducing a mathematical modeling approach of the circuitry components of the thermoregulation system in response to Methamphetamine which was first published in [1]. Later, in other chapters, we will expand this mathematical framework to study the other components of this system under different conditions such as different circadian phases, various pharmacological interventions, and exercise. This thesis is composed by materials from the following papers. ‎CHAPTER 1 uses the main idea, model, and figures from References [1]. Meanwhile, ‎CHAPTER 2 is based on [2] coauthored with me and is reformatted according to Purdue University Thesis guidelines. Also, ‎CHAPTER 3 interpolates materials from reference [3] coauthored and is reformatted to comply with Purdue University Thesis guidelines. ‎CHAPTER 4 is inserted from the reference [4] and is reformatted according to Purdue University Thesis guidelines. Finally, ‎CHAPTER 5 is based on Reference [5] and is reformatted according to Purdue University Thesis guidelines. Some materials from each of these references have been used in the introduction Chapter.