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Regulation of thoracic muscle temperature has been investigated in a number of dragonfly species but is poorly known in the large and diverse family, Gomphidae. Moreover, temperatures of other body regions have been recorded in very few ectothermic insects. In addition, correlations among multiple components of thermoregulatory behavior have rarely been examined quantitatively. Here I examine thermoregulation in Arigomphus villosipes, a medium-sized gomphid common at the shores of lakes and ponds in the northeastern USA. Measurements of the temperatures of the thorax (Tth), head (Th) and abdomen (Tab), using standard "grab and jab"techniques, indicate that both Tth and Th are relatively independent of air temperature (Ta). It is not clear whether Tth and Th are independently regulated, although some data suggest that they might be. Arigomphus villosipes can warm its thoracic musculature endothermically to maintain high Tth during cool Ta in conditions of low solar radiation intensity. However, regulation is principally behavioral, involving variation in body and wing postures and perhaps in perch substrate choice. Certain of these behaviors are closely associated to form suites of behavior that together are adapted to enhance or inhibit heating, while others are constrained by trade-offs with other functional demands. The former have a significant demonstrable effect on Tth. These combinations of behaviors results in a well-developed capacity for thermoregulation, allowing the insects to expand their activity periods and choice of perches, and probably improving male performance during competitive chases of females prior to mating. [ABSTRACT FROM AUTHOR]

Bergmann's rule originally described a positive relationship between body size and latitude in warm-blooded animals. Larger animals, with a smaller surface/volume ratio, are better enabled to conserve heat in cooler climates (thermoregulatory hypothesis). Studies on endothermic vertebrates have provided support for Bergmann's rule, whereas studies on ectotherms have yielded conflicting results. If the thermoregulatory hypothesis is correct, negative relationships between body size and temperature should occur in temporal in addition to geographical gradients. To explore this possibility, we analysed seasonal activity patterns in a bee fauna comprising 245 species. In agreement with our hypothesis of a different relationship for large (endothermic) and small (ectothermic) species, we found that species larger than 27.81 mg (dry weight) followed Bergmann's rule, whereas species below this threshold did not. Our results represent a temporal extension of Bergmann's rule and indicate that body size and thermal physiology play an important role in structuring community phenology. [ABSTRACT FROM AUTHOR]

Tortoises that live in regions where food plants grow in winter may have to cope with relatively low environmental temperatures to obtain resources. The speckled tortoise, Homopus signatus, inhabits an arid winter rainfall range where it is active in winter and spring at environmental temperatures well below its preferred body temperature. Although H. signatus is a threatened species, we have no information how it deals with low environmental temperatures. Therefore, we made continuous recordings of behaviour in nine female H. signatus on 29 days in the early spring. The group of females as a whole showed activity (i.e., behaviours other than hiding) throughout the day in a unimodal pattern. However, individual tortoises were active only for approximately 4.5 h per day and spent as much as 73% of their active time basking, mostly under the protective cover of shrubs. In addition, a negative relationship between the percentage of active time spent in sun and environmental temperature indicated that H. signatus used active behaviours other than basking to absorb heat, particularly on cold days. Tortoises completed all active behaviours other than basking in 1.2 h per day, including a mere 24 min of feeding, probably facilitated by the abundant availability of food plants in the early spring. We predict that a reduced availability of food plants for H. signatus might lead to increased active time and possibly increased predation pressure, or to a decreased proportion of active time spent basking and reduced body temperatures. [ABSTRACT FROM AUTHOR]

Population dynamics of terrestrial vertebrates are affected by climatic fluctuations, notably in ectotherms. An understanding of the interaction between physiology and demographic processes is necessary to predict the impacts of climate change. Reptiles are particularly sensitive to temperature, but only a few studies have explored the relationship between thermoregulatory strategy and demography in these animals. Using 12 years of mark-recapture data on two sympatric colubrid snakes ( Hierophis viridiflavus and Zamenis longissimus), we tested whether demographic parameters are influenced by contrasted thermoregulatory strategies. The thermophilic and conspicuous species ( H. viridiflavus) grew faster than the thermoconforming and secretive species ( Z. longissimus), and this difference was most pronounced in open habitats, suggesting that the metabolic benefits associated with high thermal preferences depend on environmental factors at small spatial scales. Survival varied annually in both species, but was not lower in H. viridiflavus despite a higher degree of exposure. In Z. longissimus, survival was negatively affected by low temperatures during the active season, possibly underlying an exposure trade-off. [ABSTRACT FROM AUTHOR]

The lack of shelter can perturb behaviors, increase stress level and thus alter physiological performance (e.g. digestive, immune or reproductive functions). Although intuitive, such potential impacts of lack of shelter remain poorly documented. We manipulated shelter availability and environmental and physiological variables (i.e. access to a heat source, predator attack, feeding status) in a viviparous snake, and assessed sun-basking behavior, digestive performance (i.e. digestive transit time, crude estimate of assimilation, regurgitation rate) and plasma corticosterone levels (a proxy of stress level). Shelter deprivation provoked a strong increase in sun-basking behavior and thus elevated body temperature, even in unfed individuals for which energy savings would have been otherwise beneficial. The lack of heat was detrimental to digestive performance; simulated predator attacks worsened the situation and entailed a further deterioration of digestion. The combination of the lack of shelter with cool ambient temperatures markedly elevated basal corticosterone level and was associated with low digestive performance. This hormonal effect was absent when only one negative factor was involved, suggesting a threshold response. Overall, our results revealed important non-linear cascading impacts of shelter availability on stress-hormone levels, behaviors and physiological performance. These results infer that shelter availability is important for laboratory studies, captive husbandry and possibly conservation plans. [ABSTRACT FROM AUTHOR]

Abstract: Herbivorous tortoises in arid, winter-rainfall regions need to forage in seasons that provide relatively little heat for their ectothermic metabolism. To help understand how tortoises exploit resources in winter-rainfall areas, I recorded ambient, soil, and body temperatures for Homopus signatus in four spring seasons, and in one summer, autumn, and winter. The spring thermal environment enabled H. signatus to maintain body temperatures that were high compared to other small tortoise species. Mature females had higher spring body temperatures than males and immature individuals, probably because mature females were developing eggs. In summer, autumn, and winter, body temperatures differed between males and females, relating to sexually different activities and retreat uses. The relatively high body temperatures of H. signatus in winter and spring, along with a non-isometric relationship between body temperature and soil temperature, suggest that tortoises thermoregulated and may need considerable time to gain heat. Additional studies should compare body temperatures of H. signatus to operative temperatures, and determine the vulnerability of the taxon to human interferences that affect behavioural time budgets and body temperatures. [Copyright &y& Elsevier]

1. Tiger beetles (Cicindela) of open habitats have served as model ectotherms in studies of the dependence of activity and habitat utilization on temperature. Potential departures from the cicindelid model were investigated in Cicindela sexguttata, a species inhabiting forests where thermal resources are patchy and ephemeral. 2. Body temperatures (Tb) were determined by inserting thermocouples into beetles immediately after observing specific behaviours in the field. Cicindela sexguttata elevated Tb by basking, foraged at a preferred Tb of 32.8 °C, and stilted, sun-faced, or sought shade when Tb exceeded 35 °C. Although these behaviours were typical of Cicindela, their set points were lower than those of species in more open habitats. 3. Illuminated substrates were utilized for basking and foraging. Beetles were dispersed throughout the forest floor in early spring, but became aggregated in light gaps when the canopy leafed out. Operative temperatures of thermal models indicated that beetles were unable to maintain the preferred Tb in shade and would not be able to maintain a preferred Tb in light gaps during the autumn, when adults are normally in diapause. 4. Beetles were confined to foraging in light gaps once the canopy was closed. Foraging rate and searching speed were independent of Tb, in contrast to other cicindelids. Adults rarely searched for prey, but ambushed small arthropods that alighted in the light gap. Dependence on patches of illumination as thermal resources may increase prey capture, intraspecific encounters, and risk of predation, and preclude foraging in the autumn when Cicindela species of open habitats are also active. [ABSTRACT FROM AUTHOR]

Clustering of organisms under cold air temperature conditions is modelled with a finite-difference method. Metabolic functions of temperature are used to simulate completely ectothermic, completely endothermic, and other organisms. To adequately match real conditions, the core temperature is kept constant at a high level, while the periphery of the organism cluster is assigned a lower temperature representing the cold conditions under which clustering is observed for organisms. The numerical model reasonably predicts the observed temperature distribution in honeybee clusters. The results do not support suggestions that organisms could overheat in the core of a cluster if they do not use thermoregulatory mechanisms to cool down. Endothermic organisms are not as efficient as ectothermic ones in heating a cluster core temperature to a given level. The general ectothermic metabolic rate function exhibited one of the highest efficiencies for heating the cluster. [ABSTRACT FROM AUTHOR]

The article discusses the concept of kleptotherms which regulate their own temperature by stealing heat from other organisms, and proposed as an additional category of thermoregulators. A condition involved in the concept is the thermal heterogeneity created by the presence of a warm organism in a cool environment. Kleptothermy is also experienced by endotherms and is usually reciprocal. A possible example of kleptothermy as documented by thermal monitoring on a tropical island is based on high stable temperatures of a sea snake.