Thermal Biology

The South American lungfish, Lepidosiren paradoxa inhabits seasonal environments in the Central Amazon and Paraná-Paraguay basins that undergo significant oscillations in temperature throughout the year. They rely on different gas exchange organs, such as gills and skin for aquatic gas exchange while their truly bilateral lungs are responsible for aerial gas exchange; however, there are no data available on the individual contributions of the skin and the gills to total aquatic gas exchange in L. paradoxa. Thus, in the present study we quantify the relative contributions of skin and gills on total aquatic gas exchange during warm (35°C) and cold exposure (20°C) in addition to the effects of aerial and aquatic hypercarbia on aquatic gas exchange and gill ventilation rate (fG; 25°C), respectively. Elevated temperature (35°C) caused a significant increase in the contribution of cutaneous (from 0.61±0.13 to 1.34±0.26ml. STPD.h(-1)kg(-1)) and branchial (from 0.54±0.17 to 1.73±0.53ml. STP...

Tropical subjects regulate core temperature with less amount of sweat against heat compared to temperate subjects through long-term heat-acclimatization. The purpose of the study is to determine whether acclimatization in tropical subjects decay during a stay in temperate area. The aim of this study, therefore, was to investigate the possible changes in the peripheral sweating mechanisms. Local sweating response activated by acetylcholine (ACh) applied iontophoretically among Malaysians with varying duration of stay in Japan and Japanese resident subjects. Directly activated (DIR) and axon reflex (AXR)-mediated sweating during ACh iontophoresis were measured by capacitance hygrometer (quantitative sudomotor axon reflex test, QSART) QSART was performed in a thermoneutral condition (2470.5 1C, 4073% rh). The sweat onset-time after the current loading was 1.05 min shorter in Malaysian with longterm stay in Japan (MLJ) than in Malaysian, and the AXR(1), AXR(2) and DIR sweating in MLJ were larger than Malaysian. From these results, suppressed neuroglandular response to ACh was confirmed in Malaysians. It is suggested that long-term heat-acclimatization acquired in tropical subjects may decay after immigration to temperate area. r

The thermal responses of 12 cicada species inhabiting Big Bend National Park, Texas, USA are investigated to determine the influence of altitude, habitat and microhabitat. The park provides an opportunity to analyze the thermal responses in animals from a variety of habitats and altitudinal gradients within a limited geographic range. The data suggest that thermal responses of cicadas are adaptations to their specific habitats. No thermal responses are significantly correlated with body size. The maximum voluntary tolerance temperature (an upper behavioral thermoregulatory point) and heat torpor temperatures show significant correlations with altitude. Variability in thermal responses can also be related to the characteristics of the microhabitat selected or the behavioral pattern of a species.

Using an electronic apparatus simulating a bird roosting in a nest at night, we examined the insulating qualities of Eurasian Tree Sparrow (Passer montanus) nests built in nest boxes under winter conditions. Nests of different construction were compared with an empty box, and with roosting in open air. Energy savings in an empty box accounted for 18%, in boxes with

Experiment was conducted with the aim of determining the effect of varying water temperature and ration size on growth and body composition of fry of the common carp, Cyprinus carpio. Common carp fry with an initial body weight (BW) of 0.86 g were fed a diet (34.9% protein, 18.3 KJ/g diet) at four ration sizes 4%, 5%, 6% and 7% of their body weight per day and reared at two water temperatures 28 and 32 °C for 60 days. Fry fed with 6% ration showed the highest mean final body weight at 28 °C. Final body weight was significantly (P<0.05) affected by ration and temperature. Cyprinus carpio fry raised at 28 °C had higher feed efficiency (FE) (44.36%) than the fry reared at 32 °C (40.98%) with 4% ration. Further, feed efficiency decreased with increase in ration levels in both temperatures. Protein efficiency ratio (PER) was higher (1.26) at 28 °C than at 32 °C (1.17). At 6% ration, common carp fry showed highest specific growth rate (SGR) (3.82%/day) at 28 °C as compared with at 32 °C (3.57%/day). A linear increase in protein and lipid contents was evident with increasing ration levels up to 6% body weight at both temperatures 28 and 32 °C. Second-order polynomial regression analysis of weight gain and SGR indicated the breakpoints at ration level 6.04% and 6.08% body weight per day at 28 and 32 °C. Hepatosomatic index (HSI) not affected by temperature and ration size while, viscerosomatic index (VSI) influenced (P<0.05) by ration size and temperature. Based on the above results, it may be concluded that 6% BW/day ration is optimal for growth of Cyprinus carpio fry at both the temperatures 28 and 32 °C.

Miniature Thermochron iButton dataloggers have transformed the ways in which researchers collect thermal data. However, one important limitation is that these dataloggers are not waterproof, which can lead to device failure and loss of data under field conditions. Several methods have been used to increase their water resistance, but no study to date has investigated whether any of these techniques affects the accuracy of temperature readings. Waterproofing potentially could affect the accuracy of iButtons by biasing temperatures or altering rates of warming and cooling. We compared temperature profiles of unmodified Thermochron iButtons (model DS1921G) to iButtons that we coated with a clear plastic dip (designed to coat tool handles) to determine whether this waterproof coating affects the accuracy of temperatures they record. We also compared temperatures recorded by uncoated and coated iButtons that were embedded within physical models that mimic frog body temperatures. Finally, we used our field data to test whether coating iButtons with plastic prevents failure of dataloggers during fieldwork. Although we found statistically significant differences between the temperatures recorded by uncoated and coated iButtons, and also between uncoated and coated iButtons embedded in frog models, these effects were relatively small (0-1.3 1C). We also found that coating iButtons with plastic reduced the likelihood of device failure under field conditions (from 8.3% to 0%). We conclude that coating Thermochron iButtons with plastic is an affordable and reliable method of waterproofing dataloggers that prevents device failure and data loss with minimal influence on temperature readings.

The experimental research and heat transfer calculation of dog's tongue was processed on the basis of Traditional Chinese Medicine (TCM). Firstly, the blood perfusion rate of dog tongue was measured by the method of invasive. Secondly, the two-dimensional temperature fields of specific cross-section of tongue were calculated by the finite element method. Lastly, some conclusions were drawn, that inside the tongue body the blood perfusion change can make blood vessel to expand or constrict, and affect surface temperature field of tongue, on the other hand, the tongue cross-section temperature distribution is chiefly affected by the artery, blood vessel area and location. The above researches were carried out in order to seek the major factor that affects the tongue surface temperature distribution, and try to explain the relationship between tongue temperature and ''tongue color'', which is a very important concept in Tongue Inspection of TCM, and if tongue surface temperature distribution can reflect the state of ''tongue color'' indirectly, these calculation results can help to analyze heat transfer characteristic of organism. In addition, the research method can be used to calculate the two-dimensional temperature field in various blood perfusion rate and multi-blood vessels affection. r

Thermoregulatory studies of ectothermic organisms are an important tool for ecological physiology, evolutionary ecology and behavior, and recently have become central for evaluating and predicting global climate change impacts. Here, we present a novel combination of field, laboratory, and modeling approaches to examine body temperature regulation, habitat thermal quality, and hours of thermal restriction on the activity of two sympatric, aridlands horned lizards (Phrynosoma cornutum and Phrynosoma modestum) at three contrasting Chihuahuan Desert sites in Mexico. Using these physiological data, we estimate local extinction risk under predicted climate change within their current geographical distribution. We followed the Hertz et al. (1993, Am. Nat., 142, 796-818) protocol for evaluating thermoregulation and the Sinervo et al. (2010, Science, 328, 894-899) eco-physiological model of extinction under climatic warming. Thermoregulatory indices suggest that both species thermoregulate effectively despite living in habitats of low thermal quality, although high environmental temperatures restrict the activity period of both species. Based on our measurements, if air temperature rises as predicted by climate models, the extinction model projects that P. cornutum will become locally extinct at 6% of sites by 2050 and 18% by 2080 and P. modestum will become extinct at 32% of sites by 2050 and 60% by 2080. The method we apply, using widely available or readily acquired thermal data, along with the modeling, appeared to identify several unique ecological traits that seemingly exacerbate climate sensitivity of P. modestum.

This study was carried out to determine upper (CTMax) and lower (CTMin) thermal tolerance, acclimation response ratio (ARR) and thermal tolerance polygon of the European sea bass inhabiting the Iskenderun Bay, the most southeasterly part of the Mediterranean Sea, at three acclimation temperatures (15, 20, 25 1C). Acclimation temperature significantly affected the CTMin and CTMax values of the fish. At 0.3 1C min À 1 cooling or heating rate, CTMin ranged from 4.10 to 6.77 1C and CTMax ranged from 33.23 to 35.95 1C in three acclimation temperatures from 15 to 25 1C. Thermal tolerance polygon for the juveniles at the tested acclimation temperatures was calculated to be 296.14 1C 2 . In general, the current data show that our sea bass population possesses acclimation response ratio (ARR) values (0.25-0.27) similar to some tropical species. The cold tolerance values attained for this species ranged from 4.10 to 6.77 1C, suggesting that cold winter temperatures may not pose danger during the culture of European sea bass in deep ponds or high water exchange rate systems. Upper thermal tolerance is more of a problem in the southern part of the Mediterranean as maximum water temperature in ponds may sometimes exceed 33-34 1C, during which underground cool-water should be used to lower ambient water temperature in the mid-summer. For successful culture of sea bass in ponds, temperature should be maintained around 25 1C throughout the year and this can be managed under greenhousing systems using underground well-waters, commonly available in the region.

Temperature had a significant and positive effect on the foraging and growth of juvenile common carp Cyprinus carpio (90-105 mm) between 16 and 28 1C. Metrics measured were feeding rate (items s À 1 ), functional response (feeding rate as a function of food density), specific growth rate and incremental fork lengths. Experiments that were conducted at 16, 20, 24 and 28 1C and used two food types revealed a strong thermal influence on foraging, with the highest feeding rates achieved at 24 1C. Functional responses also revealed optimal feeding rates in relation to food density occurred at temperatures 4 20 1C. Specific growth rate and incremental fork lengths were depressed at 16 and 28 1C when compared to those achieved at 20 and 24 1C. These outputs suggest an increase in foraging and growth of C. carpio according to a thermal gradient that were maximal between 24 and 28 1C.

Critical thermal minima (CTMin) and maxima (CTMax) values were determined for the Pacific white shrimp Litopenaeus vannamei post-larvae and juveniles at four different acclimation temperatures (15, 20, 25, and 30 1C). The CTMin of shrimp at these acclimation temperatures were 7. 82, 8.95, 9.80, and 10.96 1C for post-larvae and 7.50, 8.20, 10.20, and 10.80 1C for juveniles, respectively, at 1 1C h À 1 cooling rate. The CTMax values were 35.65, 38.13, 39.91, and 42.00 1C for post-larvae and 35. 94, 38.65, 40.30, and 42.20 1C for juveniles at the respective acclimation temperatures. Both acclimation temperature and size of the shrimp affected CTMin values of L. vannamei (P o 0.01). Overall, juveniles displayed significantly lower CTMin values than the post-larvae (P o 0.0001). However, the CTMax response by post-larvae and juveniles were not significantly different from each other and no interaction was determined between the acclimation temperature and development stage (P 4 0.01). The area of the thermal tolerance polygon over four acclimation temperatures (15, 20, 25, and 30 1C) for the post-larvae of L. vannamei was calculated to be 434.94 1C 2 . The acclimation response ratio (ARR) values were high ranging from 0.35 to 0.44 for both post-larvae and juveniles. L. vannamei appears to be more sensitive to low temperatures than other penaeid species and its cold tolerance zone ranged from 7.5 to 11 1C. In successful aquaculture temperature must never fall below 12 1C to prevent mortalities. Upper thermal tolerance is less of a problem as in most subtropical regions maximum water temperature rarely exceeds 34 1C, but care should be given if shallow ponds with low water renewal rate are being used.

Whether melanism plays a significant role in thermoregulation has been a persistent question in studies of thermal biology of ectotherms. This review provides a synthesis of the thermal melanism hypothesis which states that dark individuals (i.e. lower skin reflectance) are at an advantage under conditions of low temperature since they heat up faster than light individuals at a given level of solar radiation. Although skin color is an important trait in the thermal biology of ectotherms, it has rarely been explored in non-insect models. We draw on the available literature to assess the validity of four key assumptions that underlie this hypothesis. Ample support was found for the assumption that melanistic diurnal species inhabit cooler areas than lighter species and that melanism results in greater fitness in cold climates. By contrast, little direct support could be found for the assumption that there is a consistent melanism-body size tradeoff. Finally, the assumption that color, thermal physiology and behavior are coadapted has some support but requires further investigation. Overall, the functional, molecular and adaptive mechanisms of thermal melanism await further study. r

In this study, we examined infrared thermograms in the course of time of six African zoo elephants and observed two phenomena. First, we noticed independent thermal windows, highly vascularised skin areas, on the whole elephants' body and second we observed distinct and sharply delimited hot sections on the elephants' pinnae. The frequency of thermal windows increased with increasing ambient temperature and body weight. We assume that the restriction of an enhanced cutaneous blood flow to thermal windows might enable the animal to react more flexibly to its needs with regard to heat loss. With this understanding, the use of thermal windows in heat loss might be seen as a fine-tuning mechanism under thermoneutral conditions.

Komodo dragons from hatchlings ( E0.1 kg) to adults (r 80 kg) express the full magnitude of varanid species size distributions. We found that all size groups of dragons regulated a similar preferred body temperature by exploiting a heterogeneous thermal environment within savanna, forest and mangrove habitats. All dragons studied, regardless of size, were able to regulate a daytime active body temperature within the range 34-35.6 1C for 5.1-5.6 h/day. The index of effectiveness of thermoregulation (a numerical rating of thermoregulatory activity) was not different among size groups of dragons. However, the index of closeness of thermoregulation, which rates the variability of body temperature, suggests a greater precision for regulating a preferred body temperature for medium compared to small and large dragons. Reference copper cylinders simulating small, medium and large Komodo dragons heated and cooled at the same rate, whereas actual dragons of all size groups heated faster than they cooled. Larger dragons heated and cooled more slowly than smaller ones. The mean operative environmental temperatures of copper cylinders representing medium sized dragons were 42.5, 32.0 and 29.41 C for savannah, forest and mangrove habitats, respectively. The index for average thermal quality of a habitat as measured by the absolute difference between operative environmental temperature and the dragon's thermal range suggests the forest habitat offers the highest thermal quality to dragons and the savannah the lowest. The percent of total daytime that the operative environmental temperature was within the central 50% of the body temperatures selected by dragons in a thermal gradient was 45%, 15%, and 9% for forest, mangrove and savannah, respectively. Forest habitat offers the most suitable thermal environment and provides the greatest number of hours with conditions falling within the dragon's thermal activity zone.

1) Measurement of physiological control of warming and cooling in reptiles requires calculating the thermal time constant (t) of the animal. (2) Previously reported methods of estimating t are sensitive to multiple problems including measurement error in operative environmental temperature and equilibrium body temperature, drift of environmental temperatures, requirements for extremely simple thermal environments, and ill conditioning of the estimation techniques themselves. (3) We propose a physiologically based heat transfer model which is less sensitive to common experimental errors, more numerically robust, and can provide physiologically meaningful estimates of time constants.

a b s t r a c t 1. The effect of temperature on the activity of the freshwater snail Pomacea canaliculata was investigated through field surveys and laboratory trials. 2. During winter most snails in the field were inactive but not in a deep lethargic state; the temperature at which half of the snails were active was 13-15 1C. 3. The time spent active and feeding increased with temperature between 10 and 30 1C, exposure time being unimportant except in foul water at 35 1C, while time spent crawling remained constant above 10 1C. 4. Activity decreased above 30 1C but no heat coma was observed with temperatures raised to 36.2 1C. 5. Under fluctuating temperatures, the rate of change in the percentage of active snails during cooling was higher than during warming, whereas the temperature at which half of the snails were active was lower.

A physically based model was built to predict the transient body temperature of lizards in a thermally heterogeneous environment. Six heat transfer terms were taken into account in this model: solar radiation, convective heat flow, longwave radiation, conductive heat flow, metabolic heat gain and respiratory energy loss. In order to enhance the model predictive power, a Monte Carlo simulation was employed to calibrate the bio-physical parameters of the target animal. Animal experiments were conducted to evaluate the calibrated body temperature model in a terrarium under a controlled thermal environment. To avoid disturbances of the animal, thermal infrared imagers were used to measure the land surface temperature and the body temperature. The results showed that the prediction accuracy of lizard's transient temperature was substantially increased by the use of Monte Carlo techniques (RMSE ¼ 0.59 1C) compared to standard model parameterization (RMSE ¼1.35 1C). Because the model calibration technique presented here is based on physical principles, it should be also useful in more complex, field situations.

The effects of morphological factors (body surface area (A D ), body mass and surface to mass ratio (A D =M)) on exercise heat stress responses in a hot wet (HW) (351C 80% rh) and hot dry (HD) climate (451C, 20% rh) of equal WBGT (C31.61C) were studied in 30 and 25 subjects respectively. In both climates there were positive correlations of T re with A D =M; negative with A D and mass, giving the bigger subjects an ''advantage'' that remained (A D =M) when data were corrected for differences in ' V V O2max ; which accounted for a substantial part of the variance in T re : The observed A D =M effect contradicts earlier studies but is consistent with model calculations. r

The thermoregulatory behavior of the giant keyhole limpet Megathura crenulata was determined in a horizontal thermal gradient during the day at 18.9 1C and 18.3 1C for the night. The final preferendum determined for giant keyhole limpets was of 18.6 7 1.2 1C.

There is a demand in the livestock industry for alternative assessments of feed efficiency. Infrared thermography was tested for predicting heat production, methane production and for the detection of physiological events (e.g. heat increment of feeding) in dairy cattle. Multiple body locations were infrared scanned concomitantly with the measurement of the animals' gaseous exchange. Infrared thermography can be successfully applied for assessing heat and methane production, through the analysis of feet temperature and temperature difference between left and right flanks, respectively. This technology is also useful for assessing physiological responses to milking and feeding.

We studied the relationship between locomotor performance and temperature in Liolaemus pictus argentinus, from the Andean-Patagonian forest, Argentina. We determined the running speed in long and sprint runs at four different body temperatures, the panting threshold, and minimum critical temperature. The results are discussed in relation to body temperature in the field and thermal preference in the laboratory (T pref ). L. p. argentinus achieved higher speed in sprint runs than in long runs at all temperatures. In order to know if pregnancy constrains performance in this viviparous species, the differences between pregnant females and the other adults were analysed. Pregnant females were at a disadvantage when running long distances, but in sprint runs they were able to run as efficiently as the rest of the individuals, suggesting that they mainly use sprint runs and this may explain their conspicuous more-withdrawn behaviour. In long runs, the performance optimal temperature for L. p. argentinus (T o ¼ 30.7 1C) was below the 25th percentile for all body temperatures selected in the laboratory (set-point range of T pref ¼34.6-37.9 1C), but similar to the mean field body temperature (32.1 1C). However, in sprint runs the T o (36.3 1C) was within the set-point range of T pref . The mean panting threshold (42.8 1C) and the mean minimum critical temperature (6.9 1C) were similar to those of other liolaemids. The results are evidence that L. p. argentinus is well-adapted to the temperatures available in their environment and that the species has a T pref that allows the achievement of maximal locomotor performance in the most frequently used and probably the most important run type, the sprint run.

The position and shape of thermal performance curves (TPCs, the functions relating temperature to physiological performance) for ecologically relevant functions will directly affect the fitness of ectotherms and therefore should be under strong selection. However, thermodynamic considerations predict that relationships between the different components of the TPC will confound its evolutionary optimization. For instance, the ''jack-of-all-temperatures'' hypothesis predicts a trade-off between the breadth of the TPC and the maximal performance capacity; the ''warmer is better'' hypothesis suggests that low thermal optima will come with low absolute performances. Semi-aquatic organisms face the additional challenge of having to adjust their TPCs to two environments that are likely to differ in mean temperature and thermal variability. In this paper, we examine how parameters of the TPCs for maximal running and swimming speed have co-evolved in the semi-aquatic newt genus Triturus. We consider evolutionary relationships between the width and the height of the TPCs, the optimal temperatures and maximal performance. Phylogenetic comparative analyses reveal that in Triturus, swimming and running differ substantially in the (co-)variation of TPC parameters. Whereas evolutionary changes in the TPC for swimming primarily concern the shape of the curve (generalist versus specialist), most interspecific variation in running speed TPCs involves shifts in overall performance across temperatures.

The obligatory cost of living for endotherms is measured by basal metabolic rate (BMR), a variable that is known to change after thermal acclimation. However, the relative timing between variation in ambient temperature and BMR is not well understood. In this study, we addressed this problem in the sparrow Zonotrichia capensis, studying whether previous thermal history affects the response of BMR to a new acclimation temperature. We found that after 4 weeks of acclimation either to 30 or 15 1C birds exhibited significant differences in BMR from pre-acclimation levels. Nevertheless, after a reacclimation to the opposite treatment for six additional weeks, in the group previously acclimated to warm conditions the change in BMR was significantly greater than in the group previously acclimated to cold. We also found differences in the mass of the small intestine between groups but constancy in the mass of liver, kidney and heart masses at the end of the experiments. Our results indicate that the thermal history affects metabolic adjustments and highlights the importance of considering this when evaluating the plasticity of metabolic traits in small birds.

Crocodilians have temperature-dependent sex determination (TSD) in which incubation temperature determines sex of embryo. Global warming is expected to alter hatchling sex ratio, leading to the extinction of small populations. Regional climate influence on crocodile nest microclimate and hatchlings' characteristics is poorly known. Here, microclimate in natural nests of American crocodile (Crocodylus acutus) and its relation with incubation length, hatchling sex and nesting success was studied in Banco Chinchorro Biosphere Reserve (Mexico) from 2007 to 2010. Temperature and relative humidity in different locations within and outside the nests were registered by data loggers. Incident solar radiation above nest was calculated from hemispheric photographs. Incubation length, proportion of hatchling reaching complete development and hatchling sex were determined at hatching. Nest temperatures exhibited a cyclic daily fluctuation due to solar radiation, which is the major heat source for nests. Clutch temperature was relatively stable and its daily amplitude was negatively correlated with clutch depth and size. Rainfall was the major source of clutch temperature decrease. Clutch and metabolic temperatures increased significantly during incubation. A small sample size failed to demonstrate a statistical relationship between length of incubation and mean clutch temperature. Proportion of embryos reaching complete development depended on maximum and minimum clutch temperature, maximum daily amplitude of clutch temperature and maximum decrease in clutch temperature on a period ≤4 day. Results confirmed a Female–Male–Female TSD pattern for C. acutus, with 31 and 32.5 °C as possible pivotal temperatures. Population and hatchling sex ratios were male-biased and fate of crocodiles of Banco Chinchorro could depend on the magnitude of temperature increase in the future.► I studied microclimate of natural nests of Crocodylus acutus. ► Nest temperatures exhibited a cyclic daily fluctuation due to solar radiation. ► Rainfall is the major source of clutch temperature decrease. ► Hatchlings sex ratio and embryos' survival depend on incubation temperature. ► C. acutus has a type II TSD pattern with 31 and 32.5 °C as possible pivotal temperatures.

Piaractus mesopotamicus were acclimated to 351C (group I) and 151C (group II). In group I, temperature was decreased from 351C to 151C, followed by a return to 351C, while in group II, temperature rose to 351C and returned to 151C. For each temperature, oxygen uptake ( '

l. Thermoreguiatory set points -i.e. the body temperatures at which heat-seeking or cooling behaviour are initiated -of the lacertid lizard Podarcis muralis were measured by infra-red thermography in animals exposed to light of different spectral compositions.

We evaluated the thermal biology of two sympatric saxicolous species of the genus Phymaturus, endemic from the Argentine Payunia region. Taking into account that the distributional range of Phymaturus roigorum (the largest species) is greater than the range of P. payuniae, we evaluated the habitat (type of rocks) used by these species. We recorded body temperature and operative temperatures in different habitats, and we determined the preferred body temperature in the laboratory. We compared the thermal quality of habitats occupied and not occupied by Phymaturus payuniae, and the accuracy and effectiveness of thermoregulation between species.

Global warming and climate change adversely affect livestock and poultry production sectors under tropical and subtropical conditions. Heat stress is amongst the most significant stressors influencing poultry productivity in hot climate regions, causing substantial economic losses in poultry industry. These economic losses are speculated to increase in the coming years with the rise of global temperature. Moreover, modern poultry strains are more susceptible to high ambient temperature. Heat stress has negative effects on physiological response, growth performance and laying performance, which appeared in the form of reducing feed consumption, body weight gain, egg production, feed efficiency, meat quality, egg quality and immune response. Numerous practical procedures were used to ameliorate the negative impacts of increased temperature; among them the dietary manipulation, which gains a great concern in different regions around the world. These nutritional manipulations are feed additives (natural antioxidants, minerals, electrolytes, phytobiotics, probiotics, fat, and protein), feed restriction, feed form, drinking cold water and others. However, in the large scale of poultry industry, only a few of these strategies are commonly used. The current review article deliberates the different practical applications of useful nutritional manipulations to mitigate the heat load in poultry. The documented information will be useful to poultry producers to improve the general health status and productivity of heat-stressed birds via enhancing stress tolerance, oxidative status and immune response, and thereby provide recommendations to minimize production losses due to heat stress in particular under the growing global warming crisis.

Thermal limits in ectotherms may arise through a mismatch between O 2 supply and demand. At higher temperatures, the ability of their cardiac and ventilatory activities to supply O 2 becomes insufficient to meet their elevated O 2 demand. Consequently, higher levels of O 2 in the environment are predicted to enhance heat tolerance, while reductions in O 2 are expected to reduce thermal limits. Here, we extend previous research on thermal limits and oxygen limitation in aquatic insect larvae and report critical upper temperatures in nymphs of the damselfly Calopteryx virgo (Linnaeus, 1758) exposed to different levels of O 2 . In addition, we explore the potential for a mechanistic link between O 2 conditions and thermal plasticity by exposing nymphs to two consecutive extreme heat events, using different levels of O 2 in the second exposure. As predicted, hypoxia severely lowered critical temperatures. However, thermal tolerance was not improved under hyperoxia. Damselfly nymphs may be precluded to take advantage of hyperoxia if O 2 uptake and delivery is controlled locally near the caudal gills where most of the gas exchange occurs. The same asymmetrical effects of hypoxia and hyperoxia on heat tolerance in terrestrial insects could be similarly explained if tracheal opening and/or ventilation are not centrally regulated. Prior exposure to hypoxia enhanced critical thermal maxima in subsequent heat exposures and hyperoxia negated this hardening effect, indicating potential for oxygen-driven heat hardening in these aquatic insects. Our study provides broad confirmation for oxygen limitation as a key mechanism setting upper thermal limits, pointing to a vital role for heat shock proteins in reducing O 2 requirements by slowing down rates of protein denaturation.

The effects of different temperatures on in vitro-grown microcuttings and as a pre-treatment in cutting-donor seedlings of Eucalyptus saligna Smith and Eucalyptus globulus Labill were investigated in relation to adventitious rooting both with and without the exogenous root-inducing phytohormone auxin. E. globulus was more sensitive to continuous higher temperatures applied to donor plants and cuttings; the latter yielded overall best rooting response in day/night cycles of 30 C/20 C. In general, E. saligna was more resistant to higher temperatures and root growth was strongly inhibited by 15 C. The presence of exogenous auxin promoted rooting, particularly at lower and higher temperatures. r