Selected Body Temperature Research Articles

Integrating behavioural thermoregulatory strategy into the animal personality framework using the common lizard, Zootoca vivipara as a model

The study of consistent between-individual behavioural variation in single (animal personality) and across two or more behavioural traits (behavioural syndrome) is a central topic of behavioural ecology. Besides behavioural type (individual mean behaviour), behavioural predictability (environment-independent within-individual behavioural variation) is now also seen as an important component of individual behavioural strategy. Research focus is still on the ‘Big Five’ traits (activity, exploration, risk-taking, sociability and aggression), but another prime candidate to integrate to the personality framework is behavioural thermoregulation in small-bodied poikilotherms. Here, we found animal personality in thermoregulatory strategy (selected body temperature, voluntary thermal maximum, setpoint range) and ‘classic’ behavioural traits (activity, sheltering, risk-taking) in common lizards (Zootoca vivipara). Individual state did not explain the between-individual variation. There was a positive behavioural type—behavioural predictability correlation in selected body temperature. Besides an activity—risk-taking syndrome, we also found a risk-taking—selected body temperature syndrome. Our results suggest that animal personality and behavioural syndrome are present in common lizards, both including thermoregulatory and ‘classic’ behavioural traits, and selecting high body temperature with high predictability is part of the risk-prone behavioural strategy. We propose that thermoregulatory behaviour should be considered with equal weight to the ‘classic’ traits in animal personality studies of poikilotherms employing active behavioural thermoregulation.

Hydration state does not affect selected body temperature during gravidity or gravidity duration in pythons (Antaresia childreni)

The embryonic development of many ectothermic species are highly sensitive to temperature and typically have a higher thermal optima than do most other physiological processes. Thus, female ectotherms often maintain a higher and more carefully controlled body temperature when she is supporting developing embryos (early development in oviparous species, throughout development in viviparous species). Considering the positive correlation between body temperature and evaporative water loss, this response could potentially exacerbate female water imbalance in water-limited environments, suggesting that female water balance and egg development may be in conflict. Using Children's pythons (Antaresia childreni), we hypothesized that water deprivation reduces thermophily during gravidity. We split reproductive females into two thermal treatments: those provided with a continuously available thermal gradient of 25–45 °C and those kept at a constant 31 °C. We also had seven non-reproductive females that were provided a thermal gradient. Within each thermal treatment group, we alternatingly assigned females to either have or not have water throughout gravidity. We found that reproduction increased female body temperature, but this increase was not affected by water regime. Reproduction also increased plasma osmolality, and lack of water during gravidity exacerbated this effect. We also found that thermal treatment, but not water regime, significantly influenced gravidity duration, with females given a thermogradient having a shorter gravidity duration, likely as a result of having a higher average body temperature than did the females provided constant heat. Finally, we found that females provided water throughout gravidity had greater clutch masses than did females without water. Further research is needed to improve scientific understanding of the interactions among water balance, body temperature, and various physiological performances.

Trade-Offs among Immune Mechanisms: Bacterial-Challenged Spodoptera frugiperda Larvae Reduce Nodulation Reactions during Behavioral Fever.

Insect innate immunity is composed of cellular and humoral reactions, the former acting via circulating hemocytes and the latter via immune signaling that lead to the production of antimicrobial peptides and phenol oxidase-driven melanization. Cellular immunity involves direct interactions between circulating hemocytes and invaders; it includes internalization and killing microbes (phagocytosis) and formation of bacterial-laden microaggregates which coalesce into nodules that are melanized and attached to body walls or organs. Nodulation can entail investing millions of hemocytes which must be replaced. We hypothesized that biologically costly hemocyte-based immunity is traded off for behavioral fevers in infected larvae of fall armyworms, Spodoptera frugiperda, that were allowed to fever. We tested our hypothesis by infecting larvae with the Gram-negative bacterium, Serratia marcescens, placing them in thermal gradients (TGs) and recording their selected body temperatures. While control larvae selected about 30 °C, the experimental larvae selected up 41 °C. We found that 4 h fevers, but not 2, 6 or 24 h fevers, led to increased larval survival. Co-injections of S. marcescens with the prostaglandin (PG) biosynthesis inhibitor indomethacin (INDO) blocked the fevers, which was reversed after co-injections of SM+INDO+Arachidonic acid, a precursor to PG biosynthesis, confirming that PGs mediate fever reactions. These and other experimental outcomes support our hypothesis that costly hemocyte-based immunity is traded off for behavioral fevers in infected larvae under appropriate conditions.

Oxygen environment and metabolic oxygen demand predictably interact to affect thermal behavior in a lizard, Sceloporus occidentalis.

The climate crisis necessitates predicting how organisms respond to changing environments, but this requires understanding the mechanisms underlying thermal tolerance. The Hierarchical Mechanisms of Thermal Limitation (HMTL) hypothesis proposes that respiratory capacity and marginal stability of proteins and membranes interact hierarchically to determine thermal performance and limits. An untested prediction of the HMTL hypothesis is that behavioral anapyrexia (i.e., reduced body temperature in hypoxia) is exacerbated when metabolic demand is high. We tested this prediction by manipulating western fence lizards' (Sceloporus occidentalis) metabolic demand and oxygen environment, then measuring selected body temperatures. Lizards with elevated metabolic demand selected lower body temperatures at higher oxygen concentrations than resting lizards, but this occurred only at oxygen concentrations <12% O2 , suggesting thermal limits are unaffected by naturally-occurring oxygen variation. Given our results and the ubiquity of behavioral anapyrexia, the HMTL hypothesis may generally explain how oxygen and temperature interactively affect reptile performance.

The Thermal Biology of Takydromus kuehnei Indicates Tropical Lizards From High Elevation Have Not Been Severely Threatened by Climate Change

Climate change poses different threats to animals across latitudes. Tropical species have been proposed to be more vulnerable to climate change. However, the responses of animals from tropical mountains to thermal variation and climate change have been scarcely studied. Here, we investigated the thermal biology traits of a tropical lizard (Takydromus kuehnei) distributed at high elevations (&amp;gt;950 m) and evaluated the vulnerabilities of T. kuehnei by thermal biology traits, thermal safety margin, and thermoregulatory effectiveness. The average active body temperatures of T. kuehnei in the field were 26.28°C and 30.65°C in April and June, respectively. The selected body temperature was 33.23°C, and the optimal temperature for locomotion was 30.60°C. The critical thermal minimum and critical thermal maximum temperatures were 4.79°C and 43.37°C, respectively. Accordingly, the thermal safety margin (1.23°C) and thermoregulatory effectiveness (1.23°C) predicted that T. kuehnei distributed in tropical mountains were not significantly depressed by environmental temperatures. This study implies that high-elevation species in tropical regions may not be severely threatened by ongoing climate change and highlights the importance of thermal biology traits in evaluating the vulnerability of species to climate change.

Tree Removal Likely Improves Thermal Quality of Basking Sites for an Imperiled Timber Rattlesnake Population at the Northern Edge of Its Range

Lack of natural disturbance in many forests in northeastern North America has resulted in increased canopy cover and a reduction of open-habitat patches. Crotalus horridus (Timber Rattlesnake) in this region depends upon open basking and gestation sites, and its populations have declined markedly. We evaluated the utility of mechanical tree removal to restore potential basking habitat for a highly imperiled Timber Rattlesnake population in New Hampshire. We used a before–after, control–impact study to test for the effects of tree removal on environmental temperature and Timber Rattlesnake and other wildlife use of 3 potential basking sites. Mean temperatures were significantly higher and more variable post-treatment, while minimum temperatures were relatively unaffected. The number of temperature readings within the span of selected body temperatures of gravid female Timber Rattlesnakes (25.2–31.7 °C) increased post-treatment. Using time-lapse cameras, we detected rattlesnakes during 5 days at post-treatment sites but on only 1 day at a control site. Detections of potential rattlesnake prey species did not change following treatment, and few potential rattlesnake predators were detected pre- or post-treatment. Our results suggest that tree removal around potential basking sites likely improves thermal habitat quality for Timber Rattlesnakes.

Comparative thermal ecology parameters of the mexican dusky rattlesnake (Crotalus triseriatus).

Montane habitats exhibit a high degree of thermal heterogeneity, and thus provide considerable thermoregulatory challenges for ectotherms. Comparative analyses provide an opportunity to understand how variation in abiotic factors (e.g., operative temperatures, thermal quality) can affect life history traits within species. We studied the thermal ecology of three populations of the rattlesnake Crotalus triseriatus inhabiting different volcanoes in the central region of Mexico using the Hertz et al. (1993) protocol. The average body temperature of dusky rattlesnakes from the three study sites was 22.4°C; mean active body temperature was higher in site 2 than in sites 1 and 3, but no differences between females, males and juveniles nor an interaction among site and sex was found. The thermal quality was low in the three sites, particularly in sites 1 and 3. Thermoregulation accuracy statistically differed among populations: individuals from site 2 were more accurate thermoregulating, while individuals from site 1 were the least accurate. Compared to other snakes, dusky rattlesnakes can be considered as a eurythermic species, which can often be active at relatively low body temperatures.

Shifts in thermal preference of introduced Asian house geckos (Hemidactylus frenatus) in temperate regions of southeastern Australia

Despite its tropical origin, the Asian house gecko (Hemidactylus frenatus) is currently invading higher latitudes around the world. In this study, we investigated whether the introduced geckos in the subtropical/temperate region of southeastern Australia have shifted their thermal biology to cope with colder temperatures. In the lab, we measured the body temperatures of geckos from Thailand and Australia in a cost-free thermal gradient. Native H. frenatus from Thailand displayed a diel pattern of thermoregulation. Geckos maintained higher body temperatures during mid-afternoon and at dusk but selected cooler temperatures during the night. Introduced geckos showed a similar pattern of thermoregulation, but selected lower body temperatures in summer (mean=28.9°C) and winter (mean=25.5°C) than native geckos (mean=31.5°C). While the Asian house geckos from Thailand did not alter their body temperatures after feeding, their conspecifics from southeastern Australia selected body temperatures that were 1.6-3.1°C higher after feeding. In conclusion, our study shows that invasive house geckos in Australia have shifted their preferred body temperatures downwards relative to their native conspecifics in Thailand, presumably as a result of plasticity or natural selection. Our findings suggest that these tropical geckos have adapted to colder regions, and thus, they may spread much further than expected for a tropical ectotherm.

Thermophilic response post feeding in Pleurodema nebulosum (Anura: Leptodactylidae) from Monte desert, Argentina.

We studied the thermophilic response to feeding of a typical desert adapted anuran from the Monte Desert. Our aim was to evaluate thermal changes in the selected body temperature of adult frogs of Pleurodema nebulosum, and measure the intestinal passage time, and food digestion. Our results show that after feeding, they selected higher micro-environmental temperatures ~ + 2°C than frogs that remained starved. Pleurodema nebulosum would present a postprandial thermophilic response. The time of retention of food in the digestive tract was thermo-dependent, being lower in those individuals who were incubated at high temperatures (25°C) compared to those subjected to lower temperatures (20°C). Although we did not detect effects of temperature on digestive efficiency, the mass of faecal material indicates an increase at temperatures closer to the selected ones, suggesting that the defecation rate is influenced by temperature. Laiuoperinae frogs are characterized by explosive breeding behavior and fast growing rate. The digestive efficiency is essential for acquiring energy necessary for growth, reproduction and refuge-seeking, among others. In this framework, the differential selection of temperatures between moments of fasting and feeding allows the frogs to maintain a high digestive efficiency, maximizing the absorption of nutrients.

Heat seekers: A tropical nocturnal lizard uses behavioral thermoregulation to exploit rare microclimates at night.

Environmental temperatures play a vital role in the physiological and behavioral activity of ectotherms. Behavioral thermoregulation allows animals to modify their body temperature to optimize functions critical to fitness, including digestion, growth, reproduction, and locomotor performance. Diurnal reptiles are a classic model system to answer questions related to thermal ecology, whereas behavioral thermoregulation in nocturnal species is thought to be strongly constrained by low environmental thermal heterogeneity at night. The few studies describing the thermal ecology of nocturnal reptiles indicate a majority of thermoregulatory behavior (if any) occurs during the day within diurnal retreats, but few examined this behavior throughout the night. In tropical systems, thermal heterogeneity may remain high, even at night, allowing nocturnal ectotherms to thermoregulate through conduction on surfaces that retain heat after sunset. We investigated the thermoregulatory behavior of a tropical nocturnal gecko (Australian house gecko, Gehyra dubia) by measuring its preferred temperature in a thermal gradient, and selected body temperatures using radio telemetry, in relation to available operative environmental temperatures obtained using thermal models. Preferred body temperatures of geckos ranged from 31.4 ± 0.59-34.5 ± 0.55 °C in a laboratory thermal gradient. In the field, during winter, geckos were more effective thermoregulators than in the summer. In low thermal quality habitats, geckos sought rare, warm microclimates at night to maintain body temperatures warmer than most available environmental temperatures, and were highly effective thermoregulators. For ectotherms, appropriate environmental temperatures are a vital resource for survival, similar to food or shelter. The ability to exploit rare microclimates is especially important for nocturnal species, as heterogeneity of environmental temperatures is reduced at night compared to the day. In a warming world, it is vital to understand the thermal ecology of nocturnal ectotherms, as other species may shift to become more nocturnal to avoid lethal diurnal temperatures.

Selected body temperature in Mexican lizard species

Lizards are vertebrate ectotherms, which like other animals maintain their body temperature (Tb) within a relatively narrow range in order to carry out crucial physiological processes during their life cycle.

Phenology and the physiological niche are co‐adapted in a desert‐dwelling lizard

Abstract A major goal of seasonal biology is to understand how selection on phenology and the physiological niche interact. In oviparous species, fitness variation across the growing season suggests that phenological shifts will alter selective environments experienced by embryos. We hypothesize that physiology could become co‐adapted with phenology; such that embryos perform better in the environmental conditions they are adapted to compared to embryos adapted to other environments (temporal matching). Here, we tested for temporal matching to seasonal changes in the environmental temperatures with toad‐headed lizard, Phrynocephalus przewalskii, which inhabits the temperate desert steppe of China. We used a split‐clutch reciprocal experiment, by incubating eggs from early‐ and late‐breeding females at rising and falling temperature regimes, respectively, to separate the influence of intrinsic (genetic and parental) vs. extrinsic factors (developmental plasticity or acclimatization) on the performance and fitness of offspring. Eggs from early‐breeding females were with higher quality than those from late‐breeding females, likely due to better maternal provisioning. Offspring from early‐breeding females had higher selected body temperatures and metabolic rates than those from late‐breeding females. Falling temperatures that may indicate the end of the growing season, reduced incubation duration and increased metabolic rates for both early and late eggs, compared to rising temperatures. Late hatchlings had higher growth rates when incubated at falling compared to rising temperatures, while growth rates of early hatchlings were not sensitive to incubation temperature. Thus, growth and survival rates of late embryos were similar to early embryos under falling temperatures, despite early embryos being of generally higher quality. Overall, our study confirms that “early is higher quality.” Intrinsic factors dominate offspring performance and fitness, with a general advantage for early embryos throughout the season. We found some support for temporal matching, demonstrating that late embryos with lower quality have physiological strategies that are specialized to late‐season environments, allowing them to attain similar fitness in late‐season environments to that of early embryos. A plain language summary is available for this article.

Would behavioral thermoregulation enable pregnant viviparous tropical lizards to cope with a warmer world?

Sceloporus lizards depend on external heat to achieve their preferred temperature (Tsel ) for performing physiological processes. Evidence both in the field and laboratory indicates that pregnant females of this Genus select body temperatures (Tb ) lower than 34 °C as higher temperatures may be lethal to embryos. Therefore, thermoregulation is crucial for successful embryo development. Given the increase in global air temperature, it is expected that the first compensatory response of species that inhabit tropical climates will be behavioral thermoregulation. We tested whether viviparous Sceloporus formosus group lizards in the wild exhibited differences in thermoregulatory behavior to achieve the known Tsel for developing embryos regardless of local thermal conditions. We quantified field active body temperature, thermoregulatory behavior mechanisms (time of sighting, microhabitat used and basking time) and available microhabitat thermal conditions (i.e. operative temperature) for 10 lizard species during gestation, distributed along an altitudinal gradient. We applied both conventional and phylogenic analyses to explore whether Tb or behavioral thermoregulation could be regulated in response to different thermal conditions. These species showed no significant differences in field Tb during gestation regardless of local thermal conditions. In contrast, they exhibited significant differences in their behavioral thermoregulation associated with local environmental conditions. Based on these observations, the differences in thermoregulatory behavior identified are interpreted as compensatory adjustments to local thermal conditions. We conclude that these species may deal with higher temperatures predicted for the tropics by modulating their thermoregulatory behavior.

Temperature selection by juvenile tuatara (Sphenodon punctatus) is not influenced by temperatures experienced as embryos

Most reptiles thermoregulate to achieve body temperatures needed for biological processes, such as digestion and growth. Temperatures experienced during embryogenesis may also influence post-hatching growth rate, potentially through influencing post-hatching choice of temperatures. We investigated in laboratory settings whether embryonic temperatures (constant 18°C, 21°C and 22°C) influence selected body temperatures (Tsel) of juvenile tuatara (Sphenodon punctatus), providing a possible mechanism for differences in growth rates. We found that incubation temperature does not influence Tsel. Although the average daily mean Tsel was 21.6 ± 0.3°C, we recorded individual Tsel values up to 33.5°C in juvenile tuatara, which is higher than expected and above the panting threshold of 31–33°C reported for adults. We found diel patterns of Tsel of juvenile tuatara, observing a general pattern of two apparent peaks and troughs per day, with Tsel being significantly lower around dawn and at 1500h than any other time. When comparing our results with other studies on tuatara there is a remarkable consistency in mean Tsel of ~ 21°C across tuatara of different ages, sizes and acclimatization histories. The ability of juvenile tuatara to withstand a wide range of temperatures supports their former widespread distribution throughout New Zealand and warrants further investigation into their plasticity to withstand climate warming, particularly where they have choices of habitat and the ability to thermoregulate.

The effect of skin reflectance on thermal traits in a small heliothermic ectotherm

Variation in colour patterning is prevalent among and within species. A number of theories have been proposed in explaining its evolution. Because solar radiation interacts with the pigmentation of the integument causing light to either be reflected or absorbed into the body, thermoregulation has been considered to be a primary selective agent, particularly among ectotherms. Accordingly, the colour-mediated thermoregulatory hypothesis states that darker individuals will heat faster and reach higher thermal equilibria while paler individuals will have the opposite traits. It was further predicted that dark colouration would promote slower cooling rates and higher thermal performance temperatures. To test these hypotheses we quantified the reflectance, selected body temperatures, performance optima, as well as heating and cooling rates of an ectothermic vertebrate, Lampropholis delicata. Our results indicated that colour had no influence on thermal physiology, as all thermal traits were uncorrelated with reflectance. We suggest that crypsis may instead be the stronger selective agent as it may have a more direct impact on fitness. Our study has improved our knowledge of the functional differences among individuals with different colour patterns, and the evolutionary significance of morphological variation within species.

温度驯化对红耳滑龟幼龟选择体温、热耐受性和抗氧化酶活性的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 温度驯化对红耳滑龟幼龟选择体温、热耐受性和抗氧化酶活性的影响 DOI: 10.5846/stxb201408101597 作者: 作者单位: 温州大学 生命与环境科学学院,温州大学 生命与环境科学学院,温州大学 生命与环境科学学院,温州大学 生命与环境科学学院,温州大学 生命与环境科学学院,温州大学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目(31170376);浙江省大学生科技创新活动计划(2013R424029);温州大学实验室开放项目(12SK56A) Influence of temperature acclimation on selected body temperature, thermal tolerance, and antioxidant enzyme activity of juvenile red-eared slider turtles (Trachemys scripta elegans) Author: Affiliation: College of Life and Environmental Sciences,Wenzhou University,College of Life and Environmental Sciences,Wenzhou University,College of Life and Environmental Sciences,Wenzhou University,College of Life and Environmental Sciences,Wenzhou University,College of Life and Environmental Sciences,Wenzhou University,College of Life and Environmental Sciences,Wenzhou University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:温度驯化对变温动物的生理和行为表现会产生重要影响,不同物种的驯化反应不尽相同。红耳滑龟(Trachemys scripta elegans)为外来入侵种,在中国许多地区发现了野外种群,对当地生物多样性产生了一定程度的威胁。为了探讨红耳滑龟幼体的热适应表现,在5个恒定温度(16,20,26,32℃和36℃)下驯化幼龟30d后,检验幼龟的选择体温(Tsel),耐受低温(CTMin)、耐受高温(CTMax)和耐受温度范围(TRR),以及骨骼肌、心肌和肝脏的过氧化物岐化酶(SOD)活力、过氧化氢酶(CAT)活力和丙二醛(MDA)含量是否受驯化温度影响。结果显示:驯化温度显著影响幼龟的Tsel、CTMin和CTMax,并随驯化温度的升高而升高,但对TRR无显著影响。驯化温度显著影响骨骼肌、心肌和肝脏的SOD活力。驯化温度显著影响肝脏的MDA含量,而对骨骼肌和心肌的MDA含量无显著影响。驯化温度显著影响心肌和肝脏的CAT活力,对骨骼肌CAT活力无显著影响。以上结果表明:温度驯化会影响红耳滑龟幼体选择体温和热耐受能力,符合越热越好假设;同时会影响组织的抗氧化能力。 Abstract:As an important environmental factor, temperature affects the growth, reproduction, physiology, behavior, and offspring phenotype of reptiles. The influence of thermal acclimation on physiological and behavioral performance has been documented in many ectotherm animals, although the acclimation responses of different species may be not identical. The red-eared slider turtle (Trachemys scripta elegans) is an alien invasive species found in China. Wild populations have been found to be a threat to local biodiversity in many areas. In this paper, critical thermal minima (CTMin) and critical thermal maxima (CTMax) are used to assess the thermal resistance of juvenile red-eared slider turtles. In addition, the selected body temperature (Tsel) is used to determine the species' preferred temperature. Our study aimed to determine whether acclimation temperature would affect the Tsel, CTMin, CTMax, thermal resistance range (TRR), the activity of superoxide dismutase (SOD) and catalase (CAT), and the malondialdehyde (MDA) content of the skeletal muscles, cardiac muscles, and liver. In order to examine their thermal adaptive performance at different temperatures, we selected 90 juvenile turtles weighing between 40.0 and 44.3 g, randomly divided them into 5 groups with similar average weights (P=0.141), and acclimated them to five thermal conditions (16, 20, 26, 32℃ and 36℃) for 30 days. After acclimation, Tsel were measured using a thermometer (UT-325) in thermal gradient groove, while CTMin and CTMax were measured in binder incubators. SOD and CAT activity, as well as the MDA content were measured using commercial kits produced by Jiancheng Biotech Co. Ltd., Nanjing, China, according to the manufacturer's instructions. Then, a one-way ANOVA was used to test the effects of acclimation temperature on Tsel, CTMin, CTMax, TRR, SOD and CAT activity, and the MDA content of different tissues. The results showed that acclimation temperature had significant effects on the Tsel (P < 0.0001), CTMin (P < 0.0001), and CTMax (P < 0.01) of juvenile turtles, but had no significant effect on the TRR (P=0.212). Tsel, CTMin, and CTMax increased with acclimation temperature. Acclimation temperature had a significant impact on SOD activity in the skeletal muscles, cardiac muscles, and liver, as well as on the MDA content of the liver (all P < 0.05). However, it had no effect on the MDA content of the skeletal and cardiac muscles (all P > 0.05). There was higher SOD activity in the skeletal and cardiac muscles at high temperatures (26-36℃) than at low temperatures (16-20℃); meanwhile, in the liver, higher SOD activity and MDA content were observed at medium temperatures (20-32℃). Acclimation temperature had a significant effect on CAT activity in the cardiac muscles and liver (all P < 0.05), but no effect on that in skeletal muscles (P=0.55). In cardiac muscles, CAT activity was significantly lower at 36℃ than at other temperatures, while in the liver CAT activity peaked at 16℃. This indicates that acclimation temperature affects the selected body temperature and thermal tolerance of juvenile red-eared slider turtles, with higher temperatures generally having more favorable effects. The antioxidant activity in the tissues was also affected by differences in acclimation temperature. 参考文献 相似文献 引证文献

Does tail autotomy affect thermoregulation in an accurately thermoregulating lizard? Lessons from a 2200‐m elevational gradient

AbstractTail autotomy is an antipredatory defense that allows lizards to escape predator attacks by shedding their tails. While the benefits of preserving life are indisputable, tail loss implies a number of physiological, social, reproductive and even metabolic costs derived from tail regeneration and reduced motility. In addition, predation risk is increased in lizards with autotomized tails. Metabolic rates increase with body temperature, which in ectotherms depends on external heat sources. Ectotherm thermoregulation is costly in terms of time consumption and exposure to predators, this cost depending on habitat thermal quality. In this work, we seek to disentangle the effects of tail autotomy on field and selected body temperature of an accurately thermoregulating lizard Psammodromus algirus in different thermal environments along a 2200‐m elevational gradient. We test two non‐mutually exclusive hypotheses. According to a physiological hypothesis, we expect lizards with autotomized tails to show higher body temperatures that allow them to regenerate lost tissues faster, at least when the thermal environment is not limiting (at mid and low elevations). By contrast, according to an ethological hypothesis, we expect lizards with autotomized tails to avoid exposure to predators by reducing thermoregulation time, thus showing lower temperatures than lizards with non‐autotomized tails. However, we found that the tail state did not significantly affect lizard field or selected body temperatures. On the one hand, a warmer thermal optimum could imply greater exposure to predators during basking, making motility‐impaired lizards with autotomized tails more vulnerable, which could explain why the physiological hypothesis of autotomy thermal effect does not apply. On the other hand, lower body temperatures could be physiologically costly for lizards, which, together with the other costs resulting from tail autotomy, could jeopardize lizard fitness. Therefore, both hypotheses were not supported.

Thermal ecology of the post–metamorphic Andean toad (Rhinella spinulosa) at elevation in the monte desert, Argentina

Rhinella spinulosa is an anuran toad species distributed latitudinal and altitudinal (1200–5000m) from Peru to Argentina, inhabiting mountain valleys in the Andes. Considering the broad range of habitats where they live, it is important to understand the thermal physiological mechanisms, thermal tolerances and physiological adaptations for surviving in rigorous environments. We investigated the thermal parameters (field body temperature, selected body temperature, locomotor performance in field and laboratory conditions, and thermal extremes) during diurnal activity for a population of juvenile, post–metamorphosed toads (Rhinella spinulosa) from the Monte Desert of San Juan, Argentina. Post-metamorphic toads are active from approximately 1100–1900 (in contrast to nocturnal adult toads). Our findings show that these toads have a wide thermal tolerance range, ranging from a critical thermal maximum of 36.9°C to crystallization temperatures below 0°C. During their active period, toads always showed suboptimal thermal conditions for locomotion. Despite the suboptimal condition for the locomotion, diurnal activity is likely to confer thermal advantages, allowing them to search for food and increase digestion and growth rates. We also found that the toads are capable of super-cooling, which prevents mortality from freezing when the environmental temperatures drop below 0°C. The environmental temperatures are below zero at night, when toads are inactive and take refuge under rocks. In summary, this toad population demonstrates high thermal plasticity, as shown by a relatively high level of activity sustained over a wide range of ambient temperature (~35°C). These thermal adaptations allow this species of juvenile toads to inhabit a wide range of altitudes and latitudes.

Selected body temperature of nine species of Mexican horned lizards (Phrynosoma)

Temperature plays an important role in the behavior, ecology, physiology, and evolution of reptiles. Herein, we present selected body temperatures on 9 species of Phrynosoma under laboratory conditions, and note congeneric differences related to altitude and reproductive mode. The results are discussed with those of other phrynosomatid lizards.

Termorregulación de dos poblaciones de lagartijas simpátridas: Sceloporus lineolateralis y Sceloporus poinsettii (Squamata: Phrynosomatidae) en Durango, México

Environmental temperature is an important factor that regulates activity and physiological processes of ectotherms. Because sympatric species are exposed to similar thermal niche conditions, closely related species could present similar thermal requirements. This similarity may generate interspecific competition for optimal thermal space. The thermal ecology of the sympatric viviparous lizards Sceloporus lineolateralis and S. poinsettii (Sceloporus torquatus and Sceloporus poinsettii groups, respectively) were studied in natural populations in Peñón Blanco, Durango, Mexico. We found that active body temperatures and selected body temperatures were similar among species. However, S. poinsettii exhibited higher efficiency and accuracy of thermoregulation because the preferred thermal range of this species was wider. Finally their thermal preferences are analogous to those previously reported for the both groups and the genus.