Temperature seasonality plays a pivotal role in shaping the thermal biology of ectotherms. However, we still have a limited understanding of how ectotherms maintain thermal balance in the face of varying temperatures, especially in fossorial species. Due to thermal buffering underground, thermal ecology theory predicts relaxed selection pressure over thermoregulation in fossorial ectotherms. As a result, fossorial ectotherms typically show low thermoregulatory precision and low evidence of thermotactic behaviours in laboratory thermal gradients. Here, we evaluated how temperature selection (T sel) and associated behaviours differed between seasons in a fossorial amphibian, the spotted salamander (Ambystoma maculatum). By comparing thermoregulatory parameters between the active and overwintering seasons, we show that A. maculatum engages in active behavioural thermoregulation despite being fossorial. In both seasons, T sel was consistently offset higher than acclimatization temperatures. Thermoregulation differed between seasons, with salamanders having higher T sel and showing greater evidence of thermophilic behaviours in the active compared with the overwintering season. Additionally, our work lends support to experimental assumptions commonly made but seldom tested in thermal biology studies. Ultimately, our study demonstrates that the combination of careful behavioural and thermal biology measurements is a necessary step to better understand the mechanisms that underlie body temperature control in amphibians.

Gravid female lizards often experience reduced thermal preferences and impaired locomotor performance. These changes have been attributed to the physical burden of the clutch, but some authors have suggested that they may be due to physiological adjustments. We compared the thermal biology and locomotor performance of the lizard Liolaemus wiegmannii 1 week before and 1 week after oviposition. We found that gravid females had a thermal preference 1°C lower than that of non-gravid females. This was accompanied by a change in the thermal dependence of maximum running speed. The thermal optimum for locomotor performance was 2.6°C lower before oviposition than after. At relatively low temperatures (22 and 26°C), running speeds of females before oviposition were up to 31% higher than for females after oviposition. However, at temperatures above 26°C, females achieved similar maximum running speeds (∼1.5 m s-1) regardless of reproductive stage. The magnitude of the changes in thermal parameters and locomotor performance of L. wiegmannii females was independent of relative clutch mass (clutches weighed up to 89% of post-oviposition body mass). This suggests that the changes are not simply due to the clutch mass, but are also due to physiological adjustments. Liolaemus wiegmannii females simultaneously adjusted their own physiology in a short period in order to improve locomotor performance and allocated energy for embryonic development during late gravid stage. Our findings have implications for understanding the mechanisms underlying life histories of lizards on the fast extreme of the slow-fast continuum, where physiological exhaustion could play an important role.

Temperature is one of the most important factors in the life histories of ectotherms, as body temperature has an undeniable effect on growth, activity, and reproduction. Lizards have a wide variety of strategies to acquire and maintain body temperature in an optimal range. The \"Thermal Melanism Hypothesis\" proposes that individuals with lower skin reflectance can heat up faster as a result of absorbing more solar radiation compared to lighter conspecifics. Therefore, having a darker coloration might be advantageous in cold habitats. Dorsal skin reflectance has been found to change rapidly with body temperature in several lizard species, and it can also vary over longer, seasonal time scales. These variations may be important in thermoregulation, especially in lizards that inhabit areas with a large temperature variation during the year. Here, we study how dorsal reflectance fluctuates with body temperature and varies among seasons. We compared dorsal skin reflectance at three body temperature treatments, and measured thermal rates (i.e., heat and cool rate, thermic lapse, and net heat gain) by elevation (2500-4100 m) and seasons (spring, summer, and autumn) in the mesquite lizard, Sceloporus grammicus. Our results show that lizards were darker at high elevations and during the months with the lowest environmental temperatures. The rate of obtaining and retaining heat also varied during the year and was highest during the reproductive season. Our results indicate that the variation of dorsal skin reflectance and thermal rates follows a complex pattern in lizard populations and is affected by both elevation and season.

The environment is changing rapidly, and considerable research is aimed at understanding the capacity of organisms to respond. Changes in environmental temperature are particularly concerning as most animals are ectothermic, with temperature considered a key factor governing their ecology, biogeography, behaviour and physiology. The ability of ectotherms to persist in an increasingly warm, variable, and unpredictable future will depend on their nutritional status. Nutritional resources (e.g. food availability, quality, options) vary across space and time and in response to environmental change, but animals also have the capacity to alter how much they eat and what they eat, which may help them improve their performance under climate change. In this review, we discuss the state of knowledge in the intersection between animal nutrition and temperature. We take a mechanistic approach to describe nutrients (i.e. broad macronutrients, specific lipids, and micronutrients) that may impact thermal performance and discuss what is currently known about their role in ectotherm thermal plasticity, thermoregulatory behaviour, diet preference, and thermal tolerance. We finish by describing how this topic can inform ectotherm biogeography, behaviour, and aquaculture research.

Climate change is currently considered one of the major threats to biodiversity and is associated with an increase in the frequency and intensity of extreme weather events, such as heatwaves. Heatwaves create acutely stressful conditions that may lead to disruption in the performance and survival of ecologically and economically important organisms, such as insect pollinators. In this study, we investigated the impact of simulated heatwaves on the performance of queenless microcolonies of Bombus terrestris audax under laboratory conditions. Our results indicate that heatwaves can have significant impacts on bumblebee performance. However, contrary to our expectations, exposure to heatwaves did not affect survival. Exposure to a mild 5-day heatwave (30-32 °C) resulted in increased offspring production compared to those exposed to an extreme heatwave (34-36 °C) and to the control group (24 °C). We also found that brood-care behaviours were impacted by the magnitude of the heatwave. Wing fanning occurred occasionally at temperatures of 30-32 °C, whereas at 34-36 °C the proportion of workers engaged in this thermoregulatory behaviour increased significantly. Our results provide insights into the effects of heatwaves on bumblebee colony performance and underscore the use of microcolonies as a valuable tool for studying the effects of extreme weather events. Future research, especially field-based studies replicating natural foraging conditions, is crucial to complement laboratory-based studies to comprehend how heatwaves compromise the performance of pollinators. Such studies may potentially help to identify those species more resilient to climate change, as well as those that are most vulnerable.

Behavioural, physiological and biochemical mechanisms constitute the adaptive capacities that allow marine ectotherms to explore the environment beyond their thermal optimal. Limitations to the efficiency of these mechanisms define the transition from moderate to severe thermal stress, and serve to characterise the thermoregulatory response in the zone of thermal tolerance. We selected a tropical population of Hippocampus erectus to describe the timing of the physiological and biochemical mechanisms in response to the following increments in water temperature: (i) 4°C abrupt (26-30°C in <5 min); (ii) 7°C abrupt (26-33°C); (iii) 4°C gradual (1°C every 3 h) and (iv) 7°C gradual (1.5°C every 3 h). The routine metabolic rate (Rrout) of juvenile H. erectus was measured immediately before and after 0.5, 12 and 28 h of being exposed to each thermal treatment. Samples of muscle and abdominal organs were taken to quantify indicators of aerobic and anaerobic metabolism and antioxidant enzymes and oxidative stress at each moment throughout exposure. Results showed a full thermoregulatory response within 0.5 h: Rrout increased in direct correspondence with both the magnitude and rate of thermal increase; peroxidised lipids rapidly accumulated before the antioxidant defence was activated and early lactate concentrations suggested an immediate, yet temporary, reduction in aerobic scope. After 12 h, Rrout had decreased in sea horses exposed to 30°C, but not to 33°C, where Rrout continued high until the end of trials. Within 28 h of thermal exposure, all metabolite and antioxidant defence indicators had been restored to control levels (26°C). These findings testify to the outstanding thermal plasticity of H. erectus and explain their adjustment to rapid fluctuations in ambient temperature. Such features, however, do not protect this tropical population from the deleterious effects of chronic exposure to temperatures that have been predicted for the future.

Outside of scientific circles, climate change is a hotly debated topic due to all its consequences. Changes in the temperature can affect aquatic organisms and it is important to understand and to detect earlier signals. This study aimed to analyze how a Neotropical fish species responds to temperature increases, using proteomic analysis as a tool. For this, fish of the species Rhamdia quelen, male and female, were exposed to two temperatures: 25 °C and 30 °C. After 96 h, the animals were anesthetized, euthanized and the liver was collected for proteomic analysis. Using freely available online software and databases (e.g. MetaboAnalyst, Gene Ontology and UniProt), we define the altered proteins in both sexes: 42 in females and 62 in males. Data are available via ProteomeXchange with identifier PXD046475. Differences between the two temperatures were observed mainly in the amino acid metabolic pathways. The cellular process and the immune response was altered, indicating that effects at lower levels of biological organization could serve as a predictor of higher-level effects when temperature rise affects wildlife populations. Thus, we conclude that the increase in temperature is capable of altering important cellular and physiological processes in R. quelen fish, with this response being different for males and females.

Changes in environmental temperature may induce variations in thermal tolerance and sensitivity in ectotherm organisms. These variations generate plastic responses that can be analyzed by examining their Thermal Performance Curves (TPCs). Additionally, some performance traits, like locomotion, could be affected by other factors such as biological interactions (e.g., predator-prey interaction). Here, we evaluate if the risk of predation modifies TPCs in Mendoza four-eyed frog (Pleurodema nebulosum, Burmeister, 1861) and Guayapa\'s four-eyed frog (Pleurodema guayapae, Barrio, 1964), two amphibian species that occur in ephemeral ponds in arid environments. We measured thermal tolerances and maximum swimming velocity at six different temperatures in tadpoles under three situations: control, exposure to predator chemical cues, and exposure to conspecific alarm cues. TPCs were fitted using General Additive Mixed Models. We found that curves of tadpoles at risk of predation differed from those of control mainly in thermal sensitivity parameters. Our work confirms the importance of biotic interactions have in thermal physiology.

In animals, the success of particular lineages can be measured in terms of their number of species, the extent of their geographic range, the breadth of their habitats and ecological niches, and the diversity of their morphological and life-history traits. Here, we review the distribution, ecology, morphology and life history of skinks, a diverse lineage of terrestrial vertebrates. We compared key traits between the three subfamilies of skinks, and between skinks and non-scincid lizards. There are currently 1743 described species of skink, which represent 24% of global lizard diversity. Since 2010, 16% of lizard descriptions have been of skinks. The centres of skink diversity are in Australia, New Guinea, southeast Asia, Oceania, Madagascar and central Africa. Compared with non-scincid lizards, skinks have larger distributional ranges, but smaller body sizes. Sexual size dimorphism is rare in skinks. Almost a quarter (23%) of skinks exhibit limb reduction or loss, compared with just 3% of non-scincid lizards. Skinks are more likely to be viviparous (34% of species) compared with non-scincids (13%), and have higher clutch/litter sizes than non-scincids. Although skinks mature later than non-scincids, their longevity is similar to that exhibited by other lizard groups. Most skinks (88%) are active foragers, and they are more likely to be carnivorous than non-scincids. Skinks are more likely to be diurnal or cathemeral than other lizard groups, but they generally have lower field body temperatures compared with non-scincids. The success of skinks appears to be both a result of them hitting upon a winning body plan and ecology, and their capacity to regularly deviate from this body plan and adapt their ecology and life history (e.g. repeated limb reduction and loss, transitions to viviparity) to prevailing conditions.

Cold tolerance of adult medflies has been extensively studied but the effect of subfreezing temperatures on the immature stages remains poorly investigated, especially as far as different populations are regarded. In this study, we estimated the acute cold stress response of three geographically divergent Mediterranean fruit fly populations originating from Greece (Crete, Volos) and Croatia (Dubrovnik) by exposing immature stages (eggs, larvae, pupae) to subfreezing temperatures. We first determined the LT50 for each immature stage following one hour of exposure to different temperatures. Then eggs, larvae and pupae of the different populations were exposed to their respective LT50 for one hour (LT50 = -11 °C, LT50 = -4.4 °C, LT50 = -5 °C for eggs, larvae and pupae, respectively). Our results demonstrate that populations responded differently depending on their developmental stage. The population of Dubrovnik was the most cold-susceptible at the egg stage, whereas in that of Crete it was at the larval and pupal stage. The population of Volos was the most cold-tolerant at all developmental stages. The egg stage was the most cold-tolerant, followed by pupae and finally the 3rd instar wandering larvae. This study contributes towards understanding the cold stress response of this serious pest and provides data for important parameters that determine its successful establishment to unfavorable environments with an emphasis on range expansion to the northern, more temperate regions of Europe.