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The presence of Mytilus galloprovincialis, widely known as the Mediterranean mussel, have been genetically certified from Coliumo Bay to the Magellan Strait, in central and southern Chile, respectively. To correlate the geographic distribution of this species along the Chilean coast with its physiological tolerance to upper temperatures, experiments were carried out with adults and larval stages. Trochophore, umbonate veliger, and pre-metamorphic larvae were submitted to experimental temperatures from 17-33°C, during 24 h to determine the upper temperature limit. Meanwhile, adult experiments were carried with specimens having different previous physiological background: spring-summer acclimation (November-January), and fall-winter acclimation (August-October) and exposed to temperature range of 17-33°C for period of 24, 48, 72 and 96 h, to verify mortality and byssus formation. Results showed that at larvae stages, the 50% of mortality occurred at 27°C, with 100% mortality at 30°C. Adult stages reached the 55% mortality exposed for 48 h at 30°C and 100% mortality in 72 h at the same temperature. The byssus secretion become failing at 27°C and ceased at 30°C. [ABSTRACT FROM AUTHOR]

Foraging methods are highly variable, but can be grouped into two modes: searching and ambush. While research has focused on the functioning of each mode, the question of how animals choose which to use has been largely neglected. Here we consider a forager that exploits prey that are patchily distributed in space and time. This forager can either sit and wait for prey to appear or search for prey, which is more likely to result in encounters with prey but costs more energy and/or exposes the forager to greater predation risk. The currency that natural selection appears to have optimized will be determined by the additional costs of searching and whether there is a risk of starvation. We therefore compare the predictions of models based on currencies that consider only energy and predation risk to state-dependent models in which energy reserves are used to trade off predation rate, starvation rate and investment in growth. The choice of currency qualitatively affects how mode should change when prey abundance and prey patchiness increase. We show how differing prey distributions can explain variation in effects of experimentally increasing prey abundance. Our work has several implications for the study of foraging mode, population dynamics and the methods used to assess population size. [ABSTRACT FROM AUTHOR]

The impact of warming on the persistence and distribution of ectotherms is often forecasted from their warming tolerance, inferred as the difference between their upper thermal limit and macroclimate temperature. Ectotherms, however, are thermally adapted to their microclimates, which can deviate substantially from macroscale conditions. Ignoring microclimates can therefore bias estimates of warming tolerance. We compared warming tolerance of an insect across its ontogeny when calculated from macro- and microclimate temperatures. We used a heat balance model to predict experienced microclimate temperatures from macroclimate, and we measured thermal limits for several life stages. The model shows a concomitant increase in microclimate temperatures and thermal limits across insect ontogeny, despite the fact that they all share the same macroclimate. Consequently, warming tolerance, as estimated from microclimate temperature, remained constant across ontogeny. When calculated from macroclimate temperature, however, warming tolerance was overestimated by 7–10oC, depending on the life stage. Therefore, errors are expected when predicting persistence and distribution shifts of ectotherms in changing climates using macroclimate rather than microclimate. [ABSTRACT FROM AUTHOR]

Body size ( BS) varies in response to several selective pressures. In ectotherms, thermal inertia may affect thermoregulation, since larger BSs increase heat conservation as Bergmann originally stipulated for endotherms. However, Bergmann's rule is controversial in ectotherms. The heat balance hypothesis states that ectotherms' thermoregulatory capability is relevant for trends in BS. In cold climates, larger BSs would be advantageous for small thermoregulating ectotherms, by increasing heat conservation. However, BS implies a delaying effect on heating too; therefore, ectotherms may need another trait to compensate the later effect. Thermal melanism hypothesis posits that melanism increases heat gain, and may be adaptive for animals inhabiting cold climates. We propose that the higher solar radiation absorption from increased melanism may be such a compensatory trait. We expect BS and melanism to increase with latitude in response to seasonal temperatures and solar radiation. To test this, we studied the monophyletic L iolaemus goetschi group of lizard species across its 2200 km (32-48° S latitude) range. We used phylogenetically informed analyses to study geographic variation of BS and melanism (dorsal, ventral and total) in relation to temperatures, thermal amplitude, cloudiness and net solar radiation. Our results show that lizards' BS increases latitudinally in relation to thermal amplitude and temperature. Only ventral melanism varied latitudinally, but all melanism variables varied in response to cloudiness and net radiation. The relationship between BS and melanism was significant and positive in all cases. We suggest thermal inertia may be a fair candidate mechanism explaining geographic variation in BS (heat balance hypothesis), while melanism may influence heat gain according to the thermal melanism hypothesis. However, it remains unclear why latitudinal variation is related to ventral instead of dorsal melanism, and further investigation is needed to clarify the relationship between BS and melanism in light of cold climates. [ABSTRACT FROM AUTHOR]

The Thermal Adaptation Hypothesis posits that the warmer, aseasonal tropics generates populations with higher and narrower thermal limits. It has largely been tested among populations across latitudes. However, considerable thermal heterogeneity exists within ecosystems: across 31 trees in a Panama rainforest, surfaces exposed to sun were 8 °C warmer and varied more in temperature than surfaces in the litter below. Tiny ectotherms are confined to surfaces and are variously submerged in these superheated boundary layer environments. We quantified the surface CTmin and CTmaxs (surface temperatures at which individuals grew torpid and lost motor control, respectively) of 88 ant species from this forest; they ranged in average mass from 0.01 to 57 mg. Larger ants had broader thermal tolerances. Then, for 26 of these species we again tested body CTmaxs using a thermal dry bath to eliminate boundary layer effects: body size correlations observed previously disappeared. In both experiments, consistent with Thermal Adaptation, CTmaxs of canopy ants averaged 3.5-5 °C higher than populations that nested in the shade of the understory. We impaled thermocouples in taxidermy mounts to further quantify the factors shaping operative temperatures for four ant species representing the top third (1-30 mg) of the size distribution. Extrapolations suggest the smallest 2/3rds of species reach thermal equilibrium in <10s. Moreover, the large ants that walk above the convective superheated surface air also showed more net heating by solar radiation, with operative temperatures up to 4 °C higher than surrounding air. The thermal environments of this Panama rainforest generate a range of CTmax subsuming 74% of those previously recorded for ant populations worldwide. The Thermal Adaptation Hypothesis can be a powerful tool in predicting diversity of thermal limits within communities. Boundary layer temperatures are likely key to predicting the future of Earth's tiny terrestrial ectotherm populations. [ABSTRACT FROM AUTHOR]

Climate change is imposing constant and more severe environmental challenges to coastal and marine species. Regional climate and species acclimation capacity determine the communities' ecological response to stressors. Marine heatwave events are of serious threat to species fitness and survivorship, even more to the sensitive early-history stages of ectotherms. By combining modeled regional historical data and climate change predictions with manipulative experiments, we evaluated the potential impact of marine heatwaves in a widespread and abundant planktonic larvae of the fiddler crab Leptuca thayeri. Larvae survival was affected by temperature increase with lowest survival probability under higher temperature treatments regardless of pH conditions. Larval physiology was affected by both temperature increase and pH conditions. With heatwaves becoming more frequent, hotter, and lasting longer in the region, we could expect potential reductions in the larval recruitment and stocks with cascade ecological negative effects on estuarine habitats. [Display omitted] • Larvae survival was affected by temperature increase regardless of pH conditions. • Larvae heart beating and abdominal contractions were affected by temperature and pH. • Over the past 38 years Santos/São Vicente coast had a mean SST increase of 0.85 °C. • Higher intensity and duration of heatwaves are expected to reduce larval recruitment. [ABSTRACT FROM AUTHOR]

Telomere attrition is considered a useful indicator of cellular and whole-organism ageing rate. While approximately 80% of animal species undergo metamorphosis that includes extensive tissue transformations (involving cell division, apoptosis, de-differentiation and de novo formation of stem cells), the effect on telomere dynamics is unknown. We measured telomeres in Xenopus laevis developing from larvae to adults under contrasting environmental temperatures . Telomere dynamics were linked to the degree of tissue transformation during development. Average telomere length in gut tissue increased dramatically during metamorphosis, when the gut shortens by 75% and epithelial cells de-differentiate into stem cells. In the liver (retained from larva) and hindlimb muscle (newly formed before metamorphosis), telomeres gradually shortened until adulthood, likely due to extensive cell division. Tail muscle telomere lengths were constant until tail resorption, and those in heart (retained from larva) showed no change over time. Telomere lengths negatively correlated with larval growth, but for a given growth rate, telomeres were shorter in cooler conditions, suggesting that growing in the cold is more costly. Telomere lengths were not related to post-metamorphic growth rate. Further research is now needed to understand whether telomere dynamics are a good indicator of ageing rate in species undergoing metamorphosis.

Ectotherms rely heavily on the spatial variance of environmental conditions to thermoregulate. Theoretically, their fitness is maximized when they can find suitable microhabitats by moving over short distances - this condition is met when spatial variance is high at fine spatial scales. Strikingly, despite the diversity of organisms living in leaf microhabitats, little is known about the impact of warming on the spatial variance of climatic conditions at the scale of individual leaf surfaces., Here, we used experimental manipulation of ambient conditions to quantify the effects of environmental change on the thermal heterogeneity within individual leaf surfaces. We also explored the implications for behavioural thermoregulation by arthropods at a single leaf surface., Using thermography, we characterized the apple leaf microclimate in terms of span and spatial aggregation of surface temperatures across a range of air temperatures and relative humidities. Then, we assessed how thermal heterogeneity within individual leaves affected behavioural thermoregulation by the two-spotted spider mite ( Tetranychus urticae Koch) under both near-optimal and sublethal conditions in this microhabitat. We measured the upper lethal temperature threshold of the mite to define sublethal exposure., Thermal heterogeneity of individual leaves was driven mainly by ambient air temperature. Higher air temperatures gave both smaller ranges and higher spatial aggregation of temperatures at the leaf surface, such that the leaf microclimate was homogenized., Tetranychus urticae used behavioural thermoregulation at moderate air temperature, when thermal heterogeneity was high at the leaf surface. At higher air temperature, however, heterogeneity declined and spider mites did not perform behavioural thermoregulation., Warming decreases thermal heterogeneity of leaf surfaces with critical implications for arthropods - behavioural thermoregulation alone is not sufficient to escape the heat in the leaf microhabitat. Information on spatial variance of microclimatic conditions is critical for estimating how readily organisms can buffer global warming by moving. [ABSTRACT FROM AUTHOR]

Although lymphocyte-like cells secreting somatically-recombining receptors have been identified in the jawless fishes (hagfish and lamprey), the cartilaginous fishes (sharks, skates, rays and chimaera) are the most phylogenetically distant group relative to mammals in which bona fide immunoglobulins (Igs) have been found. Studies of the antibodies and humoral immune responses of cartilaginous fishes and other cold-blooded vertebrates (bony fishes, amphibians and reptiles) are not only revealing information about the emergence and roles of the different Ig heavy and light chain isotypes, but also the evolution of specialised adaptive features such as isotype switching, somatic hypermutation and affinity maturation. It is becoming increasingly apparent that while the adaptive immune response in these vertebrate lineages arose a long time ago, it is most definitely not primitive and has evolved to become complex and sophisticated. This review will summarise what is currently known about the immunoglobulins of cold-blooded vertebrates and highlight the differences, and commonalities, between these and more "conventional" mammalian species. [ABSTRACT FROM AUTHOR]

Background The vertebrate brain is a highly energy consuming organ that requires continuous energy provision. Energy metabolism of ectothermic organisms is directly affected by environmental temperature changes and has been demonstrated to affect brain energy balance in fish. Fish were hypothesized to metabolize lactate as an additional energy substrate during acute exposure to energy demanding environmental abiotic fluctuations to support brain functionality. However, to date the pathways of lactate mobilization and transport in the fish brain are not well understood, and may represent a critical physiological feature in ectotherms during acclimation to low temperature. Results We found depressed routine metabolic rates in zebrafish during acute exposure to hypothermic (18°C) conditions accompanied by decreased lactate concentrations in brain tissues. No changes in brain glucose content were observed. Acute cold stress increased protein concentrations of lactate dehydrogenase 1 (LDH1) and citrate synthase (CS) in brain by 1.8- and- 2.5-fold, paralleled by an increased pyruvate to acetyl-CoA transformation. To test the involvement of monocarboxylate transporters (MCTs) under acute cold stress in zebrafish, we cloned and sequenced seven MCT1-4 homologues in zebrafish. All drMCT1-4 are expressed in brain tissues and in response to cold stress drmct2a and drmct4a transcripts were up-regulated 5- and 3-fold, respectively. On the contrary, mRNA levels of drmct1a, -1b and -4b in zebrafish brain responded with a down regulation in response to cold stress. By expressing drMCTs in Xenopus oocytes we could provide functional evidence that hypothermic stress leads to a 2-fold increase in lactate transport in drMCT4b expressing oocytes. Lactate transport of other paralogues expressed in oocytes was unaffected, or even decreased during cold stress. Conclusion The present work provides evidence that lactate utilization and transport pathways represent an important energy homeostatic feature to maintain vital functions of brain cells during acute cold stress in ectotherms. [ABSTRACT FROM AUTHOR]

Optimal escape theory predicts that animals facing a predation threat should react in a manner that balances perceived threats with the costs of escape. Flight distance, the distance at which animals flee in response to an approaching predator, is often used as a quantitative measure of animal risk assessment and is thus useful to examine predictions of optimal escape theory. However, applying this theory to a broader diversity of animals under more complex environmental conditions has been hampered by a paucity of data. In this study, I measure the flight distances of two freshwater turtles, the invasive Trachemys scripta elegans, and the native Emys marmorata, in an urban California water body to examine how flight distance is affected by time of day, initial visibility to the approaching predator, and the presence of conspecifics. I found that E. marmorata was more sensitive to predation risk than T. scripta and would flee earlier (at a greater distance). Time of day and the presence of conspecifics had no effect on E. marmorata's flight distance although visibility and the interaction between time and visibility did. Emys marmorata would flee earlier when visible, and in the afternoon visible turtles would flee earlier than non-visible turtles, but in the morning, visibility did not affect turtle flight distance. In contrast, T. scripta's flight distance was not affected by any measured variables, although this may be due to a lack of statistical power given the low sample size. This study demonstrates that multiple environmental characteristics influence risk assessment in turtles, and implies that interspecific differences in responses to predation threats may lead to increased competition for thermal resources between native and invasive ectotherms. This is a likely mechanism contributing to the negative impacts of T. scripta on native turtle populations, especially in urban environments. [ABSTRACT FROM AUTHOR]

Changes in environmental temperature can pose considerable challenges to animals and shifts in thermal habitat have been shown to be a major force driving species' adaptation. These adaptations have been the focus of major research efforts to determine the physiological or metabolic constraints related to temperature and to reveal the phenotypic characters that can or should adjust. Considering the current consensus on climate change, the focus of research will likely shift to questioning whether ectothermic organisms will be able to survive future modifications of their thermal niches. Organisms can adjust to temperature changes through physiological plasticity (e.g., acclimation), genetic adaptation, or via dispersal to more suitable thermal habitats. Thus, it is important to understand what genetic and phenotypic attributes-at the individual, population, and species levels-could improve survival success. These issues are particularly important for ectotherms, which are in thermal equilibrium with the surrounding environment. To start addressing these queries, we should consider what physiological or metabolic functions are responsible for the impact of temperature on organisms. Some recent developments indicate that mitochondria are key metabolic structures determining the thermal range that an organism can tolerate. The catalytic capacity of mitochondria is highly sensitive to thermal variation and therefore should partly dictate the temperature dependence of biological functions. Mitochondria contain a complex network of different enzymatic reaction pathways that interact synergistically. The precise regulation of both adenosine triphosphate (ATP) and reactive oxygen species (ROS) production depends on the integration of different enzymes and pathways. Here, we examine the temperature dependence of different parts of mitochondrial pathways and evaluate the evolutionary challenges that need to be overcome to ensure mitochondrial adaptations to new thermal environments. [ABSTRACT FROM AUTHOR]

Ecological immunology attempts to explain the variability of immune response among individuals by invoking costs and trade-offs, which may optimize the immune defence against pathogens. In ectotherms body temperature is correlated to that of the surrounding environment, so that their entire physiology, including immune functions, is influenced by the environmental temperature. We used in vitro phytohaemoagglutinin (PHA) stimulation in order to assess the effects of temperature on cell mediated adaptive response in male and female Common wall lizards (Podarcis muralis). Cell cultures were prepared from blood samples, inoculated with PHA and incubated at 22°C, 25°C, 32°C, and 38°C for three days. PHA stimulation caused proliferation of T-lymphocytes, but the effect depended on the incubation temperature. Lymphocyte proliferation was significantly impaired at both 22°C and 38°C compared to 32°C, which represented the highest levels of activation. Furthermore, lymphocyte activation was more variable in males while females were less immune suppressed than males at low temperatures. Differences between sexes suggest a possible influence of steroid hormones. [ABSTRACT FROM AUTHOR]

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Maternal temperature is known to affect many aspects of offspring phenotype, but its effect on offspring physiological thermal tolerance has received less attention, despite the importance of physiological traits in defining organismal ability to cope with temperature changes. To fill this gap, we used the marine polychaete Ophryotrocha labronica to investigate the influence of maternal temperature on offspring upper and lower thermal tolerance limits, and assess whether maternal influence changed according to the stage of offspring pre-zygotic development at which a thermal cue was provided. Measurements were taken on adult offspring acclimated to 18 or 30°C, produced by mothers previously reared at 24°C and then exposed to 18 or 30°C at an early and late stage of oogenesis. When the shift from 24°C was provided early during oogenesis, mothers produced offspring with greater cold and heat tolerance whenever mother-offspring temperatures did not match, with respect to when they matched, suggesting the presence of an anticipatory maternal effect triggered by the thermal variation. Conversely, when the cue was provided later during oogenesis, more tolerant offspring were observed when temperatures persisted across generations. In this case, maternal exposure to 18 or 30°C may have benefited offspring performance, while limitations in the transmission of the thermal cue may account for the lack of correlation between maternal experiences and offspring performance when mother-offspring environments did not match. Our results provided evidence for a trans-generational effect of temperature on physiological performance characterised by a high context dependency, and are discussed in the light of maternal pre-reproductive experiences. [ABSTRACT FROM AUTHOR]

Decreasing body size has been proposed as a universal response to increasing temperatures. The physiology behind the response is well established for ectotherms inhabiting aquatic environments: as higher temperatures decrease the aerobic capacity, individuals with smaller body sizes have a reduced risk of oxygen deprivation. However, empirical evidence of this response at the scale of communities and ecosystems is lacking for marine fish species. Here, we show that over a 40-year period six of eight commercial fish species in the North Sea examined underwent concomitant reductions in asymptotic body size with the synchronous component of the total variability coinciding with a 1-2 °C increase in water temperature. Smaller body sizes decreased the yield-per-recruit of these stocks by an average of 23%. Although it is not possible to ascribe these phenotypic changes unequivocally to temperature, four aspects support this interpretation: (i) the synchronous trend was detected across species varying in their life history and life style; (ii) the decrease coincided with the period of increasing temperature; (iii) the direction of the phenotypic change is consistent with physiological knowledge; and (iv) no cross-species synchrony was detected in other species-specific factors potentially impacting growth. Our findings support a recent model-derived prediction that fish size will shrink in response to climate-induced changes in temperature and oxygen. The smaller body sizes being projected for the future are already detectable in the North Sea. [ABSTRACT FROM AUTHOR]

Interspecific variation in metabolic rates may be associated with climate, habitat structure, and resource availability. Despite a strong link between ecology and physiology, there is a dearth in the understanding of how the costs of body maintenance change during ecological transitions. We focused on an ecologically diverse group of neotropical lizards (Tropidurinae) to investigate whether and how resting metabolic rate (RMR) evolved under divergent micro- and macrohabitat conditions. Using a phylogenetic framework, we tested whether species from hot and dry habitats had lower RMRs in relation to those from cooler and mesic habitats, and investigated whether microhabitat usage had an effect over body mass-adjusted RMRs. Our results suggest that RMRs are not phylogenetically structured in Tropidurinae. We found no correlation between metabolism, precipitation, and microhabitat usage. Species from warmer habitats had lower RMR compared to those from cooler habitats, supporting a mechanism of negative compensation in metabolic responses to temperature. Ectotherms from warmer habitats can limit energetic demand and expenditure through reduced RMR, whereas those from cooler habitats may sustain activity despite thermal constraints via increased RMR. Our work highlights the role of temperature in shaping metabolic responses in lizards, giving additional support to the notion that physiology and ecological contexts are intertwined., (© 2022 Wiley Periodicals LLC.)

Global warming is increasing mean temperatures and altering temperature variability at multiple temporal scales. To better understand the consequences of changes in thermal variability for ectotherms it is necessary to consider thermal variation at different time scales (i.e., acute, diel, and annual) and the responses of organisms within and across generations. Thermodynamics constrain acute responses to temperature, but within these constraints and over longer time periods, organisms have the scope to adaptively acclimate or evolve. Yet, hypotheses and predictions about responses to future warming tend not to explicitly consider the temporal scale at which temperature varies. Here, focusing on multicellular ectothermic animals, we argue that consideration of multiple processes and constraints associated with various timescales is necessary to better understand how altered thermal variability because of climate change will affect ectotherms., (© 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Temperature is well known to affect many biological and ecological traits, especially in ectotherms. From a physiological point of view, temperature is also positively correlated to metabolism and is often associated with an increase in reactive oxygen species (ROS) production. It has recently been suggested that ROS play a role in lifespan and resource allocation. However, only a few authors have attempted to explore the relationships between temperature, resource allocation and oxidative balance in ectotherms. Here, we measured the effect of temperature on growth, reproductive effort, offspring quantity and quality, hatching and survival rates, and the associated proximal costs, which were evaluated through the quantification of oxidative balance elements. We reared adult fish (Oryzias latipes) at two non-stressful temperatures (20 and 30°C) during a relatively long period (4 months, approximately the entire adult life). The results show a trade-off between reproduction and maintenance because investment toward growth could be neglected at the adult stage (confirmed by our results). Intriguingly, ROS-dependent damages did not differ between the two groups, probably because of the higher rate of activation of the antioxidant enzyme superoxide dismutase for warm-acclimated fish. The allocation toward antioxidant defences is associated with an earlier reproduction and a lower quality of offspring. These interesting results bring new perspectives in terms of the prediction of the impact of global warming on biota through the use of ecological theories based on oxidative balance and metabolism. [ABSTRACT FROM AUTHOR]

The physiological performance of reptiles is subject to specific body temperature ranges, which are frequently similar between closely-related species even when they inhabit sites with different thermal conditions. Pregnant females should be particularly efficient for thermoregulation because healthy embryos develop at a narrow temperature range, a potential problem in the context of current global warming. To test the idea that pregnant lizards adjust their thermoregulatory behaviour to rising temperatures, we set up an experiment with 40 pregnant Sceloporus adleri and measured daily activity and basking time at different treatments (22, 24, 26 and 28°C) for six consecutive days. Basking time significantly decreased with increasing temperature. Lizards were more active in the earliest two time periods of the day (0800-1030 and 1030-1300 hours) when compared to later hours (1530-1800) for all treatments, although the trend was less pronounced at 24 and 26°C. Unexpectedly, the probability of activity for lizards increased at 28°C. All lizards maintained a body temperature without significant differences across treatments. These results suggest that pregnant S. adleri females are able to adjust their behavioural thermoregulation to different thermal environments in a short period of time to maintain an adequate body temperature for key physiological processes such as development and growth of their offspring. [ABSTRACT FROM AUTHOR]

Climate change will increase both average temperatures and extreme summer temperatures. Analyses of the fitness consequences of climate change have generally omitted negative fitness and population declines associated with heat stress., Here, we examine how seasonal and interannual temperature variability will impact fitness shifts of ectotherms from the past (1961-1990) to future (2071-2100), by modelling thermal performance curves ( TPCs) for insect species across latitudes., In temperate regions, climate change increased the length of the growing season (increasing fitness) and increased the frequency of heat stress (decreasing fitness). Consequently, species at mid-latitudes (20-40°) showed pronounced but heterogeneous responses to climate change. Fitness decreases for these species were accompanied by greater interannual variation in fitness. An alternative TPC model and a larger data set gave qualitatively similar results., How close maximum summer temperatures are to the critical thermal maximum of a species - the thermal buffer - is a good predictor of the change in mean fitness expected under climate change. Thermal buffers will decrease to near or below zero by 2100 for many tropical and mid-latitude species., Our forecasts suggest that mid-latitude species will be particularly susceptible to heat stress associated with climate change due to temperature variation. [ABSTRACT FROM AUTHOR]

We found that body length of a minute eriophyoid mite, Abacarus panticis Keifer, increased with elevation and rainfall, decreased with temperature, and exhibited a female-biased dimorphism. There was a negative temperature–body length relation in the female instead of the male, whose size remained constant along temperature gradients. In addition, scaling of body length between sexes is not significantly different from one. We conclude that within-species body length of A. panticis conforms to Bergmann’s trend but not Rensch’s rule. Further studies could take advantage of the more rigorous and flexible hierarchical model in the revelation of scale-specific determinants of phenotypic variation. [ABSTRACT FROM AUTHOR]

We investigated whether the current distribution of Lacerta schreiberi is likely to be constrained by incubation conditions. We used an incubation experiment in the laboratory to examine the effects of temperature and moisture on lizard reproductive traits, in order to clarify the ecological processes that underlie the distribution patterns of this lizard and to build more reliable mechanistic models. We then investigated to what extent range limits of L. schreiberi coincided with those predicted from incubation experiments and actual temperature variation experienced in the field. This was done by intersecting documented presence localities of the species with interpolated spatial layers of soil temperature. Reproductive success (hatching success, morphological traits and growth rates) was strongly and negatively affected by high temperature. In contrast, incubation moisture only affected neonate size and its positive effects were only realized at moderate to low temperature. Documented temperature sensitivity suggests that successful embryonic development is likely to be compromised by available thermal conditions, and that this species is unable to colonize warmer areas such as those where L. schreiberi is absent beyond its distribution range limits. An important addition is that incubation moisture does not appear to influence overall embryonic development. We would expect contemporary climate warming to cause upward elevational shifts which may be more or less critical depending on the availability of preferred habitat. [ABSTRACT FROM AUTHOR]

Highlights: [•] Cell-based biosensors have limited field use because of high storage requirements. [•] We screened cells for extended storage capabilities. [•] Ectothermic vertebrate cells store well at the low end of the organism’s core temp. [•] Reduced cellular metabolism is essential for storage on an enclosed biochip. [•] We developed a cell-based biosensor with minimal maintenance requirements. [Copyright &y& Elsevier]

Ectothermic animals, especially insects, are probably the ones most affected, for better or worse, by variable thermic environment, for example in the case of global warming, as their metabolic rate is controlled by the ambient temperature. Parasitoid insects, at the third trophic level, are widely distributed worldwide, and they influence the population dynamics of their highly diverse insect hosts. An important feature of parasitoid wasps is their supposedly limited or non-existent capacity to synthesize lipids during adulthood. As lipid level can be expected to determine whether they engage in maintenance or reproduction, parasitoid wasps are useful biological models for investigating how evolutionary trade-offs in energy allocation to maintenance or reproduction are likely to alter in response to global climate change. To address this, we developed a state-dependent stochastic dynamic programming model, which we parameterized using empirically derived data. The model shed light on the adaptive response of parasitoids with regard to three traits: activity rate, initial egg load, and egg production over the adult female's life span. We show that in a warmer climate, parasitoids devote smaller amounts of lipids to their reproductive effort and favour maintenance over reproduction. However, the bias towards maintenance is reduced when the parasitoids are able to adapt their activity rate to the features of their environment. This model could be tailored to a wide range of organisms with limited energy intake during their adult life. [ABSTRACT FROM AUTHOR]

To elucidate the mechanisms of thermal adaptation and acclimation in ectothermic aquatic organisms from differing climates, we used a common-garden experiment for thermal stress to investigate the heat shock response of redband trout ( Oncorhynchus mykiss gairdneri) from desert and montane populations. Evidence for adaptation was observed as expression of heat shock genes in fish from the desert population was more similar to control (unstressed) fish and significantly different ( P ≤ 0.05) from those from the montane population, while F1 crosses were intermediate. High induction of heat shock proteins (Hsps) in the montane strain appeared to improve short-term survival during first exposure to high water temperatures, but high physiological costs of Hsp production may have led to lower long-term survival. In contrast, the desert strain had significantly lower heat shock response than the montane fish and F1 crosses, suggesting that these desert fish have evolved alternative mechanisms to deal with thermal stress that provide better balance of physiological costs. Genomewide tests of greater than 10 000 SNPs found multiple SNPs that were significantly associated with survival under thermal stress, including Hsp47 which consistently appeared as a strong candidate gene for adaption to desert climates. Candidate SNPs identified in this study are prime targets to screen more broadly across this species' range to predict the potential for adaptation under scenarios of climate change. These results demonstrate that aquatic species can evolve adaptive responses to thermal stress and provide insight for understanding how climate change may impact ectotherms. [ABSTRACT FROM AUTHOR]

Abstract: The strong dependence of metabolic rates on body mass has attracted the interest of ecological physiologists, as it has important implications to many aspects of biology including species variations in body size, the evolution of life history, and the structure and function of biological communities. The great diversity of observed scaling exponents has led some authors to conclude that there is no single universal scaling exponent, but instead it ranges from 2/3 to 1. Most of the telling evidence against the universality of power scaling exponents comes from ontogenetic changes. Nevertheless, there could be other sources of phenotypic variation that influence this allometric relationship at least at the intraspecific level. In order to explore the general concept of the metabolic scaling in terrestrial molluscs we tested the role of several biological and methodological sources of variation on the empirically estimated scaling exponent. Specifically, we measured a proxy of metabolic rate (CO2 production) in 421 individuals, during three generations, in three different populations. Additionally, we measured this scaling relationship in 208 individuals at five developmental stages. Our results suggest that the metabolic scaling exponent at the intraspecific level does not have a single stationary value, but instead it shows some degree of variation across geographic distribution, transgenerational change and ontogenetic stages. The major differences in the metabolic scaling exponent that we found were at different developmental stages of snails, because ontogeny involves increases in size at different rates, which in turn, generate differential energy demands. [Copyright &y& Elsevier]

Intertidal organisms are vulnerable to global warming as they already live at, or near to, the upper limit of their thermal tolerance window. The behaviour of ectotherms could, however, dampen their limited physiological abilities to respond to climate change (e.g. drier and warmer environmental conditions) which could substantially increase their survival rates. The behaviour of ectotherms is still mostly overlooked in climate change studies. Here, we investigate the potential of aggregation behaviour to compensate for climate change in an intertidal gastropod species ( Nerita atramentosa) in South Australia. We used thermal imaging to investigate (1) the heterogeneity in individual snail water content and body temperature and surrounding substratum temperature on two topographically different habitats (i.e. rock platform and boulders) separated by 250 m at both day- and night-times, (2) the potential relationship between environment temperature (air and substratum) and snail water content and body temperature, and (3) the potential buffering effect of aggregation behaviour on snail water content and body temperature. Both substratum and snail temperature were more heterogeneous at small spatial scales (a few centimetres to a few metres) than between habitats. This reinforces the evidence that mobile intertidal ectotherms could survive locally under warmer conditions if they can locate and move behaviourally in local thermal refuges. N. atramentosa behaviour, water content and body temperature during emersion seem to be related to the thermal stability and local conditions of the habitat occupied. Aggregation behaviour reduces both desiccation and heat stresses but only on the boulder field. Further investigations are required to identify the different behavioural strategies used by ectothermic species to adapt to heat and dehydrating conditions at the habitat level. Ultimately, this information constitutes a fundamental prerequisite to implement conservation management plans for ectothermic species identified as vulnerable in the warming climate. [ABSTRACT FROM AUTHOR]

The balance of energetic losses and gains is of paramount importance for understanding and predicting the persistence of populations and ecosystem processes in a rapidly changing world. Previous studies suggested that metabolic rate often increases faster with warming than resource ingestion rate, leading to an energetic mismatch at high temperature. However, little is known about the ecological consequences of this energetic mismatch for population demography and ecosystem functions. Here, we combined laboratory experiments and modelling to investigate the energetic balance of a stream detritivore Gammarus fossarum along a temperature gradient and the consequences for detritivore populations and organic matter decomposition. We experimentally measured the energetic losses (metabolic rate) and supplies (ingestion rate) of Gammarus and we modelled the impact of rising temperatures and changes in Gammarus body size induced by warming on population dynamics and benthic organic matter dynamics in freshwater systems. Our experimental results indicated an energetic mismatch in a Gammarus population where losses via metabolic rate increase faster than supplies via food ingestion with warming, which translated in a decrease in energetic efficiency with temperature rising from 5 to 20°C. Moreover, our consumer-resource model predicts a decrease in the biomass of Gammarus population with warming, associated with lower maximum abundances and steeper abundance decreases after biomass annual peaks. These changes resulted in a decrease in leaf litter decomposition rate and thus longer persistence of leaf litter standing stock over years in the simulations. In addition, Gammarus body size reductions led to shorter persistence for both leaf litter and Gammarus biomasses at low temperature and the opposite trend at high temperature, revealing that body size reduction was weakening the effect of temperature on resource and consumer persistence. Our model contributes to identifying the mechanisms that explain how thermal effects at the level of individuals may cascade through trophic interactions and influence important ecosystem processes. Considering the balance of physiological processes is crucial to improve our ability to predict the impact of climate change on carbon stocks and ecosystem functions., (© 2022 The Authors. Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.)

Environmental variation connected with seasonality is likely to affect the evolution of life-history strategies in ectotherms, but there is no consensus as to how important life-history traits like body size are influenced by environmental variation along seasonal gradients. We compared adult body size, skeletal growth, mean age, age at first reproduction and longevity among 11 common frog ( Rana temporaria) populations sampled along a 1,600-km-long latitudinal gradient across Scandinavia. Mean age, age at first reproduction and longevity increased linearly with decreasing growth season length. Lifetime activity (i.e. the estimated number of active days during life-time) was highest at mid-latitudes and females had on average more active days throughout their lives than males. Variation in body size was due to differences in lifetime activity among populations-individuals (especially females) were largest where they had the longest cumulative activity period-as well as to differences between populations in skeletal growth rate as determined by skeletochronological analyses. Especially, males grew faster at intermediate latitudes. While life-history trait variation was strongly associated with latitude, the direction and shape of these relationships were sex- and trait-specific. These context-dependent relationships may be the result of life-history trade-offs enforced by differences in future reproductive opportunities and time constraints among the populations. Thus, seasonality appears to be an important environmental factor shaping life-history trait variation in common frogs. [ABSTRACT FROM AUTHOR]

Traditional risk assessment guidelines employ acute or chronic toxicity tests for a maximum of one generation of organisms. These tests are usually performed in the laboratory at a constant standard temperature, although in the field organisms may experience different temperatures, which may be a source of additional stress. Climate change-related temperature shifts may have serious impacts on ectotherm populations that are key components of the aquatic food chains, particularly in combination with the exposure of pollutants affecting their development. Here, a chronic full life-cycle test with Chironomus riparius from the first-instar larvae in the parental (P) generation until emergence in the subsequent F1 generation was conducted at different temperatures (16 and 24°C), testing the effect of the insect growth regulator pyriproxyfen at 1, 3, 10, 30, and 100 µg/L. The emergence ratios were significantly affected by the interaction of temperature, chemical treatment, and generation, showing that, at lower temperatures, the negative effects of pyriproxyfen exposure were significantly greater in the F1 generation than in the P generation. The development rate showed that the effects of the interactions were significant in the F1 generation, underscoring the importance of extended exposure as a useful amendment to the risk assessment of those agrochemicals potentially influencing developmental and reproductive parameters in intact organisms. Moreover, results demonstrated that any difference from the standard temperature of 20°C might result in additional stress, leading to disruption of biological functions in C. riparius, highlighting the interaction among different global climate change-related variables. Environ. Toxicol. Chem. 2012; 31: 2384-2390. © 2012 SETAC [ABSTRACT FROM AUTHOR]

During the last decade, the ecological theory of adaptive radiation, and its corollary 'ecological speciation', has been a major research theme in evolutionary biology. Briefly, this theory states that speciation is mainly or largely the result of divergent selection, arising from niche differences between populations or incipient species. Reproductive isolation evolves either as a result of direct selection on mate preferences (e.g. reinforcement), or as a correlated response to divergent selection ('by-product speciation'). Although there are now many tentative examples of ecological speciation, I argue that ecology's role in speciation might have been overemphasised and that non-ecological and non-adaptive alternatives should be considered more seriously. Specifically, populations and species of many organisms often show strong evidence of niche conservatism, yet are often highly reproductively isolated from each other. This challenges niche-based ecological speciation and reveals partial decoupling between ecology and reproductive isolation. Furthermore, reproductive isolation might often evolve in allopatry before ecological differentiation between taxa or possibly through learning and antagonistic sexual interactions, either in allopatry or sympatry. Here I discuss recent theoretical and empirical work in this area, with some emphasis on odonates (dragonflies and damselflies) and suggest some future avenues of research. A main message from this paper is that the ecology of species differences is not the same as ecological speciation, just like the genetics of species differences does not equate to the genetics of speciation. [ABSTRACT FROM AUTHOR]

The traditional explanation of brain lateralization is that it avoids costly duplication of neural circuitry with the same function as well as decreasing the interference between different functions. This advantage could have important ecological implications in terms of predator–prey interactions. If species are lateralized in escape behavior at an individual level, any predator is facing individually asymmetric prey. On the other hand, if species are lateralized at a higher hierarchical level, such as at the population or species level, the predator can learn from experience arising from earlier encounters. In the present study, we investigate patterns of lateralization in 5 lizard populations of the Podarcis hispanica species complex, with the aim of analyzing the occurrence of lateralization at different hierarchical levels. Our results show that refuge selection during escape behavior is not universal in the P. hispanica species complex at different hierarchical levels, some individuals and populations are lateralized, with a consistent bias toward the refuge on the right. However, 2 populations showed no refuge preference, with lack of lateralization mainly arising due to the dominance of individuals with no preference rather than from a mix of right- and left-biased individuals. When considered at the P. hispanica species complex level, a pattern for right-refuge preference was found. [ABSTRACT FROM PUBLISHER]

The purpose of the study is to establish and calculate the relationship between the total metabolic energy per lifespan and the body mass of Ectotherms, Mammals and Aves (n=278 living organisms) with 21 orders of magnitude variation between their body mass- from Bacteria to Elephas maximum and Struthio camelus. The study shows the existence of a linear relationship between the total metabolic energy per lifespan Pls (kJ), and the body mass M (kg) of all species from type: Pls=AlsM 1.0787±0.11 with R²=0.980, coefficient Als=15.18×105kJ/kg, standard error of the exponent SE=±0.11 and 95% confidence interval of the exponent (0.968 - 1.188). The same relationship for Ectotherms, Mammals and Aves without Protozoa (n=260) is of type: Pls=AlsM 1.0089±0.042 with R²=0.897, Als =14.16×105 kJ/kg, SE= ±0.042, and 95% confidence interval of exponent (0.967-1.051). In all combinations between Ectotherms, Mammals and Aves the exponent is near to 1.0. The linear coefficient Als is the total metabolic energy, exhausted during the lifespan per 1kg body mass of given organism and appears to be relatively constant parameter, because of rising 10 times only from Ectotherms to Mammals and Aves, despite of 21 orders of magnitude difference between body mass of organisms. [ABSTRACT FROM AUTHOR]

Molecular evolution is simultaneously paced by mutation rate, genetic drift, and natural selection. Life history traits also affect the speed of accumulation of nucleotide changes. For instance, small body size, rapid generation time, production of reactive oxygen species (ROS), and high resting metabolic rate (RMR) are suggested to be associated with faster rates of molecular evolution. However, phylogenetic correlation analyses failed to support a relationship between RMR and molecular evolution in ectotherms. In addition, RMR might underestimate the metabolic budget (e.g., digestion, reproduction, or escaping predation). An alternative is to test other metabolic rates, such as active metabolic rate (AMR), and their association with molecular evolution. Here, I present comparative analyses of the associations between life history traits (i.e., AMR, RMR, body mass, and fecundity) with rates of molecular evolution of and mitochondrial loci from a large ectotherm clade, the poison frogs (Dendrobatidae). My results support a strong positive association between mass-specific AMR and rates of molecular evolution for both mitochondrial and nuclear loci. In addition, I found weaker and genome-specific covariates such as body mass and fecundity for mitochondrial and nuclear loci, respectively. No direct association was found between mass-specific RMR and rates of molecular evolution. Thus, I provide a mechanistic hypothesis of the link between AMRs and the rate of molecular evolution based on an increase in ROS within germ line cells during periodic bouts of hypoxia/hyperoxia related to aerobic exercise. Finally, I propose a multifactorial model that includes AMR as a predictor of the rate of molecular evolution in ectothermic lineages. [ABSTRACT FROM PUBLISHER]

Tropical ectotherms are regarded as being especially threatened by global warming, but the extent to which populations vary in key thermal physiological traits is little known. In general, central and peripheral populations are most likely to differ where divergent selection pressures are un-opposed by gene flow. This leads to the prediction that persistent and long-isolated lineages in peripheral regions, as revealed by phylogeography, may differ physiologically from larger centrally located lineages. We test this prediction through comparative assays of critical thermal limits (minimum and maximum critical thermal limits, CTmin, CTmax) and optimal performance parameters (B80 and Topt) across central and peripheral lineages of three species of ground-dwelling skinks endemic to the rainforests of northeast Australia. Peripheral lineages show significantly increased optimal performance temperatures (Topt) relative to central populations as well as elevated CTmin, with the latter trait also inversely related to elevation. CTmax did not vary between central and peripheral lineages, but was higher in a forest edge species than in the forest interior species. The results suggest that long-isolated populations in peripheral rainforests harbour genotypes that confer resilience to future warming, emphasizing the need to protect these as well as larger central habitats. [ABSTRACT FROM AUTHOR]

A recently developed integrative framework proposes that the vulnerability of a species to environmental change depends on the species' exposure and sensitivity to environmental change, its resilience to perturbations and its potential to adapt to change. These vulnerability criteria require behavioural, physiological and genetic data. With this information in hand, biologists can predict organisms most at risk from environmental change. Biologists and managers can then target organisms and habitats most at risk. Unfortunately, the required data (e.g. optimal physiological temperatures) are rarely available. Here, we evaluate the reliability of potential proxies (e.g. critical temperatures) that are often available for some groups. Several proxies for ectotherms are promising, but analogous ones for endotherms are lacking. We also develop a simple graphical model of how behavioural thermoregulation, acclimation and adaptation may interact to influence vulnerability over time. After considering this model together with the proxies available for physiological sensitivity to climate change, we conclude that ectotherms sharing vulnerability traits seem concentrated in lowland tropical forests. Their vulnerability may be exacerbated by negative biotic interactions. Whether tropical forest (or other) species can adapt to warming environments is unclear, as genetic and selective data are scant. Nevertheless, the prospects for tropical forest ectotherms appear grim. [ABSTRACT FROM AUTHOR]

The factors that determine species' range limits are of central interest to biologists. One particularly interesting group comprises odonates (dragonflies and damsel-flies), which show large differences in secondary sexual traits and respond quickly to climatic factors, but often have minor interspecific niche differences, challenging models of niche-based species coexistence. We quantified the environmental niches at two geographic scales to understand the ecological causes of northern range limits and the coexistence of two congeneric damselfiies (Calopteryx splendens and C. virgo). Using environmental niche modeling, we quantified niche divergence first across the whole geographic range in Fennoscandia, and second only in the sympatric part of this range. We found evidence for interspecific divergence along the environmental axes of temperature and precipitation across the northern range in Fennoscandia, suggesting that adaptation to colder and wetter climate might have allowed C. virgo to expand farther north than C. splendens. However, in the sympatric zone in southern Fennoscandia we found only negligible and nonsignificant niche differences. Minor niche differences in sympatry lead to frequent encounters and intense interspecific sexual interactions at the local scale of populations. Nevertheless, niche differences across Fennoscandia suggest that species differences in physiological tolerances limit range expansions northward, and that current and future climate could have large effects on the distributional ranges of these and ecologically similar insects. [ABSTRACT FROM AUTHOR]

Understanding the influences of sex and ambient temperature on metabolic rates of reptiles is of fundamental interest to biologists because of the role that temperature-dependent metabolic rates play in shaping behaviour, life history evolution and geographic range. We investigated the effects of sex, body mass and temperature on standard metabolic rate, respiratory quotient (RQ), and Q10 in male and female Brown Anoles, Norops sagrei. When mass-adjusted, oxygen consumption increased linearly with temperature, and there was no effect of sex. RQ did not differ by sex or temperature. Q10 was within the range published for other lizards. [ABSTRACT FROM AUTHOR]