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Heat tolerance at the immobile embryonic stage is expected to be critical in determining species vulnerability to climate change. However, how the mean and developmental plasticity of embryonic heat tolerance vary geographically, and how these geographic variations affect species' vulnerability under climate change remain unknown. We experimentally determined the mean and developmental plasticity of embryonic acute heat tolerance (EAHT, i.e., heat shock temperature at which embryonic heartbeats ceased) for three latitudinally distributed populations of an oviparous lacertid lizard. The experimental results suggested that the mean EAHT decreased with decreasing latitude and that the reaction norms of EAHT in relation to developmental temperatures showed "flat," "bell‐shaped," and "decreasing" patterns at high, medium, and low latitudes, respectively. Based on the means and plasticity of EAHT and weather data across China, we project that the heat stress frequency would increase from the present to the future and increase toward low latitudes. Furthermore, heat stress becomes more extensive with the incorporation of developmental plasticity. Incorporating the mean EAHT during the embryonic development season, heat stress frequency, and climate variables in a species distribution model projects that suitable habitats could move northward in response to ongoing climate change and shrink due to the loss of southern habitat. Moreover, even lizards within the areas that are predicted to remain highly suitable are expected to experience increases in heat stress over time, particularly at medium and low latitudes. Our study reveals geographic variation in the mean and developmental plasticity of EAHT and highlights its importance for predicting species vulnerability and range shifts in response to climate change. [ABSTRACT FROM AUTHOR]

Aspects of global change result in warming temperatures that threaten biodiversity across the planet. Eggs of non‐avian, oviparous reptiles (henceforth "reptiles") are particularly vulnerable to warming due to a lack of parental care during incubation and limited ability to behaviorally thermoregulate. Because warming temperatures will cause increases in both mean and variance of nest temperatures, it is crucial to consider embryo responses to both chronic and acute heat stress. Although many studies have considered embryo survival across constant incubation temperatures (i.e., chronic stress) and in response to brief exposure to extreme temperatures (i.e., acute stress), there are no standard metrics or terminology for determining heat stress of embryos. This impedes comparisons across studies and species and hinders our ability to predict how species will respond to global change. In this review, we compare various methods that have been used to assess embryonic heat tolerance in reptiles and provide new terminology and metrics for quantifying embryo responses to both chronic and acute heat stress. We apply these recommendations to data from the literature to assess chronic heat tolerance in 16 squamates, 16 turtles, five crocodilians, and the tuatara and acute heat tolerance for nine squamates and one turtle. Our results indicate that there is relatively large variation in chronic and acute heat tolerance across species, and we outline directions for future research, calling for more studies that assess embryo responses to acute thermal stress, integrate embryo responses to chronic and acute temperatures in predictive models, and identify mechanisms that determine heat tolerance. Highlights: We propose metrics for reptile embryo heat tolerance with respect to chronic and acute temperatures and describe how future studies can incorporate these metrics to advance our understanding of embryo thermal physiology. [ABSTRACT FROM AUTHOR]

Flight of nocturnal insects may be limited by cool nighttime environmental temperatures. We used laboratory and field experiments to explore the thermal basis of nocturnal flight in wing‐polymorphic Gryllus lineaticeps crickets consisting of long‐winged (LW), flight‐capable morphs and short‐winged (SW), flight‐incapable morphs. These crickets are a model for life history evolution and loss of flight, but their thermal requirements for flight have been unknown. We hypothesized that LW crickets achieve warm body temperatures required for flight through a combination of behavioural thermoregulation, producing heat endogenously (either by initiating muscular thermogenesis or increasing resting metabolic rate) and minimizing heat loss (by circulatory adjustments or insulation).Summer evening air temperatures in the field gradually declined from 25 to 18°C during the hours of nighttime cricket activity. Laboratory LW crickets did not fly at a body temperature of 18°C, and 60% flew at 25°C. In an experimental thermal gradient, spontaneous flight did not occur until body temperature exceeded 35°C, confirming that nocturnal field air temperature limits flight in this species.In a thermal gradient, LW crickets preferred higher temperatures (~36°C) than SW crickets (~32.5°C). In the field, all crickets were warmer than air temperature but considerably cooler than their preferred temperatures. LW crickets had higher field body temperatures (24.3°C) than SW crickets (22.3°C). LW crickets spontaneously initiated muscular thermogenesis through wing vibrations, increasing body temperature to a pre‐flight maximum of 35°C. Muscular thermogenesis was limited below 25°C. LW crickets cooled more slowly and had higher metabolic rates than SW crickets.We conclude that LW crickets prepare to fly on cool nights by gaining heat from warm substrates, activating endogenous muscular thermogenesis and reducing their cooling rate. These mechanisms are absent or less pronounced in SW crickets. The overall thermoregulatory strategy we report represents a previously unrecognized component of insect dispersal polymorphism. We suggest that thermal constraints on nocturnal flight may have contributed to evolutionary loss of flight in other insect groups. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

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. Plain Language Summary [ABSTRACT FROM AUTHOR]

Abstract The diamond core-drills were brazed with Ni Cr filler alloy in the tunnel furnace with the characteristics of the continuous heating and in the vacuum furnace, respectively. The surface morphology and interfacial microstructure between diamond and filler alloy, and filler alloy and substrate were characterized using scanning electron microscopy, energy spectrometer and X-ray diffraction. The effect of different cooling methods on the microstructure and micro-hardness of the filler alloy and substrate was investigated. Furthermore, the drilling tests were conducted, and the cutting efficiency, service life and wear behavior for both tools were comparably analyzed. The results demonstrated a layer of Cr C compound formed at the interface of diamond and filler alloy, and a diffusion band composed of Ni and Fe solid solution or compound formed at the interface between filler alloy and substrate regardless of fabricating technique. The thickness of the Cr C compound, the width of the diffusion band, the micro-hardness of the substrate and the molten solidified filler alloy for the tunnel furnace brazed diamond core-drill were greater than that of vacuum brazed tool. After drilling polished tiles using diamond core-drill, the cutting efficiency and service life of the tunnel furnace brazed core-drill were close to that of the vacuum brazed core-drill. The attrition wear was the main wear mode for both kinds of tools, and neither the pullout nor the fracture of the abrasive grains occurred during the machining. Graphical abstract Unlabelled Image Highlights • A sort of diamond core-drill was brazed in tunnel furnace, which was newly developed process. • The interfacial microstructure and cutting performance of tunnel furnace brazed diamond core-drill were investigated. • The performance of novel process brazed diamond core-drill achieved the result of the vacuum brazed diamond core-drill. [ABSTRACT FROM AUTHOR]

Temperature variability is predicted to increase in the coming century due to climate change. However, the biological impact of increased temperature variability on animals remains largely unexplored. Here, we experimentally exposed gravid viviparous lizards (Eremias multiocellata) to two thermal environments [constant daily maximum (CDM) versus variable daily maximum (VDM) treatment with the same average temperature] to address maternal and offspring responses to increased variability in ambient temperature. Females from the VDM treatment delayed parturition, but produced similar litter sizes and litter masses as did CDM females. Offspring from the VDM treatment selected higher body temperatures, had higher metabolic rates and higher growth rates, and grew to a similar size as those from the CDM treatment despite having a shorter growth period prior to hibernation. Therefore, phenotypic plasticity may be critical for lizards to respond effectively to climate change, and its role in responding to increasingly variable temperatures warrants further attention. [ABSTRACT FROM AUTHOR]

Diamonds were brazed on the substrate with nickel‑chromium (Ni Cr) filler alloy at a certain temperature for three different mesh belt speeds in the mesh belt continuous tunnel furnace, respectively. In this study, a different perspective involving the exploration of the new processes was used that could allow for the mass production of brazed diamond tools. The interfacial microstructure between the diamonds and filler alloy was analyzed by scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction. The residual stresses and mechanical properties of the brazed diamonds were determined through the laser Raman spectrum and the compressive strength or impact toughness testing equipment for superabrasives, respectively. The results illustrated the occurrence of chemical reaction at the interface of the filler alloy-diamond followed by the formation of the Cr C compound. Moreover, the thickness of the interfacial reaction layer increased with the decrease in the mesh belt speed. The brazing high temperature and development of the Cr C layer were found to be responsible for the residual stresses in the diamonds. The mechanical properties of the brazed diamond grits strongly depended on the resultant thickness of the diamond surface and the residual stresses produced during brazing. [ABSTRACT FROM AUTHOR]

The vulnerability of species to climate warming varies along latitudinal and elevational clines, but how sympatric species vary in vulnerability to climate warming remains largely unknown. We experimentally simulated nest temperatures of two sympatric lizards with divergent microhabitat preferences (Phrynocephalus przewalskii and Eremias argus), under climate warming senarios, to determine the response of embryos to increased mean temperatures and heat waves. Our study demonstrated that simulated climate warming reduced hatching success and hatchling size and growth in E. argus (that prefers closed microhabitats), but had less effect in P. przewalskii (that occupies open microhabitats). The reduced growth rate of E. argus hatchlings was associated with a decrease in metabolic rate, which was more evident in hatchling E. argus than in P. przewalskii. Our results suggest lizards that prefer closed microhabitats may be more vulnerable to climate warming than those that prefer open microhabitats; further studies are needed to test this hypothesis. More generally, the divergent responses of sympatric species to climate warming highlights the importance of distinguishing the thermal sensitivity of behavior and physiology for each species of a community, in order to make predictions about the impacts of climate warming at regional scales. Our study reveals divergent responses between sympatric species to climate warming (including heat waves). And we highlight the importance of distinguishing the thermal sensitivity of behavior and physiology in each species of a community, and of considering the response of each species as a unit of interest rather than simply the response of the community as a whole. We provide a more detailed picture of the impact of climate warming on organisms, allowing us to predict outcomes and develop more effective conservation strategies. [ABSTRACT FROM AUTHOR]

A new method for brazing diamond grains is presented. The brazing was conducted in a continuous-belt tunnel furnace under a dissociated ammonia atmosphere, which allows for a continuous large-scale production and greatly enhances productivity. To compare the brazing quality, identical samples were also brazed in a traditional vacuum oven. The surface morphology and interfacial microstructure were characterized, and the residual stresses, the static compressive strength, and the impact toughness were determined for both types of brazed diamond samples. Furthermore, grinding tests were conducted using the brazed diamond grinding discs. The results revealed that graphitization did not occur on the surface of the diamond grits. CrC and CrC were found at the interface between the diamonds and the Ni-Cr filler alloy brazed in the tunnel furnace. The residual stresses in the tunnel-brazed diamond grits were smaller than the stresses in the vacuum-brazed diamond grits in case of an identical measuring height, and the static compressive strength and the impact toughness of the etched tunnel-brazed diamond grits were 2316.7 MPa and 66.5 %, respectively, which was higher than the values obtained for the vacuum-brazed diamond grits (1865.6 MPa and 59.3 %). After grinding a granite test sample using the brazed diamond grinding discs, the fraction of abrasive grains pulled out from the surface of the tunnel-brazed grinding disc was slightly higher than the fraction of grains pulled out from the surface of the vacuum-brazed disc, whereas the overall abrasive grain fracture rate was lower at the same grinding length. [ABSTRACT FROM AUTHOR]

In order to achieve the mass production of the brazing diamond tools, brazing of diamond grains to the matrix using Ni Cr active filler alloy was investigated in the mesh belt furnace, which could realize uninterrupted brazing under ammonia dissociating atmosphere. The surface characteristics and interfacial microstructures of brazed diamond in mesh belt furnace were analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The residual stress, static compressive strength and impact toughness of the brazing diamond were measured and the corresponding results were compared to the brazing diamond grains in vacuum furnace. Results demonstrated that chemical reaction occurred between the diamond and filler alloy. The compound composed of Cr 3 C 2 and Cr 7 C 3 was formed at diamond interface and a higher bonding strength was obtained. The residual stresses of brazing diamond in mesh belt furnace were lower than that in vacuum furnace in the case of identical protruding height. However the static compressive strength and the impact toughness were higher than that in vacuum furnace. [ABSTRACT FROM AUTHOR]

Oxygen and temperature have previously been treated as different environmental stresses and studied separately in most cases. Although the oxygen-temperature interaction may provide new insight into proximate and evolutionary constraints on embryonic development and offspring fitness, it has rarely been studied in oviparous amniotes. We used a two-factor experiment [three oxygen concentrations (12, 22 and 30 %) × two temperatures (26.5 and 34 °C)] to identify the effect of the oxygen-temperature interaction on embryonic development and hatchling traits in the Chinese soft-shelled turtle, Pelodiscus sinensis. When eggs were incubated at the critically high temperature, hatching success of turtle eggs was enhanced by hyperoxia but reduced by hypoxia; this result was not observed in eggs incubated at the benign temperature. Hypoxia retarded embryonic development, and reduced body size, locomotor performance and survival rate of hatchings at the critically high temperature. However, the effects of hypoxia were greatly reduced at the benign temperature. Our study demonstrates that oxygen and temperature interact to affect not only the heat tolerance and developmental rate of embryos but also the fitness-related traits of hatchlings, suggesting that interactions among environmental factors impose significant ecological constraints on embryonic development in oviparous amniotes. [ABSTRACT FROM AUTHOR]

A range of abiotic parameters within a reptile nest influence the viability and attributes (including sex, behaviour and body size) of hatchlings that emerge from that nest. As a result of that sensitivity, a reproducing female can manipulate the phenotypic attributes of her offspring by laying her eggs at times and in places that provide specific conditions. Nesting reptiles shift their behaviour in terms of timing of oviposition, nest location and depth of eggs beneath the soil surface across spatial and temporal gradients. Those maternal manipulations affect mean values and variances of both temperature and soil moisture, and may modify the vulnerability of embryos to threats such as predation and parasitism. By altering thermal and hydric conditions in reptile nests, climate change has the potential to dramatically modify the developmental trajectories and survival rates of embryos, and the phenotypes of hatchlings. Reproducing females buffer such effects by modifying the timing, location and structure of nests in ways that enhance offspring viability. Nonetheless, our understanding of nesting behaviours in response to climate change remains limited in reptiles. Priority topics for future studies include documenting climate-induced changes in the nest environment, the degree to which maternal behavioural shifts can mitigate climate-related deleterious impacts on offspring development, and ecological and evolutionary consequences of maternal nesting responses to climate change. This article is part of the theme issue 'The evolutionary ecology of nests: a cross-taxon approach'. [ABSTRACT FROM AUTHOR]

Adaptive plasticity may shift phenotypic traits close to a new optimum for directional selection and probably facilitates adaptive evolution in new environments. However, such plasticity has rarely been reported in life-history evolution, despite overwhelming evidence of life-history variation both among and within species. In this study, the temperatures experienced by gravid females of Scincella modesta were manipulated to identify maternally induced plasticity in reproductive traits and the significance of such changes in the evolution of life history. Consistent with the geographic pattern of life history, the study demonstrated that low temperatures delayed egg oviposition, resulting in a more advanced embryonic developmental stage at oviposition and shorter incubation periods compared with warm temperatures. In addition, females maintained at low temperatures produced larger eggs and hence heavier hatchlings than those at warm temperatures. This study demonstrated that environmental temperatures can induce plastic responses in egg retention and offspring size, and these maternally mediated changes in reproductive life history seem to be adaptive in the light of latitudinal clines of these traits in natural populations. [ABSTRACT FROM AUTHOR]

Life history traits may vary within and among species. Rarely, however, are both variations examined concurrently to identify the life history adaptation. We found that female body size, offspring number and size, and incubation period showed convergent evolution in two lacertid lizards ( Takydromus wolteri and Eremias argus) that occur sympatrically in high-latitude and low-latitude localities. Females from the high-latitude population were larger and produced larger clutches than those from the low-latitude population. In both species, the incubation period was shorter for the high-latitude population than for the low-latitude population. However, the physiological mechanism underlying the shorter incubation period differed between the species. These results suggest that: (1) sympatric lizards may adopt similar reproductive strategies in response to their common environments, and (2) embryonic development of the two species follows different pathways for adaptation to low temperatures. This study highlights the importance of understanding the adaptive evolution of life history in response to environmental changes at the embryonic life stages. [ABSTRACT FROM AUTHOR]

Abstract: Most animals show seasonal cycles of reproduction (including cycling of sex steroids). Environmental cues (e.g., temperature) likely play important roles in these seasonal variations but their exact contributions remain unclear. We conducted a two-factor experiment to elucidate the effects of thermal environments and food availability on growth in body mass, testosterone (T) levels and testes morphology in male Chinese skinks [Plestiodon (Eumeces) chinensis]. Skinks in the thermal environment mimicking spring (April) conditions grew slowly but had higher plasma T levels and larger testes with more viable sperms than those in the thermal environment mimicking summer (July) conditions. Skinks exposed to high food treatment grew faster and had higher plasma T levels and more viable sperms than those exposed to low food treatment. Male growth was negatively correlated with reproductive activity as indicated by T levels and testes size. Therefore, both temperature and food availability are important environmental factors that can affect the reproductive cycle of male lizards, and the mechanisms underlying the trade-off between growth and reproduction could involve the regulation of T levels. [ABSTRACT FROM AUTHOR]

Remarkable temporal and spatial variations occur on selected body temperature (Tsel) and locomotor performance for Plestiodon (Eumeces) chinensis, commonly known as Chinese skinks. However, the significance of these variations remains elusive. This study focuses on the effects of thermal environment and food availability on P. chinensis's Tsel and locomotor performance. The duration of thermal treatment (4h and 8h) displayed significant effects on Tsel, additionally the effects of thermal treatment were also dependent on food-availability. There was no significant variation in skink's Tsel under diverse thermal treatments when sufficient food was available. However, with insufficient food source, the Tsel decreased with decrease in the duration of thermal treatment. Thermal acclimation also affected locomotor performance of P. chinensis, as the 8h thermal treatment enhanced their locomotor performance. However, food availability alone had no significant impact on the locomotor performance. Therefore, the combination of thermal acclimation and food availability could cause variations in Tsel and locomotor performance of skinks, suggesting that thermal environment and food condition in nature are important factors involved in temporal and spatial variations for Tsel and locomotor performance. [ABSTRACT FROM AUTHOR]

To achieve automatic cutting of cast stainless steel risers, a brazed diamond saw blade is developed, and cutting 304 stainless steel tests are performed on the CNC machine tool. The temperature of the blade-debris contact zone for both dry and wet cutting is measured. The vibration signal during cutting is collected and analyzed. Wear characteristics and mechanism of diamond grinding particles and processed surface quality are studied. The results indicate that the cutting temperature was low, the vibration amplitude of the system was small and the surface quality of the cut was high during wet automatic cutting of 304 stainless steel. Low cutting temperature suppressed chemical wear of diamond abrasive grains, and small vibration improved the surface quality of the cut. However, poor results were achieved when dry cutting stainless steel. It is feasible that 304 stainless steel was wet cut using brazed diamond saw blades on CNC machine tool. [Display omitted] • A brazed diamond saw blade was employed to cutting 304 stainless steel tests. • Cutting temperature, system vibration, and abrasive grains wear were investigated. • Cutting temperature was low and vibration amplitude was small during wet cutting. • No chemical wear occurred on the diamond particle in wet cutting. [ABSTRACT FROM AUTHOR]

Survival of the immobile embryo in response to rising temperature is important to determine a species' vulnerability to climate change. However, the collective effects of 2 key thermal characteristics associated with climate change (i.e., rising average temperature and acute heat events) on embryonic survival remain largely unexplored. We used empirical measurements and niche modeling to investigate how chronic and acute heat stress independently and collectively influence the embryonic survival of lizards across latitudes. We collected and bred lizards from 5 latitudes and incubated their eggs across a range of temperatures to quantify population‐specific responses to chronic and acute heat stress. Using an embryonic development model parameterized with measured embryonic heat tolerances, we further identified a collective impact of embryonic chronic and acute heat tolerances on embryonic survival. We also incorporated embryonic chronic and acute heat tolerance in hybrid species distribution models to determine species' range shifts under climate change. Embryos' tolerance of chronic heat (T‐chronic) remained consistent across latitudes, whereas their tolerance of acute heat (T‐acute) was higher at high latitudes than at low latitudes. Tolerance of acute heat exerted a more pronounced influence than tolerance of chronic heat. In species distribution models, climate change led to the most significant habitat loss for each population and species in its low‐latitude distribution. Consequently, habitat for populations across all latitudes will shift toward high latitudes. Our study also highlights the importance of considering embryonic survival under chronic and acute heat stresses to predict species' vulnerability to climate change. [ABSTRACT FROM AUTHOR]

To improve the machining efficiency of cast iron and the service life of cutting tools, a brazing diamond grinding disc was designed and fabricated. Experiments regarding the production efficiency, service life, and cutting temperature were conducted to compare the brazing diamond grinding disc and the traditional resin sand wheel sheet grinding gray cast iron HT150. The results demonstrated that the grinding efficiency and service life of the brazing diamond grinding disc were higher than that of the resin sand wheel sheet, the grinding temperature was lower than that of the resin wheel sheet, and the wear behavior of the diamond abrasive grains was mechanical wear with no chemical wear. This shows that machining gray cast iron with the brazing diamond grinding disc is feasible. Unlabelled Image • A sort of brazing diamond grinding disc was utilized in machining the gray cast iron. • The grinding efficiency, service life, grinding temperature and wear behavior of the grinding disc were investigated. • It is feasible that the brazing diamond grinding disc machines the gray cast iron. [ABSTRACT FROM AUTHOR]

Parental effects may produce adaptive or maladaptive plasticity that either facilitates persistence or increases the extinction risk of species and populations in a changing climate. However, empirical evidence of transgenerational adaptive plastic responses to climate change is still scarce. Here we conducted thermal manipulation experiments with a factorial design in a Chinese lacertid lizard (Takydromus septentrionalis) to identify the fitness consequences of parental effects in response to climate warming. Compared to present climate conditions, a simulated warming climate significantly advanced the timing of oviposition, depressed the immune capability of post-partum females, and decreased the hatching success of embryos, but did not affect female reproductive output (clutch size and egg mass). These results indicate that maternal warming negatively affects female health, and embryonic hatchability. More interestingly, we found that offspring from parents exposed to warming environments survived well under a simulated warming climate, but not under a present climate scenario. Accordingly, our study demonstrates anticipatory parental effects in response to a warming climate in an ectothermic vertebrate. However, the fitness consequences of this parental effect will depend on future climate change scenarios. [ABSTRACT FROM AUTHOR]

Evaluating the effects of temperature variations on animals plays an important role in understanding the threat of climate warming. The effects of developmental temperature on offspring performance are critical in evaluating the effects of warming temperatures on the fitness of oviparous species, but the physiological and biochemical basis of this developmental plasticity is largely unknown. In this study, we incubated eggs of the turtle Pelodiscus sinensis at low (24 °C), medium (28 °C), and high (32 °C) temperatures, and evaluated the effects of developmental temperature on offspring fitness, and metabolic enzymes in the neck and limb muscles of hatchlings. The hatchlings from eggs incubated at the medium temperature showed better fitness-related performance (righting response and swimming capacity) and higher activities of metabolic enzymes (hexokinase, HK; lactate dehydrogenase, LDH) than hatchlings from the eggs incubated at high or low temperatures. In addition, the swimming speed and righting response were significantly correlated with the HK activities in limb (swimming speed) and neck (righting response) muscles, suggesting that the developmental plasticity of energy metabolic pathway might play a role in determining the way incubation temperature affects offspring phenotypes. Integrating the fitness-related performance and the activities of metabolic enzymes, we predict that the P. sinensis from high latitude would not face the detrimental effects of climate warming until the average nest temperatures reach 32 °C. [ABSTRACT FROM AUTHOR]

Developmental rate increases exponentially with increasing temperature in ectothermic animals, but the biochemical basis underlying this thermal dependence is largely unexplored. We measured mitochondrial respiration and metabolic enzyme activities of turtle embryos (Pelodiscus sinensis) incubated at different temperatures to identify the metabolic basis of the rapid development occurring at high temperatures in reptile embryos. Developmental rate increased with increasing incubation temperatures in the embryos of P. sinensis. Correspondingly, in addition to the thermal dependence of mitochondrial respiration and metabolic enzyme activities, high-temperature incubation further enhanced mitochondrial respiration and COX activities in the embryos. This suggests that embryos may adjust mitochondrial respiration and metabolic enzyme activities in response to developmental temperature to achieve high developmental rates at high temperatures. Our study highlights the importance of biochemical investigations in understanding the proximate mechanisms by which temperature affects embryonic development. [ABSTRACT FROM AUTHOR]

Warming temperatures caused by climate change are predicted to vary temporally and spatially. For mid‐ and high‐latitude reptiles, the seasonal variation in warming temperatures experienced by embryos and hatchlings may determine offspring fitness, yet this has remained largely unexplored.To evaluate the independent and interactive influence of seasonal variation in warming temperatures on embryonic and hatchling development, we incubated eggs and reared hatchlings of a cold‐climate oviparous ectothermic species, the Heilongjiang grass lizard (Takydromus amurensis), following a 2 × 2 factorial design (present climate versus warming climate for embryos × present climate versus warming climate for hatchlings). We then evaluated embryonic and hatchling development, including hatching success, incubation period, initial hatchling body size, hatchling metabolic rate, growth rate and survival in the mesocosms.We found that warming temperatures shortened the incubation period and produced hatchlings with higher survival rates than those incubated under the present climate conditions. Similarly, hatchlings reared under a warming climate had similar growth rates and resting metabolic rates, but higher survival rates than those reared under the present climate. Hatchlings that experienced both warming incubation and warming growth conditions had the highest survival rates.This study revealed that moderate warming temperatures (Representative Concentration Pathway, RCP 4.5, 1.1–2.6°C) experienced by embryos and hatchlings interact to benefit hatchling fitness in cold‐climate oviparous ectotherms. Our study also highlighted the importance of integrating seasonal variation in warming temperatures when evaluating the responses to climate warming in multiple developmental stages in oviparous ectotherms. [ABSTRACT FROM AUTHOR]

Abstract: Geographic variation in life history traits has been extensively studied along latitudinal and altitudinal clines, but life history variation among geographically close populations has received much less attention. We collected gravid female toad-headed lizards (Phrynocephalus przewalskii) and environmental data from three localities (Alxa Zuoqi, Alxa Youqi, and Shandan) across the Gobi desert in China, to examine among-population differences in reproductive strategies. The precipitation was significantly lower in Alxa Youqi than Alxa Zouqi and Shandan. Food availability was highest in Shandan, lowest in Alxa Zuoqi, with Alxa Youqi in between. Females from Shandan population were larger and produced more and larger eggs than their counterparts from the other two populations. Incubation period also differed among the populations, with the lowest incubation period in Alxa Youqi population, and the longest incubation period in Alxa Zuoqi population. Our data on the physiological mechanisms of incubation period indicated that the shortened incubation period in Alxa Youqi population was due to advanced embryogenesis completed prior to oviposition rather than higher embryonic heart rates during incubation. Therefore, our data support the hypothesis that geographically close populations can show different reproductive strategies if environmental factors vary among these populations. [Copyright &y& Elsevier]

Identifying intrinsic and extrinsic sources of variation in life history traits among populations has been well-studied at the post-embryonic stage but rarely at the embryonic stage. To reveal these sources of variation in the developmental success of embryos, we measured the physical characteristics of nest environments and conducted reciprocal egg-swap experiments in two populations of the toad-headed agamid lizard (Phrynocephalus przewalskii), isolated from each other by a mountain range. We determined the effects of population origin and nest environment on embryonic and offspring traits related to developmental success, including incubation period, hatching success, and offspring growth and survival. Females from the northern population constructed deeper nests that were colder and wetter than those from the southern population. Northern embryos had higher hatching success than the southern embryos when incubated at the northern nest environment, but not when they were incubated at the southern nest environment. The southern hatchlings grew faster than the northern hatchlings when incubated at the southern nest environment, but not after incubation at the northern nest environment. These phenomena likely reflect local adaptation of embryonic development to their nest environments among populations in lizards. In addition, the southern hatchlings had higher survivorship than the northern hatchlings regardless of nest environment, suggesting the southern population has evolved a superior phenotype at the hatchling stage to maximize its fitness. [ABSTRACT FROM AUTHOR]

Research on the thermal ecology and physiology of free‐living organisms is accelerating as scientists and managers recognize the urgency of the global biodiversity crisis brought on by climate change. As ectotherms, temperature fundamentally affects most aspects of the lives of amphibians and reptiles, making them excellent models for studying how animals are impacted by changing temperatures. As research on this group of organisms accelerates, it is essential to maintain consistent and optimal methodology so that results can be compared across groups and over time. This review addresses the utility of reptiles and amphibians as model organisms for thermal studies by reviewing the best practices for research on their thermal ecology and physiology, and by highlighting key studies that have advanced the field with new and improved methods. We end by presenting several areas where reptiles and amphibians show great promise for further advancing our understanding of how temperature relations between organisms and their environments are impacted by global climate change. Highlights: we provide a useful "how to" guide for studying the thermal ecology of reptiles and amphibians.We highlight key studies on reptiles and amphibians that help us understand the impacts of the climate crisis on biodiversity. [ABSTRACT FROM AUTHOR]

Natural nests of egg-laying birds and reptiles exhibit substantial thermal variation, at a range of spatial and temporal scales. Rates and trajectories of embryonic development are highly sensitive to temperature, favouring an ability of embryos to respond adaptively (i.e. match their developmental biology to local thermal regimes). Spatially, thermal variation can be significant within a single nest (top to bottom), among adjacent nests (as a function of shading, nest depth etc.), across populations that inhabit areas with different weather conditions, and across species that differ in climates occupied and/or nest characteristics. Thermal regimes also vary temporally, in ways that generate differences among nests within a single population (e.g. due to seasonal timing of laying), among populations and across species. Anthropogenic activities (e.g. habitat clearing, climate change) add to this spatial and temporal diversity in thermal regimes. We review published literature on embryonic adaptations to spatio-temporal heterogeneity in nest temperatures. Although relatively few taxa have been studied in detail, and proximate mechanisms remain unclear, our review identifies many cases in which natural selection appears to have fine-tuned embryogenesis to match local thermal regimes. Developmental rates have been reported to differ between uppermost versus lower eggs within a single nest, between eggs laid early versus late in the season, and between populations from cooler versus warmer climates. We identify gaps in our understanding of thermal adaptations of early (embryonic) phases of the life history, and suggest fruitful opportunities for future research. [ABSTRACT FROM AUTHOR]

Sessile organisms with thermally sensitive developmental trajectories are at high risk from climate change. For example, oviparous reptiles with temperature-dependent sex determination (TSD) may experience strong (potentially disastrous) shifts in offspring sex ratio if reproducing females are unable to predict incubation conditions at the time of oviposition. How then have TSD reptile taxa persisted over previous periods of extreme climatic conditions? An ability of embryos to move within the egg to select optimal thermal regimes could buffer ambient extremes, but the feasibility of behavioral thermoregulation by embryos has come under strong challenge. To test this idea, we measured thermal gradients within eggs in semi-natural nests of a freshwater turtle species with TSD, manipulated embryonic thermoregulatory ability, and modeled the effects of embryonic thermoregulation on offspring sex ratios. Behavioral thermoregulation by embryos accelerated development and influenced offspring sex ratio, expanding the range of ambient conditions under which nests produce equal numbers of male and female offspring. Model projections suggest that sex ratio shifts induced by global warming will be buffered by the ability of embryos to influence their sexual destiny via behavioral thermoregulation. • By moving within the egg, a turtle embryo can influence its own sex • That ability expands the range of nest conditions producing an equal sex ratio • Thermoregulation by embryos should buffer populations against climate change Climate change may be disastrous for egg-laying species in which nest temperatures determine offspring sex. However, Ye, Ma, et al. find that impact may be reduced by the ability of embryos to thermoregulate: that is, to move within the egg to select specific thermal regimes. [ABSTRACT FROM AUTHOR]

Abstract: The fitness consequence of maternal nest‐site choice has attracted increasing scientific attention, but field studies identifying the long‐term effects of nest‐site choice on offspring survival and reproductive success are still rare in vertebrates. To investigate the consequences of nest‐site choice in lizards, we quantified the thermal and hydric conditions of nest sites that were chosen by female toad‐headed agama (Phrynocephalus przewalskii) in the desert steppe of northern China. We also determined the effect of nest‐site choice on embryonic development and survival and on offspring growth, survival and maturity by comparing the embryos and offspring from maternally and randomly chosen nest sites. We found that female toad‐headed agama chose warm and moist nest sites that improved the developmental rate and survivorship of embryos and promoted the post‐hatching growth, sexual maturity, reproduction and fitness of offspring, thereby improving their reproductive success. Such studies on short‐lived lizards across multiple stages of embryonic and postembryonic ontogeny are critical for fully understanding the fitness consequences of nest‐site choice. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]

The sex determination mechanism for the Chinese soft-shelled turtle (Pelodiscus sinensis) is subject to controversy. Some populations have been shown to possess sex chromosomes and thus genotypic sex determination (GSD), while others were reported to exhibit temperature-dependent sex determination (TSD). To test whether TSD and GSD coexist in this species or whether populations differ in their sex-determining system, we conducted egg incubation experiments to investigate how temperature influences hatchling sex in a wide range of populations of this species in China. In parallel, we used comparative genome hybridization (CGH) to study the micro-sex chromosomes of adult P. sinensis in the 2 populations that were previously identified to be TSD. The incubation experiments showed that temperature did not affect hatchling sex in any of the studied populations. CGH indicated that turtles have micro-sex chromosomes of the female heterogametic (ZZ/ZW) system in the 2 disputed populations. These results indicate that P. sinensis is a GSD rather than a TSD species. Thus, the apparent coexistence of TSD and GSD in this species is the result of previous misdiagnosis in purportedly TSD populations. © 2015 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Light is an environmental factor that is known to profoundly affect embryonic development in some oviparous vertebrates, but such effects are unstudied in reptiles. We investigated the light sensitivity of lizard embryos by examining the thickness and light transmittance of eggshells as well as the effect of light on embryonic development and hatchling traits in four lizard species, the Chinese skink (Plestiodon chinensis), the northern grass lizard (Takydromus septentrionalis), the oriental leaf-toed gecko (Hemidactylus bowringii) and the Japanese gecko (Gekko japonicus). The eggshells were thinner and thus had higher light transmittance in Chinese skink than the other three species. Light exposure during incubation significantly accelerated the embryonic development in all species, with higher light intensity resulting in faster embryonic development. Interestingly, light stimulation negatively influenced hatchling size and survival in skinks, but had no effect in lacertids and geckos. This interspecific discrepancy not only relates to the differences in thickness and light transmittance of eggshells, but might also reflect the differences in the reproductive habits of these species. Given the diversity of light conditions that reptile embryos face during development, studies on the response of reptile embryos to light may offer a unique opportunity to understand the mechanisms of embryonic light sensitivity in animals. [ABSTRACT FROM AUTHOR]

The role of heat shock proteins (HSPs) in heat tolerance has been demonstrated in cultured cells and animal tissues, but rarely in whole organisms because of methodological difficulties associated with gene manipulation. By comparing HSP70 expression patterns among representative species of reptiles and birds, and by determining the effect of HSP70 overexpression on embryonic development and hatchling traits, we have identified the role of HSP70 in the heat tolerance of amniote embryos. Consistent with their thermal environment, and high incubation temperatures and heat tolerance, the embryos of birds have higher onset and maximum temperatures for induced HSP70 than do reptiles, and turtles have higher onset and maximum temperatures than do lizards. Interestingly, the trade-off between benefits and costs of HSP70 overexpression occurred between life-history stages: when turtle embryos developed at extreme high temperatures, HSP70 overexpression generated benefits by enhancing embryo heat tolerance and hatching success, but subsequently imposed costs by decreasing heat tolerance of surviving hatchlings. Taken together, the correlative and causal links between HSP70 and heat tolerance provide, to our knowledge, the first unequivocal evidence that HSP70 promotes thermal tolerance of embryos in oviparous amniotes. [ABSTRACT FROM AUTHOR]