Genetic parameter estimation for juvenile growth and upper thermal tolerance in turbot(Scophthalmus maximus Linnaeus)

Twenty-six half-sib groups （53 full-sib families） of turbot,Scophthalmus maximus Linnaeus, were obtained by artificial insemination. We measured growth in the offspring （40-50 individuals/family） and subjected them to a thermal tolerance challenge over a period of 34 d. There was no significant difference in daily mor-tality （range： 0.580%-1.391%） between Days 1-13 during the thermal tolerance challenge. However, daily cumulative mortality increased rapidly between Days 14 and 29, especially on Days 15 and 16 （20.232% and 34.377%, respectively）. Mortality was highest on Day 16 （14.145%）. We estimated the genetic parameters using the average information restricted maximum likelihood method. We used a likelihood ratio test to evaluate the significance of effects in models with and without identity as an effect, and compared the final log-likelihoods （maximum log L）. Lastly, we estimated phenotypic and genetic correlation between the up-per thermal tolerance limit （UTT） and body weight （BW）. In this study, the positive phenotypic correlation was low between UTT and BW （0.093±0.029）. The genetic correlation between UTT and BW was negative （-0.044±0.239）. The heritability for upper thermal tolerance was low （0.087±0.032）, which is of approximate-ly moderate heritability. The heritability for body weight was high （0.303±0.074）. Our results suggest there is significant potential for improvement in the culture of turbot by selective breeding.

Antisense-Mediated Depletion of Tomato Chloroplast Omega-3 Fatty Acid Desaturase Enhances Thermal Tolerance

A chloroplast-localized tomato （Lycopersicon esculentum Mill.） ω-3 fatty acid desaturase gene （LeFADT） was isolated and characterized with regard to its sequence, response to various temperatures, and function in antisense transgenic tomato plants. The deduced amino acid sequence had four histidine-rich regions, of which three regions were highly conserved throughout the whole ω-3 fatty acid desaturasegene family. Southern blotting analysis showed that LeFAD7was encoded by a single copy gene and had two homologous genes in the tomato genome. Northern blot showed that LeFAD7 was expressed in all organs and was especially abundant in leaf tissue. Meanwhile, expression of LeFAD7 was induced by chilling stress （4 ℃）, but was inhibited by high temperature （45 ℃）, in leaves. Transgenic tomato plants were produced by integration of the antisense LeFAD7DNA under the control of a CaMV35S promoter into the genome. Antisense transgenic plants with lower 18 ： 3 content could maintain a higher maximal photochemical efficiency （Fv/Fm） and O2 evolution rate than wild-type plants. These results suggested that silence of the LeFAD7 gene alleviated high-temperature stress. There was also a correlation between the low content of 18 ： 3 resulting from silence of the LeFAD7 gene and tolerance to high-temperature stress.

Differences in Thermal Preference and Tolerance among Three Phrynocephalus Lizards (Agamidae) with Different Body Sizes and Habitat Use

We acclimated adults of two viviparous （Phrynocephalus guinanens＆ and P. vlangalii） and one oviparous （P. versicolor） species of toad-headed lizards （Agamidae） to 28 ℃, 33 ℃ and 38 ℃ to examine whether thermal preference （preferred body temperature, Tp） and thermal tolerance （critical thermal minimum, CTMin; critical thermal maximum, CTMax） were affected by acclimation temperature, and correlate with body size and habitat use. Both Tp and CTMax were highest in P. versicolor and lowest in P. vlangalii, with P. guinanensis in between. The two viviparous species did not differ in CTMin and thermal tolerance range, and they both were more resistant to low temperatures and had a wider range of thermal tolerance than the oviparous species. Both CTMin and CTMax shifted upward as acclimation temperature increased in all the three species. Tp was higher in the lizards acclimated to 33 ℃ than in those to 28 ℃ or 38 ℃. The range of thermal tolerance was wider in the lizards acclimated to 28 ℃ than in those to 33 ℃ or 38 ℃. The data showed that： 1） thermal preference and tolerance were affected by acclimation temperature, and differed among the three species of Phrynocephalus lizards with different body sizes and habitat uses; 2） both Tp and CTMax were higher in the species exchanging heat more rapidly with the environment, and CTMin was higher in the species using warmer habitats during the active season; and 3） thermal preference and tolerance might correlat with body size and habitat use in Phrynocephalus lizards.

Thermal Biology of Cold-climate Distributed Heilongjiang Grass Lizard,Takydromus amurensis

Thermal biology traits reflect thermal adaptations to an environment and can be used to infer responses to climate warming in animal species.Within a widespread genus or species,assessing the latitudinal or altitudinal gradient of thermal physiological traits is essential to reveal thermal adaptations and determine future vulnerability to climate warming geographically.We determined the thermal biology traits of a cold-climate distributed lizard,Takydromus amurensis,and integrated published thermal biology traits within the genus Takydromus to reveal a preliminary geographical pattern in thermal adaptation.The mean selected body temperature(cloaca temperature;T_(sel)),critical thermal maximum(CT_(max)),critical thermal minimum(CT_(min)),and optimal temperature for locomotion(i.e.,sprint speed;T_(opt)) of T.amurensis were 32.6,45.1,3.1,and 33.4℃,respectively.The resting metabolic rates of T.amurensis were po sitively related to temperature from 18℃ to 38℃.We compared the traits of tropical T.sexlineatus,subtropical T.septentrionalis,and T.wolteri with T.amurensis and found that the CT_(max) and thermal tolerance range(the difference between CT_(max) and CT_(min);TTR) increased toward high latitudes,whereas CT_(min) increased toward low latitudes in these four Takydromus lizards.According to this preliminary pattern,we speculate the species at medium and low latitudes would be more vulnerable to extreme heat events caused by ongoing climate warming.We highlight the importance of integrating thermal biology traits along geographical clues,and its potential contribution to evaluate the vulnerabilities of species in the context of climate warming.

Landscape effects on the thermotolerance of carabid beetles and the role of behavioral thermoregulation

Physiological thermotolerance and behavioral thermoregulation are central to seasonal cold adaptation in ectothermic organisms.For species with enhanced mobility,behavioral responses may be of greater importance in the cold stress response.Employing the carabid beetles as a study organism,the current study compared physiological thermotolerance and behavioral thermoregulation in carabid species inhabiting cereal fields in different landscape contexts,from fine grain heterogeneous“complex”landscapes to homogenous“simple”landscapes.Physiological thermotolerance was determined via measurement of the CTmin and chill coma temperature.Behavioral responses to cold temperature exposure were determined employing a purpose built arena,and thoracic temperature measured to estimate the efficacy of the behavior as a form of behavioral thermoregulation.Results revealed an influence of landscape composition on the cold tolerance of carabid beetles,although species differed in their sensitivity to landscape intensification.A reduced effect of landscape on the thermotolerance of larger carabid beetles was observed,thought to be the consequence of greater mobility preventing local acclimation to microclimatic variation along the landscape intensification gradient.Investigation into behavioral thermoregulation of the 3 largest species revealed burrowing behavior to be the main behavioral response to cold stress,acting to significantly raise carabid body temperature.This finding highlights the importance of behavioral thermoregulation as a strategy to evade cold stress.The use of behavioral thermoregulation may negate the need to invest in physiological thermotolerance,further offering explanation for the lack of landscape effect on the physiological thermotolerance of larger carabids.

Heat tolerance may determine activity time in coprophagic beetle species (Coleoptera:Scarabaeidae)

Although reports have documented loss of species diversity and ecological services caused by stressful temperature changes that result from climate change,some species cope through behavioral compensation.As temperatures and magnitudes of temperature extremes increase,animals should compensate to maintain fitness(such as through temporary behavioral shifts in activity times).Appropriate timing of activity helps avoid competition across species.Although coprophagic dung beetles exhibit species-specific temporal activity times,it is unknown whether temperature drives evolution of these species-specific temporal activity times.Using nine dung beetle species(three each of diurnal,crepuscular,and nocturnal species),we explored differences in heat stress tolerance measured as critical thermal maxima(CTmax;the highest temperature allowing activity)and heat knockdown time(HKDT;survival time under acute heat stress)across these species,and examined the results using a phylogenetically informed approach.Our results showed that day-active species had significantly higher CTmax(diurnal>crepuscular=nocturnal species),whereas crepuscular species had higher HKDT(crepuscular>nocturnal>diurnal species).There was no correlation between heat tolerance and body size across species with distinct temporal activity,and no significant phylogenetic constraint for activity.Species with higher CTmax did not necessarily have higher HKDT,which indicates that species may respond differently to diverse heat tolerance metrics.Acute heat tolerance for diurnal beetles indicates that this trait may constrain activity time and,under high acute temperatures with climate change,species may shift activity times in more benign environments.These results contribute to elucidate the evolution of foraging behavior and management of coprophagic beetle ecosystem services under changing environments.

Effects of developmental plasticity on heat tolerance may be mediated by changes in cell size in Drosophila melanogaster

There is a growing interest in the physiology underpinning heat tolerance of ectotherms and their responses to the ongoing rise in temperature.However,there is no consensus about the underlying physiological mechanisms.According to''the maintain aerobic scope and regulate oxygen supply^hypothesis,responses to warming at different organizational levels contribute to the ability to safeguard energy metabolism via aerobic pathways.At the cellular level,a decrease in cell size increases the capacity for the uptake of resources(e.g.,food and oxygen),but the maintenance of electrochemical gradients across cellular membranes implies greater energetic costs in small cells.In this study,we investigated how different rearing temperatures atTected cell size and heat tolerance in the fruit fly Drosophila melanogaster.We tested the hypothesis that smallcr-celled flies are more tolerant to acute,intense heat stress whereas larger-celled flies are more tolerant to chronic,mild heat stress.We used the thermal tolerance landscape framework,which incorporates the intensity and duration of thermal challenge.Rearing temperatures strongly affected both cell size and survival times.We found different effects of developmental plasticity on tolerance to either chronic or acute heat stress.Warm-reared flies had both smaller cells and exhibited higher survival times under acute,intense heat stress when compared to cold-reared flies.However,under chronic,mild heat stress,the situation was reversed and cold-reared flies,consisting of larger cells,showed better survival.These differences in heat tolerance could have resulted from direct effects of rearing temperature or they may be mediated by the correlated changes in cell size.Notably,our results are consistent with the idea that a smaller cell size may confer tolerance to acute temperatures via enhanced oxygen supply,while a larger cell may confer greater tolerance to chronic and less intense heat stress via more efTicient use of resources.

Survival in spatially variable thermal environments:Consequences of induced thermal defense

As Earth’s climate warms,plants and animals are likely to encounter increased frequency and severity of extreme thermal events,and the ensuing destruction is likely to play an important role in structuring ecological communities.However,accurate prediction of the population-scale consequences of extreme thermal events requires detailed knowledge of the small-scale interaction between individual organisms and their thermal environment.In this study I propose a simple model that allows one to explore how individual-to-individual variation in body temperature and thermal physiology determines what fraction of a population will be killed by an extreme thermal event.The model takes into account the possibility that each individual plant or animal can respond to an event by adjusting its thermal tolerance in proportion to the stress it encounters.When thermal stress is relatively mild,the model shows that a graded physiological response of this sort leads to increased survivorship.However,the model predicts that in more severe events a proportional induced defense can actually reduce survivorship,a counterintuitive possibility that is not predicted by standard theory.The model can easily be tailored to different species and thermal environments to provide an estimate of when,where and how physiology can buffer the effects of climate warming.

Assessing the potential for satellite image monitoring of seagrass thermal dynamics:for inter-and shallow sub-tidal seagrasses in the inshore Great Barrier Reef World Heritage Area,Australia

Seagrass meadows are at increasing risk of thermal stress and recent work has shown that water temperature around seagrass meadows could be used as an indicator for seagrass condition.Satellite thermal data have not been linked to the thermal properties of seagrass meadows.This work assessed the covariation between 20 in situ average daily temperature logger measurement sites in tropical seagrass meadows and satellite derived daytime SST(sea surface temperature)from the daytime MODIS and Landsat sensors along the Great Barrier Reef coast in Australia.Statistically significant(R2=0.787–0.939)positive covariations were found between in situ seagrass logger temperatures and MODIS SST temperature and Landsat sensor temperatures at all sites along the reef.The MODIS SST were consistently higher than in situ temperature at the majority of the sites,possibly due to the sensor’s larger pixel size and location offset from field sites.Landsat thermal data were lower than field-measured SST,due to differences in measurement scales and times.When refined significantly and tested over larger areas,this approach could be used to monitor seagrass health over large(106 km2)areas in a similar manner to using satellite SST for predicting thermal stress for corals.

Context-dependent integrated stress resistance promotes a global invasive pest

In nature,insects concurrently face multiple environmental stressors,a sce-nario likely increasing with climate change.Integrated stress resistance(ISR)thus often improves fitness and could drive invasiveness,but how physiological mechanisms influ-ence invasion has lacked examination.Here,we investigated cross-tolerance to abiotic stress factors which may influence range limits in the South American tomato pinworm a global invader that is an ecologically and socially damaging crop pest.Specifically,we tested the effects of prior rapid cold-and heat-hardening(RCH and RHH),fasting,and desiccation on cold and heat tolerance traits,as well as starvation and desiccation sur-vivability between T.absoluta life stages.Acclimation effects on critical thermal minima(CT_(min))and maxima(CT_(max))were inconsistent,showing significantly deleterious effects of RCH on adult CT_(max) and CT_(min) and,conversely,beneficial acclimation effects of RCH on larval CT_(min).While no beneficial effects of desiccation acclimation were recorded for desiccation tolerance,fasted individuals had significantly higher survival in adults,whereas fasting negatively affected larval tolerances.Furthermore,fasted and desiccation acclimated adults had significantly higher starvation tolerance,showing strong evidence for cross-tolerance.Our results show context-dependent ISR traits that may promote T.absoluta fitness and competitiveness.Given the frequent overlapping occurrence of these divergent stressors,ISR reported here may thus partly elucidate the observed rapid global spread of T.absoluta into more stressful environments than expected.This information is vital in determining the underpinnings of multistressor responses,which are fundamental in forecasting species responses to changing environments and management responses.

Environmental temperatures,physiology and behavior limit the range expansion of invasive Burmese pythons in southeastern USA

A well-established population of Burmese pythons resides in the Everglades of southern Florida.Prompted in part by a report that identified much of southern USA as suitable habitat for expansion or establishment of the Burmese python,we examined the plausibility of this snake to survive winters at sites north of the Everglades.We integrated daily low and high temperatures recorded from October to February from 2005-2011 at Homestead,Orlando and Gainesville,Florida;and Aiken,South Carolina,with minimum temperatures projected for python digestion(16℃),activity(5℃)and survival(0℃).Mean low and high temperatures decreased northward from Homestead to Aiken and the number of days of freezing temperatures increased northward.Digestion was impaired or inhibited for 2 months in the Everglades and up to at least 5 months in Aiken,and activity was increasingly limited northward during these months.Reports of overwinter survivorship document that a single bout of low and freezing temperatures results in python death.The capacity for Burmese pythons to successfully overwinter in more temperate regions of the USA is seemingly prohibited because they lack the behaviors to seek refuge from,and the physiology to tolerate,cold temperatures.As tropical Southeast Asia is the source of the Everglades Burmese pythons,we predict it is unlikely that they will be able to successfully expand to or colonize more temperate areas of Florida and adjoining states due to their lack of behavioral and physiological traits to seek refuge from cold temperatures.

Cold adaptation does not alter ATP homeostasis during cold exposure in Drosophila melanogaster

In insects and other ectotherms,cold temperatures cause a coma resulting from loss of neuromuscular function,during which ionic and metabolic homeostasis are progressively lost.Cold adaptation improves homeostasis during cold exposure,but the ultimate targets of selection are still an open question.Cold acclimation and adaptation remodels mitochondrial metabolism in insects,suggesting that aerobic energy production during cold exposure could be a target of selection.Here,we test the hypothesis that cold adaptation improves the ability to maintain rates of aerobic energy production during cold exposure by using^(31)P NMR on live flies.Using lines of Drosophila melanogaster artificially selected for fast and slow recovery from a cold coma,we show that cold exposure does not lower ATP levels and that cold adaptation does not alter aerobic ATP production during cold exposure.Cold-hardy and cold-susceptible lines both experienced a brief transition to anaerobic metabolism during cooling,but this was rapidly reversed during cold exposure,suggesting that oxidative phosphorylation was sufficient to meet energy demands below the critical thermal minimum,even in cold-susceptible flies.We thus reject the hypothesis that performance under mild low temperatures is set by aerobic ATP supply limitations in D.melanogaster,excluding oxygen and capacity limitation as a weak link in energy supply.This work suggests that the modulations to mitochondrial metabolism resulting from cold acclimation or adaptation may arise from selection on a biosynthetic product(s)of those pathways rather than selection on ATP supply during cold exposure.