Proteome plasticity in response to persistent environmental change.

Temperature is a variable component of the environment, and all organisms must deal with or adapt to temperature change. Acute temperature change activates cellular stress responses, resulting in refolding or removal of damaged proteins. However, how organisms adapt to long-term temperature change remains largely unexplored. Here we report that budding yeast responds to long-term high temperature challenge by switching from chaperone induction to reduction of temperature-sensitive proteins and re-localizing a portion of its proteome. Surprisingly, we also find that many proteins adopt an alternative conformation. Using Fet3p as an example, we find that the temperature-dependent conformational difference is accompanied by distinct thermostability, subcellular localization, and, importantly, cellular functions. We postulate that, in addition to the known mechanisms of adaptation, conformational plasticity allows some polypeptides to acquire new biophysical properties and functions when environmental change endures.

Variable thermal plasticity of leaf functional traits in Andean tropical montane forests.

Tropical montane forests (TMFs) are biodiversity hotspots and provide vital ecosystem services, but they are disproportionately vulnerable to climate warming. In the Andes, cold-affiliated species from high elevations are being displaced at the hot end of their thermal distributions by warm-affiliated species migrating upwards from lower elevations, leading to compositional shifts. Leaf functional traits are strong indicators of plant performance and at the community level have been shown to vary along elevation gradients, reflecting plant adaptations to different environmental niches. However, the plastic response of such traits to relatively rapid temperature change in Andean TMF species remains unknown. We used three common garden plantations within a thermosequence in the Colombian Andes to investigate the warming and cooling responses of key leaf functional traits in eight cold- and warm-affiliated species with variable thermal niches. Cold-affiliated species shifted their foliar nutrient concentrations when exposed to warming, while all other traits did not significantly change; contrastingly, warm-affiliated species were able to adjust structural, nutrient and water-use efficiency traits from acquisitive to conservative strategies in response to cooling. Our findings suggest that cold-affiliated species will struggle to acclimate functional traits to warming, conferring warm-affiliated species a competitive advantage under climate change.

Heatwaves do not limit recovery following defoliation but alter leaf drought tolerance traits.

As heatwave frequency increases, they are more likely to coincide with other disturbances like insect defoliation. But it is unclear if high temperatures after defoliation impact canopy recovery or leaf traits which may affect response to further stressors like drought. To examine these stressor interactions, we subjected defoliated (DEF) and undefoliated (UNDEF) oak saplings to a simulated spring heatwave of +10°C for 25 days. We measured gas exchange, leaf area recovery, carbohydrate storage, turgor loss point (ΨTLP ), and minimum leaf conductance (gmin ). During the heatwave, stem respiration exhibited stronger thermal acclimation in DEF than UNDEF saplings, while stomatal conductance and net photosynthesis increased. The heatwave did not affect leaf area recovery or carbohydrate storage of DEF saplings, but reflush leaves had higher gmin than UNDEF leaves, and this was amplified by the heatwave. Across all treatments, higher gmin was associated with higher daytime stomatal conductance and a lower ΨTLP . The results suggest defoliation stress may not be exacerbated by higher temperatures. However, reflush leaves are less conservative in their water use, limiting their ability to minimise water loss. While lower ΨTLP could help DEF trees maintain gas exchange under mild drought, they may be more vulnerable to dehydration under severe drought.

Long-term warming increased carbon sequestration capacity in a humid subtropical forest.

Tropical and subtropical forests play a crucial role in global carbon (C) pools, and their responses to warming can significantly impact C-climate feedback and predictions of future global warming. Despite earth system models projecting reductions in land C storage with warming, the magnitude of this response varies greatly between models, particularly in tropical and subtropical regions. Here, we conducted a field ecosystem-level warming experiment in a subtropical forest in southern China, by translocating mesocosms (ecosystem composed of soils and plants) across 600 m elevation gradients with temperature gradients of 2.1°C (moderate warming), to explore the response of ecosystem C dynamics of the subtropical forest to continuous 6-year warming. Compared with the control, the ecosystem C stock decreased by 3.8% under the first year of 2.1°C warming; but increased by 13.4% by the sixth year of 2.1°C warming. The increased ecosystem C stock by the sixth year of warming was mainly attributed to a combination of sustained increased plant C stock due to the maintenance of a high plant growth rate and unchanged soil C stock. The unchanged soil C stock was driven by compensating and offsetting thermal adaptation of soil microorganisms (unresponsive soil respiration and enzyme activity, and more stable microbial community), increased plant C input, and inhibitory C loss (decreased C leaching and inhibited temperature sensitivity of soil respiration) from soil drying. These results suggest that the humid subtropical forest C pool would not necessarily diminish consistently under future long-term warming. We highlight that differential and asynchronous responses of plant and soil C processes over relatively long-term periods should be considered when predicting the effects of climate warming on ecosystem C dynamics of subtropical forests.

Variable influence of photosynthetic thermal acclimation on future carbon uptake in Australian wooded ecosystems under climate change.

Climate change will impact gross primary productivity (GPP), net primary productivity (NPP), and carbon storage in wooded ecosystems. The extent of change will be influenced by thermal acclimation of photosynthesis-the ability of plants to adjust net photosynthetic rates in response to growth temperatures-yet regional differences in acclimation effects among wooded ecosystems is currently unknown. We examined the effects of changing climate on 17 Australian wooded ecosystems with and without the effects of thermal acclimation of C3 photosynthesis. Ecosystems were drawn from five ecoregions (tropical savanna, tropical forest, Mediterranean woodlands, temperate woodlands, and temperate forests) that span Australia's climatic range. We used the CABLE-POP land surface model adapted with thermal acclimation functions and forced with HadGEM2-ES climate projections from RCP8.5. For each site and ecoregion we examined (a) effects of climate change on GPP, NPP, and live tree carbon storage; and (b) impacts of thermal acclimation of photosynthesis on simulated changes. Between the end of the historical (1976-2005) and projected (2070-2099) periods simulated annual carbon uptake increased in the majority of ecosystems by 26.1%-63.3% for GPP and 15%-61.5% for NPP. Thermal acclimation of photosynthesis further increased GPP and NPP in tropical savannas by 27.2% and 22.4% and by 11% and 10.1% in tropical forests with positive effects concentrated in the wet season (tropical savannas) and the warmer months (tropical forests). We predicted minimal effects of thermal acclimation of photosynthesis on GPP, NPP, and carbon storage in Mediterranean woodlands, temperate woodlands, and temperate forests. Overall, positive effects were strongly enhanced by increasing CO2 concentrations under RCP8.5. We conclude that the direct effects of climate change will enhance carbon uptake and storage in Australian wooded ecosystems (likely due to CO2 enrichment) and that benefits of thermal acclimation of photosynthesis will be restricted to tropical ecoregions.

Cross-species gut microbiota transplantation predictably affects host heat tolerance.

The gut microbiome is known to influence and have regulatory effects in diverse physiological functions of host animals, but only recently has the relationship between host thermal biology and gut microbiota been explored. Here, we examined how early-life manipulations of the gut microbiota in larval amphibians influenced their critical thermal maximum (CTmax) at different acclimation temperatures. We stripped the resident microbiome from egg masses of wild-caught wood frogs (Lithobates sylvaticus) via an antibiotic wash, and then inoculated the eggs with pond water (control), no inoculation, or the intestinal microbiota of another species that has a wider thermal tolerance - green frogs (Lithobates clamitans). We predicted that this cross-species transplant would increase the CTmax of the recipient wood frog larvae relative to the other treatments. In line with this prediction, green frog microbiome-recipient larvae had the highest CTmax while those with no inoculum had the lowest CTmax. Both the microbiome treatment and acclimation temperature significantly influenced the larval gut microbiota communities and α-diversity indices. Green frog microbiome-inoculated larvae were enriched in Rikenellaceae relative to the other treatments, which produce short-chain fatty acids and could contribute to greater energy availability and enhanced heat tolerance. Larvae that received no inoculation had a higher relative abundance of potentially pathogenic Aeromonas spp., which negatively affects host health and performance. Our results are the first to show that cross-species gut microbiota transplants alter heat tolerance in a predictable manner. This finding has repercussions for the conservation of species that are threatened by climate change and demonstrates a need to further explore the mechanisms by which the gut microbiota modulate host thermal tolerance.

The incubation environment does not explain significant variation in heart rate plasticity among avian embryos.

The conditions an organism experiences during development can modify how they plastically respond to short-term changes in their environment later in life. This can be adaptive because the optimal average trait value and the optimal plastic change in trait value in response to the environment may differ across different environments. For example, early developmental temperatures can adaptively modify how reptiles, fish and invertebrates metabolically respond to temperature. However, whether individuals within populations respond differently (a prerequisite to adaptive evolution), and whether this occurs in birds, which are only ectothermic for part of their life cycle, is not known. We experimentally tested these possibilities by artificially incubating the embryos of Pekin ducks (Anas platyrhynchos domesticus) at constant or variable temperatures. We measured their consequent heart rate reaction norms to short-term changes in egg temperature and tracked their growth. Contrary to expectations, the early thermal environment did not modify heart rate reaction norms, but regardless, these reaction norms differed among individuals. Embryos with higher average heart rates were smaller upon hatching, but heart rate reaction norms did not predict subsequent growth. Our data also suggests that the thermal environment may affect both the variance in heart rate reaction norms and their covariance with growth. Thus, individual avian embryos can vary in their plasticity to temperature, and in contrast to fully ectothermic taxa, the early thermal environment does not explain this variance. Because among-individual variation is one precondition to adaptive evolution, the factors that do contribute to such variability may be important.

Environmental variation associated with overwintering elicits marked metabolic plasticity in a temperate salmonid, Salvelinus fontinalis.

Poleward winters commonly expose animals, including fish, to frigid temperatures and low food availability. Fishes that remain active over winter must therefore balance trade-offs between conserving energy and maintaining physiological performance in the cold, yet the extent and underlying mechanisms of these trade-offs are not well understood. We investigated the metabolic plasticity of brook char (Salvelinus fontinalis), a temperate salmonid, from the biochemical to whole-animal level in response to cold and food deprivation. Acute cooling (1°C day-1) from 14°C to 2°C had no effect on food consumption but reduced activity by 77%. We then assessed metabolic performance and demand over 90 days with exposure to warm (8°C) or cold winter (2°C) temperatures while fish were fed or starved. Resting metabolic rate (RMR) decreased substantially during initial cooling from 8°C to 2°C (Q10=4.2-4.5) but brook char exhibited remarkable thermal compensation during acclimation (Q10=1.4-1.6). Conversely, RMR was substantially lower (40-48%) in starved fish, conserving energy. Thus, the absolute magnitude of thermal plasticity may be masked or modified under food restriction. This reduction in RMR was associated with atrophy and decreases in in vivo protein synthesis rates, primarily in non-essential tissues. Remarkably, food deprivation had no effect on maximum oxygen uptake rates and thus aerobic capacity, supporting the notion that metabolic capacity can be decoupled from RMR in certain contexts. Overall, our study highlights the multi-faceted energetic flexibility of Salvelinus spp. that likely contributes to their success in harsh and variable environments and may be emblematic of winter-active fishes more broadly.

Interindividual variation among Culex pipiens larvae in terms of thermal response.

This study aims to determine the phenological characteristics of thermal responses in the larvae of a Culex pipiens complex field population at the individual level under the influence of thermal regime of its habitat. The analysis is based on a structured population model quantifying the thermal responses of development time and survival under variable conditions and characterising the variety between the larvae (interindividual variety). During the study performed in Turkish Thrace on a monthly basis between May 2021 and June 2022, a total of 3744 larvae were reared as peer larval cohorts and 2330 larvae as siblings in artificial containers to be fully exposed to the natural thermal condition that was recorded hourly. The development process of larvae was monitored daily from egg to adult. As a result, a total of 4788 adult mosquitoes emerged, with a development period ranging from 8 to 52 days in the females and 7 to 50 days in the males, and the survival rate was found to range from 0% to 100%. Both parameters varied by month and individuals, and the variations manifested itself, particularly in the colder periods. The results indicate that the variation between the individuals in terms of thermal response in the larvae of C. pipiens, along with the thermal acclimation ability, appears to be fate determinant in resisting fluctuating thermal regimes, surviving in concurrent climate change and adapting to new conditions with modifications in the seasonal phenology, such as maintaining reproductive dynamics throughout the winter thanks to global warming.

Substrate and adenylate limit subtropical tree fine-root respiration under soil warming.

How root respiration acclimates to global warming remains unclear, especially in subtropical forests that play a key role in the global carbon budget. In a large-scale in situ soil warming experiment, the occurrence of, and mechanisms controlling over, the acclimation of fine-root respiration of Cunninghamia lanceolata during the fourth year of warming were investigated. Specific respiration rates (at reference temperature of 20°C; SRR20 ) were measured with exogenous glucose addition, uncoupler addition, or no addition, and root morphological and chemical traits were also measured. Warming decreased SRR20 by 18.4% only during summer, indicating partial thermal acclimation of fine-root respiration under warming. Warming did not change fine-root N concentration, showing no possible enzyme limitation on respiration. Warming decreased root soluble sugar/starch ratio in summer, and glucose addition increased respiration only under warming, indicating a warming-induced substrate limitation on respiration. Uncoupler addition also stimulated respiration only under warming, showing a warming-induced adenylate limitation on respiration. These findings suggest that thermal acclimation of root respiration in subtropical forests, which is at least partially constrained by substrate and adenylate use, is conducive to reducing ecosystem carbon emissions and mitigating the positive feedback between atmospheric CO2 and climate warming.

Seasonal variability in resilience of a coral reef fish to marine heatwaves and hypoxia.

Climate change projections indicate more frequent and severe tropical marine heatwaves (MHWs) and accompanying hypoxia year-round. However, most studies have focused on peak summer conditions under the assumption that annual maximum temperatures will induce the greatest physiological consequences. This study challenges this idea by characterizing seasonal MHWs (i.e., mean, maximum, and cumulative intensities, durations, heating rates, and mean annual occurrence) and comparing metabolic traits (i.e., standard metabolic rate (SMR), Q10 of SMR, maximum metabolic rate (MMR), aerobic scope, and critical oxygen tension (Pcrit )) of winter- and summer-acclimatized convict tang (Acanthurus triostegus) to the combined effects of MHWs and hypoxia. Fish were exposed to one of six MHW treatments with seasonally varying maximum intensities (winter: 24.5, 26.5, 28.5°C; summer: 28.5, 30.5, 32.5°C), representing past and future MHWs under IPCC projections (i.e., +0, +2, +4°C). Surprisingly, MHW characteristics did not significantly differ between seasons, yet SMR was more sensitive to winter MHWs (mean Q10 = 2.92) than summer MHWs (mean Q10 = 1.81), despite higher absolute summer temperatures. Concurrently, MMR increased similarly among winter +2 and +4°C treatments (i.e., 26.5, 28.5°C) and all summer MHW treatments, suggesting a ceiling for maximal MMR increase. Aerobic scope did not significantly differ between seasons nor among MHW treatments. While mean Pcrit did not significantly vary between seasons, warming of +4°C during winter (i.e., 28.5°C) significantly increased Pcrit relative to the winter control group. Contrary to the idea of increased sensitivity to MHWs during the warmest time of year, our results reveal heightened sensitivity to the deleterious effects of winter MHWs, and that seasonal acclimatization to warmer summer conditions may bolster metabolic resilience to warming and hypoxia. Consequently, physiological sensitivity to MHWs and hypoxia may extend across larger parts of the year than previously expected, emphasizing the importance of evaluating climate change impacts during cooler seasons when essential fitness-related traits such as reproduction occur in many species.

Substrate availability and not thermal acclimation controls microbial temperature sensitivity response to long-term warming.

Microbes are responsible for cycling carbon (C) through soils, and predicted changes in soil C stocks under climate change are highly sensitive to shifts in the mechanisms assumed to control the microbial physiological response to warming. Two mechanisms have been suggested to explain the long-term warming impact on microbial physiology: microbial thermal acclimation and changes in the quantity and quality of substrates available for microbial metabolism. Yet studies disentangling these two mechanisms are lacking. To resolve the drivers of changes in microbial physiology in response to long-term warming, we sampled soils from 13- and 28-year-old soil warming experiments in different seasons. We performed short-term laboratory incubations across a range of temperatures to measure the relationships between temperature sensitivity of physiology (growth, respiration, carbon use efficiency, and extracellular enzyme activity) and the chemical composition of soil organic matter. We observed apparent thermal acclimation of microbial respiration, but only in summer, when warming had exacerbated the seasonally-induced, already small dissolved organic matter pools. Irrespective of warming, greater quantity and quality of soil carbon increased the extracellular enzymatic pool and its temperature sensitivity. We propose that fresh litter input into the system seasonally cancels apparent thermal acclimation of C-cycling processes to decadal warming. Our findings reveal that long-term warming has indirectly affected microbial physiology via reduced C availability in this system, implying that earth system models including these negative feedbacks may be best suited to describe long-term warming effects on these soils.

Cardiac remodeling caused by cold acclimation is reversible with rewarming in zebrafish (Danio rerio).

Cold acclimation of zebrafish causes changes to the structure and composition of the heart. However, little is known of the consequences of these changes on heart function or if these changes are reversible with rewarming back to the initial temperature. In the current study, zebrafish were acclimated from 27℃ to 20°C, then after 17 weeks, a subset of fish were rewarmed to 27°C and held at that temperature for 7 weeks. The length of this trial, 23 weeks, was chosen to mimic seasonal changes in temperature. Cardiac function was measured in each group at 27°C and 20°C using high frequency ultrasound. It was found that cold acclimation caused a decrease in ventricular cross-sectional area, compact myocardial thickness, and total muscle area. There was also a decrease in end-diastolic area with cold acclimation that reversed upon rewarming to control temperatures. Rewarming caused an increase in the thickness of the compact myocardium, total muscle area, and end-diastolic area back to control levels. This is the first experiment to demonstrate that cardiac remodeling, induced by cold acclimation, is reversible upon re-acclimation to control temperature (27°C). Finally, body condition measurements reveal that fish that had been cold-acclimated and then reacclimated to 27°C, were in poorer condition than the fish that remained at 20°C as well as the control fish at week 23. This suggests that the physiological responses to the multiple changes in temperature had a significant energetic cost to the animal. SUMMARY STATEMENT: The decrease in cardiac muscle density, compact myocardium thickness and diastolic area in zebrafish caused by cold acclimation, was reversed with rewarming to control temperatures.

Handling the heat - photosynthetic thermal stress in tropical trees.

Warming climate increases the risk for harmful leaf temperatures in terrestrial plants, causing heat stress and loss of productivity. The heat sensitivity may be particularly high in equatorial tropical tree species adapted to a thermally stable climate. Thermal thresholds of the photosynthetic system of sun-exposed leaves were investigated in three tropical montane tree species native to Rwanda with different growth and water use strategies (Harungana montana, Syzygium guineense and Entandrophragma exselsum). Measurements of chlorophyll fluorescence, leaf gas exchange, morphology, chemistry and temperature were made at three common gardens along an elevation/temperature gradient. Heat tolerance acclimated to maximum leaf temperature (Tleaf ) across the species. At the warmest sites, the thermal threshold for normal function of photosystem II was exceeded in the species with the highest Tleaf despite their higher heat tolerance. This was not the case in the species with the highest transpiration rates and lowest Tleaf . The results point to two differently effective strategies for managing thermal stress: tolerance through physiological adjustment of leaf osmolality and thylakoid membrane lipid composition, or avoidance through morphological adaptation and transpiratory cooling. More severe photosynthetic heat stress in low-transpiring montane climax species may result in a competitive disadvantage compared to high-transpiring pioneer species with more efficient leaf cooling.

Drought and warming alter gross primary production allocation and reduce productivity in a widespread pasture grass.

Carbon allocation determines plant growth, fitness and reproductive success. However, climate warming and drought impacts on carbon allocation patterns in grasses are not well known, particularly following grazing or clipping. A widespread C3 pasture grass, Festuca arundinacea, was grown at 26 and 30°C in controlled environment chambers and subjected to drought (65% reduction relative to well-watered controls). Leaf, root and whole-plant carbon fluxes were measured and linked to growth before and after clipping. Both drought and warming reduced gross primary production and plant biomass. Drought reduced net leaf photosynthesis but increased the leaf respiratory fraction of assimilated carbon. Warming increased root respiration but did not affect either net leaf photosynthesis or leaf respiration. There was no evidence of thermal acclimation. Moreover, root respiratory carbon loss was amplified in the combined drought and warming treatment and, in addition to a negative carbon balance aboveground, explained an enhanced reduction in plant biomass. Plant regrowth following clipping was strongly suppressed by drought, reflecting increased tiller mortality and exacerbated respiratory carbon loss. These findings emphasize the importance of considering carbon allocation patterns in response to grazing or clipping and interactions with climatic factors for sustainable pasture production in a future climate.

Wheat respiratory O2 consumption falls with night warming alongside greater respiratory CO2 loss and reduced biomass.

Warming nights are correlated with declining wheat growth and yield. As a key determinant of plant biomass, respiration consumes O2 as it produces ATP and releases CO2 and is typically reduced under warming to maintain metabolic efficiency. We compared the response of respiratory O2 and CO2 flux to multiple night and day warming treatments in wheat leaves and roots, using one commercial (Mace) and one breeding cultivar grown in controlled environments. We also examined the effect of night warming and a day heatwave on the capacity of the ATP-uncoupled alternative oxidase (AOX) pathway. Under warm nights, plant biomass fell, respiratory CO2 release measured at a common temperature was unchanged (indicating higher rates of CO2 release at prevailing growth temperature), respiratory O2 consumption at a common temperature declined, and AOX pathway capacity increased. The uncoupling of CO2 and O2 exchange and enhanced AOX pathway capacity suggest a reduction in plant energy demand under warm nights (lower O2 consumption), alongside higher rates of CO2 release under prevailing growth temperature (due to a lack of down-regulation of respiratory CO2 release). Less efficient ATP synthesis, teamed with sustained CO2 flux, could thus be driving observed biomass declines under warm nights.

Temperature acclimation of leaf respiration differs between marsh and mangrove vegetation in a coastal wetland ecotone.

Temperature acclimation of leaf respiration (R) is an important determinant of ecosystem responses to temperature and the magnitude of temperature-CO2 feedbacks as climate warms. Yet, the extent to which temperature acclimation of R exhibits a common pattern across different growth conditions, ecosystems, and plant functional types remains unclear. Here, we measured the short-term temperature response of R at six time points over a 10-month period in two coastal wetland species (Avicennia germinans [C3 mangrove] and Spartina alterniflora [C4 marsh grass]) growing under ambient and experimentally warmed temperatures at two sites in a marsh-mangrove ecotone. Leaf nitrogen (N) was determined on a subsample of leaves to explore potential coupling of R and N. We hypothesized that both species would reduce R at 25°C (R25 ) and the short-term temperature sensitivity of R (Q10 ) as air temperature (Tair ) increased across seasons, but the decline would be stronger in Avicennia than in Spartina. For each species, we hypothesized that seasonal temperature acclimation of R would be equivalent in plants grown under ambient and warmed temperatures, demonstrating convergent acclimation. Surprisingly, Avicennia generally increased R25 with increasing growth temperature, although the Q10 declined as seasonal temperatures increased and did so consistently across sites and treatments. Weak temperature acclimation resulted in reduced homeostasis of R in Avicennia. Spartina reduced R25 and the Q10 as seasonal temperatures increased. In Spartina, seasonal temperature acclimation was largely consistent across sites and treatments resulting in greater respiratory homeostasis. We conclude that co-occurring coastal wetland species may show contrasting patterns of respiratory temperature acclimation. Nonetheless, leaf N scaled positively with R25 in both species, highlighting the importance of leaf N in predicting respiratory capacity across a range of growth temperatures. The patterns of respiratory temperature acclimation shown here may improve the predictions of temperature controls of CO2 fluxes in coastal wetlands.

Fatty acid oxidation: a neglected factor in understanding the adjustment of mitochondrial function to cold temperatures.

For ectothermic species, adaptation to thermal changes is of critical importance. Mitochondrial oxidative phosphorylation (OXPHOS), which leverages multiple electron pathways to produce energy needed for survival, is among the crucial metabolic processes impacted by temperature. Our aim in this study was to identify how changes in temperature affect the less-studied electron transferring flavoprotein pathway, fed by fatty acid substrates. We used the planarian Dugesia tigrina, acclimated for 4 weeks at 10°C (cold acclimated) or 20°C (normothermic). Respirometry experiments were conducted at an assay temperature of either 10 or 20°C to study specific states of the OXPHOS process using the fatty acid substrates palmitoylcarnitine (long chain), octanoylcarnitine (medium chain) or acetylcarnitine (short chain). Following cold acclimation, octanoylcarnitine exhibited increases in both the OXPHOS and electron transfer (ET, non-coupled) states, indicating that the pathway involved in medium-chain length fatty acids adjusts to cold temperatures. Acetylcarnitine only showed an increase in the OXPHOS state as a result of cold acclimation, but not in the ET state, indicative of a change in phosphorylation system capacity rather than fatty acid ß-oxidation. Palmitoylcarnitine oxidation was unaffected. Our results show that cold acclimation in D. tigrina caused a specific adjustment in the capacity to metabolize medium-chain fatty acids rather than an adjustment in the activity of the enzymes carnitine-acylcarnitine translocase, carnitine acyltransferase and carnitine palmitoyltransferase-2. Here, we provide novel evidence of the alterations in fatty acid ß-oxidation during cold acclimation in D. tigrina.

Understanding costs and benefits of thermal plasticity for pest management: insights from the integration of laboratory, semi-field and field assessments of Ceratitis capitata (Diptera: Tephritidae).

The relative costs and benefits of thermal acclimation for manipulating field performance of pest insects depend upon a number of factors including which traits are affected and how persistent any trait changes are in different environments. By assessing plastic trait responses of Ceratitis capitata (Mediterranean fruit fly) across three distinct operational environments (laboratory, semi-field, and field), we examined the influence of different thermal acclimation regimes (cool, intermediate [or handling control], and warm) on thermal tolerance traits (chill-coma recovery, heat-knockdown time, critical thermal minimum and critical thermal maximum) and flight performance (mark-release-recapture). Under laboratory conditions, thermal acclimation altered thermal limits in a relatively predictable manner and there was a generally positive effect across all traits assessed, although some traits responded more strongly. By contrast, dispersal-related performance yielded strongly contrasting results depending on the specific operational environment assessed. In semi-field conditions, warm- or cold-acclimated flies were recaptured more often than the control group at cooler ambient conditions suggesting an overall stimulatory influence of thermal variability on low-temperature dispersal. Under field conditions, a different pattern was identified: colder flies were recaptured more in warmer field conditions relative to other treatment groups. This study highlights the trait- and context-specific nature of how thermal acclimation influences traits of thermal performance and tolerance. Consequently, laboratory and semi-field assessments of dispersal may not provide results that extend into the field setting despite the apparent continuum of environmental complexity among them (laboratory < semi-field < field).

Effects of long-term exposure to high temperature on growth performance, chemical composition, hematological and histological changes, and physiological responses in hybrid catfish [♂Clarias gariepinus (Burchell, 1822) ×♀C. macrocephalus (Günther, 1864)].

The anthropogenic and climate-driven rise in water temperature is expected to have an effect on the physiological functions of ectothermic species. In the present study, hybrid catfish were subjected to three different temperatures (27, 32, and 37 °C) for 50 days to examine the effect of long-term exposure to high temperatures on growth and physiological parameters. The results showed that acclimation temperature improves growth and feed utilization with a quadratic effect (P < 0.05). The highest performance was observed at 32 °C, but fish acclimated at 37 °C decreased growth and feed utilization. In addition, skin darkening was observed in fish acclimated with increasing temperatures. Fat content of whole-body, liver, and dorsal muscle of fish was decreased by increasing temperatures (P < 0.05). Higher temperature levels significantly increased in all blood parameters (P < 0.05), except for high-density lipoprotein cholesterol, which was quadratically decreased (P = 0.004). Fish acclimated with increasing temperature also altered gill and liver histology such as gill shortening, hyperplasia and edema in the connective tissue, severe hyperplasia of epithelial cells, and desquamation, hepatocyte vacuolization, nuclei displacement, and pyknotic hepatic cells. While mucus cells were periphery distributed in the subcutaneous skin. In addition, cuboidal shape-like of club cells and melanophores were also observed in fish acclimated at 37 °C resulting in increased epithelial layer thickness. After fish subjected to increasing temperature exhibited an increase in the number of operculum movement and number of gasping for air (P < 0.05) in all acclimated groups. While fish challenged at 37 °C showed higher critical thermal maximum (CTmax, 41.33 °C) than those of the other groups. Overall, the maximum temperature (37 °C) may rick to hybrid catfish. To prevent physiological damage to the fish, as well as reduction of growth and productivity, the temperature in the aquaculture setting should be kept below 37 °C.