Body size dictates physiological and behavioural responses to hypoxia and elevated water temperatures in Murray cod (Maccullochella peelii).

BackgroundFrom the viewpoint of fungal virulence in mammals, thermal tolerance can be defined as the ability to grow in the 35°C to 40°C range, which is essential for inhabiting these hosts.ResultsWe used archival information in a fungal collection to analyze the relationship between thermal tolerance and genetic background for over 4,289 yeast strains belonging to 1,054 species. Fungal genetic relationships were inferred from hierarchical trees based on pairwise alignments using the rRNA internal transcribed spacer and large subunit rDNA (LSU) sequences. In addition, we searched for correlations between thermal tolerance and other archival information including antifungal susceptibility, carbon sources, and fermentative capacity. Thermal tolerance for growth at mammalian temperatures was not monophyletic, with thermally tolerant species being interspersed among families that include closely related species that are not thermal tolerant. Thermal tolerance and resistance to antifungal drugs were not correlated, suggesting that these two properties evolved independently. Nevertheless, the ability to grow at higher temperatures did correlate with origin from lower geographic latitudes, capacity for fermentation and assimilation of certain carbon sources.ConclusionsThermal tolerance was significantly more common among ascomycetous than basidiomycetous yeasts, suggesting an explanation for the preponderance of ascomycetous yeasts among human pathogenic fungi. Analysis of strain maximum tolerable temperature as a function of collection time suggested that basidiomycetous yeasts are rapidly adapting to global warming. The analysis identified genera with a high prevalence of the thermal-tolerant species that could serve as sources of emerging pathogenic fungi.Electronic supplementary materialThe online version of this article (doi:10.1186/s12915-015-0127-3) contains supplementary material, which is available to authorized users.

Heat adhesion duration: A new high-throughput abalone thermal tolerance assessment method

In fishes, performance failure at high temperature is thought to be due to a limitation on oxygen delivery (the theory of oxygen and capacity limited thermal tolerance, OCLTT), which suggests that thermal tolerance and hypoxia tolerance might be functionally associated. Here we examined variation in temperature and hypoxia tolerance among 41 families of Atlantic salmon (Salmo salar), which allowed us to evaluate the association between these two traits. Both temperature and hypoxia tolerance varied significantly among families and there was a significant positive correlation between critical maximum temperature (CTmax) and hypoxia tolerance, supporting the OCLTT concept. At the organ and cellular levels, we also discovered support for the OCLTT concept as relative ventricle mass (RVM) and cardiac myoglobin (Mb) levels both correlated positively with CTmax (R(2)=0.21, P<0.001 and R(2)=0.17, P=0.003, respectively). A large RVM has previously been shown to be associated with high cardiac output, which might facilitate tissue oxygen supply during elevated oxygen demand at high temperatures, while Mb facilitates the oxygen transfer from the blood to tissues, especially during hypoxia. The data presented here demonstrate for the first time that RVM and Mb are correlated with increased upper temperature tolerance in fish. High phenotypic variation between families and greater similarity among full- and half-siblings suggests that there is substantial standing genetic variation in thermal and hypoxia tolerance, which could respond to selection either in aquaculture or in response to anthropogenic stressors such as global climate change.

Three-way cross hybrid abalone exhibit heterosis in growth performance, thermal tolerance, and hypoxia tolerance

The expression pattern of hsp70 plays a critical role in thermal tolerance of marine demersal fish: Multilevel responses of Paralichthys olivaceus and its hybrids (P. olivaceus ♀ × P. dentatus ♂) to chronic and acute heat stress

Thermal dependence of growth and metabolism can influence thermal preference and tolerance in marine ectotherms, including threatened and data-deficient species. Here, we quantified the thermal dependence of physiological performance in neonates of a tropical shark species (blacktip reef shark, Carcharhinus melanopterus) from shallow, nearshore habitats. We measured minimum and maximum oxygen uptake rates (ṀO2 ), calculated aerobic scope, excess post-exercise oxygen consumption and recovery from exercise, and measured critical thermal maxima (CTmax), thermal safety margins, hypoxia tolerance, specific growth rates, body condition and food conversion efficiencies at two ecologically relevant acclimation temperatures (28 and 31°C). Owing to high post-exercise mortality, a third acclimation temperature (33°C) was not investigated further. Acclimation temperature did not affect ṀO2 or growth, but CTmax and hypoxia tolerance were greatest at 31°C and positively associated. We also quantified in vitro temperature (25, 30 and 35°C) and pH effects on haemoglobin-oxygen (Hb-O2) affinity of wild-caught, non-acclimated sharks. As expected, Hb-O2 affinity decreased with increasing temperatures, but pH effects observed at 30°C were absent at 25 and 35°C. Finally, we logged body temperatures of free-ranging sharks and determined that C. melanopterus neonates avoided 31°C in situ We conclude that C. melanopterus neonates demonstrate minimal thermal dependence of whole-organism physiological performance across a seasonal temperature range and may use behaviour to avoid unfavourable environmental temperatures. The association between thermal tolerance and hypoxia tolerance suggests a common mechanism warranting further investigation. Future research should explore the consequences of ocean warming, especially in nearshore, tropical species.

Northern snakeheads are an invasive piscivorous fish from east Asia. First reported from the Chesapeake Bay in 2004, they have now expanded their range throughout most of the watershed. Little is known about the physiology of Channa argus despite concerns over its dispersal ability and fitness in different environments. To evaluate the null hypothesis that dispersal capacity of Channa argus is unrelated to environmental conditions, we raised wild caught Channa argus juveniles under 3 different levels of salinity (0, 5 and 10‰) and temperature (15, 20 and 25°C). After at least 2 weeks of acclimation, thermal tolerance was tested both with critical thermal maxima (CT max ) and critical thermal minima (CT min ) tests. Locomotor performance and growth rate were used as proxies for fitness. Locomotor ability was assessed by sprinting the fish through a laser-detection array before and after the thermal tolerance testing. Northern snakeheads tolerated extremes of temperature from 1.1 to 42.3°C, and they displayed robust phenotypic plasticity of thermal tolerance. The ΔCT max of 0.47°C/°C of acclimation temperature and ΔCT min of 0.41°C/°C of acclimation temperature exceeded values reported for most other fishes. Growth rate was also temperature dependent, increasing ~3 fold from the 15°C to the 25°C treatment. Neither thermal tolerance or growth rate were significantly affected by the acclimation salinity however sprinting performance was determined by a complex interaction between temperature and salinity. Individual sprinting ability varied substantially, ranging from size corrected velocities of 68.1 to 138.1 cm*s -1 , but was highly repeatable within a day and across the entire experiment. Sprint performance was temperature dependent, but only at the two higher salinities. Sprinting ability in freshwater was unaffected by temperature as found for most other fishes. Conversely, sprinting ability was salinity dependent, but only at 15°C. At the two higher temperatures, sprinting ability was unaffected by salinity. There was no significant relationship between individual locomotor performance and thermal tolerance. Our conclusion is that the eurythermal and euryhaline Channa argus should have little trouble exploiting most estuarine and freshwater habitats on the east coast of the United States apart from more saline habitats in the winter when their ability to escape predators or capture prey may be somewhat compromised. Funded by the Towson University Graduate School This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

The hypothesis of oxygen limitation of thermal tolerance proposes that critical temperatures are set by a transition to anaerobic metabolism, and that upper and lower tolerances are therefore coupled. Moreover, this hypothesis has been dubbed a unifying general principle and extended from marine to terrestrial ectotherms. By contrast, in insects the upper and lower limits are decoupled, suggesting that the oxygen limitation hypothesis might not be as general as proposed. However, no direct tests of this hypothesis or its predictions have been undertaken in terrestrial species. We use a terrestrial isopod (Armadillidium vulgare) and a tenebrionid beetle (Gonocephalum simplex) to test the prediction that thermal tolerance should vary with oxygen partial pressure. Whilst in the isopod critical thermal maximum declined with declining oxygen concentration, this was not the case in the beetle. Efficient oxygen delivery via a tracheal system makes oxygen limitation of thermal tolerance, at a whole organism level, unlikely in insects. By contrast, oxygen limitation of thermal tolerances is expected to apply to species, like the isopod, in which the circulatory system contributes significantly to oxygen delivery. Because insects dominate terrestrial systems, oxygen limitation of thermal tolerance cannot be considered pervasive in this habitat, although it is a characteristic of marine species.

The 70-kDa heat shock protein response in two intertidal sculpins, Oligocottus maculosus and O. snyderi: relationship of hsp70 and thermal tolerance

The weak association between hypoxia tolerance and thermal tolerance increases the susceptibility of abalone to climate change

Thermal tolerance tests on Acropora millepora, a common Indo-Pacific hard coral, have shown that adult corals can acquire increased thermal tolerance by shuffling existing type C to type D Symbiodinium zooxanthellae when subjected to increased seawater temperatures. We report here dimethylsulphoniopropionate (DMSP) concentrations in A. millepora and examine links between DMSP concentrations, zooxanthellae clade, and bleaching tolerance. DMSP analysis on native and transplanted corals from three locations in the Great Barrier Reef indicated that the lower thermal tolerance in type C zooxanthellae coincided with variable DMSP concentrations, whilst the more thermal tolerant type D zooxanthellae had more stable areal DMSP concentrations as seawater temperatures increased. Our results suggest this increased thermal tolerance in type D zooxanthellae may reflect the ability of these coral symbionts to conserve their antioxidant DMSP levels to relatively constant concentrations, enabling the coral to overcome the build-up of oxygen free radicals in the cytoplasm of A. millepora. A conceptual diagram illustrates how the antioxidants DMS (P) participate in the bleaching process by scavenging oxygen free radicals and form DMSO, thus moderating coral bleaching and increasing thermotolerance.

Plants respond to high temperature stress by the synthesis of an assortment of heat shock proteins that have been correlated with an acquired thermal tolerance to otherwise lethal temperatures. This study was conducted to determine whether genotypic differences in acquired thermal tolerance were associated with changes in the pattern of heat shock protein synthesis. The pattern of heat shock protein synthesis was analyzed by (35)S-methionine incorporation in wheat (Triticum aestivum L.) varieties exhibiting distinct levels of acquired thermal tolerance. Significant quantitative differences between the cultivars Mustang and Sturdy were observed in the HSP exhibiting apparent molecular weights of 16, 17, 22, 26, 33, and 42 Kilodaltons. Genotypic differences in the synthesis of the small subunit of ribulose 1,5-bisphosphate carboxylase/oxygenase were observed at 34 degrees C. Two-dimensional electrophoretic analysis revealed unique proteins (16, 17, and 26 kilodaltons) in the thermal tolerant variety Mustang that were absent in the more thermal sensitive variety Sturdy. These results provide a correlation between the synthesis of specific low molecular weight heat shock proteins and the degree of thermal tolerance expressed following exposure to elevated temperatures.

High-throughput screening of thermal tolerant candidate genes in the ivory shell (Babylonia areolata) based on the yeast strain INVSc1.

In this study, we determine critical (CTMax) and lethal (LTMax) thermal tolerance, acclimation response ration (ARR), rate of oxygen consumption and stress in two potential ornamental fishes of the North Eastern Hill region of India, Danio dangila and Brachydanio rerio. The fishes were collected from wild and acclimatized at 18°C for 30 days. The fishes were then constantly reared at temperature regime of 20, 25, 30 and 35°C separately in insulated plastic tank for 45 days. Fishes from each rearing temperature were subjected to constant rate of increase at 1.0°C/min to determine the thermal tolerance. The results implicate significant increase (p<0.05) in CTMax (36.2±0.02, 37.7±0.31, 39.6±0.07, 40.9±0.10) and LTMax (38.1±0.08, 39.8±0.06, 40.0±0.07, 41.1±0.04) in D. dangila with increasing acclimation temperatures of 20, 25, 30 and 35°C, respectively. Similarly, CTMax (36.4±0.05, 37.2±0.04, 38.7±0.03, 39.8±0.01) and LTMax (39.8±0.03, 40.4±0.02, 41.2±0.06, 42.2±0.03) increased significantly (p<0.05) in B. rerio with increasing acclimation temperatures. Inter species variation was evident between the temperatures. Oxygen consumption rate increased (p<0.05) with increasing temperature in both the species. Overall, our results suggest that B. rerio is more thermal tolerant and show better adaptation in comparison to D. dangila.

Aphids, similar to all insects, are ectothermic and, consequently, are greatly affected by environmental conditions. The peach potato aphid Myzus persicae (Sulzer) has a global distribution, although it is not known whether populations display regional adaptations to distinct climatic zones along its distribution and vary in their ability to withstand and acclimate to temperature extremes. In the present study, lethal temperatures were measured in nine anholocyclic clones of M. persicae collected along a latitudinal cline of its European distribution from Sweden to Spain. The effects of collection origin and intra‐ and intergenerational acclimation on cold and heat tolerance, as determined by upper and lower lethal temperatures (ULT50 and LLT50, respectively), were investigated. Lethal temperatures of M. persicae were shown to be plastic and could be altered after acclimation over just one generation. Lower lethal temperatures were significantly depressed in eight of nine clones after acclimation for one generation at 10°C (range: −13.3 to −16.2°C) and raised after acclimation at 25°C (range: −10.7 to −11.6°C) compared with constant 20°C (range: −11.9 to −12.9°C). Upper lethal temperatures were less plastic, although significantly increased after one generation at 25°C (range: 41.8–42.4°C) and in five of nine clones after acclimation at 10°C. There was no evidence of intergenerational acclimation over three generations. Thermal tolerance ranges were expanded after acclimation at 10 and 25°C compared with constant 20°C, resulting in aphids reared at 10°C surviving over a temperature range that was approximately 2–6°C greater than those reared at 25°C. There was no clear relationship between lethal temperatures and latitude. Large scale mixing of clones may occur across Europe, thus limiting local adaption in thermal tolerance. Clonal type, as identified by microsatellite analysis, did show a relationship with thermal tolerance, notably with Type O clones being the most thermal tolerant. Clonal types may respond independently to climate change, affecting the relative proportions of clones within populations, with consequent implications for biodiversity and agriculture.