Physiological Thermal Tolerance Research Articles

Temperature dependence of fish performance in the wild: links with species biogeography and physiological thermal tolerance

Summary Temperature strongly regulates the distribution and fitness of ectotherms, and many studies have measured the temperature dependence of physiological performance in controlled laboratory settings. In contrast, little is known about how temperature influences ectotherm performance in the wild, so the ecological significance of physiological performance as measured in the laboratory is unclear. Our aim was to measure the temperature dependence of performance in the wild for several species of fishes and to explore how temperatures that maximize performance in the wild (ToptE) are related to species biogeographies. We gathered body activity and growth data from the wild for nine tropical and temperate fish species, and by fitting thermal performance curves to these data, compared ToptE to species‐specific warm range boundary temperatures (the average temperature of the warmest month at equatorward range limits). To explore the degree to which trends in the wild reflect trends in physiological performance measured in the laboratory, we also compiled published data on the temperature dependence of aerobic metabolic scope in fishes and compared these to our wild fish data. We found ToptE in the wild was strongly correlated with warm range boundary temperatures, and that the difference between these two temperatures (the ‘environmental heating tolerance’) was smaller for more‐tropical species. Comparison with laboratory data revealed that ToptE approaches warm boundary temperatures in the wild at the same rate that the optimal temperature for aerobic scope (ToptAS) approaches upper critical temperatures (upper Tcrit) for aerobic scope in the laboratory, meaning that environmental heating tolerances in wild fishes closely mirror physiological heating tolerance (i.e. upper Tcrit − ToptAS) in captive fishes. Our comparison of field‐ and laboratory‐derived data highlights the ecological significance of aerobic metabolic scope in fishes and suggests wild fish species tend to perform best near the highest temperatures encountered in their range while maintaining a safety margin from the deleterious effects of upper critical temperatures.

Could behaviour and not physiological thermal tolerance determine winter survival of aphids in cereal fields?

Traits of physiological thermotolerance are commonly measured in the laboratory as predictors of the field success of ectotherms at unfavourable temperatures (e.g. during harsh winters, heatwaves, or under conditions of predicted global warming). Due to being more complicated to measure, behavioural thermoregulation is less commonly studied, although both physiology and behaviour interact to explain the survival of ectotherms. The aphids Metopolophium dirhodum, Rhopalosiphum padi and Sitobion avenae are commercially important pests of temperate cereal crops. Although coexisting, these species markedly differ in winter success, with R. padi being the most abundant species during cold winters, followed by S. avenae and lastly M. dirhodum. To better understand the thermal physiology and behavioural factors contributing to differential winter success, the lethal temperature (physiological thermotolerance) and the behaviour of aphids in a declining temperature regime (behavioural thermotolerance) of these three species were investigated. Physiological thermotolerance significantly differed between the three species, with R. padi consistently the least cold tolerant and S. avenae the most cold tolerant. However, although the least cold tolerant of the study species, significantly more R. padi remained attached to the host plant at extreme sub-zero temperatures than S. avenae and M. dirhodum. Given the success of anholocyclic R. padi in harsh winters compared to its anholocyclic counterparts, this study illustrates that behavioural differences could be more important than physiological thermotolerance in explaining resistance to extreme temperatures. Furthermore it highlights that there is a danger to studying physiological thermotolerance in isolation when ascertaining risks of ectotherm invasions, the establishment potential of exotic species in glasshouses, or predicting species impacts under climate change scenarios.

Thermal tolerance of the nektonic puerulus stage of spiny lobsters and implications of ocean warming

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 515:173-186 (2014) - DOI: https://doi.org/10.3354/meps10979 Thermal tolerance of the nektonic puerulus stage of spiny lobsters and implications of ocean warming Quinn P. Fitzgibbon*, Nicole Ruff, Sean R. Tracey, Stephen C. Battaglene Fisheries and Aquaculture, Institute for Marine & Antarctic Studies (IMAS), University of Tasmania, Private Bag 49, Hobart, Tasmania 7001, Australia *Corresponding author: quinn.fitzgibbon@utas.edu.au ABSTRACT: Recent recruitment declines in important spiny lobster fisheries worldwide have triggered conjecture about negative impacts of anthropogenically induced environmental change on their long-lived planktonic larval life stages. Puerulus larvae are the critical transitional stage between pelagic larval development and coastal juvenile recruitment and may be particularly sensitive to environmental change due to immature cardiorespiratory capacity and exceptional energy demands associated with shoreward migration. We measured Sagmariasus verreauxi pueruli energy metabolism and defined their thermal tolerance, which are considered against published coastal recruitment data and spatially explicit ocean warming scenarios. The upper threshold of the thermal optimum window (upper pejus temperature range) was defined by the temperature optimum for aerobic scope. Within the upper pejus temperature range, pueruli had diminished aerobic capacity for physiological performance and used more of their finite lipid reserves to support an amplified metabolism. Sea surface temperatures at the northern extent of their natural range already reach the upper pejus range, and monitoring settlement data from the wild indicted that fewer puerulus successfully recruit during hot seasons in this area. Our study provides some evidence that physiological thermal tolerance constraints are already limiting post-larval recruitment. Predicted increases in water temperatures for their rapidly warming habitat will amplify the thermal challenge experienced by pueruli and may result in large shifts in lobster distribution and significant re-shuffling of species assemblages, creating challenges for sustainable natural resource management. KEY WORDS: Ecophysiology · Larvae · Metabolism · Recruitment · Climate change · Sagmariasus verreauxi · Temperature Full text in pdf format PreviousNextCite this article as: Fitzgibbon QP, Ruff N, Tracey SR, Battaglene SC (2014) Thermal tolerance of the nektonic puerulus stage of spiny lobsters and implications of ocean warming. Mar Ecol Prog Ser 515:173-186. https://doi.org/10.3354/meps10979 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 515. Online publication date: November 18, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Variations in physiological responses to thermal stress in congeneric limpets in the Mediterranean Sea

Cardiac activity (Arrhenius breakpoint temperatures and Q10 relationships) and heat shock response (hsp70 expression) were measured in the congeneric limpets Patella rustica, P. caerulea and P. ulyssiponensis in order to test the relationship between their vertical distribution and physiological thermal tolerance. These species exhibit different vertical distributions along Mediterranean shores and despite the narrow tidal range in the Mediterranean, they experience different environmental conditions and consequently had specific thermal windows. Cardiac activity of the upper zoned P. rustica was maintained at higher temperatures than its mid- or low shore counterparts, P. caerulea and P. ulyssiponensis. P. rustica had the highest Arrhenius breakpoint temperature (37.9±2.1°C, mean±SD), followed by P. caerulea (35.9±2.6°C), and finally the low-zoned P. ulyssiponensis (32.2±2.3°C). The same pattern was found for Q10 relationships. Expression of hsp70 increased at 34°C and kept increasing with temperature in P. rustica. In P. caerulea, expression reached a maximum at 36°C and decreased at 38°C, suggesting that hsp70 expression in P. rustica provides a more efficient defence against thermal stress than in P. caerulea. As summer environmental temperatures in the Mediterranean regularly reach 35 to 38°C, performances of these limpets suggest that they are already living at the edges of their thermal window, and further temperature changes may have large-scale consequences for these keystone species.

Trans-generational plasticity in physiological thermal tolerance is modulated by maternal pre-reproductive environment in the polychaeteOphryotrocha labronica

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

Who likes it hot? A global analysis of the climatic, ecological, and evolutionary determinants of warming tolerance in ants

AbstractEffects of climate warming on wild populations of organisms are expected to be greatest at higher latitudes, paralleling greater anticipated increases in temperature in these regions. Yet, these expectations assume that populations in different regions are equally susceptible to the effects of warming. This is unlikely to be the case. Here, we develop a series of predictive models for physiological thermal tolerances in ants based on current and future climates. We found that tropical ants have lower warming tolerances, a metric of susceptibility to climate warming, than temperate ants despite greater increases in temperature at higher latitudes. Using climatic, ecological and phylogenetic data, we refine our predictions of which ants (across all regions) were most susceptible to climate warming. We found that ants occupying warmer and more mesic forested habitats at lower elevations are the most physiologically susceptible to deleterious effects of climate warming. Phylogenetic history was also a strong indicator of physiological susceptibility. In short, we find that ants that live in the canopies of hot, tropical forest are the most at risk, globally, from climate warming. Unfortunately this is where many, perhaps most, ant and other species on Earth live.