Determining environmental causes of biological effects: the need for a mechanistic physiological dimension in conservation biology

Targeted and untargeted metabolomic profiles in wild rabbit does (Oryctolagus cuniculus) of different breeding states (pregnant and lactating)

Ecological nutrition aims to unravel the extensive web of nutritional links that drives animals in their interactions with their ecological environments. Nutrition plays a key role in the success of European wild rabbit (Oryctolagus cuniculus) and could be affected by the breeding status of the animals and reflected in the metabolome of this species. As nutritional needs are considerably increased during pregnancy and lactation, the main objective of this work was to determine how the breeding status (pregnant and lactating) of European wild rabbit does affects nutritional requirements and their metabolome (using targeted and untargeted metabolomics), aiming to find a useful biomarker of breeding status and for monitoring nutritional requirements. To address this gap, 60 wild European rabbits were studied. Animals were divided according to their breeding status and only pregnant (n = 18) and lactating (n = 11) rabbit does were used (n = 29 in total). The body weight and length of each animal were analyzed. The relative and absolute chemical composition of the gastric content and whole blood sample were taken, and targeted and untargeted metabolomics were analyzed. As a main result, there were no differences in biometric measurements, gastric content, and targeted metabolomics, except for live weight and nonesterified fatty acids (NEFA), as pregnant animals showed higher live weight (+12%; p = 0.0234) and lower NEFA acid levels (-46%; p = 0.0262) than lactating females. Regarding untargeted metabolomics, a good differentiation of the metabolome of the two breeding groups was confirmed, and it was proven that pregnant animals showed higher plasmatic levels of succinic anhydride (3.48 more times; p = 0.0236), succinic acid (succinate) (3.1 more times; p = 0.0068) and propionic acid (3.98 more times; p = 0.0121) than lactating animals. However, lactating animals showed higher levels of N-[(3a,5b,7b)-7-hydroxy-24-oxo-3-(sulfoxide) cholan-24-yl]-Glycine (cholestadien) (2.4 more times; p < 0.0420), 4-maleyl-acetoacetate (MAA) (3.2 more times; p < 0.0364) and irilone (2.2 more times; p = 0.0451) than pregnant animals, any of these metabolites could be used as a potential biomarker. From these results, it can be concluded that the most notable changes were observed in the metabolome of individuals, with most of the changes observed being due to energy and protein mobilisation.

Health Risk Assessment of Heavy Metals in Marine Fish Caught from the Northwest Persian Gulf

Marine fish may become contaminated as a result of environmental pollution including hazardous metals. Due to the presence of metalloids and toxic metals such as cadmium, lead, copper, and zinc in fish tissue, it may endanger health, considering the countless benefits of consuming fish, which can harm the human body if consumed in toxic amounts. Therefore, it is vital to monitor the concentration of metals in fish meat to ensure compliance with food safety regulations and protect the consumer. We considered the levels of Ni, Zn, Cu, Pb, and Cd in 60 marine fish samples (3 species) collected from coastal areas of the northwestern coast of the Persian Gulf and estimated their health risk. Mean concentrations of Ni, Zn, Cu, Pb, and Cd were 1.88 ± 0.07 µg/g, 27.16 ± 8.11 µg/g, 11.55 ± 4.12 µg/g, 14 ± 0.06 µg/g, and 0.19 ± 0.03 µg/g wet weight. Estimated average daily intakes (EDIs) for adults and children of Ni, Zn, Cu, Pb, and Cd were 0.89-4.15 μg/kg bw/day, 12.89-60.02 μg/kg bw/day, 5.47-25.53 μg/kg bw/day, 0.54-2.51 μg/kg bw/day, and 0.09-0.42 μg/kg bw/day. Our analysis revealed elevated levels of Ni and Pb in the fish samples, raising concerns about potential health hazards associated with their consumption. This study provides critical insights into heavy metal contamination in marine fish, highlighting the need for ongoing monitoring and proactive measures to ensure safe seafood consumption in the northwest Persian Gulf.

Allostatic interoceptive overload across psychiatric and neurological conditions

Emerging theories emphasize the crucial role of allostasis (anticipatory and adaptive regulation of the body's biological processes) and interoception (integration, anticipation, and regulation of internal bodily states) in adjusting physiological responses to environmental and bodily demands. This review explores the disruptions in integrated allostatic interoceptive mechanisms in psychiatric and neurological disorders, including anxiety, depression, Alzheimer's disease, and frontotemporal dementia. We assess the biological mechanisms associated with allostatic interoception, including whole-body cascades, brain structure and function of the allostatic interoceptive network, heart-brain interactions, respiratory-brain interactions, the gut-brain-microbiota axis, peripheral biological processes (inflammatory, immune), and epigenetic pathways. These processes span psychiatric and neurological conditions and call for developing dimensional and trans-nosological frameworks. We synthesize new pathways to understand how allostatic interoceptive processes modulate interactions between environmental demands and biological functions in brain disorders. We discuss current limitations of the framework and future transdisciplinary developments. This review opens a new research agenda for understanding how allostatic interoception involves brain predictive coding in psychiatry and neurology, allowing for better clinical application and the development of new therapeutic interventions.

Climate change and its effects on body size and shape: the role of endocrine mechanisms

In many organisms, rapidly changing environmental conditions are inducing dramatic shifts in diverse phenotypic traits with consequences for fitness and population viability. However, the mechanisms that underlie these responses remain poorly understood. Endocrine signalling systems often influence suites of traits and are sensitive to changes in environmental conditions; they are thus ideal candidates for uncovering both plastic and evolved consequences of climate change. Here, we use body size and shape, a set of integrated traits predicted to shift in response to rising temperatures with effects on fitness, and insulin-like growth factor-1 as a case study to explore these ideas. We review what is known about changes in body size and shape in response to rising temperatures and then illustrate why endocrine signalling systems are likely to be critical in mediating these effects. Lastly, we discuss research approaches that will advance understanding of the processes that underlie rapid responses to climate change and the role endocrine systems will have. Knowledge of the mechanisms involved in phenotypic responses to climate change will be essential for predicting both the ecological and the long-term evolutionary consequences of a warming climate. This article is part of the theme issue 'Endocrine responses to environmental variation: conceptual approaches and recent developments'.

Using a metabolomics approach to investigate the sensitivity of a potential Arctic-invader and its Arctic sister-species to marine heatwaves and traditional harvesting disturbances

Coastal species are threatened by fishing practices and changing environmental conditions, such as marine heatwaves (MHW). The mechanisms that confer tolerance to such stressors in marine invertebrates are poorly understood. However, differences in tolerance among different species may be attributed to their geographical distribution. To test the tolerance of species occupying different thermal ranges, we used two closely related bivalves the softshell clam Mya arenaria (Linnaeus, 1758), a cold-temperate invader with demonstrated potential for establishment in the Arctic, and the blunt gaper Mya truncata (Linnaeus, 1758), a native polar species. Clams were subjected to a thermal stress, mimicking a MHW, and harvesting stress in a controlled environment. Seven acute temperature changes (2, 7, 12, 17, 22, 27, and 32 °C) were tested at two harvesting disturbance intensities (with, without). Survival was measured after 12 days and three tissues (gills, mantle, and posterior adductor muscle) collected from surviving individuals for targeted metabolomic profiling. MHW tolerance differed significantly between species: 26.9 °C for M. arenaria and 17.8 °C for M. truncata, with a negligeable effect of harvesting. At the upper thermal limit, M. arenaria displayed a more profound metabolomic remodelling when compared to M. truncata, and this varied greatly between tissue types. Network analysis revealed differences in pathway utilization at the upper MHW limit, with M. arenaria displaying a greater reliance on multiple DNA repair and expression and cell signalling pathways, while M. truncata was limited to fewer pathways. This suggests that M. truncata is ill equipped to cope with warming environments. MHW patterning in the Northwest Atlantic may be a strong predictor of population survival and future range shifts in these two clam species. As polar environments undergo faster rates of warming compared to the global average, M. truncata may be outcompeted by M. arenaria expanding into its native range.

Role of climatic variability in shaping intraspecific variation of thermal tolerance in Mediterranean water beetles

The climatic variability hypothesis (CVH) predicts that organisms in more thermally variable environments have wider thermal breadths and higher thermal plasticity than those from more stable environments. However, due to evolutionary trade-offs, taxa with greater absolute thermal limits may have little plasticity of such limits (trade-off hypothesis). The CVH assumes that climatic variability is the ultimate driver of thermal tolerance variation across latitudinal and altitudinal gradients, but average temperature also varies along such gradients. We explored intraspecific variation of thermal tolerance in three typical Mediterranean saline water beetles (families Hydrophilidae and Dytiscidae). For each species, we compared two populations where the species coexist, with similar annual mean temperature but contrasting thermal variability (continental vs. coastal population). We estimated thermal limits of adults from each population, previously acclimated at 17, 20, or 25 °C. We found species-specific patterns but overall, our results agree with the CVH regarding thermal ranges, which were wider in the continental (more variable) population. In the two hydrophilid species, this came at the cost of losing plasticity of the upper thermal limit in this population, supporting the trade-off hypothesis, but not in the dytiscid one. Our results support the role of local adaptation to thermal variability and trade-offs between basal tolerance and physiological plasticity in shaping thermal tolerance in aquatic ectotherms, but also suggest that intraspecific variation of thermal tolerance does not fit a general pattern among aquatic insects. Overlooking such intraspecific variation could lead to inaccurate predictions of the vulnerability of aquatic insects to global warming.

Methodological advice for the young at heart investigator: Triangulation to build better foundations

In medicine and science, one is typically taught the main theories in a discipline or field along with standard models before receiving more instructions on how to apply certain methods. The aim of this work is not to address one method, but rather methodology, the study and evaluation of methods, by taking a philosophy of science detour. In this, a critique of biomedicine will be used as a starting point to address some positions regarding reductionism, specifying notions such as systems and mechanisms, as well as regarding the mind-body problem discussing psychosomatic medicine and psychoneuroimmunology. Some recommendations to make science more pluralistic, robust and translationally-relevant will then be made as a way to foster constructive debates on reductionism and the mind-body problem and, in turn, favor more interdisciplinary research.

Nutritional ecology of European rabbit (Oryctolagus cuniculus): Factors affecting chemical composition of gastric content

Nutritional ecology seeks to unravel the extensive web of nutritional links that directs animals in their interactions with their ecological and social environments. European rabbit (Oryctolagus cuniculus) populations its endemic locations are declining and it is considered a keystone species of the Mediterranean ecosystem prompteing the interest in its conservation. The main aim of this study was to determine the nutritional composition of the diet of European rabbits through the relative and absolute chemical composition of the gastric content. To address this objective, gastric content was collected from 80 European rabbits in a Mediterranean area for the analysis of its chemical composition. To this end, gastric content was analyzed for dry matter (DM), organic matter (OM), ash, crude protein (CP), highly digestible nonnitrogenous nutrients (HDNN), neutral detergent fibre (NDF), acid detergent fibre (ADF) and lignin. The rabbits were divided into two groups: EMPTY and FULL, depending on the level of stomach filling, directly related to food intake. Our results revealed a positive correlation between the rabbits weight with DM in the gastric content, total gastric content with DM in the gastric content, and DM in gastric content with all chemical parameters analysed. The mean relative values obtained were 8.8%, 25.5%, 40.4% and 25.4%, for ash, CP, NDF and HDNN, respectively. Moreover, EMPTY rabbits had both a proportional (+19%, p = 0.002 and -40%; p = 0.004, on NDF and HDNN, respectively) and absolute (-38%, p = 0.014, -52%; p = 0.012, -52%; p = 0.011 and +83%; p = 0.008 for OM, ash, HDNN, and lignin, respectively) different proportion of nutrients in gastric contents than FULL animals. Since there is a connection between this availability and the fitness of this species, understanding the chemical composition of the rabbit's diet can be utilised to delve into its biology. Our study provides information that will help elucidate the factors affecting the chemical composition of the gastric content of European rabbits to assist land use planners and conservationists in identifying sites for conservation in Mediterranean ecosystems.

The nutritional strategy of European rabbits is affected by age and sex: Females eat more and have better nutrient optimisation

The ecological interest in the European rabbit (Oryctolagus cuniculus) has grown since it was declared an endangered species. Nutrition is fundamental in its dispersion and the key to its success. This is the main reason why knowledge of their nutritional preferences/requirements could play a fundamental role in rabbit biology and, therefore, in their conservation. The objectives of the work will be to elucidate how age and sex affect both nutritional preferences/requirements, and the nutrient optimisation of European rabbits. To address this gap, 70 wild European rabbits were studied. The rabbits were divided according to their age: adult (n = 43) and young (n = 27). Two groups were differentiated according to the adult rabbits' sex: females (n = 28) and males (n = 15). We analysed the relative (%) and absolute (g) chemical composition of the rabbits' gastric contents: dry matter (DM), ashes (ASH), crude protein (CP), ether extract (EE), neutral detergent fibre (NDF), acid detergent fibre (ADF), and lignin, hemicelluloses and celluloses, highly digestible nonnitrogenous nutrients (HDNN: fat, starch, and soluble fibre), well from the blood was analysed with plasmatic urea nitrogen (PUN), nonesterified fatty acid (NEFA) and glucose (GLU). As a nutrient optimisation measure, the following indices between blood metabolites and stomach content were calculated: PUN/CP total content, NEFA/DM total content and GLU/DM total content ratios. Our works showed that age and sex affected the nutritional strategy of rabbits. Regarding age: adults showed lower CP (-14%; p = 0.0217) and higher HDNN (+21%; p = 0.0399) relative content than young rabbits, and absolute amount of most nutrients: DM (+59%; p = 0.001), OM (+43%; p = 0.0049), ASH (+54%; p = 0.0085), Hemicelluloses (+73%; p = 0.0084), Cellulose (+27%; p = 0.0452), and HDNN (+63%; p = 0.0012). In addition, adults showed better nutrient optimisation. Sex did not affect the relative chemical composition of the gastric content, but it showed a clear higher gastric content by females (+85%; p < 0.0001) and higher intake of most of the absolute chemical components: DM (+64%; p < 0.001), CP (+56%; p = 0.0005), OM (+58%; p = 0.0001), ASH (+44%; p = 0.0123), HDNN (+39%; p = 0.001), NDF (+59%; p = 0.001), ADF (+64%; p = 0.0003), lignin (+82%; p = 0.0036) and cellulose (+58%; p = 0.0002). Finally, we observed that females had better nutrient optimisation than males. This works supports the idea that feeding ecology and nutrition are particularly relevant to reproductive success and fitness in wild animals.

Oxygen availability and body mass modulate ectotherm responses to ocean warming

In an ocean that is rapidly warming and losing oxygen, accurate forecasting of species' responses must consider how this environmental change affects fundamental aspects of their physiology. Here, we develop an absolute metabolic index (Φ_A) that quantifies how ocean temperature, dissolved oxygen and organismal mass interact to constrain the total oxygen budget an organism can use to fuel sustainable levels of aerobic metabolism. We calibrate species-specific parameters of Φ_A with physiological measurements for red abalone (Haliotis rufescens) and purple urchin (Strongylocentrotus purpuratus). Φ_A models highlight that the temperature where oxygen supply is greatest shifts cooler when water loses oxygen or organisms grow larger, providing a mechanistic explanation for observed thermal preference patterns. Viable habitat forecasts are disproportionally deleterious for red abalone, revealing how species-specific physiologies modulate the intensity of a common climate signal, captured in the newly developed Φ_A framework.

How can physiology best contribute to wildlife conservation in a warming world?

Global warming is now predicted to exceed 1.5°C by 2033 and 2°C by the end of the 21st century. This level of warming and the associated environmental variability are already increasing pressure on natural and human systems. Here we emphasize the role of physiology in the light of the latest assessment of climate warming by the Intergovernmental Panel on Climate Change. We describe how physiology can contribute to contemporary conservation programmes. We focus on thermal responses of animals, but we acknowledge that the impacts of climate change are much broader phylogenetically and environmentally. A physiological contribution would encompass environmental monitoring, coupled with measuring individual sensitivities to temperature change and upscaling these to ecosystem level. The latest version of the widely accepted Conservation Standards designed by the Conservation Measures Partnership includes several explicit climate change considerations. We argue that physiology has a unique role to play in addressing these considerations. Moreover, physiology can be incorporated by institutions and organizations that range from international bodies to national governments and to local communities, and in doing so, it brings a mechanistic approach to conservation and the management of biological resources.

Biological mechanisms matter in contemporary wildlife conservation

Given limited resources for wildlife conservation paired with an urgency to halt declines and rebuild populations, it is imperative that management actions are tactical and effective. Mechanisms are about how a system works and can inform threat identification and mitigation such that conservation actions that work can be identified. Here, we call for a more mechanistic approach to wildlife conservation and management where behavioral and physiological tools and knowledge are used to characterize drivers of decline, identify environmental thresholds, reveal strategies that would restore populations, and prioritize conservation actions. With a growing toolbox for doing mechanistic conservation research as well as a suite of decision-support tools (e.g., mechanistic models), the time is now to fully embrace the concept that mechanisms matter in conservation ensuring that management actions are tactical and focus on actions that have the potential to directly benefit and restore wildlife populations.

Thermal performance curve of endurance running at high temperatures in deer mice

The impacts of warming temperatures associated with climate change on performance are poorly understood in most mammals. Thermal performance curves are a valuable means of examining the effects of temperature on performance traits, but they have rarely been used in endotherms. Here, we examined the thermal performance curve of endurance running capacity at high temperatures in the deer mouse (Peromyscus maniculatus). Endurance capacity was measured using an incremental speed test on a treadmill, and subcutaneous temperature in the abdominal region was measured as a proxy for body temperature (Tb). Endurance time at 20°C was repeatable but varied appreciably across individuals, and was unaffected by sex or body mass. Endurance capacity was maintained across a broad range of ambient temperatures (Ta) but was reduced above 35°C. Tb during running varied with Ta, and reductions in endurance were associated with Tb greater than 40°C when Ta was above 35°C. At the high Ta that limited endurance running capacity (but not at lower Ta), Tb tended to rise throughout running trials with increases in running speed. Metabolic and thermoregulatory measurements at rest showed that Tb, evaporative water loss and breathing frequency increased at Ta of 36°C and above. Therefore, the upper threshold temperatures at which endurance capacity is impaired are similar to those inducing heat responses at rest in this species. These findings help discern the mechanisms by which deer mice are impacted by warming temperatures, and provide a general approach for examining thermal breadth of performance in small mammals.

Integrating animal physiology into the adaptive management of restored landscapes

Global-scale ecological changes and intensifying habitat destruction and have caused alarming declines in wildlife populations, resulting in a great need for concerted efforts towards their conservation. Despite this, animals are frequently overlooked in restoration and management initiatives and therefore populations often do not reassemble following disturbance without re-establishing habitat that meets their abiotic and biotic requirements. However, restoration ecologists broadly lack insight into the physiological mechanisms that can govern the responses of fauna to environmental change and management. Therefore, we conducted a literature search for studies reporting a mechanistic understanding of faunal habitat suitability and selection in restored landscapes to deliver an updated perspective on the integration of animal ecophysiology and restoration ecology. Of the 75,442 studies that we identified discussing ecological restoration in the last 50 years, only 8,627 (11.4%) did so in the context of fauna from which 912 studies (1.2%) examined habitat selection, 35 studies (0.05%) integrated physiology and only 15 studies (0.02%) explored thermal biology, despite temperature being one of the most pervasive drivers of physiological functioning. To combat this, we developed a conceptual framework that can guide restoration ecophysiology and promote innovative, multidisciplinary research through an established adaptive management structure. While physiological tools and approaches are currently underutilised in restoration practice, integrating them into ecological restoration, and environmental management more broadly, will offer exciting new opportunities to describe, explain and predict the responses of fauna to environmental change occurring, and that yet to come.

A coastal Ramsar site on transition to hypoxia and tracking pollution sources: a case study of south-west coast of India

Coastal lakes and estuaries are considered economic drivers for coastal communities by delivering invaluable economic and ecosystem services. The coastal ecosystems are facing recurrent hypoxia events (dissolved oxygen; DO < 2.0 mg L^-1) and are emerging as a major threat to ecosystem structure and functioning. The Ashtamudi Lake, (area = 56 km²), is one of the Ramsar sites in the State of Kerala and located on the SW coast of India. The waterways are extensively used for backwater tourism and for fishery activities. This paper discusses the spatio-temporal variation of water quality attributes with emphasis on hypoxia during non-monsoon and monsoon seasons. The extent of hypoxia on fishery diversity was discussed. The Southern Zone, adjacent to the urban area, shows the hypoxic condition with higher concentration of BOD, NO₃-N, and NH₄-N. The hypoxic condition is largely limited to the Southern Zone in both seasons. The occurrence of low DO in the lake is highly related to salinity and organic load in the lake system. The tracking of pollution sources in the lake system was also done through identification of pollution potential zones and found that catchments adjacent to Southern and Western Zones (urban regions) are the major source of pollution. The study suggests that hypoxia is chiefly attributed to anthropogenic interventions in the form of discharge of wastes into the lake causing overloading of nutrients and organic effluents, decrease in the freshwater supply, the absence of proper freshwater mixing or dilution, and effluent discharge from nearby urban centers.

Latitude-Induced and Behaviorally Thermoregulated Variations in Upper Thermal Tolerance of Two Anuran Species

Although thermal tolerance along geographical gradients gives an insight into species' response to climate change, current studies on thermal tolerance are strongly skewed towards global-scale patterns. As a result, intraspecific variations are often assumed to be constant, despite a lack of evidence. To understand population-specific responses to thermal stress, we investigated the presence of intraspecific variations in the critical thermal maximum (CTmax) of tadpoles in two anuran species, Rana uenoi and Bufo sachalinensis. The study was conducted across a five-degree latitudinal gradient in the Republic of Korea. We exposed the tadpoles to increasing temperatures and recorded the CTmax for 270 R. uenoi individuals from 11 sites, collected in rice paddies, and for 240 B. sachalinensis individuals from ten sites, collected in reservoirs. We also recorded the swimming performance and behavior of the tadpoles when placed in an experimental apparatus during CTmax measurements. We then used linear regressions to determine the relationship between abiotic factors and CTmax. In R. uenoi, we found a positive relationship between latitude and CTmax, but the tadpoles did not display specific thermoregulatory behaviors. In B. sachalinensis, none of the abiotic factors such as climate and geographic coordinates were related to CTmax, but we detected a tendency to swim close to the water surface when water temperature was increasing. For R. uenoi, we tentatively relate the CTmax variability across the latitudinal gradient to a physiological adaptive response associated with habitat characteristics that are assumed to be fluctuating, as the species inhabits small water bodies prone to drying out. In the case of B. sachalinensis, the behavior observed may be linked to oxygen depletion and thermoregulation, as it may buffer temperature changes in the absence of physiological adjustment. These findings suggest that intra-specific variations in CTmax are greater than generally accounted for, and thermal conditions of natural environments are important for understanding thermal tolerance in ectothermic species. Our results highlight that species' specific responses to climate warmings need to be studied to better protect species against climate change.

Fire and rain: A systematic review of the impacts of wildfire and associated runoff on aquatic fauna

Climate and land-use changes are expected to increase the future occurrence of wildfires, with potentially devastating consequences for freshwater species and ecosystems. Wildfires that burn in close proximity to freshwater systems can significantly alter the physicochemical properties of water. Following wildfires and heavy rain, freshwater species must contend with complex combinations of wildfire ash components (nutrients, polycyclic aromatic hydrocarbons, and metals), altered light and thermal regimes, and periods of low oxygen that together can lead to mass mortality events. However, the responses of aquatic fauna to wildfire disturbances are poorly understood. Here we provide a systematic review of available evidence on how aquatic animals respond to and recover from wildfire disturbance. Two databases (Web of Science and Scopus) were used to identify key literature. A total of 83 studies from across 11 countries were identified to have assessed the risk of wildfires on aquatic animals. We provide a summary of the main ecosystem-level changes associated with wildfires and the main responses of aquatic fauna to such disturbances. We pay special focus to physiological tools and biomarkers used to assess how wildfires impact aquatic animals. We conclude by providing an overview of how physiological biomarkers can further our understanding of wildfire-related impacts on aquatic fauna, and how different physiological tools can be incorporated into management and conservation plans and serve as early warning signs of wildfire disturbances.

Limited Physiological Compensation in Response to an Acute Microclimate Change in a Malagasy Bat

Rapid environmental changes are challenging for endothermic species because they have direct and immediate impacts on their physiology by affecting microclimate and fundamental resource availability. Physiological flexibility can compensate for certain ecological perturbations, but our basic understanding of how species function in a given habitat and the extent of their adaptive scope is limited. Here we studied the effect of acute, experimental microclimate change on the thermal physiology of two populations of the widespread Malagasy bat, Macronycteris commersoni. Populations of this species are found roosting under contrasting conditions, i.e., in a constant hot and humid cave or below foliage unprotected from fluctuations in ambient conditions. We exposed free-ranging individuals of each population to the respective opposite condition and thus to novel microclimate within an ecologically realistic scope while measuring metabolic rate and skin temperature. Cave bats in forest setting had a limited capacity to maintain euthermia to the point that two individuals became hypothermic when ambient temperature dropped below their commonly experienced cave temperature. Forest bats on the other hand, had difficulties to dissipate heat in the humid cave set-up. The response to heat, however, was surprisingly uniform and all bats entered torpor combined with hyperthermia at temperatures exceeding their thermoneutral zone. Thus, while we observed potential for flexible compensation of heat through “hot” torpor, both populations showed patterns suggestive of limited potential to cope with acute microclimate changes deviating from their typically occupied roosts. Our study emphasizes that intraspecific variation among populations could be misleading when assessing species’ adaptive scopes, as variation may arise from genetic adaptation, developmental plasticity or phenotypic flexibility, all of which allow for compensatory responses at differing time scales. Disentangling these mechanisms and identifying the basis of variation is vital to make accurate predictions of species’ chances for persisting in ever rapidly changing habitats and climates.

Effects of acute temperature increases on House sparrow (Passer domesticus) pectoralis muscle myonuclear domain

With rapid climate change, heat wave episodes have become more intense and more frequent. This poses a significant threat to animals, and forces them to manage these physiologically challenging conditions by adapting and/or moving. As an invasive species with a large niche breadth, House sparrows (Passer domesticus) exhibit high phenotypic flexibility that caters to seasonal changes in function and metabolism. For example, their pectoral muscle complex exhibits size and mass plasticity with winter and summer acclimation. Here, we investigated the effects of acute whole-organism heat stress to 43°C on cellular-level changes in House sparrow pectoralis muscle myonuclear domain (MND), the volumetric portion each nucleus is responsible for, that have gone overlooked in the current literature. House sparrows were separated into a control group, a heat-shocked group subjected to thermal stress at 43°C for 24 h, and a recovery group that was returned to room temperature for 24 h after experiencing the same temperature treatment. Here, we found that heat-shocked and recovery groups demonstrated a decrease in number of nuclei per millimeter of fiber and increase in MND, when compared with the control. We also found a significant positive correlation between fiber diameter and MND in the recovery group, suggesting the possibility that nuclei number constrains the extent of muscle fiber size. Together, these results show that acute heat shock alters House sparrow pectoralis muscle cellular physiology in a rigid way that could prove detrimental to long-term muscle integrity and performance.

Chemical niches and ionoregulatory traits: applying ionoregulatory physiology to the conservation management of freshwater fishes

Alterations in water chemistry can challenge resident fish species. More specifically, chemical changes that disrupt ion balance will negatively affect fish health and impact physiological and ecological performance. However, our understanding of which species and populations are at risk from ionoregulatory disturbances in response to changing freshwater environments is currently unclear. Therefore, we propose a novel framework for incorporating ionoregulatory physiology into conservation management of inland fishes. This framework introduces the concepts of fundamental chemical niche, which is the tolerable range of chemical conditions for a given species based on laboratory experiments, and realized chemical niche, which is the range of chemical conditions in which a species resides based on distribution surveys. By comparing these two niches, populations that may be at risk from ionoregulatory disturbances and thus require additional conservation considerations can be identified. We highlight the potential for commonly measured ionoregulatory traits to predict fundamental and realized chemical niches but caution that some traits may not serve as accurate predictors despite being important for understanding ionoregulatory mechanisms. As a sample application of our framework, the minimum pH distribution (realized niche) and survival limit pH (fundamental niche) of several North American fishes were determined by systematic review and were compared. We demonstrate that ionoregulatory capacity is significantly correlated with a realized niche for many species, highlighting the influence of ionoregulatory physiology on fish distribution patterns along chemical gradients. Our aim is that this framework will stimulate further research in this field and result in a broader integration of physiological data into conservation management decisions for inland waters.

APT: An Automated Probe Tracker From Gene Expression Data

Out of currently available semi-automatic tools for detecting diagnostic probes relevant to a pathophysiological condition, ArrayMining and GEO2R of NCBI are most popular. The shortcomings of ArrayMining and GEO2R are that both tools list the probes ordering them on the basis of their individual statistical level of significances with only difference of statistical methods used by them. While the latest tool GEO2R outputs either top 250 or all genes following its own ranking mechanism, ArrayMining requires number of probes to be inputted by the user. This study provided a way for automatic selection of probe-set that can be obtained from the voting of outputs resulted from statistical methods, t-Test, Mann-Whitney Test and Empirical Bayes Moderated t-test. It was also intriguing to find that the parameters of these statistical methods can be represented as a mathematical function of group fisher's discriminant ratio of a disease-control expression data-pair. Result of this fully automatic method, APT shows 88.97 percent success in comparison to 80.40 and 87.60 percent successes of ArrayMining and GEO2R respectively to include reported probes. Furthermore, out of 10 fold cross validation and 5 new test cases, APT shows a better performance than both ArrayMining and GEO2R in regards to sensitivity and specificity.

What is physiologging? Introduction to the theme issue, part 2

The physiological mechanisms by which animals regulate energy expenditure, respond to stimuli and stressors, and maintain homeostasis at the tissue, organ and whole organism levels can be described by 'physiologging'-that is, the use of onboard miniature electronic devices to record physiological metrics of animals in captivity or free-living in the wild. Despite its origins in the 1960s, physiologging has evolved more slowly than its umbrella field of biologging. However, the recording of physiological metrics in free-living animals will be key to solving some of the greatest challenges in biodiversity conservation, issues pertaining to animal health and welfare, and for inspiring future therapeutic strategies for human health. Current physiologging technologies encompass the measurement of physiological variables such as heart rate, brain activity, body temperature, muscle stimulation and dynamic movement, yet future developments will allow for onboard logging of metrics relating to organelle, molecular and genetic function. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.

Corticosterone mediates a growth-survival tradeoff for an amphibian exposed to increased salinity

Life-history tradeoffs are common across taxa, but growth-survival tradeoffs-usually enhancing survival at a cost to growth-are less frequently investigated. Increased salinity (NaCl) is a prevalent anthropogenic disturbance that may cause a growth-survival tradeoff for larval amphibians. Although physiological mechanisms mediating tradeoffs are seldom investigated, hormones are prime candidates. Corticosterone (CORT) is a steroid hormone that independently influences survival and growth and may provide mechanistic insight into growth-survival tradeoffs. We conducted a 24-day experiment to test effects of salinity (<32-4000 mg/L) on growth, development, survival, CORT responses, and tradeoffs among traits of larval Northern Leopard Frogs (Rana pipiens). We also experimentally suppressed CORT signaling to determine whether CORT signaling mediates effects of salinity and a growth-survival tradeoff. Increased salinity reduced survival, growth, and development. Suppressing CORT signaling in conjunction with salinity reduced survival further but also attenuated the negative effects of salinity on growth, development, and water content. CORT of control larvae increased or was stable with growth and development but decreased with growth and development for those exposed to salinity. Therefore, salinity dysregulated CORT physiology. Across all treatments, larvae that survived had higher CORT than larvae that died. By manipulating CORT signaling, we provide strong evidence that CORT physiology mediates the outcome of a growth-survival tradeoff and enhances survival. To our knowledge, this is the first study to concomitantly measure tradeoffs between growth and survival and experimentally link these changes to CORT physiology. Identifying mechanistic links between stressors and fitness-related outcomes is critical to enhance our understanding of tradeoffs.

A role for lakes in revealing the nature of animal movement using high dimensional telemetry systems

Movement ecology is increasingly relying on experimental approaches and hypothesis testing to reveal how, when, where, why, and which animals move. Movement of megafauna is inherently interesting but many of the fundamental questions of movement ecology can be efficiently tested in study systems with high degrees of control. Lakes can be seen as microcosms for studying ecological processes and the use of high-resolution positioning systems to triangulate exact coordinates of fish, along with sensors that relay information about depth, temperature, acceleration, predation, and more, can be used to answer some of movement ecology's most pressing questions. We describe how key questions in animal movement have been approached and how experiments can be designed to gather information about movement processes to answer questions about the physiological, genetic, and environmental drivers of movement using lakes. We submit that whole lake telemetry studies have a key role to play not only in movement ecology but more broadly in biology as key scientific arenas for knowledge advancement. New hardware for tracking aquatic animals and statistical tools for understanding the processes underlying detection data will continue to advance the potential for revealing the paradigms that govern movement and biological phenomena not just within lakes but in other realms spanning lands and oceans.

The physiological ups and downs of thermal variability in temperate freshwater ecosystems

Freshwater fish face a variety of spatiotemporal thermal challenges throughout their life. On a broad scale, temperature is an important driver of physiological, behavioural and ecological patterns and ultimately affects populations and overall distribution. These broad patterns are partly underpinned by the small-scale local effects of temperature on individuals within the population. Climate change is increasing the range of daily thermal variation in most freshwater ecosystems, altering behaviour and performance of resident fishes. The aim of this review is understanding how daily thermal variation in temperate rivers affects individual fish physiology, behaviour and overall performance. The following are highlighted in this study: (a) the physical characteristics of rivers that can either buffer or exacerbate thermal variability, (b) the effects of thermal variability on growth and metabolism, (c) the approaches for quantifying thermal variation and thermal stress and (d) how fish may acclimatize or adapt to our changing climate.

Researcher perspectives on challenges and opportunities in conservation physiology revealed from an online survey

Conservation physiology represents a recently emerging arm of conservation science that applies physiological tools and techniques to understand and solve conservation issues. While a multi-disciplinary toolbox can only help to address the global biodiversity crisis, any field can face challenges while becoming established, particularly highly applied disciplines that require multi-stakeholder involvement. Gaining first-hand knowledge of the challenges that conservation physiologists are facing can help characterize the current state of the field and build a better foundation for determining how it can grow. Through an online survey of 468 scientists working at the intersection of physiology and conservation, we aimed to identify characteristics of those engaging in conservation physiology research (e.g. demographics, primary taxa of study), gauge conservation physiology's role in contributing to on-the-ground conservation action, identify the perceived barriers to achieving success and determine how difficult any identified barriers are to overcome. Despite all participants having experience combining physiology and conservation, only one-third considered themselves to be 'conservation physiologists'. Moreover, there was a general perception that conservation physiology does not yet regularly lead to tangible conservation success. Respondents identified the recent conceptualization of the field and the broader issue of adequately translating science into management action as the primary reasons for these deficits. Other significant barriers that respondents have faced when integrating physiology and conservation science included a lack of funding, logistical constraints (e.g. sample sizes, obtaining permits) and a lack of physiological baseline data (i.e. reference ranges of a physiological metric's 'normal' or pre-environmental change levels). We identified 12 actions based on suggestions of survey participants that we anticipate will help deconstruct the barriers and continue to develop a narrative of physiology that is relevant to conservation science, policy and practice.

Fine-scale conditions across mangrove microhabitats and larval ontogeny contributes to the thermal physiology of early stage brachyurans (Crustacea: Decapoda)

Most marine ectotherms require the successful completion of a biphasic larval stage to recruit into adult populations. Recruitment of larvae into benthic habitats largely depends on biological interactions and favourable environmental conditions such as the inescapable diurnal thermal and tidal exposures. Hence, assessing how different taxa metabolically respond to variations in temperature is imperative to understand the community and ecosystem dynamics at both local and global scales. The present study aimed to investigate the effects of acute temperature variation on the physiology of stage-specific brachyuran larvae collected from different microhabitats at two mangrove forests in South Africa. Results indicate that the conditions within microhabitats, which larvae experience, likely influence their physiology, based on respirometry, to short-term acute temperature exposures. Furthermore, the larval thermal optimum shifted ontogenetically to become increasingly eurythermic as individuals developed from stage I zoea through to megalopa. Mangrove crab larvae in their early stages are hence increasingly vulnerable to acute temperature exposures, which could be particularly harmful to the persistence of populations if thermally stressful events increase in magnitude and frequency.

Seasonality of primary productivity affects coastal species more than its magnitude

While the importance of extreme conditions is recognised, patterns in species' abundances are often interpreted through average environmental conditions within their distributional range. For marine species with pelagic larvae, temperature and phytoplankton concentration are key variables. Along the south coast of South Africa, conspicuous spatial patterns in recruitment rates and the abundances of different mussel species exist, with focal areas characterized by large populations. We studied 15 years of sea surface temperature (SST) and chlorophyll-a (chl-a) satellite data, using spectral analyses to partition their temporal variability over ecologically relevant time periods, including seasonal (101 to 365 days) and intra-seasonal cycles (20 to 100 days). Adult cover and mussel recruitment were measured at 10 sites along the south coast and regression models showed that about 70% of the variability in recruitment and adult cover was explained by seasonal variability in chl-a, while mean annual chl-a and SST only explained 30% of the recruitment, with no significant effect for adult cover. SST and chl-a at two upwelling centres showed less predictable seasonal cycles during the second half of the study period with a significant cooling trend during austral autumn, coinciding with one of the mussel reproductive peaks. This likely reflects recent changes in the Agulhas Current, the world's largest western boundary current, which affects coastal ecosystems by driving upwelling. Similar mechanisms probably operate in other marine systems with the potential to affect the distribution patterns of key ecosystem engineers. We propose that variability in the characteristic timescales of environmental fluctuations can explain the spatial patterns of abundance of foundational species by affecting larval recruitment. This is especially important in a context of global and pervasive climate change, as shifts in the periodicity of environmental fluctuations appear to reflect large scale climatic teleconnections driven by anthropogenic forcing.

The role of mechanistic physiology in investigating impacts of global warming on fishes

Warming of aquatic environments as a result of climate change is already having measurable impacts on fishes, manifested as changes in phenology, range shifts and reductions in body size. Understanding the physiological mechanisms underlying these seemingly universal patterns is crucial if we are to reliably predict the fate of fish populations with future warming. This includes an understanding of mechanisms for acute thermal tolerance, as extreme heatwaves may be a major driver of observed effects. The hypothesis of gill oxygen limitation (GOL) is claimed to explain asymptotic fish growth, and why some fish species are decreasing in size with warming; but its underlying assumptions conflict with established knowledge and direct mechanistic evidence is lacking. The hypothesis of oxygen- and capacity-limited thermal tolerance (OCLTT) has stimulated a wave of research into the role of oxygen supply capacity and thermal performance curves for aerobic scope, but results vary greatly between species, indicating that it is unlikely to be a universal mechanism. As thermal performance curves remain important for incorporating physiological tolerance into models, we discuss potentially fruitful alternatives to aerobic scope, notably specific dynamic action and growth rate. We consider the limitations of estimating acute thermal tolerance by a single rapid measure whose mechanism of action is not known. We emphasise the continued importance of experimental physiology, particularly in advancing our understanding of underlying mechanisms, but also the challenge of making this knowledge relevant to the more complex reality.

The Shrinking Resource Base of Pastoralism: Saami Reindeer Husbandry in a Climate of Change

The productive performance of large ungulates in extensive pastoral grazing systems is modulated simultaneously by the effects of climate change and human intervention independent of climate change. The latter includes the expansion of private, civil and military activity and infrastructure and the erosion of land rights. We used Saami reindeer husbandry in Norway as a model in which to examine trends in, and to compare the influence of, both effects on a pastoral grazing system. Downscaled projections of mean annual temperature over the principal winter pasture area (Finnmarksvidda) closely matched empirical observations across 34 years to 2018. The area, therefore, is not only warming but seems likely to continue to do so. Warming notwithstanding, 50-year (1969–2018) records of local weather (temperature, precipitation and characteristics of the snowpack) demonstrate considerable annual and decadal variation which also seems likely to continue and alternately to amplify and to counter net warming. Warming, moreover, has both positive and negative effects on ecosystem services that influence reindeer. The effects of climate change on reindeer pastoralism are evidently neither temporally nor spatially uniform, nor indeed is the role of climate change as a driver of change in pastoralism even clear. The effects of human intervention on the system, by contrast, are clear and largely negative. Gradual liberalization of grazing rights from the 18th Century has been countered by extensive loss of reindeer pasture. Access to ~50% of traditional winter pasture was lost in the 19th Century owing to the closure of international borders to the passage of herders and their reindeer. Subsequent to this the area of undisturbed pasture within Norway has decreased by 71%. Loss of pasture due to piecemeal development of infrastructure and to administrative encroachment that erodes herders' freedom of action on the land that remains to them, are the principal threats to reindeer husbandry in Norway today. These tangible effects far exceed the putative effects of current climate change on the system. The situation confronting Saami reindeer pastoralism is not unique: loss of pasture and administrative, economic, legal and social constraints bedevil extensive pastoral grazing systems across the globe.

Exploring the Utility of Hair Endocannabinoids for Monitoring Homeostasis in Bonobos

AbstractQuantifying physiological challenges has gained increasing importance in evolutionary biology, behavioral physiology, and conservation. One matrix that is particularly useful for obtaining long-term records of physiological changes in mammals is hair. Potential markers are components of the endocannabinoid (EC) system, which regulates homeostasis of the brain as well as the endocrine and immune systems. Here, we present results from the first study to measure ECs (anandamide [AEA], 2-archidonyl glycerol [2-AG]) and EC-like compounds (N-palmitoylethanolamine [PEA], N-oleoylethanolamine [OEA], N-stearoylethanolamine [SEA]) in the hair of a nonhuman primate. We found that AEA, SEA, PEA, and OEA can be reliably measured in hair samples. When comparing the measurements of hair from different body parts, we found that variations of some analytes suggest that hair location is likely to affect results. For changes in health status, measurements of ECs and EC-like compounds reflected differences at both intra- and interindividual levels. We concluded that the EC system potentially provides novel tools to assess well-being, health status, and metabolic stress-not only in the hair of humans but also in that of domestic and wild animals. Measuring changes in ECs and EC-like compounds may improve the long-term monitoring of health status in captive and wild primates and may serve as a useful measure in animal welfare programs.

One hundred research questions in conservation physiology for generating actionable evidence to inform conservation policy and practice

Environmental change and biodiversity loss are but two of the complex challenges facing conservation practitioners and policy makers. Relevant and robust scientific knowledge is critical for providing decision-makers with the actionable evidence needed to inform conservation decisions. In the Anthropocene, science that leads to meaningful improvements in biodiversity conservation, restoration and management is desperately needed. Conservation Physiology has emerged as a discipline that is well-positioned to identify the mechanisms underpinning population declines, predict responses to environmental change and test different in situ and ex situ conservation interventions for diverse taxa and ecosystems. Here we present a consensus list of 10 priority research themes. Within each theme we identify specific research questions (100 in total), answers to which will address conservation problems and should improve the management of biological resources. The themes frame a set of research questions related to the following: (i) adaptation and phenotypic plasticity; (ii) human-induced environmental change; (iii) human-wildlife interactions; (iv) invasive species; (v) methods, biomarkers and monitoring; (vi) policy, engagement and communication; (vii) pollution; (viii) restoration actions; (ix) threatened species; and (x) urban systems. The themes and questions will hopefully guide and inspire researchers while also helping to demonstrate to practitioners and policy makers the many ways in which physiology can help to support their decisions.

Does temperature at local scale explain thermal biology patterns of temperate tadpoles?

Most of the literature on temperature-organism interactions rely on mean temperature (mostly air), disregarding the real complexity of this variable. There is a growing consensus about the importance of considering the temperature fluctuations as a mechanism improving organism's performance. Tadpoles are small body size ectotherm organisms that behave isothermally with their environment. As such, are good models for studying their thermal biology relative to their immediate environment. We studied six anuran tadpole species in North Patagonia, Alsodes gargola, Hylorina sylvatica, Batrachyla taeniata, Pleurodema thaul, P. bufoninum and Rhinella spinulosa, distributed in a West-East altitudinal cline with different environments and thermal conditions. We evaluated the relationship between thermal descriptors at a local scale and the thermal biology patterns of these temperate tadpoles. We estimated thermal tolerance limits and thermal sensitivity of locomotion of each species. The different aquatic environments showed important differences in local thermal conditions, associated with observed differences in the thermal traits in these tadpoles. Species exposed to lower temperature fluctuations and lower environmental mean temperatures showed lower swimming optimal temperatures and narrower thermal tolerance ranges. We found greater variability in the upper than in the lower critical limits in these Patagonian anuran tadpoles. Minimum critical temperatures were close to freezing temperature, possibly in detriment of their tolerance to high temperatures. Overall, our results suggest that these species are adapted to low temperatures. Finally, warming tolerances and predicted thermal safety margins, show that none of the studied species appear to be under thermal stress that may compromise their survival at the present time or in the near future, under a moderate climate change scenario.

Physiological responses of rosewoods Dalbergia cochinchinensis and D. oliveri under drought and heat stresses

Dalbergia cochinchinensis and D. oliveri are classified as vulnerable and endangered, respectively, in the IUCN Red List and under continued threat from deforestation and illegal harvesting for rosewood. Despite emerging efforts to conserve and restore these species, little is known of their responses to drought and heat stress, which are expected to increase in the Greater Mekong Subregion where the species co‐occur and are endemic. In this study of isolated and combined drought and heat effects, we found that D. oliveri had an earlier stomatal closure and more constant midday water potential in response to increasing drought level, suggesting that D. oliveri is relatively isohydric while D. cochinchinensis is relatively anisohydric. Heat shock and drought had synergistic effects on stomatal closure. Our results indicate contrasting relationships in water relations, photosynthetic pigment levels, and total soluble sugars. An increase in chlorophyll a was observed in D. cochinchinensis during drought, and a concomitant increase in carotenoid content likely afforded protection against photo‐oxidation. These physiological changes correlated with higher total soluble sugars in D. cochinchinensis. By contrast, D. oliveri avoided drought by reducing chlorophyll content and compromising productivity. Anisohydry and drought tolerance in D. cochinchinensis are adaptations which fit well with its ecological niche as a pioneering species with faster growth in young trees. We believe this understanding of the stress responses of both species will be crucial to their effective regeneration and conservation in degraded habitats and in the face of climate change.

Metabolic traits in brown trout (Salmo trutta) vary in response to food restriction and intrinsic factors

Metabolic rates vary hugely within and between populations, yet we know relatively little about factors causing intraspecific variation. Since metabolic rate determines the energetic cost of life, uncovering these sources of variation is important to understand and forecast responses to environmental change. Moreover, few studies have examined factors causing intraspecific variation in metabolic flexibility. We explore how extrinsic environmental conditions and intrinsic factors contribute to variation in metabolic traits in brown trout, an iconic and polymorphic species that is threatened across much of its native range. We measured metabolic traits in offspring from two wild populations that naturally show life-history variation in migratory tactics (one anadromous, i.e. sea-migratory, one non-anadromous) that we reared under either optimal food or experimental conditions of long-term food restriction (lasting between 7 and 17 months). Both populations showed decreased standard metabolic rates (SMR-baseline energy requirements) under low food conditions. The anadromous population had higher maximum metabolic rate (MMR) than the non-anadromous population, and marginally higher SMR. The MMR difference was greater than SMR and consequently aerobic scope (AS) was higher in the anadromous population. MMR and AS were both higher in males than females. The anadromous population also had higher AS under low food compared to optimal food conditions, consistent with population-specific effects of food restriction on AS. Our results suggest different components of metabolic rate can vary in their response to environmental conditions, and according to intrinsic (population-background/sex) effects. Populations might further differ in their flexibility of metabolic traits, potentially due to intrinsic factors related to life history (e.g. migratory tactics). More comparisons of populations/individuals with divergent life histories will help to reveal this. Overall, our study suggests that incorporating an understanding of metabolic trait variation and flexibility and linking this to life history and demography will improve our ability to conserve populations experiencing global change.

Long-term exposure to low 17α-ethinylestradiol (EE2) concentrations disrupts both the reproductive and the immune system of juvenile rainbow trout, Oncorhynchus mykiss

Estrogenic endocrine disrupting compounds (EEDCs), such as ethinylestradiol (EE2), are well studied for their impact on the reproductive system of fish. EEDCs may also impact the immune system and, as a consequence, the disease susceptibility of fish. It is currently not yet known whether the low concentrations of EEDCs that are able to disrupt the reproductive system of trout are effective in disrupting the immune system and the fish host resistance towards pathogens, too, or whether such immunodisruptive effects would occur only at higher EEDC concentrations. Therefore, in the present study we compare the effect thresholds of low 17α-ethinylestradiol concentrations (1.5 and 5.5 EE2 ng/L) on the reproductive system, the immune system, the energy expenditures and the resistance of juvenile rainbow trout (Oncorhynchus mykiss) against the parasite Tetracapsuloides bryosalmonae - the etiological agent of proliferative kidney disease (PKD) of salmonids. The parasite infection was conducted without injection and under low pathogen exposure concentrations. The disease development was followed over 130 days post infection - in the presence or absence of EE2 exposure. The results show that the long-term EE2 exposure affected, at both concentrations, reproductive parameters like the mRNA levels of hepatic vitellogenin and estrogen receptors. At the same concentrations, EE2 exposure modulated the immune parameters: mRNA levels of several immune genes were altered and the parasite intensity as well as the disease severity (histopathology) were significantly reduced in EE2-exposed fish compared to infected control fish. The combination of EE2 exposure and parasite infection was energetically costly, as indicated by the decreased values of the swim tunnel respirometry. Although further substantiation is needed, our findings suggest that EE2 exerts endocrine disruptive and immunomodulating activities at comparable effect thresholds, since reproductive and immune parameters were affected by the same, low EE2 concentrations.

Visualizing connectivity of ecological and evolutionary concepts-An exploration of research on plant species rarity

Understanding the ecological and evolutionary factors that influence species rarity has important theoretical and applied implications, yet the reasons why some species are rare while others are common remain unresolved. As a novel exploration of scientific knowledge, we used network analysis conceptually to visualize the foci of a comprehensive base of >800 studies on plant species rarity within the context of ecology and evolution. In doing so, we highlight existing research strengths that could substantiate novel syntheses and gaps that could inspire new research. Our results reveal strong integrated foci on population dynamics with other ecological concepts. In contrast, despite the potential for ecological and evolutionary processes to interact, few studies explored the interplay of environmental factors and microevolutionary patterns. The cellular and molecular biology, physiology, and plasticity of rare plant species within both ecological and evolutionary contexts similarly provide avenues for impactful future investigations.

The endemic and endangered Maugean Skate (Zearaja maugeana) exhibits short-term severe hypoxia tolerance

The endangered and range-restricted Maugean skate (Zearaja maugeana) is subjected to large environmental variability coupled with anthropogenic stressors in its endemic habitat, Macquarie Harbour, Tasmania. However, little is known about the basic biology/physiology of this skate, or how it may respond to future environmental challenges predicted from climate change and/or increases in human activities such as aquaculture. These skate live at a preferred depth of 5-15 m where the dissolved oxygen (DO) levels are moderate (~55% air saturation), but can be found in areas of the Harbour where DO can range from 100% saturation to anoxia. Given that the water at their preferred depth is already hypoxic, we sought to investigate their response to further decreases in DO that may arise from potential increases in anthropogenic stress. We measured oxygen consumption, haematological parameters, tissue-enzyme capacity and heat shock protein (HSP) levels in skate exposed to 55% dissolved O₂ saturation (control) and 20% dissolved O₂ saturation (hypoxic) for 48 h. We conclude that the Maugean skate appears to be an oxyconformer, with a decrease in the rate of O₂ consumption with increasing hypoxia. Increases in blood glucose and lactate at 20% O₂ suggest that skate are relying more on anaerobic metabolism to tolerate periods of very low oxygen. Despite these metabolic shifts, there was no difference in HSP70 levels between groups, suggesting this short-term exposure did not elicit a cellular stress response. The metabolic state of the skate suggests that low oxygen stress for longer periods of time (i.e. >48 h) may not be tolerable and could potentially result in loss of habitat or shifts in their preferred habitat. Given its endemic distribution and limited life-history information, it will be critical to understand its tolerance to environmental challenges to create robust conservation strategies.

Animal responses to environmental variation: physiological mechanisms in ecological models of performance in deer (Cervidae)

Context Proper assessment of the consequences of environmental variation on animals depends on our ability to predict how they will perform under different circumstances. This requires two kinds of information. We need to know which environmental factors influence animal performance and their mode of action, i.e. whether a given factor acts alone or through interaction with other factors, directly or indirectly, instantaneously or after a delay and so on. This essentially correlative process falls within the domain of ecology. We also need to know what determines the direction, amplitude and limits of animal responses to environmental variation and change. This essentially experimental process falls within the domain of physiology. Physiological mechanisms are frequently poorly integrated within the correlative framework of ecological models. This is evident where programmed responses are attributed to environmental forcing and where the effect of environmental factors is evaluated without reference to the physiological state and regulatory capacity of the animal on which they act. Aims Here we examine ways in which the impacts of external (environmental) stimuli and constraints on performance are moderated by the animals (deer) on which they impinge. Key results The analysis shows (1) how trade-offs in foraging behaviour, illustrated by the timing of activity under the threat of predation, are modulated by integration of short-term metabolic feedback and animal emotions that influence the motivation to feed, (2) how the influence of thermal and nutritional challenges on performance, illustrated by the effect of weather conditions during gestation on the body mass of reindeer (Rangifer tarandus) calves at weaning, depends on the metabolic state of the female at the time the challenge occurs and (3) how annual cycles of growth, appetite and reproduction in seasonal species of deer are governed by innate circannual timers, such that their responses to seasonal changes in food supply are anticipatory and governed by rheostatic systems that adjust homeostatic set- points, rather than being purely reactive. Conclusions Concepts like ‘maintenance’ and ‘energy balance’, which were originally derived from non-seasonal domestic ruminants, are unable to account for annual cycles in metabolic and nutritional status in seasonal deer. Contrasting seasonal phenotypes (fat and anoestrous in summer, lean and oestrous in winter) represent adaptive solutions to the predictable challenges presented by contrasting seasonal environments, not failure of homeostasis in one season and its success in another. Implications The analysis and interpretation of responses to environment in terms of interaction between the external stimuli and the internal systems that govern them offer a more comprehensive, multifaceted understanding of the influence of environmental variation on performance in deer and open lines of ecological enquiry defined by non-intuitive aspects of animal function.

Physiological implications of climate change for a critically endangered Australian marsupial

Extreme weather events (e.g. heatwaves and droughts) can expose animals to environmental conditions outside of their zones of physiological tolerance, and even resistance, and impact long-term viability of populations and species. We examined the thermal and hygric physiology of the critically endangered western ringtail possum (Pseudocheirus occidentalis), a member of a family of marsupial folivores (Pseudocheiridae) that appear particularly vulnerable to environmental extremes. Basal metabolic rate and other standard physiological variables measured at an ambient temperature of 30°C conformed to values for other marsupials. At lower temperatures, body temperature decreased slightly, and metabolic rate increased significantly at 5°C. At higher temperatures, possums experienced mild hyperthermia and increased evaporative heat loss by licking rather than panting. Their point of relative water economy (–8.7°C) was more favourable than other pseudocheirid possums and the koala (Phascolarctos cinereus). We predict that western ringtail possums should tolerate low ambient temperatures well and be more physiologically tolerant of hot and dry conditions than common (Pseudocheirus peregrinus) and particularly green (Pseudochirops archeri) ringtail possums, and koalas. Our physiological data can be incorporated into mechanistic species distribution models to test our hypothesis that western ringtail possums should physiologically tolerate the climate of habitat further inland than their current distribution, and withstand moderate impacts of climate change in the south-west of Western Australia.

Striving for population-level conservation: integrating physiology across the biological hierarchy

The field of conservation physiology strives to achieve conservation goals by revealing physiological mechanisms that drive population declines in the face of human-induced rapid environmental change (HIREC) and has informed many successful conservation actions. However, many studies still struggle to explicitly link individual physiological measures to impacts across the biological hierarchy (to population and ecosystem levels) and instead rely on a 'black box' of assumptions to scale up results for conservation implications. Here, we highlight some examples of studies that were successful in scaling beyond the individual level, including two case studies of well-researched species, and using other studies we highlight challenges and future opportunities to increase the impact of research by scaling up the biological hierarchy. We first examine studies that use individual physiological measures to scale up to population-level impacts and discuss several emerging fields that have made significant steps toward addressing the gap between individual-based and demographic studies, such as macrophysiology and landscape physiology. Next, we examine how future studies can scale from population or species-level to community- and ecosystem-level impacts and discuss avenues of research that can lead to conservation implications at the ecosystem level, such as abiotic gradients and interspecific interactions. In the process, we review methods that researchers can use to make links across the biological hierarchy, including crossing disciplinary boundaries, collaboration and data sharing, spatial modelling and incorporating multiple markers (e.g. physiological, behavioural or demographic) into their research. We recommend future studies incorporating tools that consider the diversity of 'landscapes' experienced by animals at higher levels of the biological hierarchy, will make more effective contributions to conservation and management decisions.

Mapping physiology: biophysical mechanisms define scales of climate change impacts

The rocky intertidal zone is a highly dynamic and thermally variable ecosystem, where the combined influences of solar radiation, air temperature and topography can lead to differences greater than 15°C over the scale of centimetres during aerial exposure at low tide. For most intertidal organisms this small-scale heterogeneity in microclimates can have enormous influences on survival and physiological performance. However, the potential ecological importance of environmental heterogeneity in determining ecological responses to climate change remains poorly understood. We present a novel framework for generating spatially explicit models of microclimate heterogeneity and patterns of thermal physiology among interacting organisms. We used drone photogrammetry to create a topographic map (digital elevation model) at a resolution of 2 × 2 cm from an intertidal site in Massachusetts, which was then fed into to a model of incident solar radiation based on sky view factor and solar position. These data were in turn used to drive a heat budget model that estimated hourly surface temperatures over the course of a year (2017). Body temperature layers were then converted to thermal performance layers for organisms, using thermal performance curves, creating 'physiological landscapes' that display spatially and temporally explicit patterns of 'microrefugia'. Our framework shows how non-linear interactions between these layers lead to predictions about organismal performance and survivorship that are distinct from those made using any individual layer (e.g. topography, temperature) alone. We propose a new metric for quantifying the 'thermal roughness' of a site (RqT, the root mean square of spatial deviations in temperature), which can be used to quantify spatial and temporal variability in temperature and performance at the site level. These methods facilitate an exploration of the role of micro-topographic variability in driving organismal vulnerability to environmental change using both spatially explicit and frequency-based approaches.