Conservation Physiology最新文献

Much progress has been made in understanding the pathophysiology of white-nose syndrome (WNS), a devastating disease that has impacted North American hibernating bats for nearly two decades. Growth of the causative fungal pathogen, Pseudogymnoascus destructans, on exposed epidermal tissue of bats creates an immune reaction that disrupts natural hibernation physiology and leads to premature expenditure of energy reserves and often death. Past work has highlighted the similarities between WNS and immune reconstitution inflammatory syndrome, but other conditions that have not been considered yet may also be relevant. We performed a transcriptomic analysis of wing tissue from naïve and exposed bats to further investigate the implications of observed differential gene expression patterns. For this analysis, we collected wing biopsy samples from 41 individuals prior to WNS emergence and 58 individuals 2-5 years after WNS emergence. We generated poly-A enriched tag-Seq libraries to compare gene expression between these groups. We then linked our findings and those of past studies to other disease systems to build hypotheses regarding mechanisms of WNS pathophysiology. We found an overrepresentation of functions related to programmed cell death and cytokine activity among upregulated genes. Importantly, we also identified upregulation of three S100 damage-associated molecular patterns (DAMPs) in exposed populations. Taken together, our findings and those of past studies suggest that infected bats experience a feedback loop of cell death among immune cells, the release of DAMPs and the stimulation of cytokine release that may act to maintain pathological immune activity. This feedback loop likely relates to cytokine storms in individuals with severe infection and possibly deteriorates into sepsis over time. Given the pathophysiology of sepsis, multiple organ dysfunction potentially contributes to the physiological disruption associated with WNS.

Changes in ocean temperature are expected to have a considerable effect on fishes through the impact of temperature on physiological performance, vital energetic processes (i.e. metabolism, foraging and swimming style) and reproductive fitness. To understand the sensitivity of an exploited population of Chrysoblephus laticeps in to temperature variability, intermittent-flow respirometry was used to quantify and compare changes in metabolic rate and aerobic scope under different temperatures (10, 16, 21 and 24°C) mimicking thermal variations experienced in the home range of this species. A total performance score was developed to represent aerobic performance across the range of test temperatures. This score was calculated for each temperature from the lower (25%), mid (50%) and upper (75%) percentiles of the aerobic scope range available for the species. The results of this study identified heterogeneity in physiological performance phenotypes amongst individuals of the exploited population. There was significant variation in the aerobic performance of high, intermediate and low performers at higher temperatures. However, differences in performance were not significant at low temperatures, where several intermediate performers maintained high performance. High performers maintained high rates of physiological performance across a broad range of temperatures, whereas low performers were physiologically limited outside of their optimal thermal range. These results suggest that individuals with a broad aerobic scope (i.e. high aerobic scope (AS) values across a range of temperatures) may likely be the most resilient to short-term thermal variability caused by marine heat waves and upwelling events in temperate coastal environments. Since the shape of thermal performance curves differs between individuals and reflects the range at which individuals can function above specified performance thresholds, individual thermal performance must be measured repeatedly in the same individual over a thermal gradient. An understanding of physiological phenotypic diversity amongst individuals is critical to understand the impacts of thermal variability on fished populations.

Rewilding and species reintroductions are increasingly important conservation strategies, involving both captive-bred and wild-rescued animals, with the goal of restoring ecosystems and supporting populations of threatened species. Over the past 30 years, the Elephant Transit Home in Sri Lanka has rescued and rehabilitated more than 150 orphaned elephant calves that were subsequently released back into the wild. Understanding how rehabilitation and release processes affect the welfare status of these calves can provide valuable information on factors affecting release outcomes. This study evaluated patterns of faecal glucocorticoid metabolite (fGCM) concentrations as a physiological indicator of stress in 10 orphaned elephants (six males, four females) rescued at ≤1 year of age and released back into Udawalawe National Park after rehabilitation at the Elephant Transit Home (release age, 6 to 8 years). Faecal samples (~2/week) were collected for 9 months pre- (n = 53 samples) and 16 months post- (n = 153 samples) release. Mean fGCM concentrations during the early post-release period (first 17 days) were significantly higher than in pre- and later post-release periods, with no differences between males and females. Results indicate elephants adapted quickly after release, likely aided by being released in a small group (n = 10) of socialized cohorts. In fact, fGCM normalized to concentrations lower on average than at the Elephant Transit Home in the months preceding release. Understanding the stress response of elephants during and after translocations is crucial for well-being and successful integration into the wild. Minimizing stress through appropriate protocols, such as selecting strong social units, is essential. Hormonal monitoring is a valuable tool that should be considered long-term to assess the adaptation, survival and eventual reproductive success of rewilded elephants.

Fishes can acclimate to a range of temperatures. However, the signalling factors controlling thermal acclimation are not well understood. Here, in two experiments, we examined the putative roles of plasma-borne factors (e.g. hormones) and skin thermoreception in the acclimation process. In experiment 1, 16°C-acclimated Atlantic cod (Gadus morhua) were subjected to a transfusion treatment by injecting plasma from 8°C (cold), 16°C (control) or 21°C (warm) acclimated cod, 10 times over four days. Plasma was collected from donor cod that were 24 h into their acclimation. In experiment 2, 16°C-acclimated goldsinny wrasse (Ctenolabrus rupestris) were exposed to an immersion treatment consisting of 10 s immersions in an 8°C (cold), 16°C (control) or 24°C (warm) water bath, repeated five times daily for five days. These brief immersions allowed for changes to skin temperature but not deeper tissues. Following these treatments, we measured the critical thermal maximum (CT_max) of all fish and the standard metabolic rate (SMR) in cod. Neither the immersions nor transfusions affected fish CT_max. However, the SMR was elevated in cod receiving plasma from cold-acclimated donors, suggesting that circulating molecules transferred from donors had initiated metabolic compensation in recipients. Thyroid hormone plasma levels were not different amongst acclimated donors and thus appear not to have been involved in the metabolic compensation. Our experiments found no evidence that brief, repeated cutaneous exposures to temperature changes can trigger acclimation, but do demonstrate a potential role of haematological endocrine control in metabolic acclimation, although further experiments will be required to investigate this process.

Artificial light at night (ALAN) is an emergent yet already global form of sensory pollution. However, its effects on marine environments remain poorly understood compared to those on terrestrial ecosystems. Low-latitude ecosystems such as shallow coral reefs might be at greater risk as they experience little change in annual day length and reef organisms rely on moonlight illumination as a zeitgeber for critical biological processes. Moreover, many coral reef fish are demersal spawners, making them vulnerable to the effects of ALAN from early life. We performed a field experiment to determine whether artificial light affects the quality of fish embryos and newly hatched larvae by exposing wild nests of the orange-fin anemonefish (Amphiprion chrysopterus) to white light emitting diode (LED) light (22 ± 2.0 lx; 4000 K) throughout the 6-day embryonic development period. We also explored whether light pollution indirectly influences offspring traits by measuring parental care investment. Exposure to ALAN altered embryo quality, leading to a reduction in egg volume (2.40%) and yolk reserves (6.11%) alongside an increase in heart rate (7.42%) a few hours before hatching. These changes reflect higher metabolic demands of embryos developing under light-polluted conditions. As parental care investment was unaffected by light pollution, our results suggest that these effects are more likely the consequence of a direct effect of ALAN on embryogenesis. In contrast, there was no influence of artificial light on the larval morphology or swimming performance, suggesting that the direct effects of ALAN on fish embryos do not cascade onto the larval stage immediately after hatching. These results may suggest that embryos compensated for ALAN exposure to maintain their early post-hatching larval performance. Further studies are needed to investigate whether light pollution exposure during embryonic development has delayed effects on larval performance during the dispersal phase or on larval survival.

Human impacts on ecosystems have intensified variation in water variability for terrestrial life, thus challenging the maintenance of water balance, or hydroregulation. The accelerated development and accessibility of technologies and computational models over the past decade have enabled researchers to predict changes in animal hydroregulation and environmental water with greater spatial and temporal precision. Focusing on reptiles and amphibians, we discuss current methods, limitations and advances for quantifying ecologically relevant metrics of environmental water stressors and organismal responses to both acute and long-term water stress that are applicable for conservation and management. We also highlight approaches that integrate environmental water data with an organism's water balance and physiological, behavioural and life history traits to predict the limits of species' responses and assess their vulnerability to climate change. Finally, we outline promising future directions and opportunities in hydroregulation studies with a conservation focus, including broader inferences about acclimation responses, linking gene expression to functional changes, and exploring inter- and transgenerational plasticity and adaptive evolution. Advances in these fields will facilitate more accurate assessments of species' capacities and the limits of hydroregulation in response to a more variable and unpredictable future climate.

White sturgeon (Acipenser transmontanus) are in decline globally, and populations in the Sacramento-San Joaquin River Basin are particularly vulnerable due to habitat impacts, variable recruitment and altered food availability, all of which are exacerbated by climate change. The minimal metabolic expenditure required to maintain homeostasis, termed standard metabolic rate (SMR), is thought to have broad ecological relevance because it correlates with other important measures of metabolic demand and a range of fitness-related behavioural traits. SMR is variable among individuals and this variation may also underlie variation in behaviour. Additionally, SMR has been shown to be phenotypically flexible in the presence of changing food availability. The objective of this study was to assess how nutritional status may affect the relationship between SMR and locomotor activity in juvenile white sturgeon. We reared white sturgeon at 15°C under an optimal feed rate (OFR, 5.3% bodyweight/day) and low feed rate (LFR, 2.6% bodyweight/day) for 6 weeks, measuring SMR and locomotor activity at the 3- and 6-week timepoints. OFR fish were significantly larger than LFR fish at both timepoints, but mass-specific SMR was not significantly different across treatment or time. We found that only fish under the greatest nutritional stress (6 weeks at LFR) showed a significant relationship between SMR and locomotor activity. This is evidence that observable correlations between physiological and behavioural traits may only become apparent under the influence of environmental stressors. As changing climate is projected to impact food web dynamics and food availability, understanding how nutritional state affects physiological and behavioural traits may help to predict how animals respond to future shifts.

Amphibians face global declines linked to anthropogenic environmental change, including modifications to freshwater habitats. Human impacts on water chemistry, including acid rain and run-off of road salt into wetlands, may affect the physiology of amphibians with aquatic life stages. Specifically, water pH varies among freshwater habitats and affects amphibian development, behaviour, and physiology. For example, changes in skin pH affect the activity of enzymes on the skin, including those involved in antimicrobial functions. In this study, we explored the ability of free-ranging amphibians to maintain homeostasis across a range of naturally occurring water pH and salinity. We sampled two species of frogs at 19 wetlands around Peterborough, Ontario, measuring water pH, water salinity, and the skin pH of northern leopard frogs (Lithobates pipiens; n = 141) and green frogs (Lithobates clamitans; n = 329). We found that water pH increased with salinity, and was weakly related to the proportion of built-up habitat around wetlands. Frog skin pH was significantly associated with water pH, but both species showed a strong ability to buffer their skin pH across a range of conditions. On average, the ventral skin pH of L. pipiens increased by 0.37 units for each 1 unit increase in water pH, while skin pH of L. clamitans increased by 0.12. Specific responses to water chemistry differed between the two species: skin pH of L. pipiens varied with demographic group and body size, but skin pH of L. clamitans did not. As human effects on wetland habitats increase, these amphibians' ability to buffer skin pH may provide some protection against anthropogenic changes in wetland water chemistry.

Serological surveillance enhances our understanding of influenza A virus (IAV) exposure and dynamics in wild bird populations. Traditional serum-based testing, while effective, poses logistical challenges for large-scale surveillance, particularly in remote regions, for small-bodied species or in scenarios such as hunter-harvested samples where serum collection can be impractical. This study evaluates the use of whole blood collected on high-quality cellulose filter strips as an alternative to serum for detecting antibodies against IAV nucleoprotein (NP) and hemagglutinin (HA) H5 and H7 targets. We tested paired serum and whole blood on filter strips collected from wild birds using the commercially available IDEXX AI MultiS Screen Ab test and in-house competitive enzyme-linked immunosorbent assays (ELISAs) developed at the National Centre for Foreign Animal Disease (NCFAD) of the Canadian Food Inspection Agency. Strong correlations (ρ = 0.77) were observed between serum and whole blood on filter strips for NP detection with the IDEXX ELISA, while moderate correlations were noted for NCFAD's NP (ρ = 0.58) and H5 (ρ = 0.65) assays. Correlation between serum and whole blood on filter strips for NCFAD's H7 assay was poor, although interpretation is limited due to the small sample size of H7 positives. Threshold optimization using the Youden index improved diagnostic performance, with optimized cutoffs identified for NP (sample-to-negative < 0.7708 for IDEXX and percentage inhibition [PI] > 39.56 for NCFAD) and H5 (PI > 20.37). Storage conditions impacted performance, with frozen whole blood on filter strips achieving higher sensitivity compared to those stored at room temperature. These findings support the use of filter strips to collect whole blood as an informative alternative for IAV serological surveillance in wild birds when serum is unavailable, provided optimal storage conditions and threshold adjustments are implemented, although serum remains the superior sample type.

Increasingly frequent and intense heatwaves are expected to elevate the risks of heat-related mortality among birds. Most studies have focused on arid-zone avifaunas and the extent to which risks will increase in other habitats, particularly humid lowlands, remains unclear. We tested the prediction that increasing air temperature and corresponding increases in humidity, and hence wet-bulb temperature (T _W; lowest temperature achievable via adiabatic evaporation), will increase exposure to conditions associated with lethal hyperthermia. We empirically determined maximum T _W (T _W-max) for an Afrotropical forest frugivore, the trumpeter hornbill (Bycanistes bucinator) as T _W-max = 31.7 ± 1.0°C. We then modelled current and future exposure to conditions associated with T _W > T _W-max across this species' range. Under a business-as-usual emissions scenario and assuming no vegetation buffering of air temperature (T _air), trumpeter hornbills will experience T _W > T _W-max for at least 1 day year^-1 over 46% of their current range, compared to 30% at present. However, the frequency of exposure will increase substantially and reach ~100 days year^-1 in parts of the southern Democratic Republic of Congo. When we incorporated the thermal buffering effect of vegetation, end-century exposure to T _W > T _W-max decreased by 0.3-66.7%, emphasizing the role of cool microsites provided by vegetation. Our analyses reveal the exposure of birds inhabiting humid environments at low latitudes to conditions associated with a risk of lethal hyperthermia under resting conditions will increase substantially in coming decades, putting a large fraction of global avian biodiversity at risk of population declines and local extinctions.