Conservation Physiology最新文献

Honeybees (Apis mellifera Linnaeus, 1758) are managed pollinators in anthropized landscapes but suffer adverse physiological effects from urbanization due to increased pollution, higher temperatures and a loss of habitat quality. Previous studies in various animal taxa have shown how responses of digestive enzymes, such as Aminopeptidase N (APN), can indicate stress conditions and thus be used to measure the harmfulness of anthropogenic disturbance. However, no studies have focused on bees. Here, we sampled honeybee foragers along an urbanization gradient in the Metropolitan City of Milan (Italy) and measured the APN activity. After briefly characterizing the midgut APN activity under different pH and temperature conditions, we found that APN activity was lower at urban sites with higher temperatures (Urban Heat Island (UHI) effect). Furthermore, an increasing proportion of meadows (semi-natural flowered areas) and a decreasing proportion of urban parks (managed urban green areas)-both higher in less urbanized sites-were associated with higher APN activity. Our results suggest that severe urban conditions may cause a reduction in APN activity, but that the UHI effect alone is not directly involved. Although the actual urbanization-related factors driving our results remain unclear, we suggest that impoverishment of food sources may play a role. As aminopeptidases are involved in pollen digestion, our results may indicate a possible impairment of the digestive capacity of honeybees in highly urbanized areas.

Catch-and-release angling is a popular recreational pastime and an essential component of many fish research programmes. Marked physiological disturbances have been documented in elasmobranchs in response to angling and handling, but skates and rays remain understudied. Here, we describe for the first time the physiological responses of the critically endangered flapper skate (Dipturus intermedius) to angling, handling and tagging in Scotland. Sixty-one skate were captured by angling as part of a tagging research programme. We assessed individual health, measured blood parameters at two time points (post-capture and prior to release) and recorded heart and respiratory rates during handling and the surgical insertion of acoustic tags. Injuries or infections were identified in 10% of individuals and attributed to prior angling in two cases. Skate generally experienced a mild metabolic acidosis characterized by decreases in blood pH and bicarbonate and increases in lactate and glucose. Respiratory acidosis characterized by limited increases in PCO₂ was also observed. The degree of acidosis was greater with warmer sea temperatures and longer fight times, and worsened during the time that skate were handled on deck. Heart rates during handling were negatively associated with body size, positively associated with temperature and also linked to time on the line. Taken together, our results suggest that elevated fight times and temperatures increase the physiological stress experienced by rod and reel-caught flapper skate. Efforts to reduce fight times and minimize heat exposure (including shading, irrigation and reduced handling time) should be beneficial for skate.

Hormones are known to be involved in life-history trade-offs as systemic signals that establish functional links among traits and regulate key behavioural and physiological transitions between states in organisms. Although major functions of many steroid hormones such as testosterone are conserved among vertebrates, circulating concentrations vary widely both within and across species, and the degree to which observed hormone concentrations mediate life-history responses to environmental variation is less understood. In this study, we investigated how faecal testosterone metabolite (FTM) concentrations varied with extrinsic and intrinsic factors. To do so, we took advantage of a 6-year period of longitudinal sampling of FTM, indicators of stress and oxidative status in a semi-captive population of Asian elephants (n = 3163 samples from 173 individuals) in Myanmar. We determined how the variation in FTM is associated with age, sex, origin (captive-born or wild-caught), seasonality of the environment, individual stress level [measured by faecal glucocorticoid metabolite (FGM) and heterophil to lymphocyte ratio (H/L)] and oxidative status (reactive oxygen metabolite concentrations and superoxide dismutase activity). We reported that FTM increased with age from juvenile to adulthood for both sexes, with higher FTM concentrations in males than females. Moreover, elephants showed significantly higher FTM concentrations during the hot season and monsoon than in the cold season. However, for the physiological indicators, we found contrasting results. While FTM concentrations were strongly positively correlated with FGM concentrations, FTM concentrations were not related to H/L ratios. Finally, we found no relationship between FTM and the oxidative status of individuals. Our study provides new insights on the factors associated with variation in testosterone concentrations-a key hormone for reproduction and fitness of individuals-in Asian elephants living in their natural environment, which has relevance for effective conservation measures of this endangered species.

Understanding plant ecophysiological functioning is critical in formulating effective ecologically based strategies to conserve and enhance resiliency and resistance in sagebrush steppe, as well as improving their restoration following degradation by interactive effects of climate change, wildland fire and invasive annual grasses. Recent research has shown increased reproductive photosynthesis following floral defoliation can be important to reproductive potential, yet how this is expressed in plant material selected for different functional attributes is unknown. To address this, we measured photosynthetic gas exchange in clipped and unclipped basal florets and flag leaves of two germplasms of the native perennial bunchgrass, bluebunch wheatgrass, var. Anatone and var. Columbia, selected for higher reproductive culm production. Clipping induced a stronger direct compensatory reproductive photosynthetic response in basal florets of Anatone compared to Columbia germplasm individuals, with no indirect compensatory response apparent in unaffected distal florets of either germplasm. Flag-leaf photosynthesis did not differ between the germplasm lines, but Columbia flag leaves did show evidence of increased photosynthesis on culms with clipped basal florets. These findings suggest selection for increased flowering culms may alter reproductive herbivory tolerance, a feature important in the convergence of herbivory and drought tolerance traits. Such information could help in planning effective seed mixes to enhance population stability across highly variable sagebrush steppe ecosystems, as well as directing future plant material selection to improve restoration success in these economically important rangelands.

Gonadal hormones play a central role in reproductive function and success. As such, quantifying reproductive hormones non-invasively in threatened, vulnerable and endangered wildlife species offers an ideal tool for assessing general and individual reproductive patterns in situ. Whilst the use of faeces as a hormone matrix is often preferred in these cases, the required enzyme immunoassays (EIAs) for measuring faecal androgen (fAM), oestrogen (fEM) and progestagen metabolite (fPM) concentrations must first be validated if a species gets investigated for the first time to ensure biologically relevant patterns can be observed. In this study we aimed to biologically validate the EIAs for monitoring fAM, fEM and fPM concentrations in Temminck's pangolin, Smutsia temminckii. Hormone metabolite concentrations derived from each EIA tested were compared between different age and sex classes. An epiandrosterone EIA effectively measured androgen levels in males, distinguishing between adult and juvenile individuals, as well as both female age classes. Similarly, the tested oestrogen EIA successfully distinguished between adult and juvenile female fEM concentrations, and both tested progestagen EIAs demonstrated adequate differences between fPM concentrations of adult and juvenile females. The now-validated EIAs offer robust tools for a non-invasive monitoring of reproductive activity in Temminck's pangolin. The development of such techniques will allow researchers to assess reproductive hormone patterns of the species in situ, whilst also paving the way for further studies in this field. Despite the small sample size due to the species' conservation status, the study provides a foundation for future research using a robust, validated, non-invasive monitoring tool. The latter can now be implemented in long-term monitoring with larger sample sizes to yield more comprehensive data, aiding in the conservation of Temminck's pangolin.

Animals in nature potentially experience multiple stressors, and those of anthropogenic origin are likely to be repeated or chronic. However, stress hormone levels are highly context-dependent and are not consistent predictors of chronic stress in wildlife. Profiling the downstream consequences of repeated stress responses, such as changes in metabolism or gene expression, may be more informative for predicting their individual-level health consequences and population-level impacts, which are key objectives for wildlife conservation. We previously found that in free-ranging juvenile elephant seals, the blubber transcriptome and proteome, but not cortisol levels, could distinguish between responses to single versus repeated stress axis stimulation. However, the blubber proteome response to stress was limited and mainly involved extra-cellular matrix proteins. In this study, we examined the plasma proteome response of four of the same animals to the repeated stress experiment, since multiple organs secrete proteins into the circulation, providing a readout of their activity and integration. We isolated plasma proteins, identified and quantified them using liquid chromatography and tandem mass spectrometry (LC-MS/MS) and compared their abundance between sampling times. We identified >200 proteins in plasma, of which 42 were altered in abundance, revealing complex protein dynamics in response to repeated stress challenges. These changes were delayed but sustained, suggesting that the plasma proteome may reflect longer term integration of multi-organ responses to recent, rather than immediate, challenges. Differentially abundant proteins included components of the osmoregulatory system, acute phase and complement proteins, organokines, apolipoproteins and hormone transport proteins, which coordinate physiological processes with significant implications for marine mammal health and may explain several aspects of marine mammal stress physiology, such as insulin resistance and high aldosterone levels. We identified several potentially novel biomarkers, such as AGT, HPX, TTR and APOA4, that may be useful for detecting recent and repeated stress exposure in marine mammals.

The study of repeatability in behaviour and activity level can be used to evaluate inter-individual differences, which are fundamental to assess the resilience of populations to environmental variation. Previous work on repeatability in wild fish populations has largely been based on acoustic telemetry or mark-and-recapture and has revealed repeatable activity patterns over relatively long periods in a number of species. Although accelerometry is a promising tool for investigating the swimming activity of fish in the wild, little is known about the repeatability of accelerometry-based traits in wild fish. Here, we used external accelerometers to investigate the swimming activity of the Patagonian grouper Acanthistius patachonicus, a rocky-reef fish with high site fidelity, which ensures a high recapture rate of accelerometer tags. Accelerometry was used to investigate the short-term repeatability of a number of activity traits, including swimming, hovering, daily median tailbeat frequency, percentage of high tailbeat frequency and total number of tailbeats at different times of the year. We found that all of the variables are repeatable over the daily scale and four out of five variables are repeatable over weekly periods. Overall, our work suggests that these traits are individual-specific for the short time period investigated. In addition, the percentage of time spent in swimming and hovering was greater in the warm season compared to the cold season, suggesting higher activity levels related to higher temperatures. These results suggest that activity traits related to swimming are repeatable and likely related to the physiological state of each individual. Finally, our work shows that accelerometry can be considered a valuable tool to explore inter-individual differences with potential applications for assessing the resilience of wild populations.

Conservation breeding programmes include translocations of animals across breeding facilities, both in and ex situ, and to/from their natural habitat. Newly reintroduced Vancouver Island marmots (VIMs) originating from the captive breeding programme are known to experience high winter mortality once reintroduced. Whilst high winter mortality rates amongst reintroduced VIM populations remain a concern of unknown causes, this health issue could potentially be linked to changes in gut microbiota prior to hibernation. Furthermore, captivity is known to impact the gut microbiota of mammals that could be crucial for hibernation. In this study, we explored the diversity of bacterial communities in the gut of captive marmots during the entire active season, both kept in captivity at in situ and ex situ facilities, as well as free-ranging marmots during the summer period. Gut microbial diversity was higher in marmots held in ex situ facilities, outside of their habitat range, compared to captive marmots held within their habitat range, and in the wild, and differences in composition were also observed. In the entire active season, animals kept in the ex situ facility had increased abundance in taxa known to be mucin degraders, sulphate producers and possible cross-feeders, whilst an increase in fibre degraders of in situ and free-ranging marmots is potentially linked to diet variation between facilities. These results confirm the interest to transfer animals held at zoos to an in situ facility before relocation and expand our understanding of microbiota variation according to hibernation cycles in the context of conservation biology.

Freshwater organisms face a complex array of environmental stressors that can negatively affect endocrine function and subsequent fitness outcomes. Hypoxia and turbidity are two environmental stressors that are increasing due to human activities that could lead to endocrine disruption and reduced reproductive output. Our research addresses how hypoxia and elevated turbidity affect traits related to reproductive success, specifically sex hormone concentrations, investment in reproductive tissues and body size. We used wild fish from two populations (a river and a swamp) of an African cichlid, Pseudocrenilabrus multicolor, to produce offspring that were reared in a full factorial split brood rearing experiment (hypoxic/normoxic × clear/turbid). River and swamp populations represent divergent habitat types with respect to the stressors of interest, being well-oxygenated but turbid or hypoxic and clear, respectively. Overall, we found evidence for plastic responses to both stressors. Specifically, we found that there was an interactive effect of oxygen and turbidity on testosterone in males from both populations. Additionally, males of both populations reared under hypoxic conditions were significantly smaller in both mass and standard length than those raised under normoxic conditions and invested less in reproductive tissues (quantified as gonadosomatic index). Hypoxia and turbidity are experienced naturally by this species, and these environmental stressors did not affect the number of eggs laid by females when experienced in the absence of another stressor (i.e. normoxic/turbid or hypoxic/clear). However, there was an interactive effect of hypoxia and turbidity, as females reared and maintained under this treatment combination laid fewer eggs. This research underscores the importance of considering the possibility of stressor interactions when determining how anthropogenic stressors affect fitness outcomes.

Freshwater organisms face multiple threats to their ecosystems, including warming associated with climate change and low dissolved oxygen (environmental hypoxia), which are both increasing in frequency and extent in freshwater systems. Understanding tolerance thresholds for these environmental stressors as well as the plasticity of responses is the key for informing the conservation of imperilled species. Direct measurement of imperilled species can be difficult, and the use of surrogate (non-imperilled but closely related) species has been proposed as a remedy, but the degree to which surrogate data are representative of the imperilled species has not been widely validated. In this study, we measured physiological performance of two species: one federally listed as Threatened in Canada (Pugnose Shiner, Miniellus anogenus) and a non-imperilled congener (Blackchin Shiner, Miniellus heterodon). Hypoxia tolerance (critical oxygen tension and loss of equilibrium) and upper thermal tolerance (CT_max) were measured streamside over a period of 5 months. We found that the Threatened Pugnose Shiner had lower tolerance to both elevated temperature and hypoxia than the non-imperilled Blackchin Shiner. The species also differed in their responses to environmental dissolved oxygen (DO). CT_max of Pugnose Shiner had a positive relationship with DO such that CT_max was lowered when environmental DO was low, whereas there was no effect of DO on CT_max of Blackchin Shiner. Blackchin Shiner also showed plasticity of hypoxia tolerance in response to changes in environmental DO, while Pugnose Shiner showed little plasticity. We conclude that Pugnose Shiner may be more sensitive to heat waves and hypoxia associated with climate change. We also assert that researchers should be cautious when using surrogate species to inform tolerance limits of imperilled species and highlight the value of measuring imperilled species directly when possible.