Conservation Physiology最新文献

Cortisol is a biomarker of grey wolf (Canis lupus) prey selection on wild ungulates. Throughout its range, wolves may prey on free-range livestock, leading to conflicts with humans. This can compromise wolf conservation through culling or poaching. We investigate whether glucocorticoid concentration could be a biomarker of individual prey selection by grey wolves that depredate on free-ranging cattle (Bos taurus). To achieve this, cortisol concentration in hair samples from live (n = 46) and wolf-preyed (n = 19) cattle was determined by enzyme-linked immunosorbent assays. The effects of intrinsic and extrinsic variables-namely age, sex and food availability-on hair cortisol concentration (HCC) were investigated through linear mixed models with farm as a random effect. The analysis revealed that, against our initial hypothesis, wolf-preyed cattle had significantly lower HCC than live cattle (P = 0.009). Additionally, HCC was lower in subadults than in adults (P = 0.002), and was negatively correlated with food availability in adults, but not in subadults (P = 0.003). These results suggest that predation risk does not necessarily equal long-term physiological stress. Alternatively, it may indicate that cattle chronically exposed to stressors (i.e. presenting higher HCC) may exhibit more effective anti-predatory behaviours. Additionally, food availability for cattle may influence wolf predation patterns, as cattle may expand their foraging area by exploring unfamiliar areas, thereby increasing the likelihood of predator encounters. Further research is required to understand the relationship between the multitude of stressors acting on free-range cattle and wolf prey selection, with the aim of assessing the risk of individual cattle and eventually managing predation risk and human-wolf conflict.

Hawksbill sea turtles (Eretmochelys imbricata) are listed as critically endangered by the International Union for the Conservation of Nature (IUCN). To implement best conservation practices for this species, its biology should be well understood. Attempting to characterize the foraging physiology of free-ranging hawksbill sea turtles is complicated by the fact that sampling is typically limited to nesting females during the reproductive season. Without data from non-reproductive periods, it is difficult to determine whether observed physiological values reflect baseline conditions or are specific to the energetically demanding nesting season. Accordingly, in this study, we described the physiology of foraging in a captive-held population of hawksbill sea turtles for an entire year. Across the year, we sampled a total of five captive adult female hawksbills at the Okinawa Churaumi Aquarium in Okinawa, Japan. We measured the concentration of β-hydroxybutyrate (BHB), triglycerides (TRGs) and testosterone. Foraging biomarkers BHB and TRGs were both significantly higher during gonadal recrudescence and breeding than during gonadal quiescence, consistent with mature animals that were not foraging actively during breeding activities. Testosterone concentration also was higher during breeding months than during non-breeding months, especially in May, which marked the onset of mating. Elevated BHB during breeding activities indicated that captive hawksbills accumulated energy reserves during the non-breeding season to invest it in breeding activities. Additionally, elevated TRGs are correlated to vitellogenesis occurring in the breeding female hawksbills.

The ability to predict how fishes respond to changes in temperature and resource variability is paramount to developing sustainable management plans and for projecting the direct and indirect effects of climate change. We developed a versatile, physiological model capable of providing size-specific estimates of fish growth and fecundity across varying temperatures and resource levels. The model includes a mechanistic representation of individual-level life history processes across diverse biogeographic and functional fish guilds, using direct, species-specific parameter estimates. We demonstrate its application to five marine species (Atlantic cod, Atlantic herring, five-bearded rockling, European sprat and thinlip mullet), which differ in life history strategies and biogeographic distributions, but all rely on intertidal nursery habitats-areas particularly susceptible to anthropogenic change. In all simulations, resource availability had a stronger influence on fish performance than temperature. Nevertheless, the model also revealed how and why higher temperatures often decreased fitness and/or survival of specific types of species. We made no changes to the model structure for different species, and the resulting model predictions were not fitted but were based on eco-physiological first principles. Comparison between modelled and empirical data collected in the shallow Wadden Sea (southern North Sea) confirmed benefits of warming to thermophilic, range-expanding species, while core (established) species at their lower latitudinal limits of their distribution face local extirpation. The model allows insight into more variables than often reported from survey and monitoring efforts, such as reproductive output. The model's broad applicability across a range of species, geographic regions and research objectives makes it valuable for generating knowledge needed to buttress actions aimed at addressing ecological and conservation challenges in a future climate.

Environmental changes can influence species development, growth, size, distribution, and abundance, and when having a negative impact, they can potentially lead to a species' decline, and ultimately its local extinction. Consequently, evaluating the impacts of ocean global change drivers, in isolation and in combination, is particularly relevant for ecologically and economically important species which guarantee food security and income for coastal communities. This study aimed to determine the physiological responses of the northern shrimp Pandalus borealis to different combinations of ocean warming (OW), acidification (OA) and hypoxia at multiple levels of its biological organization (i.e. from the whole-organism to the cell), to help in predicting with greater accuracy the fate of this species in a rapidly changing ocean. To do so, shrimp were exposed for 30 d to different combinations of seawater temperature (2, 6 or 10°C), pH (7.75 or 7.40 pH_T) and oxygen (100 or 35% relative to air saturation), and their survival, whole-organism aerobic performance, and cellular energetic capacity were characterized. Our results show that shrimp were overall tolerant to the isolated effects of OW, OA and hypoxia, but when exposed to combined drivers their survival and whole-organism aerobic performance severely decreased. Isolated and combined drivers had overall no effect on enzyme activity, suggesting a low capacity for metabolic reorganization. Nonetheless, under combined drivers, we observed an adjustment of the mitochondrial enzyme stoichiometry that might help cells to maintain their energy production efficiency. Overall, the northern shrimp's physiological status is compromised under combined ocean global change drivers, which together with the high mortality levels observed, point to a potential risk for local commercial collapse. Our results will be useful to refine mechanistic modelling for future abundance and distribution, in order to improve stock assessments, management and conservation of the northern shrimp under ongoing global changes.

Atlantic tarpon (Megalops atlanticus) are prized sportfish found through the Gulf of Mexico/America. Atlantic tarpon populations are also considered vulnerable to extinction, and thus many of the recreational fisheries targeting Atlantic tarpon in North America are limited to catch-and-release (CAR). While CAR procedures are common and effective means of protecting recreational sportfish species, it is important to recognize that species-specific traits can impact their efficacy. Here, we sought to explore the importance of Atlantic tarpon air-breathing behaviour in the context of recovery from exercise, which may impact their vulnerability to CAR angling events. A first series of experiments demonstrated that Atlantic tarpon increased air breathing rate following exposure to hypoxia-reinforcing their status as a facultative air-breather-but not following exhaustive exercise. A second series of experiments assessed whether the recovery of biochemical indicators of exhaustive exercise stress in the white muscle and plasma would be impacted by restricted air access during recovery. For fish with access to air, normal patterns of exhaustive exercise were noted in the plasma and white muscle with the exception that haematological parameters were unaffected by exercise. Access to air resulted in no significant differences in recovery profiles at the 1-h time point. Interestingly, exercise resulted in a significant and sustained reduction in red blood cell pH, which coincided with a significant impairment in oxygen binding affinity at higher oxygen partial pressures, possibly explaining why air-breathing behaviour is not beneficial during exercise recovery. Overall, these data suggest that Atlantic tarpon conform to typical patterns of exercise recovery in fishes and that no special consideration are required with respect to CAR angling.

Risk assessments have identified prey limitation as one of the strongest risk factors for juvenile salmon survival under climate change. In British Columbia, Canada, juvenile Chinook salmon (Oncorhynchus tshawytscha) may experience prolonged periods of food deprivation upon marine entry and during their first marine winter. We assessed the physiological and transcriptional consequences of food deprivation to discover and develop mRNA-based biomarkers for food deprivation in the gill of juvenile Chinook salmon. Gill and liver tissue were collected from juvenile Chinook salmon held at 16 or 8°C that were fed or food deprived for up to 56 days and during a 21-day refeeding period. Chinook salmon at 16 and 8°C were able to withstand food deprivation for periods of 35 and 56 days, respectively, with declines in body morphometrics, hepatosomatic index, insulin-like growth factor-1 and energy density observed in food-deprived individuals, followed by rapid recovery during refeeding. RNA-sequencing at the end of the food deprivation period revealed candidate biomarkers for food deprivation representing structural and functional components of the gill as well as metabolic processes like lipid storage and energy metabolism in the liver. Using the strongest 12 gill biomarkers paired with high-throughput qPCR and a random forest classification model, transcriptional signatures of food deprivation were detected within 14 to 28 days following food deprivation and persisted for at least 6 days following refeeding. These gill biomarkers can be non-lethally applied to wild juvenile salmon to answer long standing questions regarding food deprivation and the drivers of mortality during their early marine migration and overwintering.

Freshwater mussel populations are declining worldwide, but the causes and mechanisms of these declines are poorly understood. Biomarkers that reflect the health or fitness of individual mussels are needed for understanding causes of mussel declines, but existing approaches each have weaknesses. We conducted two laboratory experiments to examine the utility of the cellular energy allocation (CEA) model for assessing juvenile mussel responses to stress induced by food limitation. The CEA assesses the energetic status of an organism as CEA = E _a/E _c, where E _a is available energy reserves (total carbohydrates, protein, and lipids) and E _c is energy consumption, estimated using electron transport system (ETS) activity as a proxy for respiration rate and metabolic demands. Experiment 1 evaluated the effects of food abundance (fed and unfed) on CEA and its component biomarkers at a single temperature (mean = 26.8°C) over 23 days. Experiment 2 evaluated the response of ETS activity to food abundance (unfed, low food, high food) in relation to temperature (20, 25, 30°C) over 27 days. In Experiment 1, most constituent biomarkers were lower in unfed mussels, but CEA did not differ between treatments because E _a and E _c declined by similar magnitudes. In Experiment 2, ETS declined with decreasing food abundance, but only at 25 and 30°C, and ETS was affected by temperature only in the unfed treatment. The ETS enzyme assay can be an informative biomarker of stress, but it requires accounting for confounding factors such as food, temperature, and species identity, as well as the lag time in response of ETS relative to respiration rate. Despite its value as a robust, holistic stress biomarker in other organisms, CEA may have limited usefulness for bivalves because of their tendency to reduce feeding and energy consumption under stress, which results in a simultaneous decline in E _a and E _c.

Remnant populations of Myricaria laxiflora on river islands along the Yangtze River enter dormancy and endure varying degrees of flooding in summer, with their growth and development recovering in autumn. In this study, M. laxiflora plants were subjected to controlled flooding, and the changes in plant hormones and metabolic enzymes in different stages of recovery growth were measured to elucidate the biochemical mechanisms of summer flooding on plant recovery. Our findings indicated that flooding duration and depth significantly affected the levels of hormones during recovery growth. Compared to the control, cytokinin (CTK), gibberellin (GA) and abscisic acid (ABA) increased by 120.04%-178.53%, 26.07%-56.20% and 36.71%-79.81, respectively, while indole-3-acetic acid (IAA) decreased by 4.88%-26.38% with different flooding durations. Moreover, summer flooding altered metabolic enzymes in M. laxiflora during recovery growth. Under different flooding durations, ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and RuBisCO-activating enzyme (RCA) increased by 117.94%-185.93% and 55.51%-98.19%, respectively. With different flooding depths, RCA increased by 107.12%-190.55%, while phosphoenolpyruvate carboxylase (PEPC) decreased by 9.37%-20.92%. Pearson's correlation analysis indicated relationships between the changes in hormones (IAA, ABA, CTK and GA) and enzymes (RCA, RuBisCO and PEPC) induced by summer flooding. These correlations indicated that the alternations of hormones induced by summer flooding may influence plant physiology through the modulation of metabolic enzymes. The increasing CTK, GA, ABA, RuBisCO and RCA, and decreasing IAA and PEPC would enhance photosynthetic physiology and mitigate respiratory physiology, thereby facilitating plant recovery growth. It is suggested that riverbanks for population restoration of M. laxiflora have to annually experience a period of flooding in the in situ conservation.

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