Conservation Physiology最新文献

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.

Graphical Abstract.

Environmental and anthropogenic factors significantly drive adrenocortical activity of animals, affecting their behaviour, distribution and survival. Understanding how animals respond to such drivers is essential for effective conservation. Spraint samples from free-ranging African clawless otters (Aonyx capensis) and camera trap data were collected from study sites categorized as natural or artificially transformed based on differences in anthropogenic disturbance levels. To determine if there were significant differences in faecal glucocorticoid metabolite (fGCM) concentrations between the Natural (Kalkfontein Nature Reserve) and Transformed (Millstream Farm) sites, we ran a linear model that included sex, season, habitat type and their interaction. fGCM concentrations differed significantly between the sexes (df = 1; F _1,106 = 11.180; P = 0.001); with males (n = 32; 0.608 ± 0.367 μg/g DW) having significantly higher fGCM concentrations compared to females (n = 79; 0.414 ± 0.399 μg/g DW, P = 0.006). The fGCM concentrations differed significantly between seasons (df = 1; F _1,106 = 45.268; P < 0.001), with those in the dry winter season significantly higher (n = 66; 0.631 ± 0.420 μg/g DW), compared to the wet summer season (n = 45; 0.234 ± 0.199 μg/g DW). The fGCM concentrations differed significantly between habitat type (df = 1; F _1,106 = 6.026; P = 0.016) with fGCM concentrations of individuals from the KNR natural site (n = 34; 0.285 ± 0.199 μg/g DW) being significantly lower compared to those measured in individuals at the MF transformed site (n = 77; 0.552 ± 0.436 μg/g DW). Finally, the difference in fGCM concentrations between locations however were not dependent on season (df = 1; F _1,106 = 0.369; P = 0.544). Anthropogenic disturbance and alterations to the natural and varied prey-base of African clawless otters in an anthropogenically transformed site significantly affect their adrenocortical activity. Future research should focus on how these animals respond to anthropogenic disturbance, and what effects disturbance has on their behaviour, distribution and fitness. Mitigating human-otter conflict requires incorporating such behavioural responses into management strategies.

Brook trout (Salvelinus fontinalis) are threatened by emergent and intensifying anthropogenic stressors that have uncertain cumulative effects. Effectively managing and conserving brook trout will require robust and timely information on population health-particularly where human impacts on brook trout are multiple and intense. Advanced molecular genomic tools, such as quantitative PCR assays that identify and characterize stress in fish, may provide such information, and are advancing due to an accumulation of research on transcript-level stress responses in various fishes. We used a version of the Stress Transcriptional Profiling Chip developed by the Genomic Network for Fish Identification, Stress and Health to identify changes in gene transcription related to temperature and catch-and-release angling in wild, small stream brook trout in southern Ontario's West Credit River. We angled and took non-lethal gill tissue samples from brook trout either immediately or one hour post-capture in both cool, spring conditions and warm, midsummer conditions. Transcript abundances of heat shock transcription factor 1 (hsf1), heat shock cognate 71 kDa protein (hsc70), heat shock protein 70a (hsp70a), metallothionein A (mtA), and 11β-hydroxysteroid dehydrogenase 2 (hsd11b2) increased significantly in thermally stressful, midsummer conditions. Transcript abundances of hsf1 and insulin-like growth factor 1 (igf1) increased after angling in cool, spring conditions, but evidence of angling effects on transcript abundances was generally weak. These results contribute to a growing understanding of transcript-level stress responses in fish, which may be used to monitor brook trout population health locally, and create tools to monitor salmonid population health more broadly.

The feeding ecology of wildlife populations has important implications for individual health, population productivity and distribution patterns. For ursids (bears), food resources and feeding behaviour primarily affect population dynamics via effects on cub production and survival. Much of what is known about the feeding ecology of bears is based on analyses of tissues collected from capture-based research efforts, harvested animals or non-invasive approaches. However, inference about diet from hair has been limited by a lack of quantitative data on the timing of the moult and hair growth rates. We conducted a study to develop and test two methods of quantifying hair growth rates of three species in the family Ursidae (n = 1 polar bear, Ursus maritimus; n = 3 black bears, Ursus americanus; n = 3 grizzly bears, Ursus arctos horribilis). We implemented visual and biochemical approaches, proven safe for humans and other mammals, in a zoo setting. These methods relied on voluntary bear behaviours trained using positive reinforcement. The two methods were: (i) applying a small patch of hair dye (or bleach) on the rump or foreleg, and (ii) feeding an isotopically labelled amino acid (glycine) capsule that 'marks' time at a particular location as it is incorporated within the hair. We collected hair at regular intervals (every 1-2 weeks) for five months from body locations on the bear consistent with commonly sampled collection points in wild-caught bears. We found that both methods effectively identified periods of hair growth and detected individual and seasonal variation in hair growth rates. Average guard hair growth rates ranged between 0.10 and 1.05 mm day^-1 across the three species. This study provides the first step for developing a foundation for incorporating seasonality in wild-collected bear hair samples by assessing growth over an annual cycle.

Climate change has resulted in increased incidence and variability of warming episodes in cold-water streams that support salmonids. The capacity to acclimate to warm temperatures may allow cold-water fish to persist in spite of changing thermal regimes, but accurately predicting fish performance under fluctuating stream temperatures also requires understanding re-acclimation to cool water, which is less well understood. We tested how thermal acclimation to warm temperatures and re-acclimation to cool water affected thermal tolerance and physiological endpoints in juvenile brook trout (Salvelinus fontinalis). We show that an initial thermal exposure (22°C, ΔT = 7°C) of 3, 7 and 14 days (but not 1 day) improved critical thermal maximum (CT_max) after a 14-day re-acclimation to cooler temperatures (15°C). Fish growth during the re-acclimation period decreased with increasing duration of initial thermal exposure (22°C). Physiological parameters associated with thermal acclimation (cortisol, glucose, haematocrit and haemoglobin) were lower at 15°C re-acclimation temperature than at the initial thermal treatment (22°C) and in some cases, lower than the 15°C control. Muscle HSP70 protein increased early (1 day) as part of the warm acclimation process and remained elevated at lower levels for up to 14 days. During re-acclimation to 15°C, HSP70 decreased relative to initial measures at 22°C. Fish exposed to the longest thermal treatment (22°C for 14 days) maintained elevated CT_max after 30 days of re-acclimation to 15°C without observed differences in the measured physiological endpoints but returned to control levels after 42 days at 15°C. This work shows that high-temperature acclimation effects in brook trout are retained for up to 30 days following re-acclimation to cool temperatures, and that isolated warming events may be expected to temporarily enhance thermal tolerance in subsequent thermal challenges.