Conservation Physiology最新文献

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.

Warming in high-latitude marine ecosystems is leading to the borealization of Arctic communities. Species-specific responses to temperature provide insight into potential co-occurrence or competitive advantage between Arctic and boreal species. Ocean acidification may also lead to unique species-specific responses. At the Pacific-Arctic interface, larval distributions of the boreal Pacific cod (Gadus macrocephalus) are increasingly overlapping with those of Arctic cod (Boreogadus saida). We assessed larval metabolic capacities by measuring metabolic enzyme activities of citrate synthase (CS; aerobic metabolism), lactate dehydrogenase (LDH; anaerobic metabolism), and β-hydroxyacyl CoA dehydrogenase (HOAD; fatty acid metabolism). Throughout early development, Pacific cod enzyme activities, including glycolytic capacity, were higher, and fatty acid metabolism lower than Arctic cod enzyme activities. These responses may reflect a more active larval lifestyle of Pacific cod. Separately, larvae were reared in multiple temperatures (Pacific cod: 3, 6, 10°C; Arctic cod 1.8, 5, 7.3°C) and pCO₂ levels (ambient = ~350 μatm; high = ~1500 μatm). At the cold temperature, Pacific cod enzyme activities were higher than at the control temperature, indicating they were acclimating but less cold adapted than Arctic cod. Arctic cod HOAD activity and LDH:CS ratio were elevated under warmer temperatures suggesting increased energy demand. Elevated pCO₂ levels only affected larvae at their control temperature and resulted in decreased Pacific cod HOAD activity and increased Arctic cod CS and HOAD activities. This indicates differing sensitivities to ocean acidification between the species. Overall, Pacific cod may continue to be constrained in their northern habitat by cold temperatures, but under slight warming to optimal growing temperatures, Pacific cod will have competitive advantage over Arctic cod.

Sea trout (Salmo trutta) migrate to the seawater (SW) for increased food availability. However, heavy infestations with salmon louse (Lepeophtheirus salmonis) can make them return to freshwater (FW). The aim of the present study was to map if and how reinfection with salmon louse and repeated FW exposure affects survival, growth rate, hepatosomatic index (HSI), acid base regulation (plasma pH, strong ion difference), osmoregulation (plasma ions, osmolality) and semen quality (fertilization rate, embryo/fry survival) in sea trout. Individually tagged sea trout (~100 g) were infected with louse copepodids in SW and then switched to FW at the louse pre-adult stage. Twelve days thereafter, FW was replaced with SW, and a second similar louse infection and salinity change were performed. Treatment groups were (i) uninfected control, and infected during the first (ii), second (iii) or both (iv) infection periods. The study ended after a final three-month follow-up in FW involving egg fertilization with sperm of previously infected and uninfected control mature male trout. Lice infection did not affect fish mortality or semen quality, but elevated HSI. In SW, lice-infected fish had lower specific growth rate in weight, higher plasma pH, Na⁺, Cl^- and osmolality, and lower plasma strong ionic difference and Na⁺/Cl^- ratio compared to uninfected fish. After 48 h in FW, lice-infected fish still had higher plasma pH, while plasma Na⁺, Cl^- and osmolality were lower and plasma Na⁺/Cl^- ratio higher in infected than uninfected fish. Louse reinfection did not affect any end points compared to single infection. The results demonstrate that salmon louse disturbs sea trout's Cl^- more than Na⁺ regulation, resulting in reduced hypo-osmotic and hyper-osmotic abilities in SW and FW, respectively. Further, a strong effect of lice on acid-base regulation is evident, shown by elevated plasma pH in both SW and FW.

Rivers are under intense anthropogenic pressure, leading to increases in water temperature and changes in physicochemical properties, which threaten aquatic biota. Understanding how these environmental changes affect heat tolerance in freshwater organisms is critical for assessing the status of wild populations and predicting their vulnerability under global warming scenarios. Here, we studied how body mass and heat tolerance, measured by thermal death time (TDTs) curves under normoxic and hypoxic conditions, vary among populations of the Chilean pencil catfish Trichomycterus areolatus inhabiting a Mediterranean river in central Chile. We detected significant differences in fork length, body mass and Fulton's condition factor among populations, with fish from reference sites being significantly larger and in better condition. Although heat tolerance did not differ among populations, we found a strong effect of body mass under both normoxic and hypoxic experimental conditions. Simulations combining laboratory-derived TDTs with field-recorded water temperatures suggest that the window of vulnerability occurs at lower temperatures but over longer exposures, indicating that heat stress has chronic effects on T. areolatus. Accordingly, the cumulative survival simulation using the warmer season records is predicted to be lower in river sections with reduced levels of dissolved oxygen. While our results did not show population level differences in thermal tolerance per se, the significant effect of individual body mass may translate into varying vulnerability among populations, given their marked differences in body mass distribution. These findings highlight how the interplay between water quality, body condition and heat tolerance shapes the vulnerability of T. areolatus populations to warming. Thus, an integrated perspective is essential to properly assess the impact of global warming on wild freshwater populations.

Anthropogenically induced environmental change has contributed to population declines of important estuarine species, such as oysters. Some restoration programs focused on severely depleted oyster populations in estuarine environments are using hatchery-sourced animals to supplement low wild recruitment. However, carry-over effects, when early life experiences affect later life responses, are known to affect the success of cultured individuals in the wild. The objective of this study was to investigate carry-over effects on eastern oyster (Crassostrea virginica) larvae cultured under a range of salinities-an important environmental stressor on natural populations. Eastern oyster larvae were grown and settled across a range of salinities until large enough to transplant onto two field sites with different average salinities. Larval culture salinity significantly affected post-metamorphosed oyster growth rates until 45 days post-set, where oysters from suboptimal low salinity cultures grew faster immediately post-metamorphosed. Later, larval culture salinity significantly affected oxygen consumption rates and condition index of oysters from the field, and field site significantly interacted with larval culture salinity on physiological metrics. High larval salinity cultures produced oysters with lower energetic expenditures and higher condition index values, on average. Long-term physiological performance of animals depended on both the early culture environment and the subsequent field conditions, and because of the interaction of culture conditions and transplant site, care should be taken to select culture conditions that match those at target relocation sites.