Conservation Physiology最新文献

Faecal hormone metabolite (FHM) analyses are increasingly used as a non-invasive method to evaluate physiological stress in wild populations, especially those of conservation concern. In cetaceans, faecal collection from the ocean surface results in considerable variation in sample volume and density. Knowledge of the distribution of hormone metabolites within a faecal sample is limited, but is an important consideration when interpreting values. Here we investigated the variability of glucocorticoid (fGCM) and thyroid (fTHM) metabolites within fish-eating resident killer whale faeces by comparing mean concentration, standard deviation (SD) and coefficient of variation (CV) among three treatment groups: sub-samples, pooled sub-samples and homogenized pooled sub-samples from the same defecation event. No significant difference was found in the mean concentration of fGCM and fTHM across treatment groups. The mean SD for fGCM was significantly higher in sub-samples than in pooled and homogenized treatment groups (P < 0.05), while differences in the mean SD of fTHM were not significant among treatment groups. Overall, the CV of FHM measurements was reduced to less than 15% and 10%, respectively, by pooling and homogenizing the sub-samples prior to analysis. We found high correlation in fGCM and fTHM across all treatments, suggesting that values from sub-samples were generally representative of the overall faecal sample. These findings help guide methods for processing cetacean faecal samples and interpreting associated FHM data.

The green sea turtle (Chelonia mydas), a globally endangered marine reptile, faces significant population declines due to anthropogenic and environmental pressures. Captive rehabilitation programs are critical for conservation, yet captivity-induced physiological deviations may compromise post-release survival. This study establishes haematological and biochemical reference intervals for pre-release captive C. mydas (n = 40) various across juvenile, subadult, and adult life stages, and identifies key deviations from wild baselines. We found pronounced captivity-specific alterations, including elevated immature red blood cell counts and ghost cell counts in juveniles, which indicated dysregulated erythropoiesis and oxidative stress. Ontogenetic shifts revealed maladaptive macrocytic erythrocytosis in adults, likely linked to limited exercise and dietary imbalances. Biochemically, captive adults showed hyperproteinemia (total protein, 73.35 g/l) and dyslipidemia (total cholesterol, 8.98 mmol/l triglycerides, 1.53 mmol/l), indicating high-protein, high-fat diets, while hypoglucagonemia (glucose, 2.83 mmol/l) suggested compromised energy reserves. Age-dependent immune activity was observed, with juveniles exhibiting elevated leukocyte counts (19.34 × 10⁹/l), potentially due to chronic stress. These findings underscore metabolic and haematological adaptations in captivity that may hinder post-release resilience. Key biomarkers, such as immature red cell count, glucose, and lipid profiles, should guide release readiness assessments, thus ensuring rehabilitated turtles are physiologically primed for survival. This study provides a critical framework for enhancing the efficacy of sea turtle conservation translocations.

The blue shark (Prionace glauca) is the most frequently by-caught species in longline fisheries targeting swordfish in the Mediterranean Sea. The IUCN classifies the Mediterranean blue shark population as critically endangered, but no information on haematological or biochemical parameters is available for this population. Based on a multi-year dataset of 63 blue sharks (Prionace glauca) and 18 physiological parameters, this study provides the first detailed insights into the variability of physiological indicators following bycatch in the Mediterranean Sea. We also examined differences across three post-capture condition groups and assessed the potential influence of sex and life stage (juvenile vs. adult) on physiological variability. While no significant differences emerged between sexes or life stages, clear distinctions were observed between condition groups, particularly when compared to moribund or dead individuals (condition group 3). These sharks showed signs of enhanced physiological stress, including reduced glucose, elevated lactate, and altered osmoregulatory function (lower urea and chloride, higher phosphorus). These patterns align with stress responses previously described in other shark species. Overall, the study provides a valuable baseline for future research into the physiology and conservation of Mediterranean blue sharks' population.

Aquaculture plays a crucial role in global food security and is being increasingly used to aid species and ecosystem conservation. However, concerns over environmental impact of aquaculture expansion are driving research into ecosystem approaches to aquaculture. Ecosystem approaches to aquaculture require understanding of the relationship between aquafeeds and aquaculture species to maximize consumer growth, quantify elemental flow of nutrients and minimize waste output. Conventional bioenergetic models typically assume fixed elemental ratios to quantify metabolic processes and do not consider an organism's nutrient demand. A new bridging framework, Geometric Stoichiometry (GS), unifies nutritional geometry and ecological stoichiometry disciplines using macromolecules as currencies and dietary regulation to balance nutrient deficits and excesses by the consumer. We present the first application of the GS framework to aquaculture by investigating how different formulated feed ingredients affect intakes to maintain C:N homeostasis, growth and waste output using three opportunistic datasets for an emerging aquaculture species, slipper lobster (Thenus australiensis). Our GS model results indicate that protein sources and their inclusion levels drive the most variation in feed intake and growth. It also predicts highest nitrogenous waste for fish meal and lowest for squid by-product meal feeds. Our results highlight the need for targeted experiments to further refine the GS model to help support environmental management and formulate low-impact feeds for aquaculture.

In the field of conservation physiology, there is often a trade off between conducting research in controlled laboratory settings or in inherently variable field environments. However, this belief sets up a false dichotomy where laboratory experiments are perceived as providing precise, mechanistic understanding with low variability at the cost of environmental realism while field studies are ecologically relevant but criticized for generating inconsistent evidence that is difficult to interpret and replicate. Despite the perceived binary view, these approaches are not in opposition to one another, but rather form a continuum along increasing ecological complexity. Here, we argue that it is possible to mindfully and purposefully design studies and develop integrative collaborations in conservation physiology that span the lab-field continuum to address pressing environmentally-relevant questions that can be used to inform policy and practice. We first outline the advantages and disadvantages of different approaches to knowledge generation. We then highlight ways to bridge the lab-field divide though leveraging the advantages provided by different approaches to build a more comprehensive understanding of the natural world, including how recent technological advances can help connect lab- and field-based research. Next, we discuss the importance of partnership and collaboration across sectors for informing our understanding of ecological patterns and physiological processes. Finally, we reflect on how to best translate physiological research into action and the reciprocal role that environmental practitioners can have in driving research questions in conservation physiology.

Freshwater environments are experiencing rapid changes in seasonal temperature and water flows that could impact threatened aquatic species. Environmental stressors experienced by mothers can influence the size and quality of fish eggs creating downstream effects on larval fitness. Cool water fish species like Pacific salmon with extended periods of embryonic development may be especially vulnerable to changing environmental conditions. To gain insight into the factors influencing embryonic physiology in fish, the relationship between parental genetics, egg size and embryo metabolism was examined in developing Chinook salmon (Oncorhyncus tshawytcha) and pink salmon (Oncorhyncus gorbuscha) embryos, as these species exhibit distinct differences in egg size and life history strategies. Egg size was found to have a relatively limited effect on embryo metabolism with parental genetics having a larger effect on the embryos of these species. Maternal genetics influenced embryonic metabolic rate more in the early stages of development than at later stages of development. These findings suggest that parental genetics or epigenetics is a key factor determining the metabolic rates of salmon embryos and that genetics should be considered when seeking to understand how environmental change will impact threatened fish species, like Pacific salmon.

Sea turtle health assessments can be strengthened by developing conserved biomarkers that discriminate between healthy and diseased states. Serum amyloid A, myeloid-related protein 126 and cardiac troponin C (CTNC) were explored as potential biomarkers of sea turtle health. Plasma concentrations initially quantified using a targeted SPARCL™ assay significantly differed between moribund (n = 15) and recovered (n = 5) loggerhead turtles (Caretta caretta). There was a negative correlation between myeloid-related protein 126 and packed cell volume (r = -0.612, P = 0.005) and total solids (r = -0.497, P = 0.03) and between and Fulton's body condition index (r = -0.684, P = 0.001). Serum amyloid A showed a relatively high interquartile range (IQR) in moribund turtles and no significant correlations with clinical parameters. Myeloid-related protein 126 and cardiac troponin C were further evaluated by an enzyme-linked immunosorbent assay in a larger dataset of loggerhead, Kemp's ridley (Lepidochelys kempii) and green (Chelonia mydas) turtles. Plasma myeloid-related protein 126 was significantly lower in captive healthy (n = 7) and recovered (n = 23) turtles than in moribund (n = 25) and nesting green (n = 58) turtles. Green turtles with fibropapillomatosis (n = 10) were not significantly different from any group. Discriminating values between healthy/recovered and moribund turtles were 1.89 and 1.97 ng/ml by receiver operating characteristic and logistic regression analyses, respectively. Myeloid-related protein 126 decreased in successfully rehabilitated turtles (n = 18 turtles; n = 67 blood samples) and was negatively correlated with body condition score (r = -0.672, P < 0.001) and packed cell volume (r = -0.443, P = 0.009). Cardiac troponin C was significantly higher (P = 0.049) in moribund turtles (n = 16) compared to healthy/recovered turtles (n = 7) and in moribund samples (n = 11) compared to recovered samples (n = 11) in serially sampled turtles (P = 0.015), but was not predictive of health status. Myeloid-related protein 126 represents a strong biomarker candidate in sea turtles. Cardiac troponin C warrants further evaluation in a larger dataset and serum amyloid A requires examination of variables affecting pathophysiologic responses in sea turtles.

Invasive species can alter the ecology of protected areas, substantially lowering the habitat quality for vertebrate communities. The Lower Imenti Forest on Mt. Kenya's northeastern slope has experienced habitat disturbance, degrading the system and resulting in the establishment of invasive species, including lantana (Lantana camara), throughout the area. Following reports of high mortality and poor conditions among the African savanna elephants (Loxodonta africana) inhabiting the area, we assessed the status of two endocrine indicators of their physiological condition. Specifically, we assessed the physiological stress response by measuring faecal glucocorticoid metabolites (fGCM) and the nutritional stress response by measuring faecal thyroid (fT3) concentrations in elephant faecal samples collected in the forest. To better interpret the hormone levels, we compared the hormone concentrations in the Imenti faecal samples to concentrations from reference levels indicative of extreme nutritional stress (from faecal samples of elephants experiencing drought-induced mortality) and adrenal stress (from elephants experiencing high levels of human-elephant conflict). The concentrations of fT3, a biomarker of nutritional stress response, found in elephant faecal samples from the Lower Imenti Forest were lower than the drought-stressed reference levels, suggesting lower levels of energy intake and assimilation of forage resources in elephants from this area. The concentration of fGCM, a biomarker of physiological stress response, was higher than the human-elephant conflict reference levels, suggesting the elephants in Lower Imenti were experiencing a higher physiological stress response. We found no differences between fT3 and fGCM concentrations in samples assigned to different age classes (juvenile, subadults, adults), suggesting the physiological problems were not age specific. Findings from our physiological study suggest that restricted movement and reduced forage availability due to lantana infestation in the Lower Imenti Forest may be driving the elevated nutritional stress, potentially contributing to the concerning mortality observed in the area. We discuss the use of endocrine markers to ascertain wildlife responses to degraded habitats.