Biomarkers of oxidative status: missing tools in conservation physiology

Ocean acidification aggravates the toxicity of deltamethrin in Haliotis discus hannai: Insights from immune response, histopathology and physiological responses

Ocean acidification (OA) and other environmental factors can collectively affect marine organisms. Deltamethrin (DM), a type II pyrethroid insecticide, has been widely detected in coastal and estuarine areas, while little attention has been given to the combined effects of DM and OA. In this study, Haliotis discus hannai was exposed to three pH levels (8.1, 7.7 and 7.4) and three DM nominal concentrations (0 μg/L, 0.6 μg/L and 6 μg/L) for 14 and 28 days. The results indicated that experimental acidification and/or DM exposure led to impaired immune function and pathological damage. Additionally, acidified conditions and DM exposure induced oxidative stress, and gills are more sensitive than digestive glands. With increasing pCO2 and DM nominal concentrations, superoxide dismutase (SOD) activity decreased, whereas catalase (CAT) and glutathione S-transferase (GST) activities increased in the gills. Moreover, the expression levels of Toll-like receptor (TLR) pathway-related genes were upregulated after exposure. Integrated biomarker response (IBR) analysis proved that acidified conditions and/or DM detrimentally affected the overall fitness of H. discus hannai, and co-exposure to experimental acidification and DM was the most stressful condition. This study emphasizes the necessity of incorporating OA in future pollutant environmental assessments to better elucidate the risks of environmental disturbance.

Effects of environmental factors on the oxidative status of Anemonia viridis in aquaculture systems

Due to its depletion in natural settings, the potential for aquaculture of the cnidarian Anemonia viridis is currently attracting research interest. Knowledge about the physiology of this species is necessary to ensure optimal development of, and well-being in, aquaculture. This study tested the effects of different abiotic (limited sunlight, brackish water) and biotic (integrated multitrophic aquaculture or IMTA) conditions on A. viridis in captivity. Growth and reproduction were measured, and antioxidant status was evaluated in tentacular and columnar tissues as antioxidant enzymatic activity (superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase, glucose 6-phosphate dehydrogenase, glutathione S-transferase and DT-diaphorase), Trolox-equivalent antioxidant capacity (TEAC) and tissue lipid peroxidation (MDA). Animals in the brackish water and IMTA treatments displayed significant changes in glutathione peroxidase, glucose 6-phospate dehydrogenase and TEAC compared to control anemones, with these effects noted primarily in columnar tissue. These results support the relevance of enzymatic pathways involving glutathione as antioxidant mechanisms under osmotic disturbances or ecological interactions. Limited light intensity was not found to be detrimental to the oxidative status of the anemones, despite A. viridis harbouring photosynthetic symbionts, and enhanced growth performance parameters suggested a higher individual weight increase than in control conditions. Lipid peroxidation was not significantly affected in any experimental condition. Principal Component Analysis (PCA) suggested that similar antioxidant status parameters can correlate positively (tentacular parameters) or negatively (columnar parameters) with MDA concentration. In conclusion, aquaculture of Anemonia viridis can be improved under suitable environmental conditions supported by the evaluation of welfare markers based on antioxidant status.

An evolving roadmap: using mitochondrial physiology to help guide conservation efforts

The crucial role of aerobic energy production in sustaining eukaryotic life positions mitochondrial processes as key determinants of an animal's ability to withstand unpredictable environments. The advent of new techniques facilitating the measurement of mitochondrial function offers an increasingly promising tool for conservation approaches. Herein, we synthesize the current knowledge on the links between mitochondrial bioenergetics, ecophysiology and local adaptation, expanding them to the wider conservation physiology field. We discuss recent findings linking cellular bioenergetics to whole-animal fitness, in the current context of climate change. We summarize topics, questions, methods, pitfalls and caveats to help provide a comprehensive roadmap for studying mitochondria from a conservation perspective. Our overall aim is to help guide conservation in natural populations, outlining the methods and techniques that could be most useful to assess mitochondrial function in the field.

Hepatoprotective effects of magnolol in fatty liver hemorrhagic syndrome hens through shaping gut microbiota and tryptophan metabolic profile

BACKGROUND

Magnolol (MAG) exhibits hepatoprotective activity, however, whether and how MAG regulates the gut microbiota to alleviate fatty liver hemorrhagic syndrome (FLHS) remains unclear. Therefore, we investigated the mechanism of MAG in FLHS laying hens with an emphasis on alterations in the gut-liver axis. We randomly divided 540 56-week-old Hy-line white laying hens with FLSH into 4 groups. The birds were fed a high-fat low-protein (HFLP) diet (CON) or HELP diets supplemented with 200, 400, and 600 mg/kg of MAG (M1, M2, and M3, respectively) for 9 weeks.

RESULTS

Magnolol supplementation increased the laying rate and ameliorated hepatic damage and dysfunction by regulating lipid metabolism, improving intestinal barrier function, and shaping the gut microbiota and tryptophan metabolic profiles. Dietary MAG supplementation downregulated the expression of lipid synthesis genes and upregulated the expression of lipid transport genes at varying degrees. The intestinal barrier function was improved by 200 and 400 mg/kg of MAG supplementation, as evidenced by the increased villus height and mRNA expression of tight junction related genes. Microbiological profile information revealed that MAG changed the gut microbiota, especially by elevating the abundances of Lactobacillus, Faecalibacterium, and Butyricicoccus. Moreover, non-targeted metabolomic analysis showed that MAG significantly promoted tryptophan metabolites, which was positively correlated with the MAG-enriched gut microbiota. The increased tryptophan metabolites could activate aryl hydrocarbon receptor (AhR) and relieved hepatic inflammation and immune response evidenced by the downregulated the gene expression levels of pro-inflammatory cytokines such as interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in the liver. The fecal microbiota transplantation (FMT) experiments further confirmed that the hepatoprotective effect is likely mediated by MAG-altered gut microbiota and their metabolites.

CONCLUSIONS

Magnolol can be an outstanding supplement for the prevention and mitigation of FLHS in laying hens by positively regulating lipid synthesis and transport metabolism, improving the intestinal barrier function, and relieving hepatic inflammation by reshaping the gut microbiota and metabolite profiles through gut microbiota-indole metabolite-hepatic AhR crosstalk. These findings elucidate the mechanisms by which MAG alleviates FLHS and provide a promising method for preventing liver diseases by modulating gut microbiota and their metabolites.

The impact of Roundup® Original DI on the hemolymph metabolism and gill and hepatopancreas oxidative balance of Parastacus promatensis (Crustacea, Decapoda, Parastacidae)

In Brazil, glyphosate is present in more than 130 commercial formulations, and its toxic effects have already been tested in different species to understand its impact on biota Decapod crustaceans are widely used as experimental models due to their biology, sensitivity to pollutants, ease of collection, and maintenance under laboratory conditions. We evaluated the changes in metabolism (hemolymph) and oxidative balance markers (gill and hepatopancreas) of a crayfish (Parastacus promatensis) after exposure to Roundup® (active ingredient: glyphosate). The crayfish were captured in the Garapiá stream within the Center for Research and Conservation of Nature Pró-Mata, Brazil. We collected adult animals outside (fall) and during (spring) the breeding season. The animals were transported in buckets with cooled and aerated water from the collection site to the aquatic animal maintenance room at the university. After acclimatization, the animals were exposed to different concentrations of glyphosate (0, 65, 260, 520, and 780 µg/L). The results showed a significant variation in the hemolymph glucose, lactate, and protein levels. We observed variations in the tissue antioxidant enzymatic activity after exposure to glyphosate. Finally, the increase in oxidative damage required a high energy demand from the animals to maintain their fitness, which makes them more vulnerable to stress factors added to the habitat.

Oxidative status: A general but overlooked indicator of welfare across animal species?

Because of their ubiquity, plasticity, and direct effects on the nervous system, markers of oxidative status may be of great value to assess animal welfare across species and conditions in the wild. However, welfare biologists have not yet seized this opportunity, possibly because the validity of these markers as welfare indicators remains questionable. A validation process was, therefore, performed here using a meta-analytical approach considering three conditions assumed to impair the welfare of animals. With very few exceptions, two of the four considered markers consistently varied across these negatively-valenced conditions. By highlighting the current underrepresentation of markers of oxidative status in animal welfare studies, and by concretely illustrating that some of these markers can consistently reflect negative affective states, this article aims to encourage biologists to include these physiological markers in their toolbox to better measure, monitor, and perhaps also improve the welfare of animals in their natural habitat.

A blood-based multi-biomarker approach reveals different physiological responses of common kestrels to contrasting environments

The increase of urbanization and agricultural activities is causing a dramatic reduction of natural environments. As a consequence, animals need to physiologically adjust to these novel environments, in order to exploit them for foraging and breeding. The aim of this work was to compare the physiological status among nestling common kestrels (Falco tinnunculus) that were raised in nest-boxes located in more natural, rural, or urban areas in a landscape with a mosaic of land uses around Rome in Central Italy. A blood-based multi-biomarker approach was applied to evaluate physiological responses at multiple levels, including antioxidant concentrations, immunological functions, genotoxicity, and neurotoxicity. We found lower concentrations of glutathione and GSH:GSSG ratio values and higher proportions of monocytes in urban birds compared to the other areas. We also found higher DNA damage in rural compared to urban and natural krestels and inhibition of butyrylcholinesterase activity in urban and natural birds compared to rural area. Finally, we found similar values among study areas for respiratory burst, complement system, bactericidal capacity, and plasma non-enzymatic antioxidant capacity. These results suggest that (i) city life does not necessarily cause physiological alterations in kestrels compared to life in other habitats, and (ii) environmental pressures are likely to differ in typology and intensity across habitats requiring specific responses that a multi-biomarker approach can help to detect. Further studies are needed to assess which factors are responsible for the physiological differences among city, rural, and natural birds, and whether these differences are consistent across time and space.

Interactive abiotic and biotic stressor impacts on a stream-dwelling amphibian

Organisms within freshwater and marine environments are subject to a diverse range of often co-occurring abiotic and biotic stressors. Despite growing awareness of the complex multistress systems at play in aquatic ecosystems, many questions remain regarding how simultaneous stressors interact with one another and jointly impact aquatic species. We looked at multistress interactions in a protected stream ecosystem in Mendocino County, California. Specifically, we examined how diurnal temperature variation, turbidity, and predator cues altered the movement speed of larval Pacific giant salamanders (Dicamptodon tenebrosus). In a second experiment, we looked at how simulated low-flow summer conditions impact the expression of heat-shock proteins (HSPs) in the same species. Larvae moved almost one and a half times faster in the presence of chemical cues from trout and suspended sediment, and almost two times faster when both sediment and trout cues were present but were only marginally affected by temperature and visual cues from conspecifics. Interestingly, the order of stressor exposure also appeared to influence larval speed, where exposure to sediment and trout in earlier trials tended to lead to faster speeds in later trials. Additionally, larvae exposed to low-flow conditions had more variable, but not statistically significantly higher, expression of HSPs. Our findings highlight the potential interactive effects of an abiotic stressor, sedimentation, and a biotic stressor, and predator chemical cues on an ecologically important trait: movement speed. Our findings also demonstrate the likely role of HSPs in larval salamander survival in challenging summer conditions. Taken together, these findings show that larval D. tenebrosus responds behaviorally to biotic and abiotic stressors and suggests a possible pathway for physiological tolerance of environmental stress. Consideration of multistress systems and their effects is important for understanding the full effects of co-occurring stressors on aquatic organisms to guide appropriate conservation and management efforts based on ecologically relevant responses of organisms within an environment.

Ecophysiological responses of Liolaemus arambarensis juveniles to experimental temperature variations

Climate change increasingly influences the loss of biodiversity, especially in ectothermic organisms, which depend on environmental temperatures to obtain heat and regulate their life cycle. Studies that aim to understand the impact of temperature variation are important to better understand the possible impacts generated on the homeostasis of ectothermic organisms. Our objective was to characterize the responses of juvenile Liolaemus arambarensis lizards to abrupt changes in temperature, quantifying markers of body condition, intermediary and hormonal metabolism and oxidative balance. We collected 45 juvenile individuals of L. arambarensis (winter: 20 and summer: 25) in Barra do Ribeiro, Brazil. We transported the animals to the laboratory, where they were acclimatized for five days at a temperature of 20 °C, then divided and exposed to temperatures of 10 °C, 20 °C, 30 °C and 40 °C for 24 h. After exposure, the animals were euthanized and the brain, caudal muscle, thigh, and liver tissues were extracted for quantification of biomarkers of metabolism (glycogen and total proteins) and oxidative balance (acetylcholinesterase, superoxide dismutase, catalase, glutathione-S-transferase and lipoperoxidation) and plasma for corticosterone quantification. The results show that L. arambarensis is susceptible to sudden temperature variations, where higher temperatures caused greater activity of antioxidant enzymes, increased lipoperoxidation and higher plasma levels of corticosterone in animals eliminated in winter. The present study demonstrated that abrupt changes in temperature could significantly modify the homeostatic mechanisms of animals, which could lead to oxidative stress and a potential trade-off between survival and growth/reproduction. In this context, the organism mobilizes energy resources for survival, with possible damage to growth and reproduction. Demonstrate that a change in temperature can be a potential factor in extinction for a species given the profile of global climate change.

What happens when the lights are left on? Transcriptomic and phenotypic habituation to light pollution

Artificial light at night (ALAN) is a ubiquitous pollutant worldwide. Exposure can induce immediate behavioral and physiological changes in animals, sometimes leading to severe health consequences. Nevertheless, many organisms persist in light-polluted environments and may have mechanisms of habituating, reducing responses to repeated exposure over time, but this has yet to be tested experimentally. Here, we tested whether zebra finches (Taeniopygia guttata) can habituate to dim (0.3 lux) ALAN, measuring behavior, physiology (oxidative stress and telomere attrition), and gene expression in a repeated measures design, over 6 months. We present evidence of tolerance to chronic exposure, persistent behavioral responses lasting 8 weeks post-exposure, and attenuation of responses to re-exposure. Oxidative stress decreased under chronic ALAN. Changes in the blood transcriptome revealed unique responses to past exposure and re-exposure. Results demonstrate organismal resilience to chronic stressors and shed light on the capacity of birds to persist in an increasingly light-polluted world.

Discussion. Has the human population become a sentinel for the adverse effects of PFAS contamination on wildlife health and endangered species?

Global contamination with per- and polyfluoroalkyl substances (PFAS) poses a threat to both human health and the environment, with significant implications for ecological conservation policies. A growing list of peer-reviewed publications indicates that PFAS can harm wildlife health and that the adverse effects associated with PFAS exposure in wildlife are in concordance with human epidemiological studies. The correlation of cross-species data supports a unique perspective that humans can be regarded as a sentinel for PFAS effects in other species. The health harms due to PFAS are potentially most concerning for populations of endangered and threatened species that are simultaneously exposed to PFAS and other toxic pollutants, and also face threats to their survival due to habitat loss, degradation of ecosystems, and over-harvesting. Human epidemiological studies on the PFAS doses associated with health harm present a rich source of information about potential impacts on wildlife health due to PFAS. Our analysis suggests that national and international efforts to restrict the discharges of PFAS into the environment and to clean up PFAS-contaminated sites present an opportunity to protect wildlife from chemical pollution and to advance species conservation worldwide.

Eating in the city: Experimental effect of anthropogenic food resources on the body condition, nutritional status, and oxidative stress of an urban bioindicator passerine

Urban areas provide a constant and predictable supply of anthropogenic processed food. The House Sparrow (Passer domesticus Linnaeus, 1758), a declining urban bioindicator species, has recently been reported to have a high level of oxidative stress, with urban diet or pollutants proposed as the potential cause. In this study, we aimed to experimentally determine the effects of two urban trophic resource types (bar snack food leftovers and pet food) on sparrows' physical condition, plasma biochemical nutritional parameters, and blood oxidative status in captivity. To exclude the potential previous effect of urban pollutants, 75 House Sparrows were captured from a rural area in SE Spain and kept in outdoor aviaries. Individuals were exposed to one of three diet treatments: control diet (fruit, vegetables, poultry grain mixture), bar snack diet (ultra-processed snacks), or cat food diet (dry pellets) for 20 days. Blood samples were collected before and after diet treatments to analyze the relative change rates of 12 variables, including physical condition, nutritional status, and oxidant-antioxidant status. A principal component analysis was run to identify gradients of variables covariation, and Generalized Linear Mixed Models were used to determine the effect of diets on each selected PC and on raw variables. The bar snack diet led to signs of anemia and malnutrition, and females tended to lose body condition. The cat food diet increased oxidative stress indicators and protein catabolism. Unbalanced urban diets can affect the body condition and nutritional physiology of House Sparrows and may also induce oxidative stress despite the absence of environmental pollution.

Associations between PFAS concentrations and the oxidative status in a free-living songbird (Parus major) near a fluorochemical facility

For the past 7 decades, PFAS have been used in many different products and applications, which has led to a widespread contamination of these compounds. Nevertheless at present, little is known about the effects of these compounds on avian wildlife. Therefore, this study investigated associations between PFAS concentrations in the plasma and the oxidative status (i.e. non-enzymatic antioxidants and biomarkers of oxidative stress) in great tits at two sites near a fluorochemical manufacturing facility. Different PFAS were detected in the blood plasma with a mean ΣPFAS of 16062 pg/μL at the site closest to the facility. The PFAS profile in the plasma consisted mainly of PFOS, PFOA, PFDA and PFDoDA, where concentrations were higher for these compounds at the site closest to the plant. Our results show a clear link between PFAS and the antioxidant status of the birds; total antioxidant capacity and peroxidase activity were higher near the plant site, while the glutaredoxin activity was higher further away. Additionally, positive associations were found between PFDoDA and glutathione-S-transferase activity, between PFOS and glutathione-S-transferase activity, between PFDA and peroxidase activity, and between PFOS and peroxidase activity. Lastly, a negative association was found between plasma PFDA concentrations and the total polyphenol content. Interestingly, malondialdehyde levels did not differ between sites, suggesting lipid peroxidation was not affected. Although our results suggest that great tits with elevated PFAS concentrations did not suffer oxidative damage, the antioxidant defence responses were significantly triggered by PFAS exposure. This implies that the great tits have managed to defend themselves against the possible oxidative damage coming from PFAS contamination, although the upregulated antioxidant defences may have fitness costs. Further, experiments are needed to investigate the specific mechanisms by which PFAS induce oxidative stress in avian species.

Oxidative physiology of two small and highly migratory Arctic seabirds: Arctic terns (Sterna paradisaea) and long-tailed jaegers (Stercorarius longicaudus)

Arctic ecosystems are changing rapidly. The tundra supports nesting migratory seabirds that spend most of their year over the ocean. Migrations are demanding, but it is unclear how physiological capability may equip organisms to respond to their changing environments. For two migratory seabird species nesting in Alaska, USA, the Arctic tern (n = 10) and the long-tailed jaeger (n = 8), we compared oxidative physiology and aerobic capacity measured during incubation and we recorded individual movement paths using electronic tracking tags. Within species, we hypothesized that individuals with longer-distance migrations would show higher oxidative stress and display better aerobic capacity than shorter-distance migrants. We examined blood parameters relative to subsequent fall migration in jaegers and relative to previous spring migration in terns. We present the first measurements of oxidative stress in these species and the first migratory movements of long-tailed jaegers in the Pacific Ocean. Arctic terns displayed positive correlation of oxidative variables, or better integration than jaegers. Relative to physiological sampling, pre-breeding northward migration data were available for terns and post-breeding southward data were available for jaegers. Terns reached a farther maximum distance from the colony than jaegers (16 199 ± 275 km versus 10 947 ± 950 km) and rate of travel northward (447 ± 41.8 km/day) was positively correlated with hematocrit, but we found no other relationships. In jaegers, there were no relationships between individuals' physiology and southward rate of travel (193 ± 52.3 km/day) or migratory distance. While it is not clear whether the much longer migrations of the terns is related to their better integration, or to another factor, our results spark hypotheses that could be evaluated through a controlled phylogenetic study. Species with better integration may be less susceptible to environmental factors that increase oxidative stress, including thermal challenges or changes in prey distribution as the Arctic climate changes rapidly.

Tissue-specific assessment of oxidative status: Wild boar as a case study

In recent decades, there has been a fast-growing interest in using biomarkers of oxidative stress (BOS) in conservation programs of many vertebrate species. Biomarkers of oxidative stress can be measured in different biological samples (e.g., body fluids and tissues). However, since comparisons of the same battery of BOS among tissues of the same individual are scarce in the literature, the chosen target tissues regularly rely on arbitrary decisions. Our research aimed to determine if the oxidative status of free-ranging wild boar (Sus scrofa) naturally infected with Mycobacterium spp (etiological agent of tuberculosis, TB), varies depending on the sample where it was quantified. We compared antioxidant p-nitrophenyl esterase activity (EA), glutathione peroxidase (GPX) concentrations, and total oxidative status (TOS) in serum, lung, spleen, kidney, and muscle of 63 wild boar hunter-harvested in central Spain. Biomarkers of oxidative stress in serum had higher concentrations than in other tissues. The poor agreement between serum and other tissues highlights the importance of running complete BOS assessments in the same fluid or tissue. Further, low concentrations of BOS in tissues of TB-affected individuals were observed, and significant differences between healthy and sick boar were only detected in the serum of individuals developing mild TB and in the muscle of individuals with mild or severe disease status. However, all organs from wild boars affected with mild TB were not in oxidative imbalance compared to healthy control animals, suggesting that wild boars may cope well with TB. Our data indicate that serum and other tissues can be used as BOS in field conservation programs to monitor wildlife population health. Still, context-specific validations are needed to determine the most appropriate samples to use.

Telomeres and anthropogenic disturbances in wildlife: A systematic review and meta-analysis

Human-driven environmental changes are affecting wildlife across the globe. These challenges do not influence species or populations to the same extent and therefore a comprehensive evaluation of organismal health is needed to determine their ultimate impact. Evidence suggests that telomeres (the terminal chromosomal regions) are sensitive to environmental conditions and have been posited as a surrogate for animal health and fitness. Evaluation of their use in an applied ecological context is still scarce. Here, using information from molecular and occupational biomedical studies, we aim to provide ecologists and evolutionary biologists with an accessible synthesis of the links between human disturbances and telomere length. In addition, we perform a systematic review and meta-analysis on studies measuring telomere length in wild/wild-derived animals facing anthropogenic disturbances. Despite the relatively small number of studies to date, our meta-analysis revealed a significant small negative association between disturbances and telomere length (-0.092 [-0.153, -0.031]; n = 28; k = 159). Yet, our systematic review suggests that the use of telomeres as a biomarker to understand the anthropogenic impact on wildlife is limited. We propose some research avenues that will help to broadly evaluate their suitability: (i) further causal studies on the link between human disturbances and telomeres; (ii) investigating the organismal implications, in terms of fitness and performance, of a given telomere length in anthropogenically disturbed scenarios; and (iii) better understanding of the underlying mechanisms of telomere dynamics. Future studies in these facets will help to ultimately determine their role as markers of health and fitness in wildlife facing anthropogenic disturbances.

Phyllanthus emblica (Amla) Fruit Powder as a Supplement to Improve Preweaning Dairy Calves' Health: Effect on Antioxidant Capacity, Immune Response, and Gut Bacterial Diversity

Disease is the main reason for the use of antimicrobials in calf rearing, and antibiotics are commonly used to treat calves, including for unknown diseases. This leads to antimicrobial resistance, which is a challenge to the livestock industry and public health. Plant products containing high levels of phytochemicals may improve the immunity and resistance of calves against infections, thereby reducing the use of antimicrobials. This study aimed to investigate the effect of Phyllanthus emblica (Amla) fruit powder (PE) supplementation on antioxidant capacity and immune response of preweaning dairy calves. One hundred, 2-day-old, male Holstein calves were randomly assigned into five treatment groups receiving 0, 5, 10, 20, and 40 g/d PE supplementation. Antioxidant and immune indices and pro- and anti-inflammatory cytokines were analyzed from serum samples, whereas 16S rRNA was analyzed from rumen fluid and fecal samples. PE supplementation, at 5 g/d, protected calves against oxidative stress and improved antioxidant enzymes and immune and anti-inflammatory responses, showing its immunity-enhancing and protective roles against infections. However, the antioxidant capacity and immune response decreased with increasing PE levels, illustrating the adverse effects of PE supplementation at higher doses. The analysis of ruminal and fecal bacterial community abundance detected higher proportions of Firmicutes at an early age, and a higher Bacteroidetes to Firmicutes ratio at weaning, in calves supplemented with 5 g/d PE. This contributed to the development of the immune system in early life, and improved immune and anti-inflammatory responses at a later age. The overall results suggest that PE could be supplemented at 5 g/d for preweaning dairy calves to protect against oxidative stress and infections while maintaining normal gut microbial hemostasis.

Nutritional Metabolites as Biomarkers of Previous Feed Intake in European Rabbit (Oryctolagus cuniculus): Applications on Conservation

European wild rabbit (Oryctolagus cuniculus) populations have drastically reduced, and recently, rabbits have been classed as “endangered” by the IUCN. This animal plays an important ecological role in Mediterranean ecosystems and its introduction could significantly contribute to ecological restoration. Rabbits have high nutrient requirements that apparently cannot be covered in all ecosystems, and there are clues that nutrition can limit their abundance and density. On the other hand, some studies reflect the effects of food availability on the metabolomic status of other animal species, but there are no specific studies on this keystone species. The main aim of this work is to find biomarkers to assess the previous levels of ingestion of European rabbits (Oryctolagus cuniculus). To address this gap, gastric content and blood samples were collected from European rabbits (n = 99) in a Mediterranean area for the analysis of glucose, non-esterified fatty acids (NEFA), plasmatic urea nitrogen (PUN), albumin, glutamate and total protein metabolites. Depending on their previous feed intake (gastric content and the ratio between the gastric content and the weight of the animal), the animals were divided into two groups (lower and normal previous feed intake). Our work shows that the metabolomic profiles of the animals were affected. Levels of glucose (+82%; p = 0.0003), NEFA (−61%; p = 0.0040) and PUN (+139%; p < 0.001) were different in the animals with lower previous feed intake than the animals with normal previous feed intake. This work summarises that metabolic phenotype can be interesting when seeking to discover the limiting nutrients and food availability in diets that could affect the ecological fitness and conservation of European wild rabbits. It is important to mention that in this work, only the effects on six different metabolites have been analysed and more studies are necessary to complement the knowledge of possible metabolites that indicate the level of ingestion in this species and others. These (and new) biomarkers could be used as a tool to provide information about individual or population characteristics that other physiological parameters cannot detect, improving the conservation physiology field.

Mortality, Enzymatic Antioxidant Activity and Gene Expression of Cabbage Aphid (Brevicoryne brassicae L.) in Response to Trichoderma longibrachiatum T6

Aphids are one of the most common insect pests in greenhouse and field crops worldwide, causing significant crop yields and economic losses. The objective of this study was to determine the mortality, enzymatic antioxidant activity and gene expression of cabbage aphids (Brevicoryne brassicae L.) in response to Trichoderma longibrachiatum T6 (T6) at different time points from Day 1 to 7 after inoculation. Our results showed that the highest mortality of B. brassicae was observed on Day 7 at a concentration of 1 × 108 spores ml−1 (73.31%) after inoculation with T6 compared with the control on Day 7 (11.51%). The activities of the enzymes superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), ascorbate peroxidase (APX), glutathione peroxidase (GPX) and glutathione S-transferase (GST) were increased by 52.98%, 44.77%, 48.26%, 49.39%, 45.13% and 39.67%, respectively on Day 3 after inoculation with T6 compared to the control. Howerver increased days post treatment (dpt) decreased the activities of SOD, POD, CAT, APX, GPX and GST enzymes by 20.79%, 21.05%, 13.75%, 20.45%, 25.38%, and 19.76% repectively on Day 7 compared to control. The transcript levels of SOD, POD, CAT, GPX, and GST genes were increased by 10.87, 9.87, 12.77, 6.22 and 4.07 respectively at Day 3 after inoculation with T6 in comparison to the control. However, the SOD, POD, CAT, GPX, and GST transcription levels decreased by 0.43, 0.44, 0.35, 0.52 and 0.47 respectively, compared to control at Day 7. Our results suggest that the T6 strain has a potential effect on the antioxidant activity and mortality of B. brassicae and therefore could be used as a natural biocontrol agent against B. brassicae in the future.

Methodological confounds of measuring urinary oxidative stress in wild animals

Biomarkers of oxidative stress (OS) are useful in addressing a wide range of research questions, but thus far, they have had limited application to wild mammal populations due to a reliance on blood or tissue sampling. A shift toward non-invasive measurement of OS would allow field ecologists and conservationists to apply this method more readily. However, the impact of methodological confounds on urinary OS measurement under field conditions has never been explicitly investigated. We combined a cross-sectional analysis with a field experiment to assess the impact of four potential methodological confounds on OS measurements: (1) time of sampling, (2) environmental contamination from foliage; (3) delay between sample collection and flash-freezing in liquid nitrogen; and (4) sample storage of up to 15 months below -80°C. We measured DNA oxidative damage (8-hydroxy-2'-deoxyguanosine, 8-OHdG), lipid peroxidation (malondialdehyde, MDA), total antioxidant capacity (TAC), and uric acid (UA) in 167 urine samples collected from wild Zanzibar red colobus (Piliocolobus kirkii). We found that MDA was higher in samples collected in the morning than in the afternoon but there were no diurnal patterns in any of the other markers. Contamination of samples from foliage and length of time frozen at -80°C for up to 15 months did not affect OS marker concentrations. Freezing delay did not affect OS levels cross-sectionally, but OS values from individual samples showed only moderate-to-good consistency and substantial rank-order reversals when exposed to different freezing delays. We recommend that diurnal patterns of OS markers and the impact of storage time before and after freezing on OS marker concentrations be considered when designing sampling protocols. However, given the high stability we observed for four OS markers subject to a variety of putative methodological confounds, we suggest that urinary OS markers provide a valuable addition to the toolkit of field ecologists and conservationists within reasonable methodological constraints.

Interactive effects of ocean acidification, ocean warming, and diurnal temperature cycling on antioxidant responses and energy budgets in two sea urchins Strongylocentrotus intermedius and Tripneustes gratilla from different latitudes

To accurately predict the fitness of marine ectotherms under the climate change scenarios, interactive effects from multiple environmental stressors should be considered, such as ocean acidification (OA), ocean warming (OW) and diurnal temperature cycling (DTC). In this work, we evaluated and compared the antioxidant capacity and metabolism homeostasis of two sea urchins, viz. the temperate species Strongylocentrotus intermedius and the tropical species Tripneustes gratilla, in response to oceanic conditions under a climate change scenario. The two species were treated separately/jointly by acidic (pH 7.6), thermal (ambient temperature + 3 °C), and temperature fluctuating (5 °C fluctuations daily) seawater for 28 days. The activities of antioxidant enzymes (catalase and superoxide dismutase) and the cellular energy allocation in the urchins' gonads were assessed subsequently. Results showed that exposure to OA, OW, and DTC all induced antioxidant responses associated with metabolism imbalance in both S. intermedius and T. gratilla. The physiological adjustments and energy strategies towards exposure of OA, OW, and DTC are species specific, perhaps owing to the different thermal acclimation of species from two latitudes. Moreover, decrease of cellular energy allocation were detected in both species under combined OA, OW, and DTC conditions, indicating unsustainable bioenergetic states. The decrease of cellular energy allocation is weaker in T. gratilla than in S. intermedius, implying higher acclimation capacity to maintain the energy homeostasis in tropical urchins. These results suggest that climate change might affect the population replenishment of the two sea urchins species, especially for the temperate species.

Biomarkers of Animal Nutrition: From Seasonal to Lifetime Indicators of Environmental Conditions

Nutrition underpins survival and reproduction in animal populations; reliable nutritional biomarkers are therefore requisites to understanding environmental drivers of population dynamics. Biomarkers vary in scope of inference and sensitivity, making it important to know what and when to measure to properly quantify biological responses. We evaluated the repeatability of three nutritional biomarkers in a large, iteroparous mammal to evaluate the level of intrinsic and extrinsic contributions to those traits. During a long-term, individual-based study in a highly variable environment, we measured body fat, body mass, and lean mass of mule deer (Odocoileus hemionus) each autumn and spring. Lean mass was the most repeatable biomarker (0.72 autumn; 0.61 spring), followed by body mass (0.64 autumn; 0.53 spring), and then body fat (0.22 autumn; 0.01 spring). High repeatability in body and lean mass likely reflects primary structural composition, which is conserved across seasons. Low repeatability of body fat supports that it is the primary labile source of energy that is largely a product of environmental contributions of the previous season. Based on the disparate levels in repeatability among nutritional biomarkers, we contend that body and lean mass are better indicators of nutritional legacies (e.g., maternal effects), whereas body fat is a direct and sensitive reflection of recent nutritional gains and losses.

Untangling the oxidative cost of reproduction: An analysis in wild banded mongooses

The cost of reproduction plays a central role in evolutionary theory, but the identity of the underlying mechanisms remains a puzzle. Oxidative stress has been hypothesized to be a proximate mechanism that may explain the cost of reproduction. We examine three pathways by which oxidative stress could shape reproduction. The "oxidative cost" hypothesis proposes that reproductive effort generates oxidative stress, while the "oxidative constraint" and "oxidative shielding" hypotheses suggest that mothers mitigate such costs through reducing reproductive effort or by pre-emptively decreasing damage levels, respectively. We tested these three mechanisms using data from a long-term food provisioning experiment on wild female banded mongooses (Mungos mungo). Our results show that maternal supplementation did not influence oxidative stress levels, or the production and survival of offspring. However, we found that two of the oxidative mechanisms co-occur during reproduction. There was evidence of an oxidative challenge associated with reproduction that mothers attempted to mitigate by reducing damage levels during breeding. This mitigation is likely to be of crucial importance, as long-term offspring survival was negatively impacted by maternal oxidative stress. This study demonstrates the value of longitudinal studies of wild animals in order to highlight the interconnected oxidative mechanisms that shape the cost of reproduction.

Aminomethylphosphonic acid (AMPA) alters oxidative status during embryonic development in an amphibian species

Glyphosate's primary metabolite (aminomethylphosphonic acid, AMPA) is known to alter embryonic development at environmentally relevant concentrations in amphibians. However, we have limited understanding of the physiological mechanisms through which AMPA affects organisms. In this study, we tested whether alteration of the oxidative status is one mechanism through which AMPA affects organism performance. To this end, we analysed several oxidative status markers in hatchling tadpoles that were exposed to sublethal concentrations of AMPA during embryonic development (~16 days). We compared the influence of environmentally relevant concentrations of AMPA (from 0.07 to 3.57 μg l^-1) on the relation between developmental traits (i.e, embryonic development duration, embryonic mortality and hatchling size) and oxidative status markers known to alter homeostasis when unbalanced (superoxide dismutase (SOD), glutathione peroxidase (GPx), catalase (CAT), thiols and ratios thereof). We included measures of telomere length as an indicator of physiological state. We found that AMPA concentrations induce non-monotonic effects on some oxidative status markers with hatchlings displaying elevated antioxidant responses (elevated thiols and unbalanced SOD/(GPx + CAT) ratio). The lack of effect of AMPA on the relation between developmental traits, oxidative status and telomere length suggests that selective mortality of embryos susceptible to oxidative stress may have occurred prior to hatching in individuals less resistant to AMPA which display lower hatching success. Future studies are required to disentangle whether oxidative unbalance is a cause or a consequence of AMPA exposition. This study highlights the need to investigate effects of the metabolites of contaminants at environmental concentrations to comprehensively assess impacts of anthropogenic contamination on wildlife.

Effects of dietary tea tree oil on the growth, physiological and non-specific immunity response in the giant freshwater prawn (Macrobrachium rosenbergii) under high ammonia stress

This study aimed to investigate the effects of dietary tea tree oil (TTO) on the performance, intestinal antioxidant capacity, and non-specific immunity after ammonia nitrogen stress in Macrobrachium rosenbergii. Six experimental diets were formulated with 0, 25, 50, 100, 200, 400 mg/kg TTO, respectively. A total of 900 prawns (average initial weight, 0.39 ± 0.01 g) were randomly assigned to 6 groups in triplicate in 18 tanks. After an 8-week feeding trial, 20 prawns from each tank were changed with 20 mg/L ammonia stress for 24 h. The results showed that 100 mg/kg TTO significantly increased prawns performance and survival rate compared with the control group. Moreover, 100 and 200 mg/kg TTO significantly improved intestinal antioxidant capabilities by increasing SOD enzyme activities and decreasing MDA levels. In addition, the prawns fed with 100 mg/kg TTO diet showed the highest survival rate under ammonia stress. After ammonia stress, the group of 100 mg/kg TTO significantly improved antioxidant capacity by increasing hemolymph respiratory burst activity, as well as intestinal anti-superoxide anion activity and SOD. Coincidentally, 100 mg/kg TTO significantly upregulated the intestinal relative expression of antioxidant-related genes (peroxiredoxin-5). Further, it was found that 100 mg/kg TTO activated the toll-dorsal pathway in prawns, which performed the similar function as the classic NF-κB pathway by upregulating the TNF-α and IL-1. Finally, 100 mg/kg TTO increased the levels of iNOS activities and NO contents after ammonia stress and enhanced non-specific immunity. The results indicated that 100 mg/kg TTO could significantly improve the M. rosenbergii performance, antioxidant capacity and ammonia stress resistance. We suggested that the mechanisms may be attributed to that TTO enhanced the antioxidant capacity and non-specific immunity of M. rosenbergii via the NF-κB signal pathway.

Zn contamination stimulate agonistic behavior and oxidative stress of crayfishes (Procambarus clarkii)

BACKGROUND

As a result of the global industrial revolution, contamination of the ecosystem by heavy metals has given rise to one of the most important ecological and organismic problems. The current study aimed to evaluate the effect of Zn contamination on agonistic behavior and oxidative damage of crayfish.

METHODS

Crayfishes of the field study group were collected from a polluted area (Rosetta branch), where the highest concentration for heavy metals in water was zinc (Zn). Besides the field study group, other crayfishes were exposed to different doses of ZnSO₄ (0, 203, and 406 mg L^-1), which corresponding to Zn concentration (0, 46.03, and 92.06 mg L^-1) respectively in aquariums for consecutive four days. Agonistic behavior is quantified by decreasing fast retreat, slowly back away and no response, increasing initial claw use, active claw use, approach with the threat, approach without threat, and unrestrained behavior.

RESULTS

The result revealed that agonistic behavior increases significantly with the increase of water Zn concentration. Malondialdehyde and catalase levels increased, while glutathione concentration reduced with the increase of Zn concentration.

CONCLUSION

Our current study reveals that zinc exposure is capable of inducing an increase in the social status (agonistics behavior) and oxidative stress parameters in Procambarus clarkii. The increase in aggressive behavior may have major population-level consequences given the high mortality experienced by this crayfish.

Parasitism reduces oxidative stress of fish host experimentally exposed to PAHs

Some parasites are known to bioaccumulate some environmental pollutants within their host. We hypothesized that these parasites may be beneficial for their hosts in polluted environments. We experimentally increased long-term (five weeks) exposure to polycyclic aromatic hydrocarbons (PAHs, three levels: 0.1X, 1X, 10X environmental exposure) in European chubs (Squalius cephalus) that were naturally infected or uninfected with acanthocephalan parasites. We monitored PAHs levels in fish tissues, as well as oxidative stress, telomere length and condition indices. Although parasite infection did not significantly reduce the levels of PAHs and PAH metabolites in host tissues, host oxidative status was explained by parasitism and pollution levels. Oxidative damage increased with parasitism in fish exposed to low PAH levels (0.1X) but decreased in infected fish at higher PAH exposure (10X), thus corroborating our hypothesis. Meanwhile, antioxidant capacity did not differ in response to parasite infection nor PAHs exposure. Despite this imbalance in oxidative status, experimental increase in PAH levels did not compromise telomere length, body condition, or survival in infected and uninfected fish. This study provides the first experimental evidence that the outcome of host-parasite interactions can shift from negative to positive as pollutant exposure increases.

Impact of Oxidative Stress on Male Reproduction in Domestic and Wild Animals

Oxidative stress occurs when the levels of reactive oxygen species (ROS) overcome the antioxidant defenses of the organism, jeopardizing several biological functions, including reproduction. In the male reproductive system, oxidative stress not only impairs sperm fertility but also compromises offspring health and survival, inducing oxidative damage to lipids, proteins and nucleic acids. Although a clear link between oxidative stress and male fertility disorders has been demonstrated in humans and laboratory rodents, little information is available about the implications of impaired redox homeostasis in the male fertility of domestic and wild animals. Therefore, this review aims to provide an update regarding the intrinsic and extrinsic factors that are associated with oxidative stress in the male reproductive system and their impact on the reproductive performance of domestic and wild animals. The most recent strategies for palliating the detrimental effects of oxidative stress on male fertility are reviewed together with their potential economic and ecological implications in the livestock industry and biodiversity conservation.

DNA Damage as a Potential Non-Invasive Indicator of Welfare: A Preliminary Study in Zoo-Housed Grizzly Bears (Ursus arctos horribilis)

Measures of oxidative stress have potential for integrating positive and negative life experiences into comprehensive cellular indicators of animal welfare. We explored this possibility when three adult grizzly bear brothers at the Detroit Zoo were temporarily moved to a smaller habitat while their primary home was expanded. We expected that the spatial compression and construction activity might be sources of stress. We observed increased social play and other affiliative behavior in the smaller habitat, and we used daily fecal samples (17 to 24 per bear) to examine whether concentrations of fecal glucocorticoid metabolites (FGM) and 8-hydroxy-2′-deoxyguanosine (8-OHdG, a by-product of DNA damage) were correlated with social behavior. Our overall aim was to explore 8-OHdG as a potential indicator of welfare based on the prediction that 8-OHdG would be lower when more positive social interactions occurred. Concentrations of fecal 8-OHdG increased significantly with higher FGM concentrations, supporting a potential relationship between adrenal activity and rates of DNA damage. However, we found that on days when they engaged in higher rates of affiliative interactions, there were trends for 8-OHdG concentrations to increase for one bear and decrease for another, and no relationship for the third bear. These preliminary results should be interpreted with caution, but suggest a potential relationship between social behavior and 8-OHdG that is modulated by health, personality, or other individual factors. Further validation research is needed, but 8-OHdG may have promise as a non-invasive, cumulative indicator of animal welfare.

Advances in understanding the impacts of global warming on marine fishes farmed offshore: Sparus aurata as a case study

Monitoring variations in proteins involved in metabolic processes, oxidative stress responses, cell signalling and protein homeostasis is a powerful tool for developing hypotheses of how environmental variations affect marine organisms' physiology and biology. According to the oxygen- and capacity-limited thermal tolerance hypothesis, thermal acclimation mechanisms such as adjusting the activities of enzymes of intermediary metabolism and of antioxidant defence mechanisms, inducing heat shock proteins (Hsps) or activating mitogen-activated protein kinases may all shift tolerance windows. Few studies have, however, investigated the molecular, biochemical and organismal responses by fishes to seasonal temperature variations in the field to link these to laboratory findings. Investigation of the impacts of global warming on fishes farmed offsore, in the open sea, can provide a stepping stone towards understanding effects on wild populations because they experience similar environmental fluctuations. Over the last 30 years, farming of the gilthead sea bream Sparus aurata (Linnaeus 1758) has become widespread along the Mediterranean coastline, rendering this species a useful case study. Based on available information, the prevailing seasonal temperature variations expose the species to the upper and lower limits of its thermal range. Evidence for this includes oxygen restriction, reduced feeding, reduced responsiveness to environmental stimuli, plus a range of molecular and biochemical indicators that change across the thermal range. Additionally, close relationships between biochemical pathways and seasonal patterns of metabolism indicate a connection between energy demand and metabolic processes on the one hand, and cellular stress responses such as oxidative stress, inflammation and autophagy on the other. Understanding physiological responses to temperature fluctuations in fishes farmed offshore can provide crucial background information for the conservation and successful management of aquaculture resources in the face of global change.

Oxidative status of blue tit nestlings varies with habitat and nestling size

Oxidative status has been proposed as an important ecological and evolutionary force given that pro-oxidant metabolites damage molecules, cells and tissues, with fitness consequences for organisms. Consequently, organisms usually face a trade-off between regulating their oxidative status and other physiological traits. However, environmental stressors and the availability of dietary-derived antioxidants vary according to local conditions and, thus, organisms inhabiting different habitats face different oxidative pressures. Still, there is little information on how different environmental conditions influence the oxidative status of animals inhabiting terrestrial environments. In this work, we examined the variation in oxidative status in the blue tit (Cyanistes caeruleus), a bird species with hatching asynchrony. Specifically, we examined the oxidative status of the largest and the smallest nestlings in the brood, inhabiting four forests differing in food availability and ectoparasite prevalence. We measured lipid peroxidation (malondialdehyde; MDA) as a marker of oxidative damage, total antioxidant capacity (Trolox-equivalent antioxidant capacity; TEAC) and antioxidant enzymatic activity (catalase, glutathione S-transferase, glutathione peroxidase) in blood samples. The glutathione peroxidase (GPX) activity differed among the forests, being the highest in the pine forest and the lowest in a mixed oak (Quercus) forest in the most humid area. Lipid peroxidation was higher in larger nestlings, suggesting higher oxidative damage with an increasing growth rate. Neither brood size, laying date, nor ectoparasites were related to the oxidative status of nestlings. These results suggest that nest rearing conditions might shape the oxidative status of birds, having consequences for habitat-dependent variation in regulation of oxidative status.

Dietary Natural Plant Extracts Can Promote Growth and Modulate Oxidative Status of Senegalese Sole Postlarvae under Standard/Challenge Conditions

Simple Summary

Oxidative stress has a direct impact on the welfare of fish, affecting growth performance and health status. Natural plant extracts present a high antioxidant capacity, due to a diversity and abundant content of polyphenols. Thus, the aim of this work was to identify if plant extracts, such as curcumin, green tea, and grape seeds, can promote oxidative status, and ultimately, enhance the growth and physiological stress response of postlarvae. Our results showed that plant extracts can improve the growth and oxidative status of the fish. Moreover, they may help fish to cope under stressful conditions. Dietary formulations with natural supplements may be a viable strategy to improve fish robustness during early life stages, and can therefore contribute to the development of aquafeeds and promote the sustainability of aquaculture production.

Abstract

Plant extracts are known for their high content and diversity of polyphenols, which can improve fish oxidative status. A growth trial with Senegalese sole postlarvae (45 days after hatching) fed with one of four experimental diets—control (CTRL), and supplemented with curcumin (CC), green tea (GT), and grape seed (GS) extracts—was performed to assess if supplementation could improve growth performance and oxidative status. At the end of the growth trial, postlarvae were submitted to a thermal stress to assess their robustness. Sole growth was improved by CC and GS diets when compared to those fed the CTRL. CC and CTRL postlarvae presented the lowest oxidative damage (lipid peroxidation and protein carbonylation values). Stress-related biomarkers (heat shock protein 70 and glutathione-S-transferase) decreased in CC fish compared to those fed the CTRL diet, which might be due to a direct antioxidant capacity. In contrast, oxidative damage increased in GT and GS sole reared in standard conditions. However, after a thermal stress, GT and GS diets prevented the increase of protein carbonylation content and the decrease of antioxidant glutathione, depending on exposure time. Overall, dietary supplementation with natural extracts modulated oxidative status and stress response after a short/long-term exposure to temperature.

Heavy Metals Content in Great Shearwater (Ardenna Gravis): Accumulation, Distribution and Biomarkers of Effect in Different Tissues

The purpose of this study was to explore the usefulness of Great Shearwater (Ardenna gravis) as a bioindicator for biomonitoring programs for metal pollution. Three different metals were analysed in liver, kidney, and feathers, including cadmium, lead, and zinc. Glutathione-S-transferase, malondialdehyde, reduced glutathione, and catalase were assessed as oxidative stress biomarkers. Sex-related trends in metal accumulation also were evaluated. In liver and kidney, the mean concentrations of Zn (146.1 ± 5.14 and 108 ± 2.70 mg/kg, respectively) and Pb (0.19 ± 0.01 and 0.13 ± 0.01 mg/kg, respectively) in A. gravis were generally comparable to values reported in other studies. However, animals presented slightly higher concentrations of Cd (9.67 ± 0.65 in liver and 17.41 ± 0.84 mg/kg in kidney) than those reported in the same species sampled in Southern Atlantic waters. The slightly higher levels of Cd found in this study compared with other studies are probably affected by the location in Northern Atlantic waters (with different diet intake). In feathers, levels of Zn (70.70 ± 1.76 mg/kg) were lower than in other Ardenna shearwaters, whereas higher levels were found for Cd (0.16 ± 0.01 mg/kg) and Pb (0.84 ± 0.06 mg/kg). The lack of differences found between males and females could be influenced by the migration status, because both sexes stay in similar physiological conditions, with no laying eggs. Levels found in the feathers of the present study were related to concentrations in internal tissues below those which cause adverse effects in birds. Thus, feathers would appear as a potential noninvasive tool for metals biomonitoring in seabirds, because it is possible to quantify them. Baseline data of oxidative stress levels have been reported, both in liver and kidney, presenting no correlations with the levels of metals in these tissues. The low internal metal levels and the lack of correlations between oxidative stress metrics suggest a low risk of the environmental concentrations for seabirds.

One hundred research questions in conservation physiology for generating actionable evidence to inform conservation policy and practice

Environmental change and biodiversity loss are but two of the complex challenges facing conservation practitioners and policy makers. Relevant and robust scientific knowledge is critical for providing decision-makers with the actionable evidence needed to inform conservation decisions. In the Anthropocene, science that leads to meaningful improvements in biodiversity conservation, restoration and management is desperately needed. Conservation Physiology has emerged as a discipline that is well-positioned to identify the mechanisms underpinning population declines, predict responses to environmental change and test different in situ and ex situ conservation interventions for diverse taxa and ecosystems. Here we present a consensus list of 10 priority research themes. Within each theme we identify specific research questions (100 in total), answers to which will address conservation problems and should improve the management of biological resources. The themes frame a set of research questions related to the following: (i) adaptation and phenotypic plasticity; (ii) human-induced environmental change; (iii) human-wildlife interactions; (iv) invasive species; (v) methods, biomarkers and monitoring; (vi) policy, engagement and communication; (vii) pollution; (viii) restoration actions; (ix) threatened species; and (x) urban systems. The themes and questions will hopefully guide and inspire researchers while also helping to demonstrate to practitioners and policy makers the many ways in which physiology can help to support their decisions.

Urban ecophysiology: beyond costs, stress and biomarkers

Natural habitats are rapidly declining due to urbanisation, with a concomitant decline in biodiversity in highly urbanised areas. Yet thousands of different species have colonised urban environments. These organisms are exposed to novel urban conditions, which are sometimes beneficial, but most often challenging, such as increased ambient temperature, chemicals, noise and light pollution, dietary alterations and disturbance by humans. Given the fundamental role of physiological responses in coping with such conditions, certain physiological systems such as the redox system, metabolism and hormones are thought to specifically influence organisms' ability to persist and cope with urbanisation. However, these physiological systems often show mixed responses to urbanisation. Does this mean that some individuals, populations or species are resilient to the urban environmental challenges? Or is something missing from our analyses, leading us to erroneous conclusions regarding the impact of urbanisation? To understand the impact of urbanisation, I argue that a more integrated mechanistic and ecological approach is needed, along with experiments, in order to fully understand the physiological responses; without knowledge of their ecological and evolutionary context, physiological measures alone can be misinterpreted. Furthermore, we need to further investigate the causes of and capacity for individual plasticity in order to understand not only the impact of urbanisation, but also species resilience. I argue that abiotic and biotic urban factors can interact (e.g. pollution with micro- and macronutrients) to either constrain or relax individual physiological responses - and, thereby, plasticity - on a temporal and/or spatial scale, which can lead to erroneous conclusions regarding the impact of urbanisation.

Differential oxidative costs of locomotory and genital damage in an orb-weaving spider

In animals that regularly experience tissue loss, physiological responses may have evolved to overcome the related costs. Changes in oxidative status may reflect such self-maintenance mechanisms. Here, we investigated how markers of oxidative status vary in female orb-weaving spiders (Larinia jeskovi) by mimicking two distinct types of tissue loss they may naturally encounter: damage to their locomotory system and damage to their external genital structure (scapus), as inflicted by males during copulation (external female genital mutilation). Damage to the locomotory system resulted in a significant shift in oxidative status, reflecting investment in self-maintenance. In contrast, the loss of the scapus did not result in quantitative changes of oxidative markers. This lack of a physiological response suggests negligible physiological costs of genital mutilation for female spiders. However, not being able to remate with other males might be costly for females.

Protein metabolism and physical fitness are physiological determinants of body condition in Southern European carnivores

The physiological significance of biometric body condition indices (bBCI) is poorly understood. We hypothesized that bBCI are composite metrics of nutritional physiology, physical fitness and health. To test this hypothesis, we first compared the performance of eight bBCI, using 434 Southern European carnivores from six species as a model system; and then identified, by non-destructive methods, the hematology and serum biochemistry correlates of three selected bBCI. Fulton’s K Index, Major Axis Regression Residuals and Scaled Mass Index were the only bBCI insensitive to the effect of sex and age. The most informative physiological parameters in explaining the variation of these bBCI were the albumin (Effect Size (ES) = − 1.66 to − 1.76), urea (ES = 1.61 to 1.85) and total bilirubin (ES = − 1.62 to − 1.79). Hemoglobin and globulins (positive) and cholesterol (negative) were moderately informative (0.9 <|ES|< 1.5). This study shows that most bBCI do not control for the effect of age and sex in Southern European carnivores. Our results support that bBCI are composite measures of physiologic processes, reflecting a positive gradient from protein-poor to protein-rich diets, accompanied by increased physical fitness. Biometric body condition indices allow the integration of ecologically relevant physiological aspects in an easily obtained metric.

Timescale and colony-dependent relationships between environmental conditions and plasma oxidative markers in a long-lived bat species

To increase the applicability and success of physiological approaches in conservation plans, conservation physiology should be based on ecologically relevant relationships between physiological markers and environmental variation that can only be obtained from wild populations. Given their integrative and multifaceted aspects, markers of oxidative status have recently been considered in conservation physiology, but still need to be validated across environmental conditions and locations. Here, we examined whether inter-annual variation in two oxidative markers, plasma antioxidant capacity and plasma hydroperoxides, followed inter-annual variation in temperature anomalies and associated vegetation changes in four colonies of long-lived greater mouse-eared bats (Myotis myotis) monitored over five consecutive years. We found that the plasma antioxidant capacity of bats decreased while plasma hydroperoxide concentrations increased with increasing temperature anomalies occurring in the two weeks before blood sampling. Moreover, the antioxidant defences of these bats reflected vegetation indices, which themselves reflected the thermal conditions experienced by bats in their foraging habitat. Variation in oxidative markers therefore appears to be due to variation in thermoregulatory costs and to indirect changes in foraging costs. Overall, these results validate the use of markers of oxidative status in conservation physiology to monitor thermal perturbations recently experienced by animals in their natural habitat. However, even though oxidative markers varied in the same direction in all four bat colonies across years, the amplitude of their response differed. If these different physiological responses reflect different performances (e.g. productivity, survival rate) between colonies, this implies that, if necessary, conservation measures may need to be applied at the local scale.

Potential Benefits of Acanthocephalan Parasites for Chub Hosts in Polluted Environments

Some parasites are expected to have beneficial impacts on wild populations in polluted environments because of their bioaccumulation potential of pollutants from their hosts. The fate of organic micropollutants in host-parasite systems and the combined effect of parasitism and pollution were investigated in chub Squalius cephalus, a freshwater fish, infected (n = 73) or uninfected (n = 45) by acanthocephalan parasites Pomphorhynchus sp. from differently contaminated riverine sites. Several ubiquitous pollutants (polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), polybrominated diphenyl-ethers (PBDEs), polycyclic aromatic hydrocarbons (PAHs), phthalates, insecticides, pyrethroids, and N,N-diethyl-meta-toluamide (DEET)) and some of their metabolites were characterized for the first time in parasites and various fish matrices (muscle, liver, and stomach content). Most organic pollutants reached higher levels in parasites than in chub matrices. In contrast, metabolite levels were lower in parasite tissues compared to fish matrices. Infected and uninfected chub exhibited no significant differences in their pollutant load. Body condition, organo-somatic indices, and immunity were not affected by parasitism, and few correlations were found with chemical pollution. Interestingly, infected chub exhibited lower oxidative damage compared to uninfected fish, irrespective of their pollutant load. In light of these results, this correlative study supports the hypothesis that acanthocephalan parasites could bring benefits to their hosts to cope with organic pollution.

Striving for population-level conservation: integrating physiology across the biological hierarchy

The field of conservation physiology strives to achieve conservation goals by revealing physiological mechanisms that drive population declines in the face of human-induced rapid environmental change (HIREC) and has informed many successful conservation actions. However, many studies still struggle to explicitly link individual physiological measures to impacts across the biological hierarchy (to population and ecosystem levels) and instead rely on a 'black box' of assumptions to scale up results for conservation implications. Here, we highlight some examples of studies that were successful in scaling beyond the individual level, including two case studies of well-researched species, and using other studies we highlight challenges and future opportunities to increase the impact of research by scaling up the biological hierarchy. We first examine studies that use individual physiological measures to scale up to population-level impacts and discuss several emerging fields that have made significant steps toward addressing the gap between individual-based and demographic studies, such as macrophysiology and landscape physiology. Next, we examine how future studies can scale from population or species-level to community- and ecosystem-level impacts and discuss avenues of research that can lead to conservation implications at the ecosystem level, such as abiotic gradients and interspecific interactions. In the process, we review methods that researchers can use to make links across the biological hierarchy, including crossing disciplinary boundaries, collaboration and data sharing, spatial modelling and incorporating multiple markers (e.g. physiological, behavioural or demographic) into their research. We recommend future studies incorporating tools that consider the diversity of 'landscapes' experienced by animals at higher levels of the biological hierarchy, will make more effective contributions to conservation and management decisions.

Alteration of the Antioxidant Capacity and Gut Microbiota under High Levels of Molybdenum and Green Tea Polyphenols in Laying Hens

High dietary levels of molybdenum (MO) can negatively affect productive performances and health status of laying hens, while tea polyphenol (TP) can mitigate the negative impact of high MO exposure. However, our understanding of the changes induced by TP on MO challenged layers performances and oxidative status, and on the microbiota, remains limited. The aim of the present study was to better understand host (performances and redox balance) and microbiota responses in MO-challenged layers with dietary TP. In this study, 200 Lohmann laying hens (65-week-old) were randomly allocated in a 2 × 2 factorial design to receive a diet with or without MO (0 or 100 mg/kg), and supplemented with either 0 or 600 mg/kg TP. The results indicate that 100 mg/kg MO decreased egg production (p = 0.03), while dietary TP increased egg production in MO challenged layers (p < 0.01). Egg yolk color was decreased by high MO (p < 0.01), while dietary TP had no effect on yolk color (p > 0.05). Serum alanine transaminase (ALT), aspartate aminotransferase (AST), and malonaldehyde (MDA) concentration were increased by high MO, while total antioxidant capacity (T-AOC), xanthine oxidase (XOD) activity, glutathione s-transferase (GSH-ST), and glutathione concentration in serum were decreased (p < 0.05). Dietary TP was able to reverse the increasing effect of MO on ALT and AST (p < 0.05). High MO resulted in higher MO levels in serum, liver, kidney, and egg, but it decreased Cu and Se content in serum, liver, and egg (p < 0.05). The Fe concentration in liver, kidney, and eggs was significantly lower in MO supplementation groups (p < 0.05). High MO levels in the diet led to lower Firmicutes and higher Proteobacteria abundance, whereas dietary TP alone and/or in high MO treatment increased the Firmicutes abundance and the Firmicutes/Bacteroidetes ratio at phylum level. High MO increased the abundance of Proteobacteria (phylum), Deltaproteobacteria (class), Mytococcales (order), and Nanocystaceae (family), whereas dietary TP promoted the enrichment of Lactobacillus agilis (species). Dietary TP also enhanced the enrichment of Bacilli (class), Lactobacillates (order), Lactobacillus (family), and Lactobacillus gasseri (species). Microbiota analysis revealed differentially enriched microbial compositions in the cecum caused by MO and TP, which might be responsible for the protective effect of dietary TP during a MO challenge.

Spatio-temporal variation in oxidative status regulation in a small mammal

Life-history allocation trade-offs are dynamic over time and space according to the ecological and demographical context. Fluctuations in food availability can affect physiological trade-offs like oxidative status regulation, reflecting the balance between pro-oxidant production and antioxidant capacity. Monitoring the spatio-temporal stability of oxidative status in natural settings may help understanding its importance in ecological and evolutionary processes. However, few studies have yet conducted such procedures in wild populations. Here, we monitored individual oxidative status in a wild eastern chipmunk (Tamias striatus) population across the 2017 summer active period and over three study sites. Oxidative damage (MDA: Malondialdehyde levels) and non-enzymatic antioxidant levels (FRAP: Ferric reducing antioxidant power and HASC: Hypochlorous acid shock capacity) were quantified across time and space using assays optimized for small blood volumes. Our results showed an increase in oxidative damage mirrored by a decrease in FRAP throughout the season. We also found different antioxidant levels among our three study sites for both markers. Our results also revealed the effects of sex and body mass on oxidative status. Early in the active season, females and individuals with a greater body mass had higher oxidative damage. Males had higher HASC levels than females throughout the summer. This study shows that oxidative status regulation is a dynamic process that requires a detailed spatial and temporal monitoring to yield a complete picture of possible trade-offs between pro-oxidant production and antioxidant capacity.