Transgenerational effects of triazole fungicides on gene expression and egg compounds in non-exposed offspring: A case study using Red-Legged Partridges (Alectoris rufa)

Triazole fungicides are widely used to treat cereal seeds before sowing. Granivorous birds like the Red-legged Partridge (Alectoris rufa) have high exposure risk because they ingest treated seeds that remain on the field surface. As triazole fungicides can act as endocrine disruptors, affecting sterol synthesis and reproduction in birds several months after exposure, we hypothesized that these effects could also impact subsequent generations of exposed birds. To test this hypothesis, we exposed adult partridges (F0) to seeds treated at commercial doses with four different formulations containing triazoles as active ingredients (flutriafol, prothioconazole, tebuconazole, and a mixture of the latter two), simulating field exposure during late autumn sowing. During the subsequent reproductive season, two to four months after exposure, we examined compound allocation of steroid hormones, cholesterol, vitamins, and carotenoids in eggs laid by exposed birds (F1), as well as the expression of genes encoding enzymes involved in sterol biosynthesis in one-day-old chicks of this F1. One year later, F1 animals were paired again to investigate the expression of the same genes in the F2 chicks. We found changes in the expression of some genes for all treatments and both generations. Additionally, we observed an increase in estrone levels in eggs from partridges treated with flutriafol compared to controls, a decrease in tocopherol levels in partridges exposed to the mixture of tebuconazole and prothioconazole, and an increase in retinol levels in partridges exposed to prothioconazole. Despite sample size limitations, this study provides novel insights into the mechanisms of action of the previously observed effects of triazole fungicide-treated seeds on avian reproduction with evidence that the effects can persist beyond the exposure windows, affecting unexposed offspring of partridges fed with treated seeds. The results highlight the importance of considering long-term chronic effects when assessing pesticide risks to wild birds.

Dietary DNA metabarcoding reveals a trophic niche partitioning among sympatric Iberian sandgrouses and bustards

The study of trophic niche partitioning is of great importance for understanding community structure and species coexistence, particularly if these are threatened. Here DNA metabarcoding was used to assess the diet of four threatened steppe bird species (two bustards and two sandgrouses), with the aim of better understanding their dietary requirements, trophic interactions, and potential threats. The results showed seasonal and interspecific differences in their plant diet, with greater importance of cultivated plants during autumn and winter (around 50 % of their diet) than spring. Plants of the genus Convolvulus and of the family Brassicaceae were frequently consumed by all species. In spring, poppies (Papaver spp.) were a considerable part of their diet, and could be used as a source of carotenoids or for their anti-parasitic properties. Furthermore, results evidenced a trophic niche partitioning among species, with a marked segregation between bustard species and, to a lesser extent, between sandgrouse species. Diet similarity was generally higher between species from different orders that occur in mixed-species flocks (bustard - sandgrouse) than between species of the same order. This partitioning was probably related to a stratification in habitat use rather than to specialisation and might prevent competition to some extent. However, the homogenization of trophic resources resulting from agricultural intensification could pose an important threat, particularly during autumn, when weeds are scarcer and the most abundant trophic resource are sown seeds, which are often treated with pesticides.

Diet and Spatial Ecology Influence Red-Legged Partridge Exposure to Pesticides Used as Seed Treatment

Seed treatment with pesticides is an extended agricultural practice with a high risk to granivorous birds that consume those seeds. To characterize that risk, it is necessary to understand the ecological factors that determine the exposure chances of birds to treated seeds. We investigated how pesticide uptake by red-legged partridges was related to cultivated plant ingestion and to the use of recently sown fields. We analyzed pesticide residues in 144 fecal samples from 32 flocks and determined the plant diet composition using DNA metabarcoding. Habitat use was studied through the monitoring of 15 GPS-tagged partridges. We confirmed, through the analysis of seeds, that >80% of cereal fields from the area had seeds treated with triazole fungicides. Tebuconazole was detected in 16.6% of partridges' feces. During the sowing season, cultivated plants accounted for half of the plant diet, but no association was found between cultivated plant consumption and pesticide intake. GPS tracking revealed that tebuconazole was detected in feces when partridges had recently used sown fields, whereas nonexposed partridges showed no overlap with recently sown areas. Our results highlight the need to incorporate field ecology into the characterization of pesticide exposure to improve the efficacy of environmental risk assessment.

A non-invasive method to monitor farmland bird exposure to triazole fungicides

The treatment of seeds with pesticides is an extended practice in current agriculture. There is a high risk of exposure in granivorous birds, such as the red-legged partridge (Alectoris rufa), that can consume those seeds remaining on the surface during sowing. Fungicide exposure could in turn affect bird reproductive capacity. To better understand to what extent triazole fungicides are a threat to granivorous birds, we need an easy and reliable method to quantify field exposure. In this study, we tested a novel non-invasive method to detect the presence of triazole fungicide residues in farmland bird faeces. We experimentally exposed captive red-legged partridges to validate the method, and then applied it in a real scenario to assess exposure of wild partridges. We exposed adult partridges to seeds treated with two formulations containing triazole fungicides as active ingredients: Vincit®Minima (flutriafol 2.5%) and Raxil®Plus (prothioconazole 25% and tebuconazole 15%). We collected two types of faeces (caecal and rectal samples) immediately after exposure and 7 days later and quantified the concentrations of the three triazoles and their common metabolite (1,2,4-triazole). The three active ingredients and 1,2,4-triazole were only detected in faeces collected immediately after exposure. Triazole fungicide detection rates in rectal stool were 28.6%, 73.3% and 80% for flutriafol, prothioconazole and tebuconazole, respectively. In caecal samples, detection rates were 40%, 93.3% and 33.3%, respectively. 1,2,4-triazole was detected in 53% of rectal samples. For an applied use of the method in the field, we collected 43 faecal samples from wild red-legged partridges during autumn cereal seed sowing and found detectable levels of tebuconazole in 18.6% of the analysed wild partridges. The results of the experiment were then used to estimate actual exposure levels from this prevalence value found in wild birds. Our study shows that faecal analysis can be a useful tool to assess farmland bird exposure to triazole fungicides, when samples are fresh and the method has been validated for the detection of target molecules.

A regression-based QSAR-model to predict acute toxicity of aromatic chemicals in tadpoles of the Japanese brown frog (Rana japonica): Calibration, validation, and future developments to support risk assessment of chemicals in amphibians

Amphibian populations are undergoing a global decline worldwide. Such decline has been attributed to their unique physiology, ecology, and exposure to multiple stressors including chemicals, temperature, and biological hazards such as fungi of the Batrachochytrium genus, viruses such as Ranavirus, and habitat reduction. There are limited toxicity data for chemicals available for amphibians and few quantitative structure-activity relationship (QSAR) models have been developed and are publicly available. Such QSARs provide important tools to assess the toxicity of chemicals particularly in a data poor context. QSARs provide important tools to assess the toxicity of chemicals particularly when no toxicological data are available. This manuscript provides a description and validation of a regression-based QSAR model to predict, in a quantitative manner, acute lethal toxicity of aromatic chemicals in tadpoles of the Japanese brown frog (Rana japonica). QSAR models for acute median lethal molar concentrations (LC50-12 h) of waterborne chemicals using the Monte Carlo method were developed. The statistical characteristics of the QSARs were described as average values obtained from five random distributions into training and validation sets. Predictions from the model gave satisfactory results for the overall training set (R² = 0.72 and RMSE = 0.33) and were even more robust for the validation set (R² = 0.96 and RMSE = 0.11). Further development of QSAR models in amphibians, particularly for other life stages and species, are discussed.

Assessing Stress Response in Lizards from Agroecosystems with Different Management Practices

Despite the importance of reptiles in agroecosystems, little is known about the effects of agricultural intensification and pesticide use on these animals. We compared antioxidant and haematological biomarkers in the wild Italian wall lizards Podarcis siculus from three olive groves representing a gradient of management intensity. Lizards from the conventional grove showed induced antioxidant defences relative to those from the organic field. However, this induction did not avoid the occurrence of oxidative stress in males from intensively managed olive groves, who showed TBARS levels 58%-133% higher than males from the other sites. Haematological responses also suggested increased stress in females from the intensively managed olive groves, with a heterophil-to-lymphocyte ratio 5.3 to 14.8-fold higher than in the other sites. The observed stress responses of lizards along the studied gradient of agricultural management suggest their potential usefulness as non-destructive biomarkers to environmental stressors associated with agricultural intensification.

Bird exposure to fungicides through the consumption of treated seeds: A study of wild red-legged partridges in central Spain

Sown seeds are a key component of many farmland birds' diets due to natural food shortages in autumn and winter. Because these seeds are often treated with pesticides, their ingestion by birds can result in toxic effects. For risk assessment, data on treated seed toxicity should be combined with information about exposure risk for wild birds and the factors that modulate it. We characterized the exposure of red-legged partridges to pesticide-treated seeds through the analysis of digestive contents of birds shot by hunters (n = 194) in an agricultural region in central Spain. We measured the contribution of sown seeds to the partridges' diet and how it related to pesticide exposure. Moreover, we evaluated the influence of landscape composition on the intake of sown seeds and pesticides by partridges. During peak sowing time, seeds constituted half (50.7%) of the fresh biomass ingested by partridges, which consumed mostly winter cereal seeds (42.3% of biomass). Residues of seven fungicides and one insecticide (active ingredients) were detected in 33.0% of birds. The presence of pesticides in digestive contents was linked to the ingestion of cereal sown seeds. Moreover, dietary exposure of birds to pesticides was modulated by landscape characteristics, being lower in areas with heterogeneous landscapes, greater habitat mosaic and more natural vegetation. The estimated dietary intake of pesticides resulting from our field observations, in combination with experimental data on pesticide toxicity, raise concerns about the risks that pesticide-treated cereal seeds pose to granivorous bird populations. Our results highlight the importance of farming landscape composition and diversification, which should be considered as a priority in the agricultural policy to mitigate pesticide risks to farmland birds through the consumption of treated seeds.

Birds feeding on tebuconazole treated seeds have reduced breeding output

Drilled seeds are an important food resource for many farmland birds but may pose a serious risk when treated with pesticides. Most compounds currently used as seed treatment in the EU have low acute toxicity but may still affect birds in a sub-chronic or chronic way, especially considering that the sowing season lasts several weeks or months, resulting in a long exposure period for birds. Tebuconazole is a triazole fungicide widely used in agriculture but its toxicity to birds remains largely unknown. Our aim was to test if a realistic scenario of exposure to tebuconazole treated seeds affected the survival and subsequent reproduction of the red-legged partridge (Alectoris rufa). We fed captive partridges with wheat seeds treated with 0%, 20% or 100% of tebuconazole application rate during 25 days in late winter (i.e. tebuconazole dietary doses were approximately 0.2 and 1.1 mg/kg bw/day). We studied treatment effects on the physiology (i.e. body weight, biochemistry, immunology, oxidative stress, coloration) and reproduction of partridges. Exposed birds did not reduce food consumption but presented reduced plasmatic concentrations of lipids (triglycerides at both exposure doses, cholesterol at high dose) and proteins (high dose). The coloration of the eye ring was also reduced in the low dose group. Exposure ended 60 days before the first egg was laid, but still affected reproductive output: hatching rate was reduced by 23% and brood size was 1.5 times smaller in the high dose group compared with controls. No significant reproductive effects were found in the low dose group. Our results point to the need to study the potential endocrine disruption mechanism of this fungicide with lagged effects on reproduction. Risk assessments for tebuconazole use as seed treatment should be revised in light of these reported effects on bird reproduction.

Integrating active and passive monitoring to assess sublethal effects and mortality from lead poisoning in birds of prey

The ingestion of lead (Pb) ammunition is the most important exposure pathway to this metal in birds and involve negative consequences to their health. We have performed a passive monitoring of Pb poisoning in birds of prey by measuring liver (n = 727) and blood (n = 32) Pb levels in individuals of 16 species found dead or sick in Spain between 2004 and 2020. We also performed an active monitoring by measuring blood Pb levels and biomarkers of haem biosynthesis, phosphorus (P) and calcium (Ca) metabolism, oxidative stress and immune function in individuals (n = 194) of 9 species trapped alive in the field between 2016 and 2017. Passive monitoring results revealed some species with liver Pb levels associated with severe clinical poisoning (>30 μg/g d.w. of Pb): Eurasian griffon vulture (27/257, 10.5%), red kite (1/132, 0.8%), golden eagle (4/38, 10.5%), and Northern goshawk (1/8, 12.5%). The active monitoring results showed that individuals of bearded vulture (1/3, 33.3%), Eurasian griffon vulture (87/118, 73.7%), Spanish imperial eagle (1/6, 16.7%) and red kite (1/18, 5.6%) had abnormal blood Pb levels (>20 μg/dL). Blood Pb levels increased with age, and both monitoring methods showed seasonality in Pb exposure associated with a delayed effect of the hunting season. In Eurasian griffon, blood Pb concentration was associated with lower δ-ALAD activity in blood and P levels in plasma, and with higher blood lipid peroxidation and plasma carotenoid levels in agreement with other experimental and field studies in Pb-exposed birds. The study reveals that Pb poisoning is a significant cause of death and sublethal effects on haem biosynthesis, P metabolism and oxidative stress in birds of prey in Spain.

Egg Overspray with Herbicides and Fungicides Reduces Survival of Red-Legged Partridge Chicks

Within the environmental risk assessment conducted for pesticide registration in the European Union (EU), avian reproductive toxicity is characterized after exposing adults. However, eggs of ground-nesting species can be exposed when pesticide applications occur during laying or incubation. We simulated environmentally realistic exposure of red-legged partridge (Alectoris rufa) eggs to an herbicide (2,4-D) and a fungicide (tebuconazole) applied to winter cereal crops during the breeding season of most farmland birds. We analyzed the effects on hatching success, offspring survival, and physiology. Exposure by overspray led to greater pesticide accumulation in the eggshell or content than exposure through contact with treated soil (3.1-13.7 times higher, depending on the pesticide and target sample). Egg overspray with tebuconazole significantly increased chick mortality, which was 26% higher than that of controls. 2,4-D caused a similar but a close to significant increase (chick mortality 24% higher than controls). Exposure to either pesticide through contact with treated soils did not affect chick survival but altered some biochemical parameters posthatching. Our experiment shows that egg spraying with pesticides should be considered as a relevant exposure scenario in risk assessment procedures, given its potential to affect the reproductive success of ground-nesting farmland birds.

Multi-level analysis of exposure to triazole fungicides through treated seed ingestion in the red-legged partridge

Triazole fungicides are the most widely used products to treat cereal seeds. Granivorous birds, such as red-legged partridges (Alectoris rufa), which consume seeds left on the surface of fields after sowing, have a high risk of exposure. As triazole fungicides can affect sterol synthesis, we tested the hypothesis that treated seed consumption could alter the synthesis of sex hormones and reduce the reproductive capacity of partridges. We exposed adult partridges to seeds treated with four different formulations containing triazoles as active ingredients (flutriafol, prothioconazole, tebuconazole, and a mixture of the latter two) simulating a field exposure during the late autumn sowing season. All treatments produced biochemical changes and an overexpression of genes encoding for enzymes involved in the biosynthesis of sterols and steroid hormones, such as PMVK, ABCA1, MVD, PSCK9, DHCR7 and HSD17B7. Plasma levels of oestradiol were reduced in partridges exposed to tebuconazole. We also monitored reproduction 3 months after exposure (laying date, egg fertilization and hatching rates). We observed a 14-day delay in the laying onset of partridges that had been exposed to flutriafol as compared to controls. These results show that the consumption of seeds treated with triazole fungicides has the potential to affect granivorous bird reproduction. We recommend the evaluation of lagged reproductive effects as part of the protocols of environmental risk assessment of pesticides in wild birds in light of the effects resulting from the exposure to triazole-treated seeds.

Assessment of ecotoxicological risks to river otters from ingestion of invasive red swamp crayfish in metal contaminated areas: Use of feces to estimate dietary exposure

The invasive red swamp crayfish (Procambarus clarkii) has become a major food resource for Eurasian otters (Lutra lutra) in the Iberian Peninsula. Crayfish accumulate large amounts of metals, and hence otters could be at risk of exposure and intoxication through crayfish consumption. We conducted a food safety risk assessment for otters inhabiting two historical mining areas in central Spain affected by lead (Pb) and mercury (Hg) pollution. Estimated daily intakes (EDI) of Pb and Hg were non-invasively calculated from the proportion of crayfish remains and metal levels in otter feces. We considered that the abdominal muscle and the carcass of crayfish differ significantly in relative weight, total metal content and bioavailability of metals to reduce the uncertainty of risk characterization. Fecal concentrations of Hg and Pb in the polluted areas were 1.878 and 6.554 μg/g d. w., respectively (13-fold and 7-fold higher compared to a non-polluted area). EDI of Hg and Pb in the polluted areas were 66.02 and 78.26 μg/kg-day, respectively (14- and 8-fold higher than in the reference area). EDI from the Hg area were above minimum levels susceptible to cause neurotoxicity in mustelids, and 6.3% were above levels susceptible to cause histopathological lessions. In the Pb area, 16.7% of EDI were consistent with levels causing reproductive effects. Metal exposure through crayfish consumption might prevent or slow the recovey of otters in these polluted environments, thus this factor should be considered in management strategies aimed to protect otter populations.

Food safety risk assessment of metal pollution in crayfish from two historical mining areas: Accounting for bioavailability and cooking extractability

Here we characterize the bioaccumulation of mercury (Hg) and lead (Pb) in red swamp crayfish (Procambarus clarkii) from two river courses in Central Spain that are impacted by historical Hg and Pb mining activities, respectively. We estimate the absolute oral bioavailability of metals in crayfish tissues by means of in vitro bioaccessibility simulations, and assess whether their consumption may imply a health risk for humans by estimating target hazard quotients and safe consumption rates. We also study the effect of cooking crayfish on the mobilization of the metal body burden in the context of the traditional Spanish cuisine. The results showed that crayfish from the mining districts accumulated a high level of Hg and Pb pollution in both the tail muscle and the carcass. The in vitro bioaccessibility of Hg and Pb in the edible part was 27.86 ± 4.05 and 33.73 ± 5.91%, respectively. Absolute bioavailability was estimated to be 38.31 for Hg, and 20.21 (adults) and 67.35% (children) for Pb. Risk indices indicated that, even after adjusting for bioavailability, it is not safe to consume crayfish from the mining-impacted rivers because of their high levels of Hg and Pb. Using the carcass as a condiment for flavouring should also be avoided. The cooking procedure extracted relatively small amounts of the total Hg (8.92 ± 2.13%) and Pb (1.68 ± 0.29%) body burden. Further research that will support human and ecological risk assessment, along with the implementation of advisory measures for the local population as regards crayfish consumption, are recommended.

Immunotoxic effects of lead on birds

The ingestion of lead (Pb) shot pellets is a well-known cause of avian mortality, but exposure of birds to Pb may have other sublethal effects that can affect population sustainability. One of these effects is the alteration of the immunological status. Pb can affect most components of the avian immune system and imbalance the relationship among them. Pb exposure typically alters the ratio between T_h1- and T_h2-type responses mounted by different classes of T-lymphocytes, causing the depression of the T_h1 responses that are associated with cell-mediated immunity. Immunodepressing effects of Pb on birds are observed at blood levels above 50 μg dL^-1, but developing birds show immunodepressing effects at much lower concentrations (> 10 μg dL^-1). Impacts of Pb on the avian immune system also relate to reduced resistance to infection. We review immunotoxic effects of Pb on birds affected by shot ingestion as well as by other sources of exposure to this element.

Tools for non-invasive sampling of metal accumulation and its effects in Mediterranean pond turtle populations inhabiting mining areas

Among reptiles, freshwater turtle species have high potential for metal accumulation because of their long lifespan or their aquatic and terrestrial habits. In order to monitor metal bioaccumulation, determine potential toxic effects, and investigate tools for non-invasive metal sampling in reptiles, we studied lead (Pb) and mercury (Hg) accumulation in Mediterranean pond turtles (Mauremys leprosa) inhabiting two former mining areas, one of them with high environmental concentrations of Pb (Sierra Madrona-Alcudia Valley district) and the other one with high environmental concentrations of Hg (Almadén district). Individuals from the Pb mining area showed mean blood concentrations (i.e. 5.59 μg Pb/g dry weight, d.w.) that were higher than those measured in other populations. Blood Hg concentrations were highest (8.83 μg Hg/g d.w.) in the site close to the former Hg mines, whereas blood Hg concentrations in terrapins from another site of Almadén district, located ∼28 km downstream, were not different from locations at the non-mining area. Animals from the Pb-contaminated site showed evidence of oxidative stress, whereas those from the Hg-contaminated site showed increased activity of the antioxidant enzyme glutathione peroxidase, as well as reduced circulating levels of the main endogenous antioxidant peptide, glutathione. Concentrations measured in feces and carapace scutes were useful indicators to monitor blood concentrations of Pb, but not of Hg. Our results provide evidence of the usefulness of freshwater turtles as sentinels of chronic metal pollution, and validate non-invasive tools to advance Pb monitoring in reptiles.

Accumulation of pollutants in nestlings of an endangered avian scavenger related to territory urbanization and physiological biomarkers

We monitor pollutant accumulation and investigate associated changes at the physiological level within the population of an obligate avian scavenger, the Egyptian Vulture (Neophron percnopterus), from Catalonia (NE Spain). This population is expanding its range, presumably because of the use of human waste disposal sites as food resource. We hypothesized that habitat urbanization, presumably associated with feeding from human wastes, could influence the accumulation of persistent organic pollutants and metals. The aim of this study was to explore the relationship between accumulated pollutants and biochemical parameters in nestling blood. We used the proportion of urban surface within an 8 km radius of each nest as a proxy to study the relationship between anthropic influence and pollutant accumulation. Observed blood levels of metals, organochlorine pesticides, polychlorinated biphenyls (PCBs), per- and polyfluoroalkylated substances (PFAS) and polybrominated diphenyl ethers (PBDEs) were relatively low, as expected for nestling individuals due to short-term exposures. CB-180 and PBDEs were associated with variations in blood biochemistry parameters; hexa-BDEs appeared positively associated with activities of the enzymes aspartate aminotransferase and lactate dehydrogenase, whereas CB-180 accumulation was associated with an increased activity of creatine phosphokinase and elevated glutathione levels. Increased CB-180 levels were also related to decreased blood concentrations of calcium, cholesterol, α-tocopherol and lutein. A proportion of urban surfaces as low as 6.56% within a radius of 8 km around the nest appears related to the accumulation of CB-180, the majority of analysed PFAS and of PBDE congeners 99 and 209, and increased urbanization was also associated with decreased plasma levels of α-tocopherol and carotenoids. These associations suggest that changes in blood profiles of vitamins, carotenoids or other analytes, despite related to increased plasma levels of CB-180, would be consequence of exploitation of artificial food sources rather than of a direct effect of the pollutants.

Domestic waste disposal sites secure food availability but diminish plasma antioxidants in Egyptian vulture

Some domestic waste disposal sites (DWDS) accumulate enormous amounts of food that humans discard. This food resource is exploited by different species whose population dynamics have as a result been altered. The effects of feeding on human waste on individual health parameters such as body condition are still unknown. Traditionally, body condition in wildlife has been assessed using morphological indices based on size and weight. Expanding the range of indices to include the analysis of indicators at the physiological level can provide a more comprehensive picture of the animals' health status. In this work, we studied how different amounts of waste consumption (assessed using stable isotope analysis) affect nestling health and body condition in an expanding population of the endangered Egyptian Vulture (Neophron percnopterus). We used morphometric and physiological approaches, including plasma biochemistry, antioxidant defences and oxidative stress biomarkers. The results of the multivariate redundancy analysis and variance partitioning showed that the proportion of diet originating from DWDS is the main factor explaining physiological indicators in the studied vulture population. Nestlings that were fed on food from DWDS had lower levels of vitamins (e.g. α-tocopherol) and carotenoids (zeaxanthin and lutein), which have important functions as antioxidant defences, immunostimulant properties and ornamental purposes. Nevertheless, nestlings that were fed on food from DWDS were better nourished and experienced fewer food shortages than individuals not fed using this resource, which had lower levels of cholesterol. Possibly due to the easy access to food, breeding pairs using DWDS could have fewer difficulties in feeding their nestlings and thus could engender more regular brood sizes than those not exploiting this type of resource. Our integrative approach using diverse components was crucial for a reliable assessment of health and body condition in Egyptian Vulture nestlings and its relationship to the consumption of food derived from human-altered environments.

Exposure of black-necked grebes (Podiceps nigricollis) to metal pollution during the moulting period in the Odiel Marshes, Southwest Spain

European populations of black-necked grebes (Podiceps nigricollis) congregate every year to moult at the salt ponds of the Odiel Marshes (SW Spain). However, the Odiel Marshes are part of one of the most metal-polluted coastal estuaries in the world, which may pose risks to wildlife. We assessed the exposure of grebes to metal pollution during the critical moulting period in the Odiel Marshes and its potential to cause adverse health effects. Levels of metals in red blood pellet (as a biomarker of exposure), plasma carotenoids, eye redness, and body condition (as biomarkers of effects) were studied. Metal content was also analyzed in the brine shrimp Artemia parthenogenetica, the most important food for grebes in this hypersaline ecosystem during the moulting period. Results showed that, in comparison to toxicity thresholds, grebes had relatively high blood levels of arsenic (As), mercury (Hg) and zinc (Zn). The high loads found in Artemia and the way blood levels vary during the moulting period indicate that shrimp consumption may be the main route of metal exposure for grebes. Plasma carotenoids and body condition showed a positive association with exposure to As, while the relationship of lutein-like carotenoids with Hg accumulation was negative at the beginning of the moulting period to become positive afterwards. Moreover, eye redness was negatively affected by As accumulation. Factors including food resource availability, seasonal fluctuations in physiological status, and interannual variations in the degree of environmental contamination should be considered in monitoring efforts when using moult migrant waterbirds as sentinel species.

Brood size is reduced by half in birds feeding on flutriafol-treated seeds below the recommended application rate

Despite the efforts of the European Commission to implement measures that offset the detrimental effects of agricultural intensification, farmland bird populations continue to decline. Pesticide use has been pointed out as a major cause of decline, with growing concern about those agro-chemicals that act as endocrine disruptors. We report here on the effects of flutriafol, a ubiquitous systemic fungicide used for cereal seed treatment, on the physiology and reproduction of a declining gamebird. Captive red-legged partridges (Alectoris rufa; n = 11-13 pairs per treatment) were fed wheat treated with 0%, 20% or 100% of the flutriafol application rate during 25 days in late winter. We studied treatment effects on the reproductive performance, carotenoid-based coloration and cellular immune responsiveness of adult partridges, and their relationship with changes in oxidative stress biomarkers and plasma biochemistry. We also studied the effect of parental exposure on egg antioxidant content and on the survival, growth and cellular immune response of offspring. Exposed partridges experienced physiological effects (reduced levels of cholesterol and triglycerides), phenotypical effects (a reduction in the carotenoid-based pigmentation of their eye rings), and most importantly, severe adverse effects on reproduction: a reduced clutch size and fertile egg ratio, and an overall offspring production reduced by more than 50%. No effects on body condition or cellular immune response of either exposed adult or their surviving offspring were observed. These results, together with previous data on field exposure in wild partridges, demonstrate that seed treatment with flutriafol represents a risk for granivorous birds; they also highlight a need to improve the current regulation system used for foreseeing and preventing negative impacts of Plant Protection Products on wildlife.

Validity of fish, birds and mammals as surrogates for amphibians and reptiles in pesticide toxicity assessment

Amphibians and reptiles are the two most endangered groups of vertebrates. Environmental pollution by pesticides is recognised as one of the major factors threatening populations of these groups. However, the effects of pesticides on amphibians and reptiles have been studied for few substances, which is partly related to the fact that these animals are not included in the mandatory toxicity testing conducted as part of environmental risk assessments of pesticides. Whether risks of pesticides to amphibians and reptiles are addressed by surrogate taxa used in risk assessment is currently under debate. In order to develop a scientifically sound and robust risk assessment scheme, information needs to be gathered to examine whether fish, birds and mammals are valid surrogates for amphibians and reptiles. We updated a systematic review of scientific literature that was recently published compiling toxicity data on amphibians and reptiles. The outcome of this review was analysed with the purposes to (1) compare endpoints from amphibians and reptiles with the available information from fish, birds and mammals, and (2) develop species sensitivity distributions (SSDs) for those substances tested in at least six amphibian species (no substances were found tested in at least six reptile species) to identify a candidate amphibian model species to be used as surrogate in risk assessment. A positive correlation was found between toxicity recorded on fish and amphibians, the former revealing, in general, to be more sensitive than the latter to waterborne pollutants. In the terrestrial environment, although birds and mammals were more sensitive than amphibians and reptiles to at least 60% of tested substances, just a few weak significant correlations were observed. As a general rule, homoeothermic vertebrates are not good surrogates for reptiles and terrestrial amphibians in pesticide risk assessment. However, some chemical-dependent trends were detected, with pyrethroids and organochlorine insecticides being more toxic to amphibians or reptiles than to birds or mammals. These trends could ultimately help in decisions about protection provided by surrogate taxa for specific groups of substances, and also to determine when risk assessment of pesticides needs to pay special consideration to amphibians and reptiles. The outcome of this review reflects that there is still much information needed to reduce uncertainties and extract relevant conclusions on the overall protection of amphibians and reptiles by surrogate vertebrates.

Toward sustainable environmental quality: Priority research questions for Europe

The United Nations' Sustainable Development Goals have been established to end poverty, protect the planet, and ensure prosperity for all. Delivery of the Sustainable Development Goals will require a healthy and productive environment. An understanding of the impacts of chemicals which can negatively impact environmental health is therefore essential to the delivery of the Sustainable Development Goals. However, current research on and regulation of chemicals in the environment tend to take a simplistic view and do not account for the complexity of the real world, which inhibits the way we manage chemicals. There is therefore an urgent need for a step change in the way we study and communicate the impacts and control of chemicals in the natural environment. To do this requires the major research questions to be identified so that resources are focused on questions that really matter. We present the findings of a horizon-scanning exercise to identify research priorities of the European environmental science community around chemicals in the environment. Using the key questions approach, we identified 22 questions of priority. These questions covered overarching questions about which chemicals we should be most concerned about and where, impacts of global megatrends, protection goals, and sustainability of chemicals; the development and parameterization of assessment and management frameworks; and mechanisms to maximize the impact of the research. The research questions identified provide a first-step in the path forward for the research, regulatory, and business communities to better assess and manage chemicals in the natural environment. Environ Toxicol Chem 2018;37:2281-2295. © 2018 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals, Inc. on behalf of SETAC.

Trace element concentrations in feathers and blood of Northern goshawk (Accipiter gentilis) nestlings from Norway and Spain

Information on trace element pollution in the terrestrial environment and its biota is limited compared to the marine environment. In the present study, we collected body feathers and blood of 37 Northern goshawk (Accipiter gentilis) nestlings from Tromsø (northern Norway), Trondheim (central Norway), and Murcia (southeastern Spain) to study regional exposure, hypothesizing the potential health risks of metals and other trace elements. Blood and body feathers were analyzed by a high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) for aluminum (Al), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), selenium (Se), cadmium (Cd), mercury (Hg) and lead (Pb). The influence of regional differences, urbanization and agricultural land usage in proximity to the nesting Northern goshawks was investigated using particular spatial analysis techniques. Most trace elements were detected below literature blood toxicity thresholds, except for elevated concentrations (mean ± SD µgml^-1 ww) found for Zn (5.4 ± 1.5), Cd (0.00023 ± 0.0002), and Hg (0.021 ± 0.01). Corresponding mean concentrations in feathers (mean ± SD µgg^-1 dw) were 82.0 ± 12.4, 0.0018 ± 0.002, and 0.26 ± 0.2 for Zn, Cd and Hg respectively. Multiple linear regressions indicated region was a significant factor influencing Al, Zn, Se and Hg feather concentrations. Blood Cd and Hg concentrations were significantly influenced by agricultural land cover. Urbanization did not have a significant impact on trace element concentrations in either blood or feathers. Overall metal and trace element levels do not indicate a high risk for toxic effects in the nestlings. Levels of Cd in Tromsø and Hg in Trondheim were however above sub-lethal toxic threshold levels. For holistic risk assessment purposes it is important that the concentrations found in the nestlings of this study indicate that terrestrial raptors are exposed to various trace elements.

Effects of Lead Exposure on Sperm Quality and Reproductive Success in an Avian Model

Lead (Pb) poisoning via ingestion of shot pellets is a frequent cause of death in wild birds and also has a wide range of subclinical effects. Here we report on the sublethal effects Pb exposure has on the breeding performance of red-legged partridges (Alectoris rufa). We studied the effects of Pb exposure on sperm quality, reproductive success, egg properties, laying performance, antioxidant levels, and carotenoid-based coloration. Birds were exposed by oral gavage to one or three No. 6 Pb shot pellets (2.8 mm in diameter, mean mass ± SD: 109 ± 7.97 mg). We show that exposure to three pellets (330 mg) reduced the hatching rate of females and decreased the acrosome integrity and sperm motility of males. In addition, females exposed to 1 pellet (110 mg) produced heavier eggs and chicks, whereas males exposed to 1 pellet presented an increase in sperm vigor. Sperm viability, concentration, progressiveness or fecundation rate were not affected by Pb treatment. Pb exposure increased circulating antioxidant levels in males, whereas the percentage of carotenoid-pigmented eye-ring area decreased in exposed females. Several sperm parameters showed positive relationships with coloration and antioxidant levels, suggesting that males displaying redder ornaments may be more capable of protecting sperm from oxidative stress in the event of sublethal Pb exposure.

Lead exposure reduces carotenoid-based coloration and constitutive immunity in wild mallards

The ingestion of spent lead (Pb) from ammunition is a known cause of mortality in waterfowl, but little is known about sublethal effects produced by Pb poisoning on birds, especially in wild populations. The authors studied potential sublethal effects associated with Pb exposure in mallards (Anas platyrhynchos) from the Ebro delta (northeastern Spain) after a ban on Pb ammunition. They analyzed the relationships between blood Pb levels and oxidative stress, immune response, and carotenoid-based coloration, which are known to be influenced by oxidative stress. Levels of Pb were reduced by half from 6 yr to 9 yr after the ban. Lipid peroxidation was positively related to Pb levels in females. The δ-aminolevulinic acid dehydratase activity was suppressed by Pb exposure and negatively associated with the activity of antioxidant enzymes. Carotenoid levels were positively associated with blood Pb concentration in both sexes, and males with higher Pb levels presented a less intense coloration in legs and beak. Levels of Pb were positively related to hemolytic activity of circulating immune system components and negatively related to lysozyme levels. In summary, Pb exposure was associated in a gender-specific way with increased oxidative stress, consequences on color expression, and impaired constitutive immunity. In females, antioxidants seemed to be allocated mostly in reproduction rather than in self-maintenance, whereas males seemed to better maintain oxidative balance to the detriment of coloration. Environ Toxicol Chem 2016;35:1516-1525. © 2015 SETAC.

Pollutant accumulation patterns in nestlings of an avian top predator: biochemical and metabolic effects

The exposure to persistent pollutants such as organochlorine compounds (OCs) or metals has been associated with declines in top predator populations, which can accumulate high amounts of these pollutants from their prey. However, understanding how variation in OC and metal accumulation in wild species affects their biochemical and physiological responses is a big challenge, especially for endangered predators like the Bonelli's eagle (Aquila fasciata). This bird of prey is an interesting study model because the differences in diet composition among populations and territories can account for important pollutant uptake variations. We compared OC and metal accumulation in blood of Bonelli's eagle nestlings from three populations across Spain as a function of origin, age class (nestlings vs. adults), sex and number of siblings per nest, and related accumulation patterns to responses indicative of body condition, biochemistry and antioxidant status. Nestlings from Catalonia, the most industrialized area, showed the highest concentrations of PCBs and arsenic, and the lowest concentrations of zinc. The two former substances, together with DDTs, exerted an overall influence on nestling's physiology. PCBs and arsenic were associated with reduced retinol levels, pointing to oxidative damage in exposed individuals, which was also consistent with the low zinc levels in individuals from the polluted region. Increased plasma DDT levels were related to reduced body condition and lower levels of triglycerides. Mercury accumulation in Castile and Leon was higher in nestlings that were alone in the nest than in nestlings that shared it with a sibling; this suggests an increased mercury uptake from secondary prey in territories where preferred prey (i.e. rabbits) are scarce, which are also the territories where productivity is reduced. Overall, the results reveal a spatial variation in pollutant accumulation patterns and associated physiological effects, and suggest the major role that territory quality may have in such patterns.

Assessing the Risk of Fipronil-Treated Seed Ingestion and Associated Adverse Effects in the Red-Legged Partridge

Fipronil is an insecticide commonly used in agriculture, but there are growing concerns over its environmental impacts (e.g., harmful effects on pollinators). Fipronil-treated seed ingestion might threaten granivorous farmland birds, in particular, Gallinaceous birds that are particularly sensitive to this insecticide. We report here on exposure risk and effects in a game bird of high socioeconomic importance, the red-legged partridge (Alectoris rufa). We fed captive birds with untreated maize (controls) or with a mixture of untreated-treated maize (ratio 80:20; exposed birds) during 10 days at the beginning of the breeding period (n = 12 pairs in each group). We first show that exposed partridges did not reject treated seeds but reduced food intake and lost body condition. We further studied the effects of treated seed ingestion on adult survival, oxidative balance, plasma biochemistry, carotenoid-based coloration, cellular immune response, steroid hormone levels, and reproduction. Fipronil exposure altered blood biochemistry and sexual hormone levels and reduced cellular immune response, antioxidant levels, and carotenoid-based coloration. Exposed pairs also had reduced egg fecundation rate and produced eggs with fewer antioxidants and offspring that had reduced cellular immune response. These negative effects on adult partridges, their reproductive performance, and offspring quality highlight that fipronil-treated seed ingestion is a significant threat to wild birds.

Altered immune response in mallard ducklings exposed to lead through maternal transfer in the wild

Lead (Pb) poisoning has caused significant mortality in waterfowl populations worldwide. In spite of having been banned since 2003, prevalence of Pb shot ingestion in mallards (Anas platyrhynchos) from the Ebro delta was still 15.5% in 2011-12. We collected mallard eggs from this area to study the effects of maternally transferred Pb on eggshell properties and on immune response and oxidative balance of ducklings. Eggshell Pb levels were positively correlated with Pb levels in the blood of ducklings. Ducklings with blood Pb levels above 180 ng mL(-1) showed reduced body mass and died during the first week post hatching. Blood Pb levels positively correlated with humoral immune response, endogenous antioxidants and oxidative stress biomarkers, and negatively correlated with cellular immune response. Pb shot ingestion in birds can result in maternal transfer to the offspring that can affect their developing immune system and reduce their survival in early life stages.

Plasma levels of pollutants are much higher in loggerhead turtle populations from the Adriatic Sea than in those from open waters (Eastern Atlantic Ocean)

In this paper we determined the levels of 63 environmental contaminants, including organic (PCBs, organochlorine pesticides, and PAHs) and inorganic (As, Cd, Cu, Pb, Hg and Zn) compounds in the blood of loggerhead turtles (Caretta caretta) from two comparable populations that inhabit distinct geographic areas: the Adriatic Sea (Mediterranean basin) and the Canary Islands (Eastern Atlantic Ocean). All animals were sampled at the end of a period of rehabilitation in centers of wildlife recovery, before being released back into the wild, so they can be considered to be in good health condition. The dual purpose of this paper is to provide reliable data on the current levels of contamination of this species in these geographic areas, and secondly to compare the results of both populations, as it has been reported that marine biota inhabiting the Mediterranean basin is exposed to much higher pollution levels than that which inhabit in other areas of the planet. According to our results it is found that current levels of contamination by organic compounds are considerably higher in Adriatic turtles than in the Atlantic ones (∑PCBs, 28.45 vs. 1.12ng/ml; ∑OCPs, 1.63 vs. 0.19ng/ml; ∑PAHs, 13.39 vs. 4.91ng/ml; p<0.001 in all cases). This is the first time that levels of PAHs are reported in the Adriatic loggerheads. With respect to inorganic contaminants, although the differences were not as great, the Adriatic turtles appear to have higher levels of some of the most toxic elements such as mercury (5.74 vs. 7.59μg/ml, p<0.01). The results of this study confirm that the concentrations are larger in turtles from the Mediterranean, probably related to the high degree of anthropogenic pressure in this basin, and thus they are more likely to suffer adverse effects related to contaminants.

Influence of dissolved oxygen conditions on toxicity of ammonium nitrate to larval natterjack toads

Temporary ponds, where many amphibians from temperate regions breed, show an annual cycle with a maximum water volume in spring followed by a progressive desiccation throughout late spring and summer. This desiccation leads to a decrease in dissolved oxygen and an increase in nitrogen levels, which can additionally increase because of anthropogenic sources such as chemical fertilizers. We analyzed the toxicity posed by environmentally relevant levels of a common nitrogenous fertilizer, ammonium nitrate, at different conditions of oxygen availability to Bufo calamita tadpoles, which typically develop in ephemeral ponds. Ammonium nitrate (90.3 mg N-NO3NH4/l) and hypoxic conditions (initial dissolved oxygen 4.53 ± 0.40 mg/l) caused significant lethal effects after 7 and 12 days of exposure, respectively. At the end of experiment (16 days), mortality rates were 32.5 % in individuals exposed to the fertilizer and 15 % in those growing under hypoxic conditions. When both stressors were combined, they showed an additive effect on tadpole survival. Malformations, such as oedemas and spinal curvatures, and locomotory abnormalities, were detected after 12 days of experiment in >90 % of individuals exposed to 45.2 mg N-NO3NH4/l under hypoxic conditions, whereas none of these stressors by separate related to abnormality rates >35 %. Delayed development was also observed in tadpoles exposed to ammonium nitrate with hypoxia affecting developmental rate only after 12 days of exposure. The results are discussed in terms of potential mechanisms linking negative effects of both factors as well as in terms of potential alterations of the ecological plasticity that often allows amphibians to survive in unpredictable environments.

Adverse effects of thiram-treated seed ingestion on the reproductive performance and the offspring immune function of the red-legged partridge

Pesticide research traditionally has focused on compounds with high acute toxicity or persistence, but the adverse sublethal effects of pesticides with different properties also may have important consequences on exposed wildlife. The authors studied the effects of thiram, a fungicide used for seed coating with known effects as endocrine disruptor. Red-legged partridges (Alectoris rufa; n = 15 pairs per treatment group) were fed wheat treated with 0%, 20%, or 100% of the thiram application rate used in autumn (25 d) and late winter (10 d) to mimic cereal sowing periods. The authors studied the effects on reproductive performance, carotenoid-based ornamentation and cellular immune responsiveness of adult partridges, and their relationship with changes in oxidative stress biomarkers and plasma biochemistry. The authors also studied the effect of parental exposure on egg antioxidant content and on the survival, growth, and cellular immune response of offspring. Exposure to thiram-coated seeds delayed egg laying, reduced clutch size, and affected egg size and eggshell thickness. Partridges exposed to the 20% thiram dose exhibited reduced egg fertility and brood size (55% and 28% of controls, respectively). Chick survival was unaffected by parental exposure to treated seeds, but adverse effects on their growth rate and cellular immune response were apparent. These effects on reproduction and immune function may have important demographic consequences on farmland bird populations.

Sublethal Pb exposure produces season-dependent effects on immune response, oxidative balance and investment in carotenoid-based coloration in red-legged partridges

Ingestion of lead (Pb) shot pellets constitutes the main cause of Pb poisoning in avifauna. We studied the effects of sublethal Pb exposure on immunity, carotenoid-based coloration, oxidative stress and trade-offs among these types of responses during spring and autumn in red-legged partridges (Alectoris rufa). We evaluated constitutive immunity testing lysozyme and natural antibody levels, and blood bactericidal and phagocytic activities. We studied induced immunity by testing PHA and humoral responses. We analyzed fecal parasite and bacterial abundance and oxidative stress biomarkers. Pb exposure in spring reduced natural antibody levels, whereas in autumn, it reduced lysozyme levels and increased phagocytic activity. Pb exposure increased PHA response in both seasons, and decreased T-independent humoral response in autumn. Pb exposure also increased noncoliform and decreased coliform Gram-negative gut bacteria. In spring, Pb exposure decreased antioxidant levels and increased coloration in males, whereas in autumn, it increased retinol levels but reduced coloration in both genders. Our results suggest that in spring, Pb-exposed females used antioxidants to cope with oxidative stress at the expense of coloration, whereas Pb-exposed males increased coloration, which may reflect an increased breeding investment. In autumn, both genders prioritized oxidative balance maintenance at the expense of coloration.

Imidacloprid-treated seed ingestion has lethal effect on adult partridges and reduces both breeding investment and offspring immunity

The ingestion of imidacloprid treated seeds by farmland birds may result in exposure to toxic amounts of this insecticide. Here we report on the effects that the exposure to the recommended application rate and to 20% of that rate may produce on birds feeding on treated seeds. Experimental exposure to imidacloprid treated seeds was performed on red-legged partridges (Alectoris rufa) (n=15 pairs per treatment group: control, 20% or 100% of the recommended application rate) during two periods that corresponded to the autumn (duration of exposure: 25 days) and late winter (10 days) cereal sowing times in Spanish farmlands. We studied effects on the survival, body condition, oxidative stress biomarkers, plasma biochemistry, carotenoid-based coloration, T-cell mediated immune response and reproduction of exposed adult partridges, and on the survival and T-cell immune response of their chicks. The high dose (recommended application rate) killed all partridges, with mortality occurring faster in females than in males. The low dose (20% the recommended application rate) had no effect on mortality, but reduced levels of plasma biochemistry parameters (glucose, magnesium and lactate dehydrogenase), increased blood superoxide dismutase activity, produced changes in carotenoid-based integument coloration, reduced the clutch size, delayed the first egg lay date, increased egg yolk vitamins and carotenoids and depressed T-cell immune response of chicks. Moreover, the analysis of the livers of dead partridges revealed an accumulation of imidacloprid during exposure time. Despite the moratorium on the use of neonicotinoids in the European Union, birds may still be at high risk of poisoning by these pesticides through direct sources of exposure to coated seeds in autumn and winter.

Experimental approaches to test pesticide-treated seed avoidance by birds under a simulated diversification of food sources

Pesticide coated seeds are known to be potentially toxic for birds, but the risk of poisoning will depend on how likely the individuals are to consume them. To refine the risk assessment of coated seed consumption by birds we studied the consumption and avoidance of seeds treated with imidacloprid, thiram, maneb or rhodamine B under different scenarios of food unpredictability (diversity or changes in food sources). In a first set of experiments, we examined during four days the amount of ingested food by red-legged partridges (Alectoris rufa) when offered untreated seeds, treated seeds or both. In the latter case, we also assessed the effect of a daily interchange in the position of feeders containing treated and untreated food. A second experiment, conducted with imidacloprid only, consisted of offering, during 27 h, fixed overall amounts of treated and untreated food, equally distributed in a different number of feeders per pen (1, 2, 4 or 8 feeders of each type of food) in order to diversify food sources. All the tested pesticide-treated seeds were avoided in two-choice experiments, and imidacloprid and thiram were also avoided in one-choice experiments. We found that imidacloprid treated seeds were avoided, probably as a consequence of a conditioned aversion effect due to the post-ingestion distress. However, under a diversification of two-choice food sources with multiple feeders, imidacloprid-treated seeds were ingested by partridges at increasing amounts that can produce sublethal effects or even death. Thiram treated seeds were also initially avoided in one-choice experiment, but probably mediated by a sensory repellence that progressively decreased with time. Our results reveal that the risk of pesticide exposure in birds may increase by unpredictability of food resources or prolonged availability of coated seeds, so pesticide registration for seed coating should consider worst-case scenarios to avoid negative impacts on farmland birds.

Immunomodulation in post-metamorphic northern leopard frogs, Lithobates pipiens, following larval exposure to polybrominated diphenyl ether

Pollutants and disease are factors implicated in amphibian population declines, and it is hypothesized that these factors exert a synergistic adverse effect, which is mediated by pollutant-induced immunosuppression. Polybrominated diphenyl ethers (PBDEs) are ubiquitous pollutants that can exert immunotoxicity, making them of interest to test effects on amphibian immune function. We orally exposed Lithobates (Rana) pipiens tadpoles to environmentally realistic levels (0-634 ng/g wet diet) of a pentabromodiphenyl ether mixture (DE-71) from as soon as they became free-swimming through metamorphic climax. To assess adaptive immune response in juvenile frogs, we used an enzyme-linked immunosorbent assay to measure specific IgY production following immunization with keyhole limpet hemocyanin (KLH). Specific KLH antibody response was significantly decreased in juvenile frogs that had been exposed to PBDEs as tadpoles. When assessing innate immune responses, we found significantly different neutrophil counts among treatments; however, phagocytic activity of neutrophils was not significantly different. Secretion of antimicrobial skin peptides (AMPs) nonsignificantly decreased with increasing PBDE concentrations, and no significant effect of PBDE treatment was observed on efficacy of AMPs to inhibit chytrid fungus (Batrachochytrium dendrobatidis) growth. Our findings demonstrate that environmentally realistic concentrations of PBDEs are able to alter immune function in frogs; however, further research is needed to determine how these alterations impact disease susceptibility in L. pipiens.

Reducing Pb poisoning in birds and Pb exposure in game meat consumers: the dual benefit of effective Pb shot regulation

The use of lead (Pb) ammunition in the form of shot pellets has been identified as a Pb exposure risk in wildlife and their human consumers. We explore the hypothesis that Pb shot ban enforcement reduces the risk of avian Pb poisoning as well as Pb exposure in game meat consumers. We assessed compliance with a partial ban on Pb shot commencing in 2003 by examination of 937 waterbirds harvested by hunters between 2007 and 2012 in the Ebro delta (Spain). Prevalence of Pb shot ingestion was determined, as were Pb concentrations in liver and muscle tissue to evaluate the potential for Pb exposure in game meat consumers. Hunted birds with only embedded Pb shot (no steel) declined from 26.9% in 2007-08 to <2% over the following three hunting seasons after ban reinforcement. Pb shot ingestion in mallards decreased from a pre-ban value of 30.2% to 15.5% in the post-ban period. Liver Pb levels were predominantly defined by the presence of ingested shot, whereas muscle levels were defined by the presence of both ingested and embedded shot. Only 2.5% of mallard muscle tissue had Pb levels above European Union regulations for meat (0.1μg/g wet weight) in the 2008-09 season, when Pb shot ingestion prevalence was also at a minimum (5.1%). Effective restrictions in Pb ammunition use have a dual benefit since this reduces Pb exposure for game meat consumers due to embedded ammunition as well as reducing Pb poisoning in waterbirds.

Expression of immunoregulatory genes and its relationship to lead exposure and lead-mediated oxidative stress in wild ungulates from an abandoned mining area

Lead (Pb) is a highly toxic metal that can induce oxidative stress and affect the immune system by modifying the expression of immunomodulator-related genes. The aim of the present study was to investigate the association between Pb exposure and the transcriptional profiles of some cytokines, as well as the relationship between Pb exposure and changes in oxidative stress biomarkers observed in the spleen of wild ungulates exposed to mining pollution. Red deer and wild boar from the mining area studied had higher spleen, liver, and bone Pb levels than controls, indicating a chronic exposure to Pb pollution. Such exposure caused a depletion of spleen glutathione levels in both species and disrupted the activity of antioxidant enzymes, suggesting the generation of oxidative stress conditions. Deer from the mining area also showed an induced T-helper (Th )-dependent immune response toward the Th 2 pathway, whereas boar from the mining area showed a cytokine profile suggesting an inclination of the immune response toward the Th 1 pathway. These results indicate that environmental exposure to Pb may alter immune responses in wild ungulates exposed to mining pollution. However, evidence of direct relationships between Pb-mediated oxidative stress and the changes detected in immune responses were not found. Further research is needed to evaluate the immunotoxic potential of Pb pollution, also considering the prevalence of chronic infectious diseases in wildlife in environments affected by mining activities.

Experimental exposure of red-legged partridges (Alectoris rufa) to seeds coated with imidacloprid, thiram and difenoconazole

Pesticide coated seeds are commonly used in agriculture, and may be an important source of food for some birds in times of scarcity, as well as a route of pesticide ingestion. We tested the lethal and sub-lethal effects of treated seed ingestion by the red-legged partridge (Alectoris rufa), a game bird of high socio-economic value in Spain. One year-old partridges (n = 42 pairs) were fed for 10 days in spring (prior to breeding) with wheat treated with difenoconazole (fungicide), thiram (fungicide) or imidacloprid (insecticide), using two doses for each pesticide (the one recommended, and its double to represent potential cases of abuse of pesticides). We investigated the direct and indirect effects on the body condition, physiology, immunology, coloration and subsequent reproduction of exposed partridges. For the latter, eggs were collected, measured and incubated and the growth and survival of chicks were monitored. Thiram and imidacloprid at high exposure doses produced mortalities of 41.6 and 58.3 %, respectively. The first death was observed at day 3 for imidacloprid and at day 7 for thiram. Both doses of the three pesticides caused sublethal effects, such as altered biochemical parameters, oxidative stress and reduced carotenoid-based coloration. The high exposure doses of imidacloprid and thiram also produced a decrease in cellular immune response measured by the phytohemagglutinin test in males. Bearing in mind the limitation of the small number of surviving pairs in some treatments, we found that the three pesticides reduced the size of eggs and imidacloprid and difenoconazole also reduced the fertilization rate. In addition, both thiram and imidacloprid reduced chick survival. These experiments highlight that the toxicity of pesticide-treated seeds is a factor to consider in the decline of birds in agricultural environments.

Density effects on ammonium nitrate toxicity on amphibians. Survival, growth and cannibalism

Temporary ponds where many amphibians breed experience a gradual desiccation that leads to growing larval densities, which can reduce tadpole survival rates and increase cannibalistic interactions among carnivorous salamander larvae. Concentrations of many agrochemicals, including nitrogenous fertilizers, can also increase as the water volume decreases. We analyzed the effects of ammonium nitrate fertilizer at two larval densities on growth and survival of Rana dalmatina tadpoles, and on cannibalistic behaviors of Salamandra salamandra larvae. We observed synergistic lethal effects until day 17 of exposure, when ammonium nitrate-related mortality of tadpoles was five times greater at high than at low density. The fertilizer impaired tadpole growth. This effect was stronger at low density than at high density. In the absence of ammonium nitrate, the incidence of cannibalism was higher at high than at low larval density. However, fertilizer exposure removed this density-dependent effect, which, under field conditions, would negate some potentially advantageous effects of cannibalism such as reduced intraspecific competition and the stimulation of defensive behaviors.

Levels of organochlorine pesticides and polychlorinated biphenyls in the critically endangered Iberian lynx and other sympatric carnivores in Spain

Accumulation of organochlorine compounds is well studied in aquatic food chains whereas little information is available from terrestrial food chains. This study presents data of organochlorine levels in tissue and plasma samples of 15 critically endangered Iberian lynx (Lynx pardinus) and other 55 wild carnivores belonging to five species from three natural areas of Spain (Doñana National Park, Sierra Morena and Lozoya River) and explores their relationship with species diet. The Iberian lynx, with a diet based on the consumption of rabbit, had lower PCB levels (geometric means, plasma: <0.01 ng mL(-1), liver: 0.4ngg(-1) wet weight, fat: 87 ng g(-1)lipid weight) than other carnivores with more anthropic and opportunistic foraging behavior, such as the red fox (Vulpes vulpes; plasma: 1.11 ng mL(-1), liver: 459 ng g(-1), fat: 1984 ng g(-1)), or with diets including reptiles at higher proportion, such as the Egyptian mongoose (Herpestes ichneumon; plasma: 7.15 ng mL(-1), liver: 216 ng g(-1), fat: 540 ng g(-1)), or the common genet (Genetta genetta; liver: 466 ng g(-1), fat: 3854 ng g(-1)). Chlorinated pesticides showed interspecific variations similar to PCBs. Organochlorine levels have declined since the 80s in carnivores from Doñana National Park, but PCB levels are still of concern in Eurasian otters (Lutra lutra; liver: 3873-5426 ng g(-1)) from the industrialized region of Madrid.

Effects of chronic polybrominated diphenyl ether exposure on gonadal development in the northern leopard frog, Rana pipiens

Polybrominated diphenyl ethers (PBDEs) are bioaccumulative, persistent organic pollutants used as flame retardants in consumer goods. Concentrations of PBDEs in North American wildlife have been increasing for decades and been shown to have estrogenic effects on sexual development. No studies, however, have examined the effects of PBDEs on the sexual development of North American frogs at ecologically relevant concentrations. This study examined the effects of five dietary concentrations of DE-71 (0, 1.1, 6.1, 71.4, and 634 ng ΣPBDEs/g diet), a technical PBDE mixture, on the gonadal development of the northern leopard frog, Rana pipiens. Tadpoles were exposed chronically from the time they became free-swimming until metamorphosis. Frogs were killed either at metamorphic climax or 10 weeks after completing metamorphosis, processed for histology, and examined for alterations in sexual development. The experimental group exposed to PBDEs at 1.1 ng/g had a significantly larger proportion of females compared with the expected 50:50 sex ratio. At 10 weeks post-metamorphosis, male frogs exposed to 6.1 and 71.4 ng/g had significantly smaller testes, but all other measure of gonadal development tested showed no effects. No intersex or increased incidence of gonadal abnormality were detected. These findings indicate that PBDEs may disrupt sexual differentiation in frogs at low, environmentally relevant concentrations.

Ambient ultraviolet B radiation and prevalence of infection by Batrachochytrium dendrobatidis in two amphibian species

Chytridiomycosis, the emerging disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd) is responsible for declines and extirpations of amphibian populations worldwide. Environmental covariates modify the host-Bd interaction and thus affect the ongoing spread of the pathogen. One such covariate may be the intensity of ultraviolet B (UV-B) radiation. In a field experiment conducted in Laguna Grande de Peñalara (central Spain), a mountainous region where the presence of Bd has been documented since 1997, we analyzed the potential effect of environmental UV-B (daily maximum 2.5-3.9 W/m(2) ) on the susceptibility of larvae of the common toad (Bufo bufo) to Bd. The proportion of infected individuals increased as tadpoles developed. The prevalence of Bd was significantly lower in tadpoles exposed to environmental UV-B intensities (2.94%) than in tadpoles not exposed to the radiation (9.72%). This finding mirrors that seen for a second amphibian species, the European midwife toad (Alytes obstetricans), for which conditional prevalence (i.e., prevalence of infection conditioned on the probability of a site being infected) across the Iberian Peninsula was inversely correlated with the intensity of UV-B.

Responses of toad tadpoles to ammonium nitrate fertilizer and predatory stress: differences between populations on a local scale

Agriculture-related pollution is among the major causes of global amphibian population declines. The multiple stressors to which amphibians are exposed in the field, such as predation pressure, can make agrochemicals far more deadly than when they act in isolation. Even within a small area, diffuse agricultural pollution does not affect all aquatic environments equally, which could account for local differences in amphibian sensitivity to agrochemicals. We examined the combined effects of ammonium nitrate fertilizer (0 to 45.2 mg N-NH 4(+)/L) and predator stress on larval Western spadefoot toad (Pelobates cultripes), using adult caged male marbled newts (Triturus marmoratus) as predators. We compared the interaction between both stressors in tadpoles from two ponds separated by 3 km. No significant mortality was observed (survival > 80% in all cases). Local differences were detected when analyzing larval growth, with a significant interaction between factors for one of the two populations tested (Fornillos de Fermoselle). Although tadpoles exposed to 45.2 mg N-NH 4(+)/L were 7% smaller than controls, the presence of predators from a foreign community resulted in animals 15% larger than those raised without predators after 15 d of experiment. Interestingly, predators from the same community as the tadpoles did not affect larval growth. The length of the tadpoles from a nearby location (Mámoles) was unaffected after exposure to ammonium nitrate and predatory stress.

Influence of a combination of agricultural chemicals on embryos of the endangered gold-striped salamander (Chioglossa lusitanica)

Pollution from agrochemicals may be contributing to the global decline of amphibian populations. Environmentally relevant concentrations of a fertiliser, ammonium nitrate, and a commercial formulation of the herbicide glyphosate Roundup Plus were tested on the embryonic development of Chioglossa lusitanica. This study introduces new data at three different levels. First, we provide previously unknown information about hatchling traits of C. lusitanica. Second, we present the first ecotoxicological study of this endangered species, to which environmental pollution is considered a major threat. Third, we conduct the first experiment with an amphibian species exposed to a mixture of a glyphosate-based herbicide and a nitrogenous fertiliser. Control individuals hatched with an average (±SD) total length of 18.77 (±2.02) mm and at an average Harrison's developmental stage of 44.58 (±1.24). Mean hatching time among controls was 11.52 (±1.29) weeks. None of the chemicals or their interaction produced lethal effects; however, a significant interaction was found when analysing total length at hatching. Individuals exposed to the herbicide hatched at a larger size than controls, and this effect was especially clear when the fertiliser was added to the water. The absence of pollutant-related mortality or severe sublethal effects is in agreement with most studies indicating a high tolerance of amphibian embryos to agrochemicals. However, further research considering other life stages and additional natural factors (i.e., predators, food availability) is needed to estimate the ecological impact of chemical mixtures on C. lusitanica.

Influence of ammonium nitrate on larval anti-predatory responses of two amphibian species

Sublethal effects of toxicants can upset normal behavioural responses to predators, leading to increased predation. For example, sensory capabilities can be impaired by toxicants, leading to difficulty in detecting predators or other threats. Alteration of locomotor abilities by pollutants can also explain the difficulty of tadpoles to escape from predators. Here we assess the effects of a nitrogenous fertilizer on the response to predators shown by anuran tadpoles. In a first experiment, we chronically exposed Iberian painted frog (Discoglossus galganoi) and spadefoot toad (Pelobates cultripes) tadpoles to environmentally relevant concentrations of ammonium nitrate. After the exposure, we tested tadpoles' ability to avoid predation by the red crayfish (Procambarus clarkii). In a second experiment, we analysed the escape behaviour of P. cultripes tadpoles as a function of ammonium nitrate exposure and presence of predatory crayfishes. Tadpoles of both species that were exposed to ammonium nitrate were consumed by crayfishes faster than controls (mean time of predation: Dg controls=18.03 h, 90.3 mg N-NO(3)NH(4)/L=7.48 h; Pc controls=16.12h, 90.3 mg N-NO(3)NH(4)/L=9.46 h). Control larval P. cultripes showed specific anti-predator escape responses, whereas those exposed to the fertilizer did not. We demonstrate, for the first time in amphibians, how nitrogenous fertilizers can affect larval defensive behaviours, and thereby increase the risk of predation. Our results emphasize the importance of considering environmental stresses on the ecotoxicological studies with amphibians.

Adaptation to osmotic stress provides protection against ammonium nitrate in Pelophylax perezi embryos

The negative effects of pollution on amphibians are especially high when animals are additionally stressed by other environmental factors such as water salinity. However, the stress provoked by salinity may vary among populations because of adaptation processes. We tested the combined effect of a common fertilizer, ammonium nitrate (0-90.3 mg N-NO3NH4/L), and water salinity (0-2 per thousand) on embryos of two Pelophylax perezi populations from ponds with different salinity concentrations. Embryos exposed to the fertilizer were up to 17% smaller than controls. Survival rates of embryos exposed to a single stressor were always below 10%. The exposure to both stressors concurrently increased mortality rate (>95%) of embryos from freshwater. Since the fertilizer was lethal only when individuals were stressed by the salinity, it did not cause lethal effects on embryos naturally adapted to saline environments. Our results underscore the importance of testing multiple stressors when analyzing amphibian sensitivity to environmental pollution.

Alteration of courtship behavior because of water acidification and minor effect of ammonium nitrate in the Iberian newt (Lissotriton boscai)

Although many studies have assessed the effects of water pollution on amphibians, few have focused on the alteration of vital behaviors. Newt species usually display complex courtship behavior that may be altered by sublethal levels of contaminants. We analyzed the effects of ammonium nitrate and water acidification on courtship behavior of the Iberian newt (Lissotriton boscai). We exposed newt couples to three treatments (control, nominal 90 mg N--NO3NH4/L, and nominal pH 4) and recorded the occurrence of each of the three courtship phases (orientation, static display, and spermatophore transfer) as well as the latency to initiate courtship, overall courtship time, male perseverance, and female responsiveness. Major effects were observed in the acid treatment. Low pH inhibited orientation. None of the control couples failed to court, whereas 17% of couples from the low-pH treatment did not perform any courtship movement. Latency to initiate courting was twice as high in couples exposed to acidification as in controls. Low pH also affected the overall time of courtship and perseverance time of males in unsuccessful encounters. Ammonium nitrate did not cause any significant effect. Only the female response index and the duration of the tail-fanning movement (the major display during L. boscai courtship) were slightly reduced by the fertilizer. We report a pollution-mediated alteration of courtship behavior, to our knowledge for the first time, in amphibians. This kind of sublethal effect should be considered when estimating potential impacts of water pollution on natural populations.

Effects of ammonium nitrate exposure and water acidification on the dwarf newt: the protective effect of oviposition behaviour on embryonic survival

Embryonic mortality in many aquatic animals, including most amphibian species, is usually very high. In addition to mechanical and chemical defences, some species have developed behavioural patterns that can increase egg survival. For example, females of some newt species protect their eggs by wrapping them in leaves of aquatic plants. We have studied the effects of ammonium nitrate (nominal concentration of 90.3 mg N-NO(3)NH(4)/L) and water acidification (pH 4-5) on egg wrapping behaviour of the dwarf newt, Triturus pygmaeus, and on whether this specific behaviour may protect embryos from contamination. Although either ammonium nitrate or low pH did not inhibit oviposition, the mean percentage of eggs that were wrapped by the females was significantly lower at low pH than in controls. In order to assess the potential effects of oviposition behaviour on embryonic survival, we exposed simultaneously wrapped and unwrapped eggs to ammonium nitrate and acid pH during their development. After 25 days of exposure, ammonium nitrate reduced length and developmental stage at eclosion of the exposed individuals, regardless of whether they were wrapped or unwrapped. The fertilizer caused a significantly higher mortality in unwrapped than wrapped eggs. The potential impact of water pollution on amphibians in the field may include not only direct effects on embryonic and larval survival but also alteration of breeding behaviours, which may reduce reproductive success and ultimately affect population's condition.