Steroids in house sparrows (Passer domesticus): Effects of POPs and male quality signalling

Physiological status of House Sparrows (Passer domesticus) along an ozone pollution gradient

Mexico City is one of the most polluted cities in the world, and one in which air contamination is considered a public health threat. Numerous studies have related high concentrations of particulate matter and ozone to several respiratory and cardiovascular diseases and a higher human mortality risk. However, almost all of those studies have focused on human health outcomes, and the effects of anthropogenic air pollution on wildlife species is still poorly understood. In this study, we investigated the impacts of air pollution in the Mexico City Metropolitan Area (MCMA) on house sparrows (Passer domesticus). We assessed two physiological responses commonly used as biomarkers: stress response (the corticosterone concentration in feathers), and constitutive innate immune response (the concentration of both natural antibodies and lytic complement proteins), which are non-invasive techniques. We found a negative relationship between the ozone concentration and the natural antibodies response (p = 0.003). However, no relationship was found between the ozone concentration and the stress response or the complement system activity (p > 0.05). These results suggest that ozone concentrations in air pollution within MCMA may constrain the natural antibody response in the immune system of house sparrows. Our study shows, for the first time, the potential impact of ozone pollution on a wild species in the MCMA presenting the Nabs activity and the house sparrow as suitable indicators to assess the effect of air contamination on the songbirds.

Metabolomics: A New Approach in the Evaluation of Effects in Human Beings and Wildlife Associated with Environmental Exposition to POPs

Human beings and wild organisms are exposed daily to a broad range of environmental stressors. Among them are the persistent organic pollutants that can trigger adverse effects on these organisms due to their toxicity properties. There is evidence that metabolomics can be used to identify biomarkers of effect by altering the profiles of endogenous metabolites in biological fluids or tissues. This approach is relatively new and has been used in vitro studies mainly. Therefore, this review addresses those that have used metabolomics as a key tool to identify metabolites associated with environmental exposure to POPs in wildlife and human populations and that can be used as biomarkers of effect. The published results suggest that the metabolic pathways that produce energy, fatty acids, and amino acids are commonly affected by POPs. Furthermore, these pathways can be promoters of additional effects. In the future, metabolomics combined with other omics will improve understanding of the origin, development, and progression of the effects caused by environmental exposure.

Poisoned chalice: Use of transformed landscapes associated with increased persistent organic pollutant concentrations and potential immune effects for an adaptable carnivore

Wildlife around cities bioaccumulate multiple harmful environmental pollutants associated with human activities. Exposure severity can vary based on foraging behaviour and habitat use, which can be examined to elucidate exposure pathways. Carnivores can play vital roles in ecosystem stability but are particularly vulnerable to bioaccumulation of pollutants. Understanding the spatial and dietary predictors of these contaminants can inform pollutant control, and carnivores, at the top of food webs, can act as useful indicator species. We test for exposure to toxic organochlorines (OCs), including dichloro-diphenyl-trichloroethane (DDT) and polychlorinated biphenyls (PCBs), in a medium-sized felid, the caracal (Caracal caracal), across the peri-urban and agricultural landscapes of the city of Cape Town, South Africa. Concentrations in both blood (n = 69) and adipose tissue (n = 25) were analysed along with detailed spatial, dietary, demographic, and physiological data to assess OC sources and exposure risk. The analysis revealed widespread exposure of Cape Town's caracals to organochlorines: detection rate was 100% for PCBs and 83% for DDTs in blood, and 100% for both compounds in adipose. Caracals using human-transformed areas, such as vineyards and areas with higher human population and electrical transformer density, as well as wetland areas, had higher organochlorine burdens. These landscapes were also highly selected foraging areas, suggesting caracals are drawn into areas that co-incidentally increase their risk of exposure to these pollutants. Further, biomagnification potential was higher in individuals feeding on higher trophic level prey and on exotic prey. These findings point to bioaccumulation of OC toxicants and widespread exposure across local food webs. Additionally, we report possible physiological effects of exposure, including elevated white blood cell and platelet count, suggesting a degree of immunological response that may increase disease susceptibility. Cape Town's urban fringes likely represent a source of toxic chemicals for wildlife and require focused attention and action to ensure persistence of this adaptable mesocarnivore.

Ecotoxicology of persistent organic pollutants in birds

Considering the explosive growth of the list of persistent organic pollutants (POPs), the scientific community is combatting increasing challenges to protect humans and wildlife from the potentially negative consequences of POPs. Herein, we characterize the main aspects and progress in the ecotoxicology of POPs in avian species since 2000. The majority of previous efforts has revealed the global occurrence of high levels of various POPs in birds. Laboratory research and epidemiological studies imply that POPs exert a broad-spectrum of side-effects on birds by interfering with their endocrine, immune and neural system, reproduction, and development, and growth. However, inconsistent results suggest that the potential effects of POP exposure on the physiological parameters in birds are multifactorial, involving a multitude of biological processes, species-specific differences, gender, age and types of compounds. Great progress has been achieved in identifying the species-specific sensitivity to dioxin-like compounds, which is attributed to different amino acid residues in the ligand-binding domain of the aryl hydrocarbon receptor. Besides the conventional concentration additivity, several studies have suggested that different classes of POPs possibly act synergistically or antagonistically based on their concentration. However, ecotoxicology information is still recorded in a scattered and inadequate manner, including lack of enough avian species, limited number of POPs investigated, and insufficient geographical representation, and thus our understanding of the effects of POPs on birds remains rudimentary, although mechanistic understanding of their mode of action is progressing. Particularly, research on what happens to wild bird populations and their ecosystems under POP stress is still unavailable. Thus, our aim is to predict and trace the effects POPs at different biological organization levels, especially from the molecular, cellular and individual levels to the population, community and ecosystem levels because of the limited and scattered information, as mentioned above.

Interspecies comparison of the residue levels and profiles of persistent organic pollutants in terrestrial top predators

Serum samples from three species of living terrestrial top predators were analysed for six groups of persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane and its metabolites (DDTs), chlordane compounds (CHLs), hexachlorocyclohexane isomers (HCHs), hexachlorobenzene (HCB) and polybrominated diphenyl ethers (PBDEs). The study included three carnivore species: lion (Panthera leo), hyena (Hyena brunnea) and cheetah (Acinonyx jubatus). All samples were collected from healthy living animals between 2004 and 2005. Most of the samples (wild lions (n = 50) and hyenas (n = 11)) were collected from various locations within the Kruger National Park and Addo National Park (South Africa), while captive lions (n = 6) and cheetahs (n = 3) were collected from the Antwerp Zoo (Belgium). In general, relatively low levels of POPs were found in the studied species, varying widely within species and locations. Median concentrations of POPs were higher in captive lions (PCBs: 505 pg/mL; DDTs: 270 pg/mL; HCHs: 72 pg/mL; HCB: 34 pg/mL; CHLs: 24 pg/mL; PBDEs: 8 pg/mL) compared to wild lions (DDTs: 274 pg/mL; HCHs: 44 pg/mL; CHLs: 7.9 pg/mL; PCBs: 2.1 pg/mL; HCB: < LOQ; PBDEs: < LOQ). In the wild animals, POPs accumulated in the following order: DDTs > HCHs > CHLs > HCB > PCBs > PBDEs, while in the captive animals, the order was: PCBs > DDTs > CHLs > HCHs > HCB > PBDEs, suggesting differences in the diet of these animals. Furthermore, wild hyena contained significantly higher (p < 0.05) median levels of POPs compared to wild lions, possibly reflecting differences in metabolic capacity and/or feeding habits, together with an uneven distribution of POPs in the area where the animals lived. No previous data are available to compare for similar terrestrial top predators, such as lion, hyena and cheetah. To our knowledge, this is first study on POPs in these three species. The low POP levels found in this study were several orders of magnitude lower than those for other carnivore species, such as polar bears, grizzly bears, brown bears and wolves worldwide. The present study has revealed the need for expanding research and monitoring on occurrence, levels and disposition of POPs in the top predators of the terrestrial environment.

Can variability in corticosterone levels be related to POPs and OPEs in feathers from nestling cinereous vultures (Aegypius monachus)?

Persistent organic pollutants (POPs) are still globally distributed and some have been shown to interact with the endocrine system of birds. However, the relationship between POPs and the stress response mediated by the hypothalamic-pituitary-adrenal (HPA) axis is still poorly understood. Raising concerns are now focused on the toxic properties of emergent organophosphate ester flame retardants (OPEs), but whether OPEs interact with the HPA axis response has not yet been investigated. We measured corticosterone concentrations in feathers (CORTf) as a long-term biomarker of the bird HPA axis response and we investigated their relationship with POP and OPE concentrations in down feathers of nestling cinereous vultures (Aegypius monachus). We also examined whether high contaminant burden and high CORTf concentrations impacted the duration of chick development. The most predominant compounds were the following: p,p'-DDE (3.28 ± 0.26 ng g^-1 dw) > γ-HCH (0.78 ± 0.09 ng g^-1 dw) > BDE-99 (0.73 ± 0.09 ng g^-1 dw) > CB-153 (0.67 ± 0.04 ng g^-1 dw). The most persistent POP compounds (CB-170, -177, -180, -183, -187, -194 and p,p'-DDE) were associated (P = 0.02) with high concentrations of CORTf (range: 0.55-6.09 pg mm^-1), while no relationship was found when OPEs were tested (P > 0.05). Later egg-laying was positively associated to high levels of CORTf (P = 0.02) and reduced duration of chick development (P < 0.001), suggesting a beneficial effect of the HPA axis response on the growth of the chicks. In addition, males with high concentrations of the most persistent POP compounds tended to show a reduced duration of the nestling period (P = 0.05) and an equal fledging success than chicks with lower levels. These findings suggest that POPs, but not OPEs, may interact with the HPA axis response of chicks, although levels were not high enough to cause detrimental consequences.

Stress behaviour and physiology of developing Arctic barnacle goslings ( Branta leucopsis) is affected by legacy trace contaminants

Natural populations are persistently exposed to environmental pollution, which may adversely impact animal physiology and behaviour and even compromise survival. Responding appropriately to any stressor ultimately might tip the scales for survival, as mistimed behaviour and inadequate physiological responses may be detrimental. Yet effects of legacy contamination on immediate physiological and behavioural stress coping abilities during acute stress are virtually unknown. Here, we assessed these effects in barnacle goslings ( Branta leucopsis) at a historical coal mine site in the Arctic. For three weeks we led human-imprinted goslings, collected from nests in unpolluted areas, to feed in an abandoned coal mining area, where they were exposed to trace metals. As control we led their siblings to feed on clean grounds. After submitting both groups to three well-established stress tests (group isolation, individual isolation, on-back restraint), control goslings behaved calmer and excreted lower levels of corticosterone metabolites. Thus, legacy contamination may decisively change stress physiology and behaviour in long-lived vertebrates exposed at a young age.

Bone density and asymmetry are not related to DDT in House Sparrows: Insights from micro-focus X-ray computed tomography

In organisms, DDT (Dichlorodiphenyltrichloroethane) and its metabolites, DDE (Dichlorodiphenyldichloroethylene) and DDD (Dichlorobischlorophenylethane) are endocrine mimics. They can influence bone density and other bone structural features. This study was conducted on House Sparrows (Passer domesticus) caught from the Free State - and the Limpopo Provinces of South Africa (SA). The sites were chosen based on spraying patterns of DDT for malaria control or non-spraying. The bone mineral densities of the femurs as well as the lengths of the left- and right leg bones were determined using micro-focus X-ray computed tomography (μ-XCT). The concentrations of DDT and its metabolites in the liver were determined with gas-chromatography mass-spectrometry to provide baseline concentrations of DDT in the body, allowing comparison of the various groups of birds. There was no asymmetry between the lengths of the bones of the left- and the right legs. DDT concentrations in the liver did not correlate with bone lengths. In addition, there were no significant differences between the relative densities of the left- and right leg bones with increase of concentrations of DDT. The concentrations of DDT and its metabolites did not have a significant effect on the measured bone parameters of House Sparrows. It is possible that the concentrations of DDT and its metabolites in the environments were too low to be injurious to the birds and/or tolerance to the insecticide has developed in the birds over more than six decades of almost continuous application of DDT.

Steroid hormones and persistent organic pollutants in plasma from North-eastern Atlantic pilot whales

Persistent organic pollutants (POPs) are known to have endocrine disruptive effects, interfering with endogenous steroid hormones. The present study examined nine steroid hormones and their relationships with the concentrations of selected POPs in pilot whales (Globicephala melas) from the Faroe Islands, NE Atlantic. The different steroids were detected in 15 to all of the 26 individuals. High concentrations of progesterone (83.3-211.7pmol/g) and pregnenolone (PRE; 4.68-5.69pmol/g) were found in three adult females indicating that they were pregnant or ovulating. High androgen concentrations in two of the males reflected that one was adult and that one (possibly) had reached puberty. In males a significant positive and strong correlation between body length and testosterone (TS) levels was identified. Furthermore, positive and significant correlations were found between 4-OH-CB107/4'-OH-CB108 and 17β-estradiol in males. In adult females significant positive correlations were identified between PRE and CB149 and t-nonachlor, between estrone and CB138, -149, -187 and p,p'-DDE, between androstenedione and CB187, and between TS and CB-99 and -153. Although relationships between the POPs and the steroid hormones reported herein are not evidence of cause-effect relationships, the positive correlations between steroids and POPs, particularly in females, suggest that POPs may have some endocrine disrupting effects on the steroid homeostasis in this species.

Exposure of juvenile turbot (Scophthalmus maximus) to silver nanoparticles and 17α-ethinylestradiol mixtures: Implications for contaminant uptake and plasma steroid hormone levels

Combined exposure to engineered nanoparticles (ENPs) and anthropogenic contaminants can lead to changes in bioavailability, uptake and thus effects of both groups of contaminants. In this study we investigated effects of single and combined exposures of silver (Ag) nanoparticles (AgNPs) and the synthetic hormone 17α-ethinylestradiol (EE2) on tissue uptake of both contaminants in juvenile turbot (Scophthalmus maximus). Silver uptake and tissue distribution (gills, liver, kidney, stomach, muscle and bile) were analyzed following a 14-day, 2-h daily pulsed exposure to AgNPs (2 μg L^-1 and 200 μg L^-1), Ag⁺ (50 μg L^-1), EE2 (50 ng L^-1) and AgNP + EE2 (2 or 200 μg L^-1+50 ng L^-1). Effects of the exposures on plasma vitellogenin (Vtg) levels, EE2 and steroid hormone concentrations were investigated. The AgNP and AgNP + EE2 exposures resulted in similar Ag concentrations in the tissues, indicating that combined exposure did not influence Ag uptake in tissues. The highest Ag concentrations were found in gills. For the Ag⁺ exposed fish, the highest Ag concentrations were measured in the liver. Our results show dissolution processes of AgNPs in seawater, indicating that the tissue concentrations of Ag may partly originate from ionic release. Plasma EE2 concentrations and Vtg induction were similar in fish exposed to the single contaminants and the mixed contaminants, indicating that the presence of AgNPs did not significantly alter EE2 uptake. Similarly, concentrations of most steroid hormones were not significantly altered due to exposures to the combined contaminants versus the single compound exposures. However, high concentrations of AgNPs in combination with EE2 caused a drop of estrone (E1) (female fish) and androstenedione (AN) (male and female fish) levels in plasma below quantification limits. Our results indicate that the interactive effects between AgNPs and EE2 are limited, with only high concentrations of AgNPs triggering synergistic effects on plasma steroid hormone concentrations in juvenile turbots.

Is my study system good enough? A case study for identifying maternal effects

In this paper, we demonstrate how simulation studies can be used to answer questions about identifiability and consequences of omitting effects from a model. The methodology is presented through a case study where identifiability of genetic and/or individual (environmental) maternal effects is explored. Our study system is a wild house sparrow (Passer domesticus) population with known pedigree. We fit pedigree‐based (generalized) linear mixed models (animal models), with and without additive genetic and individual maternal effects, and use deviance information criterion (DIC) for choosing between these models. Pedigree and R‐code for simulations are available. For this study system, the simulation studies show that only large maternal effects can be identified. The genetic maternal effect (and similar for individual maternal effect) has to be at least half of the total genetic variance to be identified. The consequences of omitting a maternal effect when it is present are explored. Our results indicate that the total (genetic and individual) variance are accounted for. When an individual (environmental) maternal effect is omitted from the model, this only influences the estimated (direct) individual (environmental) variance. When a genetic maternal effect is omitted from the model, both (direct) genetic and (direct) individual variance estimates are overestimated.