Early exposure to 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) affects mating behavior of zebra finches

In ovo exposure to brominated flame retardants Part I: Assessment of effects of TBBPA-BDBPE on survival, morphometric and physiological endpoints in zebra finches

Tetrabromobisphenol A bis(2,3-dibromopropyl) ether (TBBPA-BDBPE) is an additive flame retardant used in polyolefins and polymers. It has been detected in biota, including in avian eggs, yet little is known of its effects. We assessed the pattern of TBBPA-BDBPE concentrations in songbird eggs over the incubation period, and the effects of embryonic exposure to TBBPA-BDBPE in a model songbird species, the zebra finch (Taeniopygia guttata). To assess concentrations during embryo development, eggs were injected on the day they were laid with the vehicle control (safflower oil) or 100 ng TBBPA-BDBPE/g egg, and whole egg contents were collected throughout embryonic development on day 0 (unincubated), 5, 10 and 13. To evaluate effects of embryonic exposure to TBBPA-BDBPE, eggs were injected at Hamburger-Hamilton stage 18 (∼80 h after initiation of incubation) with safflower oil only, 10, 50 or 100 ng TBBPA-BDBPE/g egg (albumin injection volume 1 μl/g). Eggs were monitored for hatching success, and nestlings were monitored for growth and survival. At 15 days post-hatch, tissues were collected to assess physiological effects. TBBPA-BDBPE was incorporated into the egg as the embryo developed, and concentrations started declining in late incubation, suggesting biotransformation by the embryo. There were no effects on hatching success, nestling survival, growth, organ somatic indices, or thyroid hormone homeostasis; however, there was evidence that body condition declined in a dose-dependent manner towards the end of the rapid nestling growth phase. This decreased body condition could be a delayed effect of early developmental exposure, or it may be the result of increased exposure to biotransformation products of TBBPA-BDBPE produced over the nestling period, which are predicted to be more bioaccumulative and toxic than the parent compound.

Mass balance study of brominated flame retardants in female captive peregrine falcons

Little is known about brominated flame retardant (BFR) dynamics in birds, especially large molecules such as decabromodiphenyl ether (BDE-209). In particular, bioaccumulation from food and transfer dynamics to eggs are poorly understood. Therefore, an input-output mass balance study of tri-decaBDEs, DBDPE and HBCDD was performed in three female peregrine falcons from a captive breeding program by analyzing their naturally contaminated food (quail, chicken (cockerels)), plasma, feces and eggs. Predominant BFRs in cockerels and quail were BDE-209 and DBDPE, as well as HBCDD in quail. The predominant BFRs found in falcon plasma were BDE-209, -153 and -183, in eggs, HBCDD, BDE-209 and -153 and in feces, BDE-209. Mean absorption efficiencies (AE) for the tetra-octabrominated BDEs ranged from 84-100% and 70% for HBCDD. The AEs for BDE-206, -207, -208 and -209 varied due to the large variability seen for feces fluxes. All egg/plasma ratios for BDEs were similar and greater than one (range 1.1-2.7), including for BDE-209, indicating efficient transfer from females to the eggs. Excretion via egg-laying was approximately 6.0-29% of the initial, pre-breeding body burden of individual penta-decaBDE congeners, (15-45% for BDE-206). HBCDD was not detected in plasma but was found in eggs, also indicating efficient transfer and excretion via eggs. Input fluxes from food exceeded the output fluxes (feces, eggs) indicating considerable metabolism for tetra-octaBDEs, possibly also for the nona-decaBDEs and HBCDD. Bioaccumulation factors calculated from lipid weight concentrations in plasma and food (BAFp) were highest for BDE-208 (31), -153 (23), -209 (19) and -207 (16) and from eggs and food (BAFe), were highest for HBCDD (140), BDE-153 (41), -208 (42), BDE-207 (24) and BDE-209 (21). BAFe and BAFp values were below 10 for BDE-47, -99 and -100. For one falcon, egg results were available from three different years and estimated half-lives were 65 d (BDE-99), 624 d (BDE-153), 31 d (BDE-154), 349 d (BDE-183), 77 d (BDE-196) and 89 d (BDE-197).

Sex-specific responses in neuroanatomy of hatchling American kestrels in response to embryonic exposure to the flame retardants bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate and 2-ethylhexyl-2,3,4,5-tetrabromobenzoate

Bis(2-ethylhexyl)-2,3,4,5-tetrabromophthalate (BEH-TEBP) and 2-ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB), flame retardant components of FireMaster 550® and 600® have been detected in tissues of wild birds. To address the paucity of information regarding potential impacts of flame retardants on the brain, brain volume regions of hatchling American kestrels (Falco sparverius) were evaluated following in ovo injection at embryonic day 5 with safflower oil or to 1 of 3 doses of either BEH-TEBP (12, 60, or 107 ng/g egg) or EH-TBB (11, 55, or 137 ng/g egg). The doses for both chemicals reflected concentrations reported in wild birds. The volumes of the hippocampus and telencephalon and volumetric differences between left and right hemispheres were measured in hatchlings (embryonic day 28). A sex-specific effect of BEH-TEBP on relative hippocampus volume was evident: the hippocampus was significantly enlarged in high-dose females compared to control females but smaller in low-dose females than the other females. There was no significant effect of EH-TBB on hippocampus volume in female kestrel hatchlings or of either chemical in male hatchlings and no effects of these concentrations of EH-TBB or BEH-TEBP on telencephalon volume or the level of symmetry between the hemispheres of the brain. In sum, embryonic exposure of female kestrels to these BEH-TEBP concentrations altered hippocampus volume, having the potential to affect spatial memory relating to ecologically relevant behavior such as prey capture, predator avoidance, and migration. Environ Toxicol Chem 2018;37:3032-3040. © 2018 SETAC.

Contrasting congener profiles for persistent organic pollutants and PAH monitoring in European storm petrels (Hydrobates pelagicus) breeding in Ireland: a preen oil versus feathers approach

Persistent organic pollutants (POPs) and polycyclic aromatic hydrocarbons (PAHs) are anthropogenic contaminants of environmental concern due to their persistence in the environment and capacity to accumulate in biota. Many of these contaminants have been found to have ill effects over wildlife and humans. Birds are known to be particularly affected through endocrine disruption and eggshell thinning. POPs have been banned or restricted through the Stockholm Convention (2001), making monitoring essential for tracking effects of regulation. Seabirds have been used as monitoring tools for being top predators and consuming a diverse array of prey in different trophic levels. Non-destructive sampling has become widely popular using feathers and preen oil, as opposed to carcasses and internal organs. This study aimed to set baseline levels of POP and PAH concentration in a highly pelagic and abundant seabird in Ireland and the Atlantic, the European storm petrel, Hydrobates pelagicus, and to investigate the profiles of contaminant congeners in preen oil and feathers, comparatively. Mean concentrations in preen oil followed: PCB (10.1 ng/g ww) > PAH (7.1 ng/g ww) > OCP (5.4 ng/g ww) > PBDE (3.9 ng/g ww), whilst mean concentrations in feathers followed the order: PAH (38.9 ng/g ww) > PCB (27.2 ng/g ww) > OCP (17.9 ng/g ww) > PBDE (4.5 ng/g ww). Congener profiles highly differed between preen oil and feathers, and little correlation was found between the matrices. These results demonstrate that the sampling of a single matrix alone (preen oil or feathers) might produce confounding results on contamination in seabirds and that more than one matrix is recommended to obtain a full picture of contamination by persistent organic pollutants.

Embryonic exposure to environmentally relevant concentrations of a brominated flame retardant reduces the size of song-control nuclei in a songbird

Environmental contaminants have the potential to act as developmental stressors and impair development of song and the brain of songbirds, but they have been largely unstudied in this context. 2,2',4,4',5-Pentabromodiphenyl ether (BDE-99) is a brominated flame retardant congener that has demonstrated endocrine disrupting effects, and has pervaded the global environment. We assessed the effects of in ovo exposure to environmentally relevant levels of BDE-99 on the neuroanatomy of the song-control system in a model songbird species, the zebra finch (Taeniopygia guttata). Embryos were exposed via egg injection to a vehicle control (DMSO), 10, 100, or 1000 ng BDE-99/g egg on the day the egg was laid. Chicks were raised to sexual maturity to investigate long-term effects of BDE-99 on the adult male brain. Three key song-control nuclei (Area X, HVC, RA) all showed a dose-dependent trend toward decreasing volume as BDE-99 concentration increased, and birds exposed to 1000 ng/g in ovo BDE-99 had significantly smaller song-control nuclei volume compared to control birds. High environmental concentrations of BDE-99 in avian tissues can be within that range and thus could affect development of the song-control system in birds, and potentially other processes. We previously found that BDE-99 exposure during the nestling period had no effect of on the song-control system, although it did have significant effects on some behaviural endpoints. Taken together, these results suggest that exposure to polybrominated diphenyl ether (PBDEs) during critical developmental windows can significantly alter neurological development. © 2018 Wiley Periodicals, Inc. Develop Neurobiol, 2018.

Ecologically-relevant exposure to methylmercury during early development does not affect adult phenotype in zebra finches (Taeniopygia guttata)

Methylmercury causes behavioural and reproductive effects in adult mammals via early developmental exposure. Similar studies in birds are limited and mostly focussed on aquatic systems, but recent work has reported high blood mercury concentrations in terrestrial, passerine songbirds. We used the zebra finch (Taeniopygia guttata) as a model to explore the long-term effects of early developmental exposure to methylmercury exposure. Chicks were dosed orally with either the vehicle control, 0.0315 µg Hg/g bw/day, or 0.075 µg Hg/g bw/day throughout the nestling period (days 1-21 post-hatching). We then measured (a) short-term effects on growth, development, and behaviour (time to self-feeding, neophobia) until 30 days of age (independence), and (b) long-term effects on courtship behaviour and song (males) and reproduction (females) once methylmercury-exposed birds reached sexual maturity (90 days post-hatching). High methylmercury treated birds had mean blood mercury of 0.734 ± 0.163 µg/g at 30 days post-hatching, within the range of values reported for field-sampled songbirds at mercury contaminated sites. However, there were no short-term effects of treatment on growth, development, and behaviour of chicks, and no long-term effects on courtship behaviour and song in males or reproductive performance in females. These results suggest that the nestling period is not a critical window for sensitivity to mercury exposure in zebra finches. Growing nestlings can reduce blood mercury levels through somatic growth and depuration into newly growing feathers, and as a result they might actually be less susceptible compared to adult birds receiving the same level of exposure.

Regulated and Unregulated Halogenated Flame Retardants in Peregrine Falcon Eggs from Greenland

Median levels of regulated flame retardants, i.e., polybrominated diphenyl ethers (PBDEs), brominated biphenyl (BB)-153, and hexabromocyclododecane (HBCD), in 33-48 eggs of peregrine falcons (Falco peregrinus) from Greenland were 1909, 359, and 5.98 ng/g lipid weight (lw), respectively, and generally intermediate to levels in North America and Europe. Unregulated flame retardants had lower median concentrations of 1.06 (2-ethylhexyl-2,3,4,5-tetrabromobenzoate, EH-TBB), 2.42 (1,2-bis(2,4,6-tribromophenoxy)-ethane, BTBPE), 0.52 (2,4,6-tribromophenyl 2,3-dibromopropyl ether, DPTE), and 4.78 (dechlorane plus) ng/g lw. Although these compounds are often described as recent replacements for PBDEs, they were also present in eggs from the 1980s. BDE-209 was the only compound with a significant increase (+7.2% annual change) between 1986 and 2014, while BB-153 and DPTE decreased significantly (-8.0% and -2.8% annual change, respectively). Dechlorane plus showed a nonsignificant increase. Individual birds, equipped with light-logging geolocators, confirmed the contaminant exposure over a large geographical area as the birds spent nearly equal time periods in their breeding and wintering grounds in Greenland and Central/South America, respectively, interrupted by 5-6 weeks of migration through North America.

Birds and flame retardants: A review of the toxic effects on birds of historical and novel flame retardants

Flame retardants (FRs) are a diverse group of chemicals, many of which persist in the environment and bioaccumulate in biota. Although some FRs have been withdrawn from manufacturing and commerce (e.g., legacy FRs), many continue to be detected in the environment; moreover, their replacements and/or other novel FRs are also detected in biota. Here, we review and summarize the literature on the toxic effects of various FRs on birds. Birds integrate chemical information (exposure, effects) across space and time, making them ideal sentinels of environmental contamination. Following an adverse outcome pathway (AOP) approach, we synthesized information on 8 of the most commonly reported endpoints in avian FR toxicity research: molecular measures, thyroid-related measures, steroids, retinol, brain anatomy, behaviour, growth and development, and reproduction. We then identified which of these endpoints appear more/most sensitive to FR exposure, as determined by the frequency of significant effects across avian studies. The avian thyroid system, largely characterized by inconsistent changes in circulating thyroid hormones that were the only measure in many such studies, appears to be moderately sensitive to FR exposure relative to the other endpoints; circulating thyroid hormones, after reproductive measures, being the most frequently examined endpoint. A more comprehensive examination with concurrent measurements of multiple thyroid endpoints (e.g., thyroid gland, deiodinase enzymes) is recommended for future studies to more fully understand potential avian thyroid toxicity of FRs. More research is required to determine the effects of various FRs on avian retinol concentrations, inconsistently sensitive across species, and to concurrently assess multiple steroid hormones. Behaviour related to courtship and reproduction was the most sensitive of all selected endpoints, with significant effects recorded in every study. Among domesticated species (Galliformes), raptors (Accipitriformes and Falconiformes), songbirds (Passeriformes), and other species of birds (e.g. gulls), raptors seem to be the most sensitive to FR exposure across these measurements. We recommend that future avian research connect biochemical disruptions and changes in the brain to ecologically relevant endpoints, such as behaviour and reproduction. Moreover, connecting in vivo endpoints with molecular endpoints for non-domesticated avian species is also highly important, and essential to linking FR exposure with reduced fitness and population-level effects.

In ovo tris(2-butoxyethyl) phosphate concentrations significantly decrease in late incubation after a single exposure via injection, with no evidence of effects on hatching success or latent effects on growth or reproduction in zebra finches

Zebra finch (Taeniopygia guttata) eggs were injected with the organophosphate triester flame retardant tris(2-butoxyethyl) phosphate (TBOEP) at 0 μg/g, 0.01 μg/g, 1 μg/g, 10 μg/g, or 50 μg/g egg. Subsets of high-dose eggs were collected throughout incubation to measure TBOEP, which started declining in late incubation and then decreased rapidly to 28% of injected concentration by hatching. The authors found no effects of TBOEP on survival, growth, or reproduction even at very high doses. Environ Toxicol Chem 2017;36:83-88. © 2016 SETAC.

Acute embryotoxic effects but no long-term reproductive effects of in ovo methylmercury exposure in zebra finches (Taeniopygia guttata)

Mercury bioaccumulates in terrestrial ecosystems as methylmercury (MeHg), yet little is known about its effects on terrestrial organisms, including songbirds. The authors used a model songbird species, the zebra finch (Taeniopygia guttata), to assess short-term embryotoxic effects of in ovo MeHg exposure on hatching success and posthatching growth and nestling survival, as well as longer-term effects on mating behavior and reproduction. Egg treatment groups included a low-MeHg dose of 0.2 μg Hg g(-1) egg (n = 36), a high-MeHg dose of 3.2 μg Hg g(-1) egg (n = 49), and a control (n = 34). Doses were dissolved in nanopure filtered water and injected into the albumen on the day eggs showed signs of viability (3 d incubation). In ovo exposure to MeHg significantly reduced hatching success (53% in the high-MeHg dose group vs 94% in vehicle controls). Among hatched chicks, however, no effects of MeHg on growth, hematological variables, or nestling survival were detected. While the in ovo injection method resulted in a dose-dependent pattern of MeHg concentrations in blood of surviving chicks at 15 d and 30 d posthatching, there was evidence of rapid excretion of MeHg with nestling age during that growth period. At reproductive maturity (90 d of age), no long-term effects of in ovo exposure to MeHg on female mating behavior, reproductive effort (egg or clutch size), or growth and survivorship of offspring were observed. Environ Toxicol Chem 2016;35:1534-1540. © 2015 SETAC.

Latent cognitive effects from low-level polychlorinated biphenyl exposure in juvenile European starlings (Sturnus vulgaris)

Ecotoxicology research on polychlorinated biphenyl (PCB) mixtures has focused principally on short-term effects on reproduction, growth, and other physiological endpoints. Latent cognitive effects from early life exposure to low-level PCBs were examined in an avian model, the European starling (Sturnus vulgaris). Thirty-six birds, divided equally among 4 treatment groups (control = 0 µg, low = 0.35 µg, intermediate = 0.70 µg, and high = 1.05 µg Aroclor 1254/g body weight), were dosed 1 d through 18 d posthatch, then tested 8 mo to 9 mo later in captivity in an analog to an open radial arm maze. Birds were subject to 4 sequential experiments: habituation, learning, cue selection, and memory. One-half of the birds did not habituate to the test cage; however, this was not linked to a treatment group. Although 11 of the remaining 18 birds successfully learned, only 1 was from the high-dosed group. Control and low-dosed birds were among the only treatment groups to improve trial times throughout the learning experiment. High-dosed birds were slower and more error-prone than controls. Cue selection (spatial or color cues) and memory retention were not affected by prior PCB exposure. The results indicate that a reduction in spatial learning ability persists among birds exposed to Aroclor 1254 during development. This may have implications for migration ability, resource acquisition, and other behaviors relevant for fitness.

Trends of polybrominated diphenyl ethers and hexabromocyclododecane in eggs of Canadian Arctic seabirds reflect changing use patterns

Due to the substantial use and release of polybrominated diphenyl ether (PBDE) flame retardants in North America, PBDE concentrations in North American marine biota are among the highest in the world. In this study, we compared PBDE concentrations and congener patterns in eggs of five seabird species (thick-billed murres, northern fulmars, black guillemots, glaucous gulls, black-legged kittiwakes) breeding at a colony in the Canadian Arctic in 1993, 2008 and 2013. Temporal trends of PBDEs (1975-2014) and another flame retardant, hexabromocyclododecane (HBCD) (2003-2014), were also examined in eggs of two seabird species, the thick-billed murre and northern fulmar. BDE-47 generally dominated the BDE congener profiles in eggs of all five species. Glaucous gulls had the highest concentrations of both ΣPBDE and BDE-47, and northern fulmars, the lowest. ΣPBDE concentrations increased exponentially in eggs of both thick-billed murres and northern fulmars from 1975 to 2003 with doubling times of 9.1 years in the murres and 7.2 years in the fulmars. From 2003 to 2008/09, ΣPBDE decreased rapidly in the murres and fulmars to concentrations not significantly different from those recorded in 1975 and 1987 for each species. After 2008/09, ΣPBDE concentrations plateaued. BDE-47 followed a similar temporal trend to that of ΣPBDE concentrations. These concentration trends were consistent with the phase-out of the penta- and octa-BDE products from the North American market in the mid-2000s. There was an overall decline in concentrations of HBCD in murre eggs from 2003 to 2014, whereas concentrations in the fulmar eggs increased from 2003 to 2006 followed by a decline to 2014. The ratio of HBCD to BDE-47 suggests that northern fulmars showed more of a European contaminant signature, and thick-billed murres, more of a North American signature.

PBDEs and other POPs in urban birds of prey partly explained by trophic level and carbon source

As urban sprawl and agricultural intensification continue to invade prime wildlife habitat, some animals, even apex predators, are managing to adapt to this new environment. Chemical pollution is one of many stressors that wildlife encounter in urban environments. Predators are particularly sensitive to persistent chemical pollutants because they feed at a high trophic level where such pollution is biomagnified. To examine levels of pollution in urban birds of prey in the Lower Mainland region of British Columbia, Canada, we analyzed persistent organic contaminants in adult birds found dead of trauma injury. The hepatic geometric mean concentration of sum polybrominated diphenyl ethers (∑PBDEs) in 13 Cooper's hawks (Accipiter cooperii) from Greater Vancouver was 1873 ng/g (lipid weight) with one bird reaching 197,000n g/g lipid weight, the highest exposure reported to date for a wild bird. Concentrations of ∑PBDEs, ∑PCBs (polychlorinated biphenyls) and, surprisingly, cyclodiene insecticides were greatest in the urban environment while those of DDE (1,1-dichloroethylene bis[p-chlorophenyl) were highest in a region of intensive agriculture. The level of most chlorinated and brominated contaminants increased with trophic level (δ(15)N). The concentrations of some contaminants, PBDEs in particular, in these birds of prey may have some toxicological consequences. Apex predators in urban environments continue to be exposed to elevated concentrations of legacy pollutants as well as more recent brominated pollutants.

Effects of the bioaccumulative polybrominated diphenyl ether flame retardant congener BDE-47 on growth, development, and reproductive success in zebra finches

This study investigated the effects of the polybrominated diphenyl ether congener, 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) on the growth and development, and subsequent breeding success of exposed zebra finches (Taeniopygia guttata). Using oral dosing procedures and treatments adjusted by weight, we treated newly hatched chicks daily for the first 20-days-post-hatch (dph) with varying treatments of BDE-47 (0, 5, 50, and 500 ng/g bw/day). Weight and tarsal measurements were monitored from hatch to 90 dph, but no differences were observed between treatment groups at any age. Treated females that reached sexual maturity were mated with untreated males; however, again no treatment effects were observed on breeding success. Analysis of tissue samples at 21 dph did indicate that debromination of BDE-47 had occurred resulting in BDE-28 and BDE-17 metabolites.

Spatial and temporal trends in brominated flame retardants in seabirds from the Pacific coast of Canada

Polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCDD) are bioaccumulative flame retardants. PBDEs increased in many ecosystems during the late 20th century, but recently have declined in some environments. To examine trends in the northern Pacific, we analysed PBDEs, HBCDD and carbon and nitrogen stable isotopes (δ13C and δ15N) to account for dietary effects in archived eggs of three seabird species from British Columbia, Canada, 1990-2011 (rhinoceros auklets, Cerorhinca monocerata; Leach's storm-petrels, Oceanodroma leucorhoa; ancient murrelets, Synthliboramphus antiquus, 2009 only). PBDEs increased until approximately 2000 and then decreased, while HBCDD increased exponentially throughout the examined period. No significant changes in dietary tracers were observed. HBCDD and ΣPBDE levels varied among species; ΣPBDE also varied among sites. Temporal changes in contaminant concentrations are unlikely to have been caused by dietary changes, and likely reflect the build-up followed by decreases associated with voluntary phase-outs and regulations implemented in North America to control PBDEs.

An assessment of the developmental toxicity of BDE-99 in the European starling using an integrated laboratory and field approach

Developmental exposure of wildlife to anthropogenic contaminants can have long-term effects that are difficult to assess in field monitoring studies, and may not be evident in laboratory studies that lack ecological components. The objective of this study was to assess the long-term effects of early exposure to contaminants under ecological conditions in a model passerine species, the European starling (Sturnus vulgaris). We selected 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) as a representative contaminant, as it is one of the major constituents of the commercial penta-BDE flame retardant mixture, and has been reported in avian egg and tissue samples worldwide. We developed a novel approach to assess the developmental toxicity of BDE-99 in starlings by combining aspects of laboratory and field studies. We dosed free-living nestlings living in natural broods in the field with environmentally relevant concentrations of BDE-99 (0-173.8 ng/g bw/day) for the duration of the nesting cycle. To simulate monitoring of long-term effects we brought birds into captivity just prior to fledging and used photoperiod manipulations to induce reproductive development. We assessed a range of physiological and development measures such as hematocrit, oxidative stress, thyroid hormones, neuroanatomy, growth, molt rate, bill color, and testes development. We found some evidence of thyroid hormone disruption, but there were no effects on any other measures of physiology or development. The European starling could serve as a valuable model species for assessing early exposure and long-term effects of anthropogenic contaminants in terrestrial wildlife using this combined field/laboratory approach.

Dissection and downstream analysis of zebra finch embryos at early stages of development

The zebra finch (Taeniopygiaguttata) has become an increasingly important model organism in many areas of research including toxicology, behavior, and memory and learning. As the only songbird with a sequenced genome, the zebra finch has great potential for use in developmental studies; however, the early stages of zebra finch development have not been well studied. Lack of research in zebra finch development can be attributed to the difficulty of dissecting the small egg and embryo. The following dissection method minimizes embryonic tissue damage, which allows for investigation of morphology and gene expression at all stages of embryonic development. This permits both bright field and fluorescence quality imaging of embryos, use in molecular procedures such as in situ hybridization (ISH), cell proliferation assays, and RNA extraction for quantitative assays such as quantitative real-time PCR (qtRT-PCR). This technique allows investigators to study early stages of development that were previously difficult to access.

Developmental impairment in eurasian dipper nestlings exposed to urban stream pollutants

Avian studies of endocrine disruption traditionally have focused on reproductive impairment, given that many environmental contaminants affect sex steroid hormones. There is also increasing interest in altered thyroid function, and associated early development, particularly in altricial species with extended developmental windows. Both types of effect are relevant under the complex pollutant conditions created in streams draining urban areas, but case studies are scarce. Therefore, the authors measured breeding performance, as well as nestling growth, condition, and plasma thyroid hormones, in 87 Eurasian dipper (Cinclus cinclus) nests on 36 urban and rural streams in south and mid-Wales (UK); invertebrate prey data were also collected. The objective of the present study was to evaluate whether urban stream pollution or food scarcity might affect reproduction or development in this specialized aquatic songbird. Clutch sizes and egg fertility were similar on rural and urban streams, whereas nest success was actually higher at urban sites and food abundance was not significantly reduced. However, subtle but important differences were apparent. Urban nestlings were significantly lighter than rural nestlings for their body size (condition index), and brood sex ratios were increasingly male biased with increasing urbanization. The nestling thyroid hormone profile closely reflected urban land use, whereas depressed triiodothyronine (T3) hormones and poorer body condition were associated with higher exposure to polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) at urbanized sites. These data suggest that PCBs, PBDEs, and/or accompanying contaminants in urban streams could be affecting dipper nestling development, with potential consequences for the birds' fitness.

Long-term exposure to decabrominated diphenyl ether impairs CD8 T-cell function in adult mice

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental pollutants that accumulate to high levels in human populations that are subject to occupational or regional industry exposure. PBDEs have been shown to affect human neuronal, endocrine and reproductive systems, but their effect on the immune system is not well understood. In this study, experimental adult mice were intragastrically administered 2,2′,3,3′,4,4′,5,5′,6,6′-decabromodiphenyl ether (BDE-209) at doses of 8, 80 or 800 mg/kg of body weight (bw) at 2-day intervals. Our results showed that continuous exposure to BDE-209 resulted in high levels of BDE-209 in the plasma that approached the levels found in people who work in professions with high risks of PDBE exposure. Reduced leukocytes, decreased cytokine (IFN-γ, IL-2 and TNF-α) production and lower CD8 T-cell proliferation were observed in the mice exposed to BDE-209. Additionally, mice with long-term BDE-209 exposure had lower numbers of antigen-specific CD8 T cells after immunization with recombinant Listeria monocytogenes expressing ovalbumin (rLm-OVA) and the OVA-specific CD8 T cells had reduced functionality. Taken together, our study demonstrates that continuous BDE-209 exposure causes adverse effects on the number and functionality of immune cells in adult mice.

Polybrominated diphenyl ethers and multiple stressors influence the reproduction of free-ranging tree swallows (Tachycineta bicolor) nesting at wastewater treatment plants

Reproductive success of birds is influenced by maternal factors, ambient temperatures, predation, food supply, and/or exposure to environmental contaminants e.g., flame retardants (FRs). Reproduction of tree swallows (Tachycineta bicolor) was compared among waste water treatment plants (WWTPs) and a reference reservoir in Ontario, Canada (2007-2010), to determine the importance of exposure to polybrominated diphenyl ether (PBDEs) FRs within a complex contaminant cocktail, relative to natural and biological factors known to influence avian reproduction. The birds primarily consumed insects emerging from the reference reservoir and WWTP outflows, where effluent mixed with receiving waters. FR egg concentrations were dominated by 5 PBDE congeners (∑5PBDEs): 2,2'.4,4',5-pentabromodiphenyl ether (BDE-99), 2,2',4,4'-tetrabromodiphenyl ether (BDE-47), 2,2'4,4',6-pentabromodiphenyl ether (BDE-100), 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE-153), and 2,2',4,4',5,6'-hexabromodiphenyl ether (BDE-154), with much lower concentrations of decabromodiphenylether (BDE-209), hexabromocyclododecane (HBCDD), and novel FRs. Although higher than ∑5PBDEs, polychlorinated biphenyls (PCBs) egg concentrations were unlikely to affect the swallows' reproduction. Clutch size and timing, fledging, breeding success, and predation, varied significantly among sites, generally being poorer at WWTP1 and better at WWTP2. The early reproductive stages were sensitive to some FRs at measured concentrations. The ∑5PBDEs, maternal age, and minimum ambient temperatures predicted onset of egg laying in the most parsimonious statistical model, and there were positive relationships between egg size and HBCDD or BDE-209 concentrations. However, there were no significant correlations with any reproductive measures, individual BDE congeners or low concentrations of novel FRs, in this first such report for novel FRs and wild birds. Tree swallows are passerines, and passerines may differ from birds of prey in their reproductive sensitivity to PBDE exposure: lay date, minimum temperatures, and predation, but not PBDE exposure, predicted reproductive productivity. Overall, there was some influence of the PBDEs available in these WWTP outflows on early reproductive parameters, but not reproductive output, of these passerines.

Embryological staging of the Zebra Finch, Taeniopygia guttata

Zebra Finches (Taeniopygia guttata) are the most commonly used laboratory songbird species, yet their embryological development has been poorly characterized. Most studies to date apply Hamburger and Hamilton stages derived from chicken development; however, significant differences in development between precocial and altricial species suggest that they may not be directly comparable. We provide the first detailed description of embryological development in the Zebra Finch under standard artificial incubation. These descriptions confirm that some of the features used to classify chicken embryos into stages are not applicable in an altricial bird such as the Zebra Finch. This staging protocol will help to standardize future studies of embryological development in the Zebra Finch.

An assessment of in ovo toxicity of the flame retardant 1,2-dibromo-4-(1,2-dibromoethyl) cyclohexane (TBECH) in the zebra finch

Embryonic toxicity of a brominated flame retardant, TBECH (1,2-dibromo-4-(1, 2-dibromoethyl) cyclohexane) was investigated using the zebra finch (Taeniopygia guttata) as our model. Using in ovo dosing procedures, we injected the technical TBECH compound, consisting of 50:50 α-/β-isomers, directly into the yolk of freshly laid eggs at concentrations of 2.3-94 ng/g egg. No significant effects were observed in terms of growth or survival for either pre-hatch embryos or post-hatch chicks. Analysis of tissue samples at various developmental stages suggests that α-/β-TBECH was metabolized rapidly, and thus is unlikely to cause any direct, long-term effects on the development of zebra finch embryos or offspring.

The effect of polychlorinated biphenyls on the song of two passerine species

Polychlorinated biphenyls (PCBs) are synthetic chemical pollutants with demonstrated detrimental toxic and developmental effects on humans and wildlife. Laboratory studies suggest that PCBs influence behavior due to their effects on endocrine and neurological systems, yet little is known about the behavioral consequences of sublethal PCB exposure in the field. Additionally, specific PCB congener data (in contrast to total PCB load) is necessary to understand the possible effects of PCBs in living organisms since number and position of chlorine substitution in a PCB molecule dictates the toxicity and chemical fate of individual PCB congeners. We non-lethally investigated total PCB loads, congener specific PCB profiles, and songs of black-capped chickadees (Poecile atricapillus) and song sparrows (Melospiza melodia) along a historical PCB gradient at the Hudson River in New York State. Our results indicate that black-capped chickadees and song sparrows have higher total blood PCBs in regions with higher historic PCB contamination. The two bird species varied substantially in their congener-specific PCB profiles; within sites, song sparrows showed a significantly higher proportion of lower chlorinated PCBs, while black-capped chickadees had higher proportions of highly chlorinated PCBs. In areas of PCB pollution, the species-specific identity signal in black-capped chickadee song varied significantly, while variation in song sparrow trill performance was best predicted by the mono-ortho PCB load. Thus, PCBs may affect song production, an important component of communication in birds. In conclusion, we suggest that the ramifications of changes in song quality for bird populations may extend the toxic effects of environmental PCB pollution.

Eurasian dipper eggs indicate elevated organohalogenated contaminants in urban rivers

Many urban European streams are recovering from industrial, mining, and sewage pollution during the 20th century. However, associated recolonization by clean water organisms can potentially result in exposure to legacy or novel toxic pollutants that persist in the environment. Between 2008 and 2010, we sampled eggs of a river passerine, the Eurasian dipper (Cinclus cinclus), from 33 rivers in South Wales and the English borders (UK) which varied in catchment land use from rural to highly urbanized. Dipper egg δ(15)N and δ(13)C stable isotopes were enriched from urban rivers while δ(34)S was strongly depleted, effectively discriminating their urban or rural origins at thresholds of 10% urban land cover or 1000 people/km(2). Concentrations of total polychlorinated biphenyls (PCBs) and polybrominated biphenyl ethers (PBDEs) were positively related to urban land cover and human population density while legacy organochlorine pesticides such as p,p'-DDE, lindane, and hexachlorobenzene were found in higher concentrations at rural sites. Levels of PBDEs in urban dipper eggs (range of 136-9299 ng/g lw) were among the highest ever reported in passerines, and some egg contaminants were at or approaching levels sufficient for adverse effects on avian development. With the exception of dieldrin, our data shows PCBs and other organochlorine pesticides have remained stable or increased in the past 20 years in dipper eggs, despite discontinued use.

Developmental exposure to a brominated flame retardant: an assessment of effects on physiology, growth, and reproduction in a songbird, the zebra finch

Mixtures of polybrominated diphenyl ethers (PBDEs) have been widely used as additive flame retardants, and BDE-99 is one of the most predominant congeners found in the environment. BDE-99 has been reported in avian samples worldwide, yet knowledge of its toxicity to birds is minimal. We assessed the short- and long-term effects of nestling exposure to environmentally relevant levels of BDE-99 in a model passerine, the zebra finch. Early exposure to BDE-99 did not affect hematocrit, oxidative stress, or thyroid hormones in either the juvenile or adult stages, and there were no effects on chick growth or survival. BDE-99 exposure caused a dose-dependent delay in timing of reproduction, but there were no other effects on reproductive success. In zebra finches, endpoints related to reproductive behavior appear to be the most sensitive to BDE-99. However, passerines overall appear to be less sensitive than birds of prey or mammals to PBDE exposure.

A three-generational study of In ovo exposure to PBDE-99 in the zebra finch

Based on a literature review of avian data for polybrominated diphenyl ethers (PBDEs), ecologically relevant doses, low (10 ng/egg), medium (100 ng/egg), and high (1,000 ng/egg) of the 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) congener along with dimethylsulfoxide (DMSO) control were injected into the yolk sac of un-incubated eggs of zebra finch, Taeniopygia guttata. Offspring development and adult phenotype were followed over three generations. No effects of in ovo PBDE exposure on hatching success, chick growth, thyroid hormone levels, or hematological traits were measured at sexual maturity (90 d posthatching). However, the authors did detect significant effects of BDE-99 treatment on adult phenotype of in ovo-exposed birds by breeding observations, in which clutch size was significantly smaller in all PBDE-dosed birds (low, medium, and high) compared with controls. A trend was also seen for longer laying intervals in PBDE-dosed birds (13-14 d) compared with control birds (8 d). In addition, a significant effect of PBDE was found on growth of the second-generation offspring of in ovo-treated females; body mass was significantly lower in the high-PBDE dosed birds compared with controls from hatch through to fledging (day 30). The authors found no evidence of effects over the longer term and in successive generations, whether in adult, reproductive phenotype of the second-generation offspring of in ovo-treated birds, or in the growth of their (third-generation) offspring. Their results suggest that egg levels as low as 10 ng/g BDE-99 may affect reproduction in small passerines by reducing clutch size.

Individual variation in body burden, lipid status, and reproductive investment is related to maternal transfer of a brominated diphenyl ether (BDE-99) to eggs in the zebra finch

Avian eggs are exposed to hydrophobic contaminants through maternal transfer. How maternal transfer of contaminants within a species is influenced by individual variation in characteristics such as body burden, yolk precursor levels, or reproductive investment is not understood. The authors investigated sources of variation in the maternal transfer of 2,2',4,4',5-pentabromodiphenyl ether (BDE-99) in zebra finches (Taeniopygia guttata). The authors dosed adult female zebra finches with levels of BDE-99 relevant to exposure in wild birds (0, 33.7 or 173.8 ng/g body wt/d) for three weeks prior to pairing. Maternal BDE-99 and very-low-density lipoprotein (VLDL) in plasma were measured during egg formation and at clutch completion, and BDE-99 was measured in the corresponding egg. The lipid-normalized egg-to-maternal tissue BDE-99 relationship decreased with increasing maternal burden. Individual variation in maternal VLDL was related to BDE-99 transfer to the eggs when BDE-99 was at background levels in control birds, but not when BDE-99 was elevated in dosed birds. The decrease in maternal plasma BDE-99 over the laying period was only significant (p < 0.05) in the high-dose birds. Finally, the decrease in BDE-99 in maternal plasma during egg-laying was significantly positively correlated with clutch mass in the high-dose group. These results suggest that the relationship between maternal and egg contaminant levels can be highly variable. This has significant implications for using eggs as indicators of adult or environmental concentrations.

Validation of an egg-injection method for embryotoxicity studies in a small, model songbird, the zebra finch (Taeniopygia guttata)

Female birds deposit or 'excrete' lipophilic contaminants to their eggs during egg formation. Concentrations of xenobiotics in bird eggs can therefore accurately indicate levels of contamination in the environment and sampling of bird eggs is commonly used as a bio-monitoring tool. It is widely assumed that maternally transferred contaminants cause adverse effects on embryos but there has been relatively little experimental work confirming direct developmental effects (cf. behaviorally-mediated effects). We validated the use of egg injection for studies of in ovo exposure to xenobiotics for a small songbird model species, the zebra finch (Taeniopygia guttata), where egg weight averages only 1 g. We investigated a) the effect of puncturing eggs with or without vehicle (DMSO) injection on egg fate (embryo development), chick hatching success and subsequent growth to 90 days (sexual maturity), and b) effects of two vehicle solutions (DMSO and safflower oil) on embryo and chick growth. PBDE-99 and -47 were measured in in ovo PBDE-treated eggs, chicks and adults to investigate relationships between putative injection amounts and the time course of metabolism (debromination) of PBDE-99 during early development. We successfully injected a small volume (5 μL) of vehicle into eggs, at incubation day 0, with no effects on egg or embryo fate and with hatchability similar to that for non-manipulated eggs in our captive-breeding colony (43% vs. 48%). We did find some evidence for an inhibitory effect of DMSO vehicle on post-hatching chick growth, in male chicks only. This method can be used to treat eggs in a dose-dependent, and ecologically-relevant, manner with PBDE-99, based on chemical analysis of eggs, hatchling and adults.