Effect of urbanization on the micronucleus frequency in birds from forest fragments

Presence of micronuclei and nuclear abnormalities in Caracara (Polyborus) plancus living in an airport area in southern Brazil

The aviation sector is believed to be responsible for considerable environmental damage attributed to emission of a large number and amount of pollutants. Airports are often surrounded by forest fragments and humid areas that attract birds of prey and hence may potentially serve as useful bioindicators. The aim of the present study was to examine genotoxic potential in raptors exposed to airport pollution using the micronucleus (MN) test and morphological changes as evidenced by bilateral symmetry. This investigation was conducted at Salgado Filho International Airport of Porto Alegre - RS as well as in private and zoological breeding grounds. The presence of metals was measured in the blood cells of the collected birds. Seventeen birds (Caracara (Polyborus) plancus) were used in this study 11 from exposed and 6 from non-exposed group. The nuclear alterations clearly indicate that organisms exposed to airport pollution exhibited a significantly higher frequency of genetic damage compared to non-exposed birds. Further, manganese and chromium were detected exclusively in the blood of the exposed group. In contrast, the analysis of bilateral symmetry did not detect any significant morphologic differences between the two groups. Therefore, data indicate that blood genotoxic stress occurs in birds of prey living in civil aviation areas as evidenced by MN frequency increase and presence of manganese and chromium.

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

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

A comprehensive overview of genotoxicity and mutagenicity associated with outdoor air pollution exposure in Brazil

This review examined the mutagenicity and genotoxicity associated with exposure to outdoor air pollutants in Brazil. A search was performed on the Web of Science database using a combination of keywords that resulted in 134 articles. After applying exclusion criteria, a total of 75 articles were obtained. The articles were classified into three categories: (1) studies with plants and animals, (2) in vitro studies, and (3) human biomonitoring. The investigations were conducted in 11 of 27 Brazilian states with the highest prevalence in the southeast and south regions. Only 5 investigations focused on the effects of burning biomass on the quality of outdoor air. Plants, especially Tradescantia pallida, were the main air pollution biomonitoring tool. When available, a significant association between levels of air pollutants and genetic damage was described. Among the in vitro studies, Salmonella/microsome is the most used test to evaluate mutagenesis of outdoor air in Brazil (n = 26). Human biomonitoring studies were the least frequent category (n = 18). Most of the investigations utilized micronucleus bioassay, in oral mucosa cells (n = 15) and lymphocytes (n = 5), and the comet assay (n = 6). The analysis in this study points to the existence of gaps in genotoxicity studies and our findings indicate that future studies need to address the variety of potential sources of pollution existing in Brazil. In addition to extent of the impacts, consideration should be given to the enormous Brazilian biodiversity, as well as the determination of the role of socioeconomic inequality of the population in the observed outcomes.

Past and future: Urbanization and the avian endocrine system

Urban environments are evolutionarily novel and differ from natural environments in many respects including food and/or water availability, predation, noise, light, air quality, pathogens, biodiversity, and temperature. The success of organisms in urban environments requires physiological plasticity and adjustments that have been described extensively, including in birds residing in geographically and climatically diverse regions. These studies have revealed a few relatively consistent differences between urban and non-urban conspecifics. For example, seasonally breeding urban birds often develop their reproductive system earlier than non-urban birds, perhaps in response to more abundant trophic resources. In most instances, however, analyses of existing data indicate no general pattern distinguishing urban and non-urban birds. It is, for instance, often hypothesized that urban environments are stressful, yet the activity of the hypothalamus-pituitary-adrenal axis does not differ consistently between urban and non-urban birds. A similar conclusion is reached by comparing blood indices of metabolism. The origin of these disparities remains poorly understood, partly because many studies are correlative rather than aiming at establishing causality, which effectively limits our ability to formulate specific hypotheses regarding the impacts of urbanization on wildlife. We suggest that future research will benefit from prioritizing mechanistic approaches to identify environmental factors that shape the phenotypic responses of organisms to urbanization and the neuroendocrine and metabolic bases of these responses. Further, it will be critical to elucidate whether factors affect these responses (a) cumulatively or synergistically; and (b) differentially as a function of age, sex, reproductive status, season, and mobility within the urban environment. Research to date has used various taxa that differ greatly not only phylogenetically, but also with regard to ecological requirements, social systems, propensity to consume anthropogenic food, and behavioral responses to human presence. Researchers may instead benefit from standardizing approaches to examine a small number of representative models with wide geographic distribution and that occupy diverse urban ecosystems.

Erythrocyte micronucleus cytome assay in Passer domesticus and environmental remote sensing for inferring the quality of wild, rural, and urban areas

The study of biomarkers in free-living birds can help to indicate the degree of contamination in distinct environments. In addition, these environments can be characterized through the information provided by satellite images. The objectives of the present study were to analyze the types and quantity of cytogenetic biomarkers in Passer domesticus (House sparrow) from three different environments, wild, rural, and urban, and to analyze them in the context of land use and anthropogenic actions. Five thousand erythrocytes per bird were analyzed for the following nuclear alterations (NA): micronuclei (MN), nuclear buds, notched nuclei, binucleated cells, nucleoplasmic bridges, nuclear tails, peripheral nuclei, and anucleated cells. In the study, wild birds exhibited five types of NA, seven types were found in rural birds, and all types were encountered in urban birds. The only NA that exceeded a frequency of 2 NA/1000 erythrocytes were peripheral nuclei in birds from the rural and urban sites, the latter environment characterized by 87% urban soil and air pollution. The highest frequencies of MN, peripheral nuclei, and anucleated erythrocytes were recorded in sparrows from the rural site (p ≤ 0.05). This area had been sprayed with chlorpyrifos 48%, the most widely used organophosphate in the region. Sparrows from the wild site, made up of 100% native forest, had higher frequencies of notched nuclei (p ≤ 0.05). A precedent is set for the use of environmental remote sensing in a complementary manner with cytogenetic biomarker studies in birds for a joint analysis in environmental assessment.

Effects of urbanisation and pollution on the heterophil/lymphocyte ratio in birds from Brazilian Cerrado

Stressing agents can cause morphophysiological and behavioural changes in several animals, including birds, which are good study models for environmental biomonitoring. The heterophil/lymphocyte ratio (H/L) is an efficient indicator of chronic stresses in birds. In this study, we aimed to compare the H/L ratio of birds between the areas with different levels of urbanisation, anthropogenic noise and carbon monoxide (CO) emission rates. A total of 1288 birds were captured in six Cerrado forest fragments between 2013 and 2019, from which we took blood samples to produce blood smears. In each of these fragments, the noise level was measured with a sound pressure level metre. The CO rates were obtained from the National Institute for Space Research database (INPE-Brazil). There was a higher H/L ratio in individuals captured in urban areas or close to urbanisation with high anthropogenic noise levels and high CO rates, and a lower H/L ratio in individuals from preserved areas, far from urban environments with low noise levels and low CO rates. Six species (Antilophia galeata, Leoptopogon amaurocephalus, Cnemotriccus fuscatus, Lathrotriccus euleri, Turdus leucomelas and Eucometis penicillata) showed a significant difference between the areas and followed the pattern shown by the individuals. The present study showed that birds living in the urban and peri-urban sites have higher values of H/L ratio than birds from rural sites. These results suggest that the H/L ratio can be used as an environmental biomonitoring tool and an efficient parameter to assess chronic stress in birds in degraded environments.

Potential use of distinct biomarkers (trace metals, micronuclei, and nuclear abnormalities) in a heterogeneous sample of birds in southern Brazil

The analysis of metal concentrations in bird feathers and genotoxicity tests are tools used to evaluate anthropogenic impacts on ecosystems. We investigated the response of birds, used as bioindicators, to disturbances observed in three areas with distinctive environmental characteristics (natural, agricultural, and urban) in southern Brazil. For this purpose, we quantified metals (Mn, Cu, Cr, and Zn) in feathers and determined the number of micronuclei (MN) and other nuclear abnormalities (NA) in 108 birds from 25 species and 17 families captured in the study area. No significant differences was found in the metal concentrations and the number of MN and NA between the sampling areas. Zn and Cu concentrations were significantly higher in insectivorous than those in omnivorous birds. The Zn concentration was significantly different between some species, and the Cu concentration was significantly higher in juveniles than that in adults. The best generalized linear models showed that omnivorous birds had more MN and NA and that juveniles and birds with better body condition index had increased NA numbers. This study demonstrates that the analyzed variables contribute in different ways to the result of each biomarker, mainly due to particular ecological and physiological characteristics of each species. We conclude that wild birds have the potential to be used as environmental bioindicators in the study area, but future studies should focus on one or a few species whose ecological and physiological habits are well known.

Micronucleus and different nuclear abnormalities in wild birds in the Cerrado, Brazil

Free-living birds play an important role as bioindicators in natural environments. In this study, we used the micronucleus test and nuclear erythrocyte abnormalities to investigate the difference in the genotoxic damage frequency between animals in agricultural areas (soybean planting) in relation to the conserved area. It was also discussed the bird's eating habits, which are important for ecotoxicological analysis. The results point to a difference between the insectivorous, granivorous, and omnivorous guilds. The omnivore Gnorimopsar chopi was the species that most exhibited micronucleus frequency in the protected area. In the agricultural area, the animals did not differ in the genotoxic damage frequency. In the comparison between common species in both environments, G. chopi from the agricultural area showed a micronuclei frequency almost three times higher in relation to specimens collected in the conserved area. Based on these results, this study adds to the efforts of using the micronucleus test as a simple and accessible tool for biomonitoring the wild fauna. It can be concluded that the passerine, G. chopi, due to its higher genotoxic damage frequency may be a strong candidate to indicate environmental health.

Genomic Instability and Cyto-Genotoxic Damage in Animal Species

Genomic instability is a condition that may be associated with carcinogenesis and/or physiological disorders when genetic lesions are not repaired. Besides, wild, captive, and domesticated vertebrates are exposed to xenobiotics, leading to health disorders due to cytogenotoxicity. This chapter provides an overview of tests to assess cytogenotoxicity based on micronuclei (MNi) formation. Bone marrow micronuclei test (BmMNt), peripheral blood erythrocyte micronuclei test (PBMNt), and lymphocyte cytokinesis blocking micronuclei assay (CBMN) are discussed. The most illustrative studies of these techniques applied in different vertebrates of veterinary interest are described. The values of spontaneous basal micronuclei in captive, experimental, and farm animals (rodents, hamsters, pigs, goats, cattle, horses, fish) are summarized. In addition, a flow cytometry technique is presented to reduce the time taken to record MNi and other cellular abnormalities. Flow cytometry is helpful to analyze some indicators of genomic instability, such as cell death processes and stages (necrosis, apoptosis) and to efficiently evaluate some biomarkers of genotoxicity like MNi in BmMNt, PBMNt, and CBMN. The intention is to provide veterinary professionals with techniques to assess and interpret cytogenotoxicity biomarkers to anticipate therapeutic management in animals at risk of carcinogenesis or other degenerative diseases.

Leukocyte profile of the helmeted manakin, Antilophia galeata (Passeriformes: Pipridae) in a Cerrado forest fragment

Changes in the amounts and proportions of leukocytes, known as leucocyte profiles, have been documented for several bird species and have been used to measure stress levels in these animals. The present work ascertained the biological and ecological attributes that influence the leukocyte profile of Antilophia galeata (Lichtenstein, 1823), the helmeted manakin. This species has been deemed useful in ecological studies because it responds to environmental changes. Blood samples drawn from 89 individuals of A. galeata captured in a Cerrado forest fragment were subjected to analysis under optical microscopy to identify and quantify leukocytes and micronuclei. The number of lymphocytes was greater for males, non-reproductive individuals and individuals infected with ticks. None of the leukocyte components differed in relation to age, molting or body condition index. The amount of micronuclei was correlated with values for total leukocytes, H/L ratio, heterophils, basophils and monocytes. The results suggest that reproduction may be an immunosuppressive factor for the species, producing sexual differences in lymphocyte availability. In addition, biomarkers of genotoxic damage (micronuclei) were related to the amount of leukocytes, indicating that individuals may be sensitive to environmental disturbances. Leukocyte profiles can be considered a useful tool for addressing ecological questions that are relevant to the conservation of species in degraded environments.

Genotoxicity in American kestrels in an agricultural landscape in the Baja California peninsula, Mexico

Raptors as top predators have been used as effective sentinels of environmental stressors in agricultural areas worldwide. Pollutants in agricultural areas have negative effects on top predator populations. Biomarkers such as erythrocyte nuclear abnormalities have been used as an effective measure of genotoxicity caused by exposure-particularly short-term exposure-to pollutants. We took blood samples from 54 wild specimens of American kestrel (Falco sparverius) captured in an agricultural area in Valle de Santo Domingo, Baja California Sur, Mexico in the autumns of 2018 and 2019 (n = 25) and the winters of 2019 and 2020 (n = 29). We prepared and examined blood smears to look for erythrocyte abnormalities as a means to evaluate genotoxicity. The number of abnormality types and the total frequency of abnormalities (MNs and NAs: notched, symmetrically or asymmetrically constricted, displaced, or indented nuclei) per 10,000 erythrocytes were calculated for all the specimens. We found a high frequency of abnormalities in numerous individuals, similar to those found in raptors from highly polluted areas. The best-fit generalized linear model for the number of abnormality types included season-of-the-year as the main significant predictor; the model for the total frequency of abnormalities included season and wing chord, an indicator of body size and health condition, as significant predictors. MNs frequencies were significantly related to season; NAs frequencies were related to season, wing chord length, and coverage of native vegetation around the area where the birds were captured. Abnormalities observed in the autumn closely coincide with the time when agrochemicals are applied in the area, mainly after the rains and during hot spells in late summer and early autumn. Small-sized kestrels showed higher frequencies of NAs, with an additional impact if native vegetation had been cleared for agriculture; this suggests both that resident birds are more exposed, and the observed genotoxicity has a local origin. These results, together with the ecological and physiological characteristics of the American kestrel suggest that this charismatic and widely distributed species might constitute a suitable biomonitor of genotoxicity in rural landscapes.

Effects of urban proximity and the occurrence of erythroplastids in Antilophia galeata

Air pollution can generate changes in the morphology, physiology, and behavior of several animals, including birds, which, when responding to such environmental changes, can be used as biomonitors. Quantitative and qualitative analyses of erythrocyte nuclear anomalies comprise a useful tool for biomonitoring, with anucleated erythrocytes, called erythroplastids, being particularly significant. The objectives of the present study were to quantify the presence of erythroplastids in Antilophia galeata and relate their presence to distance from the nearest urban environment. Blood smears were analyzed for 80 individuals of A. galeata captured between June 2013 and October 2018 in five Cerrado forest fragments of different sizes and with different influences from urbanization. The quantity of erythroplastids differed among areas, with it being greater in fragments within a proximity with urban, and less in highly preserved areas far from an urban environment. Quantification of erythroplastids in A. galeata proved to be a useful tool for monitoring air quality.