Micronucleus Test Reveals Genotoxic Effects in Bats Associated with Agricultural Activity

DNA Damage in Bat Blood Leukocytes Using a Chromatin Dispersion Test (CDT): Biomarker of Environmental Genotoxicity

Environmental pollutants produce adverse effects on organisms and ecosystems. Biomonitoring and biomarkers offer a reasonable approach to make these assessments. Induced genetic changes can be using as a biomarker in organisms that react to a given compound in the ecosystem. Monitoring environmental genotoxicity necessitates the choice of model animals known as "sentinels or biological monitors" and the suitability of validated tests for DNA damage evaluation. We aimed to estimate the DNA damage produced by thermal stress in the leukocytes of the Mexican free-tailed bat (Tadarida brasiliensis). The DNA damage in bat leukocytes exposed to different temperatures (35 °C, 45 °C, and 55 °C) was evaluated by the adapted chromatin dispersion test (CDT) and the results were confirmed by the alkaline comet test. The CDT permitted a clear representation of leukocytes with fragmented DNA and of nonfragmented DNA. In addition, we detected nuclear anomalies in relation to cell death cellular swelling, nuclear fragmentation, and chromatin lysis. The alkaline comet assay revealed that the halos of diffuse chromatin include fragmented DNA. The assay of the method employing the CDT is well established, precise, and cost-effective for the routine quantitative analysis of DNA damage on the effect of the leukocytes of bats exposed to thermal stress. This could also apply as a sensitive screening tool for the evaluation of genotoxicity in environmental protection programs.

A paired analysis of mercury among non-invasive tissues to inform bat conservation monitoring

Contaminant exposure can harm wildlife. However, measuring contaminant exposure in wildlife can be challenging due to accessibility of species and/or sampling tissue matrices needed to answer research questions regarding exposure. For example, in bats and other taxa that roost, it may be best to collect pooled feces from colonies for minimal disturbance to species of conservation concern, but fecal contaminant concentrations do not provide contaminant bioaccumulation estimates. Thus, there is a need for quantifying relationships between sample matrices for measuring contaminant exposure to answer research questions pertaining to wildlife health and addressing conservation needs. Our goal was to determine relationships between fecal and fur total mercury (THg). To do so, we collected paired feces and fur from Mexican free-tailed bats (Tadarida brasiliensis) in summer 2023 in western Oklahoma at a maternity roost with no known Hg point source. We analyzed THg in each sample matrix for each individual (n = 48). We found no relationship between individual fecal and fur THg. However, when averaged, fur THg was 6.11 times greater than fecal THg. This factor can be used as a screening-level risk assessment of under-roost feces, which could then be followed by direct assessments of fur THg concentrations and health impacts. We encourage the use of this conversion factor across other insectivorous bat species and sites for estimating initial risks of contaminant exposure with minimal disturbance to species of conservation concern, when timely research for conservation actions are needed, and when a contaminant point source is not yet known.

Improving the science and practice of using artificial roosts for bats

Worldwide, artificial bat roosts (e.g., bat boxes, bark mimics, bat condos) are routinely deployed for conservation, mitigation, and community engagement. However, scant attention has been paid to developing best practices for the use of artificial roosts as conservation tools. Although bats readily occupy artificial roosts, occupancy and abundance data are misleading indicators of habitat quality. Lacking information on bat behavior, health, and fitness in artificial roosts, their conservation efficacy cannot be adequately validated. We considered the proximal and ultimate factors, such as evolutionarily reliable cues, that may prompt bats to preferentially use and show fidelity to suboptimal artificial roosts even when high-quality alternatives are available. Possible negative health and fitness consequences for artificial roost inhabitants include exposure to unstable and extreme microclimates in poorly designed roosts, and vulnerability to larger numbers of ectoparasites in longer lasting artificial roosts that house larger bat colonies than in natural roosts. Bats using artificial roosts may have lower survival rates if predators have easy access to roosts placed in conspicuous locations. Bats may be lured into occupying low-quality habitats if attractive artificial roosts are deployed on polluted urban and agricultural landscapes. To advance the science behind artificial bat roosts, we present testable research hypotheses and suggestions to improve the quality of artificial roosts for bats and decrease risks to occupants. Because continued loss of natural roosts may increase reliance on alternatives, such as artificial roosts, it is imperative that this conservation practice be improved.

Sampling methodology influences habitat suitability modeling for chiropteran species

Technological advances increase opportunities for novel wildlife survey methods. With increased detection methods, many organizations and agencies are creating habitat suitability models (HSMs) to identify critical habitats and prioritize conservation measures. However, multiple occurrence data types are used independently to create these HSMs with little understanding of how biases inherent to those data might impact HSM efficacy. We sought to understand how different data types can influence HSMs using three bat species (Lasiurus borealis, Lasiurus cinereus, and Perimyotis subflavus). We compared the overlap of models created from passive-only (acoustics), active-only (mist-netting and wind turbine mortalities), and combined occurrences to identify the effect of multiple data types and detection bias. For each species, the active-only models had the highest discriminatory ability to tell occurrence from background points and for two of the three species, active-only models preformed best at maximizing the discrimination between presence and absence values. By comparing the niche overlaps of HSMs between data types, we found a high amount of variation with no species having over 45% overlap between the models. Passive models showed more suitable habitat in agricultural lands, while active models showed higher suitability in forested land, reflecting sampling bias. Overall, our results emphasize the need to carefully consider the influences of detection and survey biases on modeling, especially when combining multiple data types or using single data types to inform management interventions. Biases from sampling, behavior at the time of detection, false positive rates, and species life history intertwine to create striking differences among models. The final model output should consider biases of each detection type, particularly when the goal is to inform management decisions, as one data type may support very different management strategies than another.

Non-destructive methods to assess pesticide exposure in free-living bats

Bat populations are dwindling worldwide due to anthropogenic activities like agriculture, however the role that pesticide exposure plays on these declines is unclear. To address these research gaps, we first need to develop reliable methods to detect and monitor exposure to environmental pollutants and its effects on free-living bats. The use of biomarkers is a sensitive and informative tool to study sublethal effects in wildlife, however it requires laboratory validation and integrative approaches to be applicable to free-living species. In this study, we propose a set of non-destructive biomarkers to evaluate pesticide exposure in free-ranging bats and validated their suitability with dose-exposure experiments in captivity. We selected three biomarkers that have been widely used in vertebrate ecotoxicology and that combined represent sensitive, specific, and ecologically relevant responses to pollutants: DNA damage, AChE activity, and leukocyte profiles. We used two insectivorous bat species as model species Eptesicus fuscus (laboratory) and Pteronotus mexicanus (field). We found that micronuclei frequency (genotoxicity) and AChE activity (exposure and neurotoxicity) were robust indicators of toxicant exposure. The validity of this set of endpoints was supported by their consistent performance in laboratory and field experiments as well as by the significant correlation among them. Leukocyte profile (systemic stress) results were not consistent between laboratory and field studies, suggesting further evaluation of its suitability is needed. Integrative approaches, like the one we used here, maximize the insights about toxicant effects by combining the information of single biomarkers into more meaningful inferences, which can be applied to environmental risk assessments in wildlife. Furthermore, the use of non-destructive, cost-effective biomarkers is imperative when assessing toxicant exposure and effects in vulnerable wildlife and it should be a priority in the field of wildlife toxicology.

Bats and pollution: Genetic approaches in ecotoxicology

Environmental pollution drives the decline of species and, as flying mammals, bats can be considered to be excellent indicators of environmental quality, and the analysis of genetic biomarkers in these animals can provide important parameters for the assessment of environmental health. This review verifies the trends in pollution research, in particular, the use of genetic markers in the study of bats, based on a literature search of the Web of Science and Scopus platforms. Sixteen publications were identified during the search, which focused on the timeframe between 1996 and March 2022, including investigations of the effects of heavy metals, agricultural pesticides, and radiation. The studies were based primarily on the application of biomarkers for genotoxic analysis, including the comet assay, micronucleus test, and the Polymerase Chain Reaction (PCR). Only 55 bat species have been investigated up to now, that is, 4% of the 1447 currently recognized. In general, bats exposed to polluted environments presented a higher frequency of genotoxic and mutagenic damage than those sampled in clean environments. Given the importance of the diverse ecological functions provided by bats, including pest control, pollination, and seed dispersal, it is increasingly necessary to investigate the damage caused to the health of these animals exposed to areas with high concentrations of contaminants. Although genetic biomarkers have been used to investigate physiological parameters in bats for more than two decades, then, many knowledge gaps remain, worldwide, in terms of the number of species and localities investigated.

Acute multiple toxic effects of Trifloxystrobin fungicide on Allium cepa L

Trifloxystrobin (TFS) is a strobilurin-type fungicide that should be investigated due to its risks to non-targeted organisms. The goal of this study was to assess the susceptibility of Allium cepa L. to TFS in a multi-pronged approach. For 72 h, 0.2 g/L, 0.4 g/L and 0.8 g/L doses of TFS were administered to A. cepa bulbs and the control group was treated with tap water. The toxic effects of TFS were tested, considering physiological, cytogenetic, biochemical and anatomical analyses. TFS delayed growth by reducing the rooting ratio, root elongation and weight increase. Following TFS treatments, mitotic index (MI) scores decreased, while the formation of micronucleus (MN) and chromosomal aberrations (CAs) ascended. CAs types induced by TFS were listed according to their frequency as fragment, vagrant chromosome, sticky chromosome, uneven distribution of chromatin, bridge, nucleus with vacuoles, reverse polarization and irregular mitosis. TFS provoked an increment in superoxide dismutase (SOD) and catalase (CAT) enzyme activities as well as an accumulation of malondialdehyde (MDA). Meristematic cells of A. cepa roots treated with TFS had various anatomical damages, including damaged epidermis, flattened cell nucleus, damaged cortex and thickness in the cortex cell wall. All damages arising from TFS treatments exhibited dose-dependency. The findings of the present study revealed the serious toxicity of TFS in a non-targeted plant. It should not be neglected to evaluate the potential hazards of TFS with different toxicity tests.

Vicia–Micronucleus Test Application for Saline Irrigation Water Risk Assessment

In view of climate change, increasing soil salinity is expected worldwide. It is therefore important to improve prediction ability of plant salinity effects. For this purpose, brackish/saline irrigation water from two areas in central and coastal Tunisia was sampled. The water samples were classified as C3 (EC: 2.01–2.24 dS m⁻¹) and C4 (EC: 3.46–7.00 dS m⁻¹), indicating that the water was questionable and not suitable for irrigation, respectively. The water samples were tested for their genotoxic potential and growth effects on Vicia faba seedlings. Results showed a decrease in mitotic index (MI) and, consequently, growth parameters concomitant to the appearance of micronucleus (MCN) and chromosome aberrations when the water salinity increased. Salt ion concentration had striking influence on genome stability and growth parameters. Pearson correlation underlined the negative connection between most ions in the water inappropriate for irrigation (C4) and MI as well as growth parameters. MI was strongly influenced by Mg²⁺, Na⁺, Cl⁻, and to a less degree Ca²⁺, K⁺, and SO₄²⁻. Growth parameters were moderately to weakly affected by K⁺ and Ca²⁺, respectively. Re-garding MCN, a very strong positive correlation was found for MCN and K⁺. Despite its short-term application, the Vicia-MCN Test showed a real ability to predict toxicity induced by salt ions confirming that is has a relevant role in hazard identification and risk assessment of salinity effects.

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.

Evaluation of genotoxicity in bat species found on agricultural landscapes of the Cerrado savanna, central Brazil

Habitat loss and fragmentation together represent the most significant threat to the world's biodiversity. In order to guarantee the survival of this diversity, the monitoring of bioindicators can provide important insights into the health of a natural environment. In this context, we used the comet assay and micronucleus test to evaluate the genotoxic susceptibility of 126 bats of eight species captured in soybean and sugarcane plantation areas, together with a control area (conservation unit) in the Cerrado savanna of central Brazil. No significant differences were found between the specimens captured in the sugarcane and control areas in the frequency of micronuclei and DNA damage (comet assay). However, the omnivore Phyllostomus hastatus had a higher frequency of nuclear abnormalities than the frugivore Carollia perspicillata in the sugarcane area. Insectivorous and frugivorous bats presented a higher frequency of genotoxic damage than the nectarivores in the soybean area. In general, DNA damage and micronuclei were significantly more frequent in agricultural environments than in the control area. While agricultural development is an economic necessity in developing countries, the impacts on the natural landscape may result in genotoxic damage to the local fauna, such as bats. Over the medium to long term, then DNA damage may have an increasingly negative impact on the wellbeing of the local species.

Bats are an excellent sentinel model for the detection of genotoxic agents. Study in a Colombian Caribbean region

Wildlife animals have been affected by human activities and the diminution of the areas needed to develop wildlife. In Colombia, artisanal and industrial mining focuses on gold extraction, which uses mercury and causes contamination in water sources. Bats may be susceptible to chemical contamination and primarily to bioaccumulated heavy metal contaminants in the food chain. The primary source of exposure is contaminated food and water ingest, followed by dermic exposition and inhalation. The objective was to evaluategenotoxic damage and mercury concentration in bats. Forty-five samples of blood and organs of bats captured in Ayapel and Majagual were collected. Erythrocytes were searched for micronuclei by peripheral blood smear. Mercury concentration in 45 liver and spleen samples was determined by atomic absorption spectroscopy (DMA80 TRICELL, Milestone Inc, Italy). Bats from four families were studied: Phyllostomidae (6 species), Molossidae (3 species), Vespertilionidae (1 species), and Emballonuridae (1 species). Mercury was found in all bat species from the different dietary guilds. Insectivores had the highest concentration of mercury in the liver (0,23 µg/g) and spleen (0,25 µg/g) and the highest number of micronuclei (260 micronuclei/10,000). The specimens captured in Majagual had the highest frequency of micronuclei (677 micronuclei/10,000), and those captured in Ayapel had the highest mercury concentration (0,833 µg/g). This is the first study in Colombia to report that bats could act as sentinels to the environment's genotoxic chemical agents. Mercury and a high frequency of micronuclei were found in the tissues of captured bats. In addition to mercury contamination, there could also be other contaminants affecting Chiroptera.

Multiresidues of environmental contaminants in bats from Turkey

Bat populations have been steadily declining, most likely because of anthropogenic factors. Identification and classification of these risks have crucial importance in ensuring the survival of this species. Bats often coexist with humans in urban, industrial, and agricultural areas and are potentially exposed to a range of environmental pollutants. Two bat species widely distributed in Turkey were selected, and the residues of pesticides and organic contaminants in their carcasses were analyzed using: gas chromatography-mass spectrometry, gas chromatography-tandem mass spectrometry, and liquid chromatography-tandem mass spectrometry. Species and sex specific differences were evaluated along with their potential to be used as bioindicators. During the rigor mortis period, 23 adult Pipistrellus pipistrellus (11 female and 12 male) and 19 adult Myotis myotis (9 female and 10 male) were collected and 322 contaminants (pesticides and organic contaminants) were analyzed in whole carcasses of bats by using a validated method. Multiple pesticides and organic contaminants were detected in all collected 42 bats. The most frequent contamination was detected as 4,4-DDE, followed by ethoprophos, quinalphos, methidation, paraoxon-methyl, phosalone and tetramethrin. The least common compounds were as follows: 2,4-DDD, endrin, HCH-alpha, fenamiphos sulfoxide, parathion ethyl, bitertanol, oxycarboxin, procymidone, fluazifop-butyl, trifluralin, bifenazate, DMF, fenpyroximate, PBDE-47, benzo(a)anthracene, benzo(b)fluoranthene, and benzo(g,h,i) perylene; of these only one was found in each bat. In terms of frequency and concentration, there was no significant difference between species and sex. An average of 26.1 pollutants was found in each bat. Thus, it was concluded that bats can be used as potential bioindicators in determining environmental pollution.

Going out for dinner-The consumption of agriculture pests by bats in urban areas

Insectivorous bats provide ecosystem services in agricultural and urban landscapes by consuming arthropods that are considered pests. Bat species inhabiting cities are expected to consume insects associated with urban areas, such as mosquitoes, flying termites, moths, and beetles. We captured insectivorous bats in the Federal District of Brazil and used fecal DNA metabarcoding to investigate the arthropod consumed by five bat species living in colonies in city buildings, and ascertained whether their predation was related to ecosystem services. These insectivorous bat species were found to consume 83 morphospecies of arthropods and among these 41 were identified to species, most of which were agricultural pests. We propose that bats may roost in the city areas and forage in the nearby agricultural fields using their ability to fly over long distances. We also calculated the value of the pest suppression ecosystem service by the bats. By a conservative estimation, bats save US$ 94 per hectare of cornfields, accounting for an annual savings of US$ 390.6 million per harvest in Brazil. Our study confirms that, regardless of their roosting location, bats are essential for providing ecosystem services in the cities, with extensive impacts on crops and elsewhere, in addition to significant savings in the use of pesticides.

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.