Effect of landscape tree cover, sex and season on the bioaccumulation of persistent organochlorine pesticides in fruit bats of riparian corridors in eastern Mexico

Morphophysiological alterations in fruit-eating bats after oral exposure to deltamethrin

Deltamethrin (DTM) is a synthetic pyrethroid widely used in the cultivation and management of several crops due to its insecticidal action. Application to crops of pyrethroids such as DTM can result in the exposure of water and fruit consumed by fruit bats having a high pyrethroid content which may be harmful. Therefore the objective of this study was to evaluate the effects of short-term oral exposure of the fruit-eating bats (Artibeus lituratus) to two concentrations of DTM (0.02 and 0.04 mg/kg of papaya) on histopathology of the intestine, liver and kidney. The intestine of the animals exposed to both concentrations showed inflammatory infiltrate, degeneration, necrosis and goblet cell hyperplasia as the most frequent pathologies. Besides, the acid mucins showed an increase in the frequency of non-viable cells. The liver showed hepatocyte vacuolizatio and nuclear enlargement, as well as inflammatory infiltrate and steatosis. The kidneys of the exposed animals showed and inflammatory infiltrate, benign nephrosclerosis, vacuolization and necrosis. Also, DTM reduced nitric oxide synthesis, decreased glomerular diameter and increased glycogen percentage in the proximal tubules. Our results suggest that acute exposure to DTM at low concentrations has the potential to induce pronounced histopathological changes in vital organs, such as intestine, liver and kidney of fruit-eating bats.

Bioaccumulation of pesticides and genotoxicity in anurans from southern Brazil

The expansion of agricultural activities causes habitat loss and fragmentation and the pollution of natural ecosystems through the intense use of pesticides, which may affect the populations of amphibian anurans that inhabit agricultural areas. The present study evaluated the in situ bioaccumulation of pesticides in a population of Leptodactylus luctator that occupies farmland in southern Brazil. We also compared the genotoxicity of L. luctator populations from farmland and forested areas in the same region. We analyzed the micronuclei and nuclear abnormalities of 34 adult anurans, 19 from farmland, and 15 from the forested area. We also assessed the presence of 32 pesticides in liver samples obtained from 18 farmland-dwelling anurans, using chromatographic analysis. We recorded significantly higher rates of nuclear abnormalities in the individuals from the farmland, in comparison with the forest. We detected nine pesticides in the liver samples, of which, deltamethrin was the most common and carbosulfan was recorded at the highest concentrations. The bioaccumulation of pesticides and the higher levels of genotoxic damage found in the anurans from agricultural areas, as observed in the present study, represent a major potential problem for the conservation of these vertebrates, including the decline of their populations and the extinction of species.

Miniaturized QuEChERS extraction method for the detection of multi-residue pesticides in bat muscle tissue

Habitat loss and fragmentation are among the greatest threats to biodiversity and ecosystem stability, with physiological implications on wild fauna. Bats (Microchiroptera) are small mammals with a wide variety of eating habits, and the well-being of these animals is disturbed by exposure to pesticides. This study aimed to develop a miniaturized QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) extraction method for the detection of multi-residue pesticides in bat muscle tissue using gas chromatography coupled with mass spectrometry (GC–MS). A total of 48 pesticides were tested in 250 mg of bat muscle tissue. The developed analytical method was applied to 148 bats collected from two different areas in Minas Gerais State, Southeast Region of Brazil. The method presented good sensitivity and allowed the determination of residues of 48 pesticides in bat muscle using GC–MS. The miniaturized extraction method makes the analysis feasible even when the sample volume is limited. However, no pesticide residues were detected in bats from the two areas investigated.

Short-term intake of deltamethrin-contaminated fruit, even at low concentrations, induces testicular damage in fruit-eating bats (Artibeus lituratus)

Deltamethrin (DTM) is a pyrethroid insecticide widely used for agricultural purposes. Exposure to DTM has proven to be harmful to humans, but whether low, environmental concentrations of this pesticide also poses a threat to wild mammals is still unknown. In Neotropical areas, bats play important roles in contributing to forest regeneration. We investigated the effects of DTM exposure on the reproductive function of male Neotropical fruit-eating bats (Artibeus lituratus), known for contributing to reforestation through seed dispersal in Neotropical Forests. Bats were assigned to 3 groups: control (fed with papaya); DTM2 (fed with papaya treated with DTM at 0.02 mg/kg) and DTM4 (fed with papaya treated with DTM at 0.04 mg/kg) for seven days. Bats from DTM2 and DTM4 groups showed increased testicular levels of nitric oxide and superoxide dismutase and catalase activities. The germinal epithelium from DTM4 bats showed non-viable cells and cell desquamation, indicating microscopic lesions and Leydig cells atrophy. Our results demonstrate the onset of cell degeneration that may affect the reproductive function in DTM exposed bats.

How do pesticides affect bats? – A brief review of recent publications

Abstract Increased agricultural production has been increased use of pesticides worldwide, which poses a threat to both human and environmental health. Recent studies suggest that several non-target organisms, from bees to mammals, show a wide variety of toxic effects of pesticides exposure, including impaired behavior, development and reproduction. Among mammals, bats are usually a neglected taxon among ecotoxicological studies, although they play important ecological and economical roles in forest ecosystems and agriculture through to seed dispersal and insect population control. Considering their wide variety of food habits, bats are exposed to environmental pollutants through food or water contamination, or through direct skin contact in their roosting areas. In order to better understand the risk posed by pesticides to bats populations, we compiled studies that investigated the main toxicological effects of pesticides in bats, aiming at contributing to discussion about the environmental risks associated with the use of pesticides.

Exposure to pesticides in bats

Bats provide a variety of ecological services that are essential to the integrity of ecosystems. Indiscriminate use of pesticides has been a threat to biodiversity, and the exposure of bats to these xenobiotics is a threat to their populations. This study presents a review of articles regarding the exposure of bats to pesticides published in the period from January 1951 to July 2020, addressing the temporal and geographical distribution of research, the studied species, and the most studied classes of pesticides. The research was concentrated in the 1970s and 1980s, mostly in the Northern Hemisphere, mainly in the USA. Of the total species in the world, only 5% of them have been studied, evaluating predominantly insectivorous species of the Family Vespertilionidae. Insecticides, mainly organochlorines, were the most studied pesticides. Most research was observational, with little information available on the effects of pesticides on natural bat populations. Despite the advances in analytical techniques for detecting contaminants, the number of studies is still insufficient compared to the number of active ingredients used. The effects of pesticides on other guilds and tropical species remain poorly studied. Future research should investigate the effects of pesticides, especially in sublethal doses causing chronic exposure. It is crucial to assess the impact of these substances on other food guilds and investigate how natural populations respond to the exposure to mixtures of pesticides found in the environment.

Spatiotemporal pattern models for bioaccumulation of pesticides in common herbaceous and woody plants

Pesticides are widely used in agriculture, but they can bioaccumulate in plants, entering the food chain and potentially threaten human health. Thus, this study explored the spatiotemporal patterns of pesticide bioaccumulation in plants from soil using a spatiotemporal model. Air temperature (T_Air) and relative humidity (RH_Air) were selected as the principal spatiotemporal indicators to characterize the seasonal and geographical variation of the pesticide bioaccumulation factors (BAFs; i.e., the pesticide concentration ratio of plant to soil) of the leaves of common plants. The simulation results indicate that hot and dry climates typically increase the pesticide BAFs by enhancing the transpiration rate of plants. For example, the annual average BAF of alachlor was 5.75 in Arizona, while the BAFs in states with cold and humid weather, such as Maine, were below 2.00. Additionally, the monthly average BAF of alachlor during hot seasons can be double that of other seasons in the same region. For some pesticides, the simulated BAF intervals were consistent with those reported in the literature, whereas for others, the results were inconsistent. The major reasons for these inconsistencies include differences in the pesticide application scenarios, the distribution of pesticides in different compartments, and insufficient field data for some pesticides. We also applied the simulated BAFs of pesticide in plant leaves to address the seasonal and geographical health risks of herbivores, which could help regulate pesticide standards in ecological soils.

Current Status of Ecotoxicological Studies of Bats in Brazil

Bats are sensitive to contaminants generated by agricultural activities, mining, and urbanization. In this review, we update the status of bat toxicology in Brazil. Agriculture, for example, in addition to habitat fragmentation and loss, undoubtedly affects non-target organisms through the use of pesticides. Other factors such as trace metals are a neglected problem in the country, as they can deposit on insects and plants reaching bats through the ingestion of these foods. Of the 184 species of bats in the country, only 4.9% have been investigated. The frugivorous species, Artibeus lituratus, has frequently been studied for the effects of pesticide exposure, and impacts at the cellular level on metabolism and reproduction have been observed. Given the scarcity of studies on bat ecotoxicology, we encourage national researchers and scientists elsewhere to increase knowledge of the effects of chemical contaminants on bats in Brazil.

Micronucleus and other nuclear abnormalities in exfoliated cells of buccal mucosa of bats at different trophic levels

The micronucleus (MN) test in exfoliated cells of the buccal mucosa is a relatively non-invasive method for the monitoring of populations exposed to genotoxic risks. In this study, the MN test was used as bats conservation strategy. The highest frequencies of micronuclei were recorded in the frugivorous bats sampled in both urban and agricultural environments, as well as in insectivorous bats from the urban zone. Female of this group (insectivorous) presented higher frequency of MN when compared to males. Other guilds showed no difference in gender assessments in each environment, as well as in the correlation between weight and MN. In addition to micronuclei, a number of other types of nuclear abnormality were recorded, including binucleated cells and karyolysis in the frugivores from the agricultural environment. Binucleated cells were also relatively common in urban frugivores and insectivores, and karyolysis was common in insectivores. Nectarivorous bats did not exhibit a significant increase in any type of nuclear abnormality in either environment. In summary, study results indicate that buccal mucosa of bats is a sensitive site for detecting micronuclei and other nuclear abnormalities. However, more research is needed to indicate whether xenobiotic agents are affecting this cellular integrity.

Genotoxicological analyses of insectivorous bats (Mammalia: Chiroptera) in central Brazil: The oral epithelium as an indicator of environmental quality

The micronucleus (MN) test of the human buccal mucosa was developed more than 30 years ago, although this technique has only recently been applied to wild mammals. This paper presents a pioneering study in the genotoxicological evaluation of the exfoliated cells of the buccal mucosa of bats. The assay was applied to two insectivorous bat species (Noctilio albiventris and Pteronotus parnellii) sampled in riparian corridors located in the city of Palmas (capital of the Brazilian state of Tocantins), with the results being compared with those obtained for a third insectivorous species (Nyctinomops laticaudatus), which has established a colony under a road bridge in the same region. This colony represents one of the largest molossidae populations ever recorded in Brazil. A significantly higher frequency of micronuclei was recorded in this colony, as well as a number of other nuclear abnormalities, including binucleated cells, cells with condensed chromatin and karyolysis, in comparison with the bats from the riparian corridors, indicating that the bats from the bridge colony are more susceptible to genotoxic damage. Thus, it is demonstrated the importance of the biomarker (MN) for use in wild animals and allows to conclude that colony bats are more susceptible to genotoxic damages.