The intake of water containing a mix of pollutants at environmentally relevant concentrations leads to defensive response deficit in male C57Bl/6J mice

Behavioral Responses of Imidacloprid-Dosed Farmland Birds to a Simulated Predation Risk

Sublethal exposure to imidacloprid and other neonicotinoid insecticides may affect the neurological functions of birds. As such, behavior may be compromised. Here, we tested experimentally the effects of 1 and 6 mg/kg bw of imidacloprid on the antipredator behavioral responses of the red-legged partridge (Alectoris rufa) to simulated predator threats. Sixty-six partridges were challenged in groups or individually to intra- and interspecific alarm calls, to a raptor silhouette (aerial predation risk), and to a fox model (terrestrial predation risk). Antipredator behaviors were recorded as active (escape, active vigilance) and passive (passive vigilance, crouching, and freezing) responses. Latency in response to the stimuli, percentage of individuals who responded, response duration, speed of active responses, and vocalizations were measured. In experiments with partridges in the group, crouching against simulated predation risk lasted less time in birds treated with 6 mg a.i./kg bw than in control birds. In the experiments with individual partridges, passive vigilance against the intraspecific alarm lasted longer in birds treated with 6 mg a.i./kg bw than in control birds. The observed hyperreactivity to the predatory threat after a sublethal imidacloprid exposure can have consequences on survival under field conditions, where predation is a main driver of population dynamics.

Toxicity assessment of polyethylene microplastics in combination with a mix of emerging pollutants on Physalaemus cuvieri tadpoles

Studies in recent years have shown that aquatic pollution by microplastics (MPs) can be considered to pose additional stress to amphibian populations. However, our knowledge of how MPs affect amphibians is very rudimentary, and even more limited is our understanding of their effects in combination with other emerging pollutants. Thus, we aimed to evaluate the possible toxicity of polyethylene MPs (PE-MPs) (alone or in combination with a mix of pollutants) on the health of Physalaemus cuvieri tadpoles. After 30 days of exposure, multiple biomarkers were measured, including morphological, biometric, and developmental indices, behavioral parameters, mutagenicity, cytotoxicity, antioxidant and cholinesterase responses, as well as the uptake and accumulation of PE-MPs in animals. Based on the results, there was no significant change in any of the parameters measured in tadpoles exposed to treatments, but induced stress was observed in tadpoles exposed to PE-MPs combined with the mixture of pollutants, reflecting significant changes in physiological and biochemical responses. Through principal component analysis (PCA) and integrated biomarker response (IBR) assessment, effects induced by pollutants in each test group were distinguished, confirming that the exposure of P. cuvieri tadpoles to the PE-MPs in combination with a mix of emerging pollutants induces an enhanced stress response, although the uptake and accumulation of PE-MPs in these animals was reduced. Thus, our study provides new insight into the danger to amphibians of MPs coexisting with other pollutants in aquatic environments.

Toxicity assessment of SARS-CoV-2-derived peptides in combination with a mix of pollutants on zebrafish adults: A perspective study of behavioral, biometric, mutagenic, and biochemical toxicity

The dispersion of SARS-CoV-2 in aquatic environments via the discharge of domestic and hospital sewage has been confirmed in different locations. Thus, we aimed to evaluate the possible impacts of zebrafish (Danio rerio) exposure to SARS-CoV-2 peptide fragments (PSPD-2001, 2002, and 2003) alone and combined with a mix of emerging pollutants. Our data did not reveal the induction of behavioral, biometric, or mutagenic changes. But we noticed an organ-dependent biochemical response. While nitric oxide and malondialdehyde production in the brain, gills, and muscle did not differ between groups, superoxide dismutase activity was reduced in the "PSPD", "Mix", and "Mix+PSPD" groups. An increase in catalase activity and a reduction in DPPH radical scavenging activity were observed in the brains of animals exposed to the treatments. However, the "Mix+PSPD" group had a higher IBRv2 value, with NO levels (brain), the reduction of acetylcholinesterase activity (muscles), and the DPPH radical scavenging activity (brain and muscles), the most discriminant factors for this group. The principal component analysis (PCA) and hierarchical clustering analysis indicated a clear separation of the "Mix+PSPD" group from the others. Thus, we conclude that exposure to viral fragments, associated with the mix of pollutants, induced more significant toxicity in zebrafish adults than in others.

Exposure to polystyrene nanoplastics induces an anxiolytic-like effect, changes in antipredator defensive response, and DNA damage in Swiss mice

Although the in vivo toxicity of nanoplastics (NPs) has already been reported in different model systems, their effects on mammalian behavior are poorly understood. Thus, we aimed to evaluate whether exposure to polystyrene (PS) NPs (diameter: 23.03 ± 0.266 nm) alters the behavior (locomotor, anxiety-like and antipredator) of male Swiss mice, induces brain antioxidant activity, and erythrocyte DNA damage. For this, the animals were exposed to NPs for 20 days at different doses (6.5 ng/kg and 6500 ng/kg). Initially, we did not observe any effect of pollutants on the locomotor activity of the animals (inferred via open field test and Basso mouse scale for locomotion). However, we noticed an anxiolytic-like behavior (in the open field test) and alterations in the antipredatory defensive response of mice exposed to PS NPs, when confronted with their predator potential (snake, Pantherophis guttatus). Furthermore, such changes were associated with suppressing brain antioxidant activity, inferred by lower DPPH radical scavenging activity, reduced total glutathione content, as well as the translocation and accumulation of NPs in the brain of the animals. In addition, we noted that the treatments induced DNA damage, evaluated via a single-cell gel electrophoresis assay (comet assay) applied to circulating erythrocytes of the animals. However, we did not observe a dose-response effect for all biomarkers evaluated and the estimated accumulation of PS NPs in the brain. The values of the integrated biomarker response index and the results of the principal component analysis (PCA) and the hierarchical clustering analysis confirmed the similarity between the responses of animals exposed to different doses of PS NPs. Therefore, our study sheds light on how PS NPs can impact mammals and reinforce the ecotoxicological risk associated with the dispersion of these pollutants in natural environments and their uptake by mammals.

Short-term exposure of the mayfly larvae (Cloeon dipterum, Ephemeroptera: Baetidae) to SARS-CoV-2-derived peptides and other emerging pollutants: A new threat for the aquatic environments

The input of SARS-CoV-2 or its fragments into freshwater ecosystems (via domestic or hospital sewage) has raised concerns about its possible impacts on aquatic organisms. Thus, using mayfly larvae [Cloeon dipterum (L.), Ephemeroptera: Baetidae] as a model system, we aimed to evaluate the possible effects of the combined short exposure of SARS-CoV-2-derived peptides (named PSPD-2001, PSPD-2002, and PSPD-2003 - at 266.2 ng/L) with multiple emerging pollutants at ambient concentrations. After six days of exposure, we observed higher mortality of larvae exposed to SARS-CoV-2-derived peptides (alone or in combination with the pollutant mix) and a lower-body condition index than those unexposed larvae. In the "PSPD" and "Mix+PSPD" groups, the activity of superoxide dismutase, catalase, DPPH radical scavenging activity, and the total thiol levels were also lower than in the "control" group. In addition, we evidenced the induction of nitrosative stress (inferred by increased nitrite production) and reduced acetylcholinesterase activity by SARS-CoV-2-derived peptides. On the other hand, malondialdehyde levels in larvae exposed to treatments were significantly lower than in unexposed larvae. The values of the integrated biomarker response index and the principal component analysis (PCA) results confirmed the similarity between the responses of animals exposed to SARS-CoV-2-derived peptides (alone and in combination with the pollutant mix). Although viral peptides did not intensify the effects of the pollutant mix, our study sheds light on the potential ecotoxicological risk associated with the spread of the new coronavirus in aquatic environments. Therefore, we recommend exploring this topic in other organisms and experimental contexts.

Toxicity evaluation of the combination of emerging pollutants with polyethylene microplastics in zebrafish: Perspective study of genotoxicity, mutagenicity, and redox unbalance

Despite the toxicity of microplastics (MPs) in freshwater fish has been demonstrated in previous studies, their effects when mixed with other pollutants (organic and inorganic) are poorly understood. Thus, we aimed to test the hypothesis that the association of polyethylene MPs (PE-MPs) to a mix of emerging pollutants induces more adverse genotoxic, mutagenic, and redox unbalance effects in adult zebrafish (Danio rerio), after 15 days of exposure. Although the accumulation of MPs in animals was greater in animals exposed to PE-MPs alone, erythrocyte DNA damage (comet assay) and the frequency of erythrocytic nuclear abnormalities (ENAs) evidenced in zebrafish exposed to PE-MPs alone were as pronounced as those observed in animals exposed to the mix of pollutant (alone or in combination with MPs), which constitutes the big picture of the current study. Moreover, we noticed that such effects were associated with an imbalance between pro-and antioxidant metabolism in animals, whose activity of superoxide dismutase (SOD) and catalase (CAT) was assessed in different organs which were not sufficient to counterbalance the production of reactive oxygen species [hydrogen peroxide (H₂O₂)] and nitrogen [nitric oxide (NO)] evaluated. The principal component analysis (PCA) also revealed that while the antioxidant activity was more pronounced in the brain and liver of animals, the highest production of H₂O₂ was perceived in the gills and muscles, suggesting that the biochemical response of the animals was organ-dependent. Thus, the present study did not demonstrate antagonistic, synergistic, or additive effects on animals exposed to the combination between PE-MPs and a mix of pollutants in the zebrafish, which reinforces the theory that interactions between pollutants in aquatic ecosystems may be as complex as their effects on freshwater ichthyofauna.

Toxicity of polystyrene nanoplastics and zinc oxide to mice

The toxicity of zinc oxide (ZnO NPs) and polystyrene nanoplastics (PS NaPs) has been tested in different animal models; however, knowledge about their impact on mice remains incipient. The aim of the current study is to evaluate the effects of these nanomaterials on Swiss mice after their individual exposure to a binary combination of them. The goal was to investigate whether short exposure (three days) to an environmentally relevant dose (14.6 ng/kg, i.p.) of these pollutants would have neurotoxic, biochemical and genotoxic effects on the modelss. Data in the current study have shown that the individual exposure of these animals has led to cognitive impairment based on the object recognition test, although the exposure experiment did not cause locomotor and anxiogenic or anxiolitic-like behavioral changes in them. This outcome was associated with increased nitric oxide levels, thiobarbituric acid reactive species, reduction in acetylcholinesterase activity and with the accumulation of nanomaterials in their brains. Results recorded for the assessed parameters did not differ between the control group and the groups exposed to the binary combination of pollutants. However, both the individual and the combined exposures caused erythrocyte DNA damages associated with hypercholesterolemic and hypertriglyceridemic conditions due to the presence of nanomaterials. Based on the results, the toxicological potential of ZnO NPs and PS NaPs in the models was confirmed and it encouraged further in-depth investigations about factors explaining the lack of additive or synergistic effect caused by the combined exposure to the assessed pollutants.

Toxicity and trophic transfer of polyethylene microplastics from Poecilia reticulata to Danio rerio

The potential transfer of microplastics (MPs) between vertebrates belonging to the same taxonomic group, and the impact of such a transfer on higher trophic levels remains little explored. An experimental food chain with two fish species was installed to test the hypothesis that polyethylene MPs (PE MPs) can accumulate in animals and cause behavioral, mutagenic and cytotoxic changes at upper trophic levels. Poecilia reticulata fry were exposed to MPs for 48 h and, subsequently, offered (as food) to Danio rerio adults for 10 days to simulate an upper level food chain. PE MPs quantification in fry and in different Danio rerio tissues evidenced their accumulation at the two assessed trophic levels. This finding suggested their absorption, adherence and translocation from one organism to another. The accumulation seen in D. rerio directly exposed to MPs was associated with behavioral disorders at upper trophic level. These animals presented behavior suggestive of anti-predatory response deficit when they were confronted with a potential aquatic predator (Geophagus brasiliensis). This finding was inferred through lower school cohesion, shallower school depth and shorter distance from the potential predator. In addition, animals exposed to MPs recorded higher nuclear abnormality rates and changes in the size and shape of erythrocytes and in their nuclei; this outcome has suggested mutagenic and cytotoxic effects, respectively. Based on the current results, MPs are transferred through a food chain that only involves two vertebrates. MPs enter the vertebrates' organs, change their behavior and induce mutagenic and cytotoxic processes in animals, which can cause significant ecological consequences in freshwater ecosystems.

Do predictive environmentally relevant concentrations of ZnO nanoparticles induce antipredator behavioral response deficit in Swiss mice?

The toxicity of zinc oxide nanoparticles (ZnO NPs) has been addressed in several studies; however, their effect on the mammalian group, even at environmentally relevant concentrations, remains poorly understood. The aims of the present study are to expose female Swiss mice to ZnO NP concentrations commonly faced by mammals who enter aquatic systems to perform different ecological functions and to assess the possible effects of such particles on their behavior. The test animals were placed in water added with ZnO NPs for 3 min, 2 times/day, for 21 days. Two experimental groups were set, NP1x, composed of animals subjected to ZnO NP concentration of 760 μg/L; and NP50x (control), which encompassed animals subjected to 38,000 μg/L. Based on field test results (OF), the contact with NPs did not induce locomotor deficits or anxiogenic and anxiolytic effect on the animal models. However, models exposed to NPs were not able to recognize the predatory threat posed by the presence of Pantherophis guttatus and Arapaima gigas; on the other hand, animals in the control group, who were not exposed to ZnO NPs, did not present antipredator behavioral response deficit. Furthermore, mice exposed to NPs were unable to distinguish real predators from plastic copies, and it suggests antipredator behavioral response deficit. High Zn concentrations in blood, liver, brain and skin samples are associated with deficit caused by the exposure to ZnO NPs. To the best of our knowledge, the current study is in the first to evidence that ZnO NPs induce changes in antipredator behavioral responses, even under ephemeral conditions and at low concentrations. However, the exposure to ZnO NPs can be a risk to the health of the assessed individuals and to the dynamics of their populations if the present antipredator behavioral response test results are extrapolated to the ecological context.

Ingestion of tannery effluent as a risk factor to the health of birds: A toxicological study using Coturnix coturnix japonica as a model system

Tannery industries generate large amounts of tannery effluents (TE), which have been considered highly toxic to various groups of animals. However, the identification and characterization of the impact of this mix of pollutants on birds is still highly incipient. So, our goal was to evaluate the possible biological changes of Coturnix coturnix japonica, exposed for 45 days, to different dilutions of TE (1.4%, 3.1% and 6.5%), using behavioural biomarkers, mutagenics and egg production. When submitted to the behavioural tests, quails that ingested TE presented behaviour compatible with an anxiolytic effect in the open field test; absence of emotional reactivity in the object recognition test; reduced rates of predation of Tenebrio molitor larvae (potential prey); as well as an anti-predatory defensive response deficit when confronted, especially with Felis catus males (potential predator). In addition, we observed increased biomass of the liver, increased feed conversion index and lower feed efficiency index; mutagenic effect of TE (inferred by the increase of nuclear erythrocyte abnormalities); reduced productive performance and egg quality, in addition to different staining patterns of the eggs produced by quails from the control group. Therefore, our study confirms the toxicity of TE in C. coturnix japonica, even in small dilutions. While behavioural changes demonstrate the neurotoxic potential of the pollutant, the other alterations suggest that the mechanisms of action of its chemical constituents are not selective, that is, they act systemically, acting synergistic, antagonistic or additively, causing harmful effects in animals.

Depression, anxiety-like behavior, and memory impairment in mice exposed to chitosan-coated zein nanoparticles

The advent of biotechnology provided the synthesis of nanoproducts with diverse applications in the field of medicine, agriculture, food, among others. However, the toxicity of many nanoparticles (NP) currently used, which can penetrate natural systems and impact organisms, is not known. Thus, in this study, we evaluated whether the short exposure (5 days) to low concentrations of chitosan-coated zein nanoparticles (ZNP-CS) (0.2 ng/kg, 40 ng/kg, and 400.00 ng/kg) was capable of causing behavioral alterations compatible with cognitive deficit, as well as anxiety and depression-like behavior in Swiss mice. However, we observed an anxiogenic effect in the animals exposed to the highest ZNP-CS concentration (400.00 ng/kg), without locomotor alterations suggestive of sedation or hyperactivity in the elevated plus maze (EPM) test. We also observed that the ZNP-CS caused depressive-like behavior, indicated by the longer immobile time in the tail suspension test and the animals exposed to ZNP-CS presented deficit in recognition of the new object, not related to locomotor alteration in this test. To the best of our knowledge, this is the first report of the neurotoxicity of ZNP in a mammal animal model, contributing to the biological safety assessment of these nanocomposites.

Combined Toxicity of Nitro-Substituted Benzenes and Zinc to Photobacterium Phosphoreum: Evaluation and QSAR Analysis

The single toxicity (IC₅₀) of zinc (Zn) and 11 nitro-substituted benzenes to Photobacterium phosphoreum were determined, respectively. On basis of single toxicity, the joint toxicity of binary mixtures of Zn and 11 nitro-substituted benzenes at different Zn concentrations of 0.2 IC₅₀, 0.5 IC₅₀, and 0.8 IC₅₀ were measured. The joint toxicity was evaluated by toxic unit (TU) and additive index (AI) methods. The results indicated that the joint toxicity was not only depending on the Zn concentrations but also on the substituted groups of nitro-substituted benzenes. The quantitative structure-activity relation (QSAR) equations were developed and the results showed that the toxicity of nitro-substituted benzenes has different joint effect at the different Zn concentrations. At the Zn concentration of 0.2 IC₅₀, the binary joint effects were mainly antagonism and the joint toxicity was negatively related to descriptors called VE2_B(p) and TIC3. At the Zn concentration of 0.5 IC₅₀ and 0.8 IC₅₀, the binary joint effects were mainly antagonism and simple addition, and the joint toxicity was related to the same descriptor Eig06_ AEA(dm). It indicated that the joint toxic actions were similar when combined at the medium and high concentrations of Zn.

Sub-lethal effects induced by a mixture of different pharmaceutical drugs in predicted environmentally relevant concentrations on Lithobates catesbeianus (Shaw, 1802) (Anura, ranidae) tadpoles

The increasing consumption of medications by humans has negative effects such as the increased disposal of these compounds in the environment. Little is known about how the disposal of a "drug mix" (DM) in aquatic ecosystems can affect their biota. Thus, we evaluated whether the exposure of Lithobates casteibeianus tadpoles to a DM composed of different medication classes (antibiotic, anti-inflammatory, antidepressant, anxiolytic, analgesic, and antacid drugs)-at environmentally relevant concentrations-may change their oral morphology, trigger behavioral disorders, and have mutagenic effects on erythrocyte cells. Based on our data, animals exposed to the DM showed changes in mandibular sheath pigmentation, dentition, and swimming activity, as well as atypical behavior in the social aggregation test [with co-specific and interspecific (Physalaemus cuvieri) individuals] and antipredatory defensive response deficit (chemical stimulus from Odonata larvae), after 15 exposure days. The mutagenic analysis revealed higher frequency of nuclear abnormalities in the erythrocytes of tadpoles exposed to the DM (e.g., multilobulated, blebbed, kidney-shaped, notched nucleus, binuclear, and micronucleated erythrocytes). Given the chemical complexity of the DM, we assumed that several organic functions may have been affected, either by the isolated, synergistic, antagonistic, or additive action of DM compounds. Finally, our study confirms the toxicological potential of DM in L. catesbeianus tadpoles, with emphasis to impacts that can affect the fitness of individuals and their natural populations. Thus, we suggest that more attention should be given to the disposal of medications in the environment and reinforce the need of improving water and sewage treatment systems.

Mice exposure to haloxyfop-p-methyl ester at predicted environmentally relevant concentrations leads to anti-predatory response deficit

Although the efficiency of haloxyfop-p-methyl ester (HPME) as selective herbicide is acknowledged, its impact on non-target organisms is poorly known. It is not known whether the short exposure of mammals to low HPME concentrations (consistent with a realistic contamination scenario) poses risks to these animals. Thus, the aim of the current study is to evaluate the effects of HPME on the anti-predatory behavior of female Swiss mice exposed to it. The animals were divided in groups: non-exposed (control) and exposed (route: i.p., for 2 days) to different herbicide concentrations (2.7 × 10^-4 g/kg and 2.7 × 10^-2 g/kg of body weight), which were considered environmentally relevant predicted concentrations. The animals were subjected to the open field and elevated plus-maze tests; results showed that the HPME did not lead to anxiolytic or anxiety behavior, or to locomotive changes in the tested animals, fact that was confirmed through the Basso Mouse Scale for locomotion scores. On the other hand, animals exposed to the herbicide were incapable of recognizing the snake as potential predator. Animals in the control group, exposed to a real snake (Pantherophis guttatus) remained longer in the safety zone of the test device, presented lower frequency of self-grooming behaviors for a shorter period-of-time, besides showing longer freezing time, which was not observed in animals exposed to HPME. Therefore, our study indicates the ecotoxicological potential of the herbicide, since anti-predatory behavior disorders may affect preys' responses and population dynamics.

The effects of predicted environmentally relevant concentrations of ZnO nanoparticles on the behavior of Gallus gallus domesticus (Phasianidae) chicks

The toxicity of ZnO nanoparticles (NPs) has been the subject of several investigations; however, concentrations much higher than the ones potentially found in the environment are often tested. In addition, groups of animals such as birds have not been used as model in studies in this field, fact that creates an important ecotoxicological gap in them. The aim of the present study is to investigate the effects of the exposure to environmentally relevant concentrations of ZnO nanoparticles on the anti-predatory behavior of chicks (Gallus gallus domesticus). The test animals were daily exposed to an environmentally relevant concentration of ZnO nanoparticles (0.245 mg kg^-1) and to a toxic concentration of it (245.26 mg kg^-1) through intraperitoneal injection for two days. We set a control group for comparison purposes. According to our results, ZnO nanoparticles did not affect the locomotor activity of, and did not cause anxiolytic or anxiogenic effect on, birds in the open field test. However, based on the lowest cluster score recorded during the social aggregation test, chicks exposed to ZnO nanoparticles failed to recognize the grunt of a hawk (Rupornis magnirostris) as predatory threat. Only birds in the control group recognized the test snake (Pantherophis guttatus) as potential predator. The higher Zn concentration in the brains of animals exposed to ZnO nanoparticles evidenced the capacity of these nanomaterials to cross the blood-brain barrier, even at low concentrations. This blood-brain barrier crossing could have affected the structures or neuronal mechanisms that modulate the defensive response of birds. Assumingly, even the minimal exposure to low concentrations of ZnO nanoparticles can affect birds. Our outcomes corroborate previous studies about the biological risks of water surface contamination by metal-based nanomaterials.