Micronucleus test in tadpole erythrocytes: Trends in studies and new paths

Limited contribution of photoenzymatic DNA repair in mitigating carry-over effects from larval UVB exposure: Implications for frog recruitment

Solar ultraviolet-B (UVB) radiation has increased due to stratospheric ozone depletion, climate and ecosystem changes and is a driver of amphibian population declines. Photoenzymatic repair (PER) is a critical mechanism for limiting UVB lethality in amphibian larvae. However, the link between PER and the UVB-induced effects remains understudied through long-term investigations in vivo. Here, we assessed how larval PER determines the lethal and sublethal effects induced by environmentally relevant acute UVB exposure until the juvenile phase in the Neotropical frog Odontophrynus americanus. We conducted laboratory-based controlled experiments in which tadpoles were or were not exposed to UVB and subsequently were exposed to light (for PER activation) or dark treatments. Results showed that the rates of mortality and apoptosis observed in post-UVB dark treatment are effectively limited in post-UVB light treatment, indicating PER (and not dark repair, i.e. nucleotide excision repair) is critical to limit the immediate genotoxic impact of UVB-induced pyrimidine dimers. Nonetheless, even tadpoles that survived UVB exposure using PER showed sublethal complications that extended to the juvenile phase. Tadpole responses included alterations in morphology, chromosomal instability, increased skin susceptibility to fungal proliferation, as well as increased generation of reactive oxygen species. The short-term effects were carried over to later stages of life because metamorphosis time increased and juveniles were smaller. No body abnormalities were visualized in tadpoles, metamorphs, and juveniles, suggesting that O. americanus is UVB-resistant concerning these responses. This study reveals that even frog species equipped with an effective PER are not immune to carry-over effects from early UVB exposure, which are of great ecological relevance as late metamorphosis and smaller juveniles may impact individual performance and adult recruitment to breeding. Future ecological risk assessments and conservation and management efforts for amphibian species should exercise caution when linking PER effectiveness to UVB resistance.

Prednisone and prednisolone effects on development, blood, biochemical and histopathological markers of Aquarana catesbeianus tadpoles

Synthetic glucocorticoids are often found in surface waters and can cause harmful effects to aquatic organisms such as amphibians. In this work we evaluated the effects of the drugs prednisone (PD) and prednisolone (PL) on developmental, molecular, blood, biochemical and histological markers. Aquarana catesbeianus tadpoles were exposed for 16 days to environmentally relevant concentrations of 0, 0.1, 1 and 10 µg/L of both drugs. PD increased the transcript levels of the enzyme deiodinase III (Dio3), the hormones cortisol and T4 and delayed development. Changes in the thyroid gland occurred after tadpoles were exposed to both drugs, with a reduction in the diameter and number of follicles and an increase/or decrease in area. Also, both drugs caused a decrease in lymphocytes (L) and an increase in neutrophils (N), thrombocytes, the N:L ratio and lobed and notched erythrocytes. Increased activity of the enzymes superoxide dismutase, glutathione S-transferase and glucose 6-phosphate dehydrogenase was observed after exposure to PD. Furthermore, both drugs caused an increase in the activity of the enzymes catalase and glutathione peroxidase. However, only PD caused oxidative stress in exposed tadpoles, evidenced by increased levels of malondialdehyde and carbonyl proteins. Both drugs caused an increase in inflammatory infiltrates, blood cells and melanomacrophages in the liver. Our results indicate that PD was more toxic than PL, affecting development and causing oxidative stress.

2,4-D-based herbicide underdoses cause mortality, malformations, and nuclear abnormalities in Physalaemus cuvieri tadpoles

Amphibians are considered bioindicators of the environment due to their high sensitivity and involvement in terrestrial and aquatic ecosystems. In the last two decades, 2,4-D has been one of the most widely used herbicides in Brazil and around the world, as its use has been authorized for genetically modified crops and therefore has been detected in surface and groundwater. Against this background, the aim of this work was to investigate the effects of environmentally relevant concentrations of 2,4-D-based herbicides on survival, malformations, swimming activity, presence of micronuclei and erythrocyte nuclear abnormalities in Physalaemus cuvieri tadpoles. The amphibians were exposed to six concentrations of 2,4-D-based herbicides: 0.0, 4.0, 30.0, 52.5, 75.0, and 100 μg L-1, for 168 h. At concentrations higher than 52.5 μg L-1, significantly increased mortality was observed from 24 h after exposure. At the highest concentration (100 μg L-1), the occurrence of mouth and intestinal malformations was also observed. The occurrence of erythrocyte nuclear abnormalities at concentrations of 30.0, 52.5, 75.0 and 100 μg L-1 and the presence of micronuclei at concentrations of 52.5, 75.0, and 100 μg L-1 were also recorded. These effects of 2,4-D in P. cuvieri indicate that the ecological risk observed at concentrations above 10.35 μg L-1 2,4-D may represent a threat to the health and survival of this species, i.e., exposure to 2,4-D at concentrations already detected in surface waters in the species' range is toxic to P. cuvieri.

High toxicity of agro-industrial wastewater on aquatic fauna of a South American stream: Mortality of aquatic turtles and amphibian tadpoles as bioindicators of environmental health

The aim of this study was to characterize an aquatic system of Santa Fe province (Argentina) receiving wastewater from agro-industrial activities (mainly dairy) by in situ assessment (fauna mortality, physicochemical, microbiological, and pesticide residues measurement), and ecotoxicity bioassays on amphibian tadpoles. Water and sediment samples were obtained from the Los Troncos Stream (LTS), previous to the confluence with the "San Carlos" drainage channel (SCC), and from the SCC. Biological parameters (mortality and sublethal biomarkers) were used to evaluate ecotoxicity during 10-day exposure of Rhinella arenarum tadpoles to LTS and SCC samples. Nine pesticides were detected in both LTS and SCC. Chemical and biochemical oxygen demand, ammonia, and coliform count recorded in SCC greatly exceeded limits for aquatic life protection. At SCC and LTS after the confluence with SCC, numerous dying and dead aquatic turtles (Phrynops hilarii) were recorded. In the ecotoxicity assessment, no mortality of tadpoles was observed in LTS treatment, whereas total mortality (100%) was observed in SCC treatments in dilution higher than 50% of water and sediment. For SCC, median lethal concentration and the 95% confidence limits was 18.30% (14.71-22.77) at 24 h; lowest-observed and no-observed effect concentrations were 12.5% and 6.25%, respectively. Oxidative stress and neurotoxicity were observed in tadpoles exposed to 25% SCC dilution treatment. In addition, there was a large genotoxic effect (micronuclei test) in all sublethal SCC dilution treatments (6.25%, 12.5%, and 25%). These results alert about the high environmental quality deterioration and high ecotoxicity for aquatic fauna of aquatic ecosystems affected by agro-industrial wastewater. PRACTITIONER POINTS: Great mortality of turtles was observed in a basin with a high load of agro-industrial wastewater. San Carlos Channel (SCC), where effluents are spilled, is environmentally deteriorated. The water-sediment matrix of SCC caused 100% lethality in tadpoles. SCC dilutions caused neurotoxicity, oxidative stress, and genotoxicity on tadpoles.

Impacts of horticultural environments on Rhinella arenarum (Anura, Bufonidae) populations: exploring genocytotoxic damage and demographic life history traits

Horticulture poses a significant ecological risk, as agrochemicals are applied more frequently and in larger quantities per unit of production compared to extensive crop fields. The native amphibian Rhinella arenarum serves as a reliable bioindicator of environmental health. This study aimed to assess genocytotoxic damage and demographic life history traits of R. arenarum inhabiting horticultural environments. Sampling was conducted in suburban sites in central Argentina: H1 and H2 (sites associated with horticultural activity) and a reference site, RS. Environmental parameters were recorded, and the frequency of micronuclei (Mn), nuclear abnormalities (ENA), and indicators of cytotoxic damage were determined in tadpoles and adults. Demographic variables (age at maturity, longevity, potential reproductive lifespan, size at maturity, modal lifespan) were calculated. The highest nitrate and phosphate values, along with low dissolved oxygen values, were recorded at sites H1 and H2. Organisms inhabiting horticultural environments exhibited higher frequencies of Mn and ENA, surpassing those recorded in previous studies on tadpoles from sites with extensive crop production. Size at maturity and age at maturity of females, as well as size at maturity, longevity, mean age, and mean adult SVL of males, were lower in horticultural sites. The results support the hypothesis that anuran populations inhabiting horticultural environments demonstrate a diminished health status attributed to subpar environmental quality. Monitoring endpoints at different biological levels provides information on the ecotoxicological risk for amphibians and human populations inhabiting nearby areas.

Exposure to microcrystallized cellulose affects the health of tadpoles and sheds light on the threat these materials pose to amphibians

The increasing use of cellulose-based materials (CBMs) has provided beneficial applications in different sectors. However, its release into environments may represent an ecological risk, therefore demanding that ecotoxicological studies be conducted to understand the risks (current and future) of CBM pollution. Thus, we evaluated the possible effects of microcrystalline cellulose (CMs) in Physalaemus cuvieri tadpoles. After seven days of exposure to CMs (at 58.29 and 100 mg/L), the animals were subjected to behavioral evaluation, and different biomarkers (biometric and biochemical) were evaluated. Although our data do not point to a neurotoxic effect of CMs (inferred by the absence of behavioral changes and changes in AChE and BChE activity), animals exposed to CMs showed differences in body condition. Furthermore, we noticed an increase in the frequency of erythrocyte nuclear abnormalities and DNA damage, which were correlated with the ingestion of CMs. We noticed that the antioxidant activity of tadpoles exposed to CMs (inferred by SOD, CAT, and DPPH radical scavenging activity) was insufficient to control the increase in ROS and MDA production. Furthermore, exposure to CMs induced a predominant Th2-specific immune response, marked by suppressed IFN-γ and increased IL-10 levels, with a consequent reduction in NO levels. Principal component analysis and IBRv-2 indicate, in general, a primarily more toxic response to animals exposed to the highest CM concentration. Therefore, our study evidence that CMs affect the health of P. cuvieri tadpoles and sheds light on the threat these materials pose to amphibians.

Toxic, genotoxic, mutagenic, and bioaccumulative effects of metal mixture from settleable particulate matter on American bullfrog tadpoles (Lithobates catesbeianus)

Amphibians are more susceptible to environmental stressors than other vertebrates due to their semipermeable skin and physiological adaptations to living in very specific microhabitats. Therefore, the aim of the present study was to investigate the effects of a metal mixture from settleable particulate matter (SePM) released from metallurgical industries on Lithobates catesbeianus tadpoles. Endpoints analyzed included metal bioconcentration, morphological (biometrical indices), hematological parameters (hemoglobin and blood cell count), and erythrocyte DNA damage (genotoxicity and mutagenicity). American bullfrog tadpoles (Gosner's stage 25) were kept under control condition (no contaminant addition) or exposed to a sub-lethal and environmentally relevant concentration (1 g.L-1) of SePM for 96 h. Tadpoles exposed to SePM exhibited elevated whole blood levels of Fe56, AL, Sn, Pb, Zn, Cr, Cu, Ti, Rb, V, Ce, La, Ag, As. SePM-exposed tadpoles showed a significant decrease in condition factor (12%) and increases in hepatosomatic index (25%), hemoglobin concentration (17%), and total leukocytes (82%), thrombocytes (90%), and monocytes (78%) abundance. In addition, exposed tadpoles showed higher MN and ENAs (340 and 140%, respectively) frequencies, and erythrocyte DNA damage with approximately 1.2- to 1.8-fold increases in comet parameters. Taken together, these results suggest that the multimetal mixture found in SePM is potentially genotoxic and mutagenic to L. catesbeianus tadpoles, induces stress associated with hematological changes, and negatively affects growth. Although such contamination occurs at sublethal levels, regulatory standards are needed to control the emission of SePM and protect amphibian populations.

The Use of Multiple Biomarkers to Assess the Health of Anuran Amphibians in the Brazilian Cerrado Savanna: An Ecotoxicological Approach

Changes in the natural landscape and the indiscriminate use of pesticides can have a major impact on aquatic environments and have contributed to the worldwide decline of amphibian populations. In the present study, we sampled tadpoles of three anuran amphibians (Boana albopunctata, Physalaemus cuvieri, and Dendropsophus minutus) from ponds in six different agricultural landscapes of the Brazilian Cerrado savanna and evaluated whether and to what extent genotoxic and mutagenic damage was related to land use (the amount of forest and agricultural remnants, and related physicochemical factors) and the presence of pesticides in the water of the study ponds. We also evaluated the hepatotoxicity in P. cuvieri, which was the most abundant species at five of the six sampling points. Clomazone and atrazine were the most common pesticides found in the ponds. The B. albopunctata and P. cuvieri tadpoles presented similar patterns of DNA damage among the sampling points. The least DNA damage was found in the D. minutus tadpoles, although this species was present in only one of the study ponds. More binucleated and anucleated cells were observed in B. albopunctata, but there was no significant variation among species in terms of the number of micronuclei or other erythrocytic nuclear abnormalities. Land use and physicochemical factors did not explain the variation in the DNA damage observed in the three anurans. The hepatotoxicity analyses of P. cuvieri revealed the presence of a series of alterations, including the enlargement of the sinusoids, vacuolization of the hepatocytes, the infiltration of inflammatory cells, hepatic steatosis, and dilation of the blood vessels. The interaction between physicochemical factors and the biomarkers analyzed in the present study is complex. In particular, it will be important to better elucidate which factors are contributing, either directly or indirectly, to the decline of anuran amphibian populations, especially in threatened biomes, such as the Brazilian Cerrado. In this case, we would encourage further in situ studies that assess the ecotoxicology of the landscape, together with the systematic monitoring of aquatic environments, to guarantee the long-term integrity of amphibian populations, and those of other organisms that play an essential functional role in the ecosystem. Environ Toxicol Chem 2023;42:2422-2439. © 2023 SETAC.

Mortality and toxicity of a commercial formulation of cypermethrin in Physalaemus gracilis tadpoles

This study evaluated the lethal, sublethal, and toxic of a commercial formulation of cypermethrin in the anuran species Physalaemus gracilis. In the acute test, concentrations of 100-800 μg L-1 were tested over 96 h. In the chronic test, cypermethrin concentrations recorded in nature (1, 3, 6, and 20 μg L-1) were tested for mortality and then used for the micronucleus test and erythrocyte nuclear abnormalities over a 7-days period. The LC50 determined for P. gracilis for the commercial cypermethrin formulation was 273.41 μg L-1. In the chronic test, a mortality of more than 50% was observed at the highest concentration (20 μg L-1), as it caused half of the tadpoles studied to die. The micronucleus test showed significant results at concentrations of 6 and 20 μg L-1 and recorded the presence of several nuclear abnormalities, indicating the genotoxic potential of the commercial cypermethrin formulation for P. gracilis. Cypermethrin presented a high risk to the species, indicating that it has the potential to cause several problems in the short and long term and to affect the dynamics of this ecosystem. Therefore, it can be concluded that the commercial formulation of cypermethrin had toxicological effects on P. gracilis.

Assessment of multiple biomarkers in Lithobates catesbeianus (Anura: Ranidae) tadpoles exposed to zinc oxide nanoparticles and zinc chloride: integrating morphological and behavioral approaches to ecotoxicology

The ecotoxicological risk to vertebrates posed by zinc oxide nanoparticles (ZnO NPs) is still poorly understood, especially in animals with a biphasic life cycle, which have aquatic and terrestrial phases, such as amphibians. In the present study, we investigated whether acute exposure (7 days) to ZnO NPs and zinc chloride (ZnCl₂) at three environmentally relevant concentrations (0.1, 1.0, and 10 mg L^-1) induces changes in the morphology, chondrocranium, and behavior of the tadpoles of Lithobates catesbeianus (Anura: Ranidae). Tadpoles exposed to both forms of Zn did not undergo any morphological or behavioral changes at the lowest concentrations (0.1 and 1.0 mg L^-1). However, the animals exposed to the highest concentration (10 mg L^-1) lacked oral disc structures, were smaller in size, had a longer tail, and presented changes in the position and coiling of the intestine and malformations of the chondrocranium in comparison with the control group. This indicates that ZnO NPs and ZnCl₂ altered the development of the tadpoles, causing delays in their metamorphosis and even reducing individual fitness. The tadpoles exposed to both forms of Zn at 10 mg L^-1 also had reduced mobility, especially in the presence of conspecifics. Based on these findings, we emphasize the importance of studying morphological, skeletal, and behavioral biomarkers to evaluate the toxic effects of metal-based nanoparticles in amphibians.

Ecotoxicological assessment of complex environmental matrices from the lower Paraná River basin

Sediments of aquatic ecosystems constitute the fate of most atmospheric and terrestrial pollutants. Since aquatic organisms, such as amphibians, interact with sediments, the presence of pollutants may affect their survival, growth and reproduction. So, the aim of this study was to evaluate, the sediment and water quality of five sites from the lower basin of the Paraná River (Buenos Aires, Argentina) with different anthropic impacts: Morejón stream (S1), de la Cruz stream upstream (S2) and downstream (S3), Arrecifes river (S4), tributary stream of Arrecifes river (S5). Physicochemical parameters were measured in situ (water) and in laboratory (water and sediment samples). Also, a screening of metals and pesticides was performed. Chronic (504 h) lethal toxicity bioassays were performed exposing Rhinella arenarum larvae to sediment and water samples. Oxidative stress (catalase, superoxide dismutase, glutathione S transferase, reduced glutathione and lipid peroxidation) and genotoxicity (micronuclei test) biomarkers were analyzed at acute (96 h) exposure. According to the calculated water quality index, S1 and S3 showed excellent quality, S2 good quality and, S4 and S5 poor quality. Dissolved oxygen was low in all sites (2.26-5.63 mg/L) and S5 had the highest organic matter content. Copper levels exceeded the limit for the protection of aquatic life in S2 and S4; arsenic levels exceeded its limit in S4; and selenium levels exceeded its limit in S4 and S5. Pesticides were mainly detected in water samples. Sediment from S5 showed higher sulfide and organic matter concentrations. At 504 h, no significant mortality was observed in the control group while S5 caused the greatest mortality (80%), followed by S2 (66.67%), S1 (63.33%), S3 (46.67%) and S4 (43.4%). All samples caused oxidative stress and lipid peroxidation, and samples from S4 also caused genotoxicity. The analysis of sediment and water samples was a suitable approach to assess the effects of water bodies on a native amphibian species.

Toxicity and genotoxicity of imidacloprid in the tadpoles of Leptodactylus luctator and Physalaemus cuvieri (Anura: Leptodactylidae)

Imidacloprid is a neonicotinoid insecticide used to control agricultural pests around the world. This pesticide can have adverse effects on non-target organisms, especially in aquatic environments. The present study evaluated the toxicity of an imidacloprid-based insecticide in amphibians, using Leptodactylus luctator and Physalaemus cuvieri tadpoles as study models. Spawning of both species were collected within less than 24 h of oviposition from a non-agricultural land at Erechim, Rio Grande do Sul state, Brazil. Survival, swimming activity, body size, morphological malformations, and genotoxic parameters were analyzed at laboratory conditions. A short-term assay was conducted over 168 h (7 days) with five different concentrations of imidacloprid (3–300 µg L⁻¹) being tested. The insecticide did not affect survival, although the tadpoles of both species presented reduced body size, malformed oral and intestine structures, and micronuclei and other erythrocyte nuclear abnormalities following exposure to this imidacloprid-based compound. Exposure also affected swimming activity in L. luctator, which reflected the greater sensitivity of L. luctator to imidacloprid in comparison with P. cuvieri. The swimming activity, body size, and malformations observed in L. luctator and the morphological malformations found in P. cuvieri indicated that even the lowest tested concentration of the insecticide were harmful to amphibians. At concentrations of over 3 μg L⁻¹, P. cuvieri presents a smaller body size, and both species are affected by genotoxic cell damage. This demonstrates that imidacloprid is potentially toxic for the two study species at environmentally relevant concentrations.

Chemometric modeling of acute toxicity of diverse aromatic compounds against Rana japonica

Chemicals used in our daily life show different toxic effects to the aquatic and terrestrial species and thus hamper the ecological balance. In the present time, amphibians are one of them, which are threatened to be extinct. Quantitative structure-activity relationship (QSAR) is an useful tool for prediction involving less time, money and manpower without requiring any animal experiments to assess the unavailable acute toxicity data for the untested molecules. In this study, we have developed QSAR models for ecotoxicity of some waterborne diverse aromatic compounds on an amphibian species Rana japonica (Japanese brown frog) employing Genetic Algorithm (GA) for variable selection followed by Partial Least Squares (PLS) regression method following recommendations of the Organization for Economic Co-operation and Development (OECD) for QSAR model development. Double cross-validation (DCV) followed by Best Subset Selection (BSS) were employed to select suitable models. The models displayed promising statistical quality in terms of R² (= 0.837-0.841), Q²_LOO (= 0.782-0.787), R²_pred or Q²_F1 (= 0.802-0.82) and some other internal and external validation metrics for tadpoles of Rana japonica (N_Training = 44, N_Test = 14). These models can be applied for data gap filling for a new untested compound falling within the applicability domain (AD) of the models.

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.

Toxicological aspect of bioinsecticide pyrethrum extract and expressions of apoptotic gene levels in human hepotacellular carcinoma HepG2 cells

Pyrethrum extract (PE), an important natural bioinsecticide, is extensively used across the world to control pest insects in homes and farms. The aim of this study was to evaluate the potential cytotoxic effect of PE using MTT assay and genotoxic effect using micronucleus (MN) assay. The changes in the expressions of the apoptosis genes in mRNA levels were also investigated using Real Time qPCR analysis as well as the ratio of apoptotic/necrotic cells with AnnexinV-FITC/Propidium iodide (PI) assay in HepG2 cells. PE markedly suppressed the cell proliferation on HepG2 cells. It significantly increased the frequency of micronucleus (MN) at 500 and 1000 µg/mL. PE also induced the percentage of cell population of late apoptotic/necrotic cells (FITC + PI+) and necrotic cells (FITC- PI+) especially at 4000 μg/mL analyzed by flow cytometry. PE caused significant fold changes in the expression of several apoptotic genes including APAF1, BIK, BAX, BAD, BİD, MCL-1, CASP3, CASP1, CASP2, FAS, FADD and TNFRSF1A. In particularly, the pro-apoptotic gene Hrk (Harakiri) remarkably and dose-dependently was overexpressed of the mRNA level. As a result, PE may exhibit cyto-genotoxic effects especially at higher concentrations and lead to significant changes in the expression of mRNA levels in several apoptotic genes.Highlights [Database][Mismatch]Natural bioinsecticide PE exhibited cytotoxic effect in HepG2 cells.PE significantly induced the micronucleus (MN) frequency at 500 and 1000 µg/mL.This bioinsecticide induced cell death and it lead to significant fold changes in the expression of mRNA levels in several apoptotic genes in HepG2 cells.The highest increase of the expression of mRNA levels was determined in Hrk (Harakiri) at 4000 µg/mL.

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.

A comprehensive approach using multiple biomarkers to detect damage induced by pesticides in broad-snouted caiman (Caiman latirostris) under ex-situ conditions

Caiman latirostris is one of the two species of the order Crocodylia that inhabit Argentina and is considered a species of vital ecological and economic importance in the north-east of Argentina. In this region, pesticides are the most common contaminants in natural environments and wild caiman populations are subject to this contamination constantly. The aim of this study was to evaluate the effects the main pesticides used in the region: glyphosate (GLY), cypermethrin (CYP) and chlorpyrifos (CPF) -based formulations, as well as the mixture of them, on C. latirostris juveniles under semi-controlled condition of exposure (ex-situ) during 75 days. One hundred yearling caimans (10-month-old) were equally distributed into five experimental groups (20 animals per group): a negative control (NC -tap water), GLY 2% (Roundup® Full II formulation -RU), CYP 0.12% (Atanor® formulation), CPF 0.8% (Lorsban® formulation), and a mixture of the three pesticides (Mx3: GLY 2% + CYP 0.12% + CPF 0.8%). We applied early warning biomarkers to detect damage induced by these chemicals in peripheral blood: activity of the antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD), analysis of lipid peroxidation (LPO) by the thiobarbituric acid reactive substances (TBARS), DNA damage and specific base oxidation through the standard and modified comet assay (CA), chromosome damage by micronucleus (MN) test and other nuclear abnormalities (NAs), hematological and growth parameters. Results showed a statistically significant increase in MN and NAs frequency, DNA damage, with an important contribution of base oxidation for all exposed groups compared to the NC. Total white blood cells count (TWBCC), and growth parameters showed effects mainly at the Mx3. The principal component analysis (PCA) demonstrated more sensitivity for biomarkers associated to genetic damage, including base oxidation to DNA than LPO, antioxidant enzyme modulation, immunotoxicity or growth parameters, to detect pesticides effects, applied under conditions similar to that found in natural environments.

Evaluation of the genotoxic, mutagenic, and histopathological hepatic effects of polyoxyethylene amine (POEA) and glyphosate on Dendropsophus minutus tadpoles

Herbicides improve the productivity of a monoculture by eliminating weeds, although they may also be toxic and have negative effects on non-target organisms, such as amphibians. The present study evaluated the genotoxic, mutagenic, and histopathological hepatic responses of Dendropsophus minutus tadpoles to acute exposure (96 h) to the herbicide glyphosate (GLY, 65, 130, 260 and 520 μg/L) and the surfactant polyoxyethylene amine (POEA, 1.25, 2.5, 5 and 10 μg/L). On average, 174 % more genomic damage was observed in the tadpoles exposed to all concentrations of POEA in comparison with the control, while up to seven times more micronuclei were recorded, on average, at a concentration of 5 μg/L of POEA. All the individuals exposed to 10 μg/L of POEA died. The tadpoles exposed to GLY presented 165 % more DNA damage than the control, on average, at the highest concentrations (260 and 520 μg/L), and up to six times more micronuclei at 520 μg/L. The Erythrocyte Nuclear Abnormality test (ENA) detected a relatively high frequency of cells with lobed nuclei in the tadpoles expose to POEA at 5 μg/L and binucleated cells in those exposed to GLY at 520 μg/L. The hepatic histopathological observations revealed several types of lesions in the tadpoles exposed to both GLY and POEA. Overall, then, the results of the study indicate that both GLY and POEA have potential genotoxic, mutagenic, and hepatotoxic effects in D. minutus tadpoles. We emphasize the need for further studies to monitor the amphibian populations, such as those of D. minutus, which breed in aquatic environments associated with agricultural areas. The release of pollutants into natural habitats may have significant long-term impacts on the survival of anuran tadpoles.

Habitat differences affect the nuclear morphology of the erythrocytes and the hepatic melanin in Leptodactylus fuscus (Anura) in the Brazilian Cerrado savanna

The sensitivity of anuran to the effects of habitat destruction and contamination has led to a preoccupying global decline in their populations. Morphological biomarkers such as micronuclei and other erythrocyte nuclear abnormalities (ENAs), as well as the occurrence of hepatic melanin, can be used to evaluate the effects of habitat impacts. In the present study, these two parameters were combined for the in situ assessment of the effects of soybean cultivation on the grassfrog, Leptodactylus fuscus. Specimens were also collected from a protected area to provide a reference site (non-agricultural environment). The frequency of some of the nuclear abnormalities in the animals from the soybean plantation was much higher than that recorded at the reference site, in particular micronuclei, which were 3.6 times more frequent in the plantation, lobulated nuclei (3.4 times more frequent), and reniform nuclei, which were four times more common than at the reference site. The combined analysis of all the ENAs together also revealed a frequency approximately 1.4 times higher in the animals from the soybean plantation, in comparison with the protected area. Smaller areas of hepatic melanin were observed in the specimens from the soybean plantation. These results provide further evidence of the sensitivity of anurans to habitat impacts and indicate that animals found in soybean plantations are susceptible to systematic alterations of their cells.

Multiple toxicity endpoints induced by carbon nanofibers in Amazon turtle juveniles: Outspreading warns about toxicological risks to reptiles

The toxicity of carbon-based nanomaterials (CNs) has been observed in different organisms; however, little is known about the impact of water polluted with carbon nanofibers (CNFs) on reptiles. Thus, the aim of the current study was to assess the chronic effects (7.5 months) of 1 and 10 mg/L of CNF on Podocnemis expansa (Amazon turtle) juveniles (4 months old) based on different biomarkers. Increased total organic carbon (TOC) concentrations observed in the liver and brain (which suggests CNF uptake) were closely correlated to changes in REDOX systems of turtles exposed to CNFs, mainly to higher nitrite, hydrogen peroxide and lipid peroxidation levels. Increased levels of antioxidants such as total glutathione, catalase and superoxide dismutase in the exposed animals were also observed. The uptake of CNFs and the observed biochemical changes were associated with higher frequency of erythrocyte nuclear abnormalities (assessed through micronucleus assays), as well as with both damage in erythrocyte DNA (assessed through comet assays) and higher apoptosis and necrosis rates in erythrocytes of exposed turtles. Cerebral and hepatic acetylcholinesterase (AChE) increased in turtles exposed to CNFs, and this finding suggested the neurotoxic effect of these nanomaterials. Data in the current study reinforced the toxic potential of CNFs and evidenced the biochemical, mutagenic, genotoxic, cytotoxic, and neurotoxic effects of CNFs on P. expansa.

Morphological, behavioral and genotoxic effects of glyphosate and 2,4-D mixture in tadpoles of two native species of South American amphibians

Pesticide contamination is an important factor in the global decline of amphibians. The herbicides glyphosate and 2,4-D are the most applied worldwide. These herbicides are often found in surface waters close to agricultural areas. This study aims at evaluating the chronic effects caused by glyphosate + 2,4-D mixture in Boana faber and Leptodactylus latrans tadpoles. The combined solution of the glyphosate and 2,4-D, in 5 different concentrations, was applied for 168 h. Herbicide mixtures did not affect the survival of the exposed tadpoles but growth and swimming activity were altered; besides causing several damages in the mouth and intestine. The erythrocytes showed micronuclei and other nuclear abnormalities. There is an ecological risk in the exposure of tadpoles of B. faber and L. latrans from the mixture of glyphosate + 2,4-D. Therefore, the approach used in this study provides important information on how commonly used pesticides can affect non-target organisms.

Cytotoxicity and mutagenicity of the waters of the Marrecas River (Paraná, Brazil) to bullfrogs (Lithobates catesbeianus)

Animals have a long history of assessing ecosystem responses to environmental disturbances, and amphibians stand out for presenting themselves as good animal model and bioindicators of environmental quality. The main purpose of the present work was to investigate the cellular effects of contamination of waters of the Marrecas River, located in the southwest of the state of Paraná, Brazil. Therefore, the objective of the present study was to investigate and monitor the cytotoxic and mutagenic effect, with bullfrog tadpoles, and to discuss these effects with land use along this hydrographic basin. Mutagenic effects were determined by micronucleus assay, and cytotoxicity by other nuclear changes, such as segmented cells, binucleated cells, cells with buds and reniform cells. Water samples were obtained at nine sites along the Marrecas River, covering areas with rural and urban hydrological contribution. For each site, four samples were collected, along the years 2017 and 2018, encompassing the four seasons (summer, autumn, winter, and spring). The results showed mutagenic and cytotoxic effect in four sampling sites, and only cytotoxic effect in other four sites. These effects may be due, possibly, to the use of different agrochemicals across the hydrographic basin region, which have predominant hydrological contributions from crops. Data of this study indicate the presence of cytotoxic and mutagenic contaminants in the waters of the Marrecas River, which can generate environmental problems on the river fauna/flora, and can also affect the local population health.

Genotoxic effects of glyphosate on Physalaemus tadpoles

Genotoxicity studies have revealed that pesticides bind to genetic material in non-target vertebrates, thereby impairing the genetic integrity of these animals. The main objective of this study was to determine the genotoxic damage in erythrocytes of two native South American amphibian Physalaemus cuvieri and Physalaemus gracilis, both species exposed to a glyphosate-based herbicide. We evaluated the presence of micronuclei (MN) and erythrocyte nuclear abnormalities (ENA) as biomarkers for potential genotoxic compounds. Tadpoles were exposed to doses permitted by Brazilian legislation and concentrations found naturally in Brazilian and Argentinian waters (500, 700 and 1000 μg/L). Glyphosate-based herbicide caused micronuclei formation and several types of erythrocyte nuclear abnormalities in both Physalaemus species. The total frequency of MN and ENA demonstrated the occurrence of cell damage at all tested concentrations. Glyphosate herbicide can be considered a genotoxic that may impact the genetic integrity of native populations of P. cuvieri and P. gracilis.

Mutagenic, genotoxic and morphotoxic potential of different pesticides in the erythrocytes of Podocnemis expansa neonates

Despite the damaging effects of pesticides glyphosate (Gly), atrazine (Atra) and fipronil (Fip) on different organisms, the mutagenic, genotoxic and morphotoxic potential of testudine erythrocytes in freshwater remains unknown. Thus, the aim of the present study is to assess the toxicological potential of these compounds in Podocnemis expansa (Amazonian turtles) neonates from eggs artificially incubated in substrate at different concentrations of herbicides Gly and Atra and insecticide Fip. Micronucleus test and other nuclear abnormalities, as well as comet assay and morphometric measurements taken of models' circulating erythrocytes were used as toxicity biomarkers. Pups exposed to Gly (groups Gly-65 ppb and Gly-6500 ppb) were the ones recording the largest amount of nuclear abnormalities; erythrocytes with multilobulated, notched and displaced nucleus were mostly frequent in groups Atra-2 ppb and Gly -65 ppb. All treatments (Gly-6500 ppb, Atra-2 ppb, Atra-200 ppb, Fip-4 ppb and Fip-400 ppb), except for group Gly-65 ppb, led to decreased erythrocyte area, increased "nuclear area: erythrocyte area" ratio, as well as to decreased erythrocyte and erythrocyte nuclei circularity, which highlights the clear effect on the size and shape of these cells. On the other hand, the comet assay did not evidence any genotoxic effect caused by the assessed pesticides. This is a pioneer study on the mutagenic and morphotoxic potential of pesticides in P. expansa eclodides exposed in ovo to Gly, Atra and Fip; therefore, it is an insight on how these compounds can affect the health of these animals.