Genotoxicity Effects in Freshwater Fish from a Brazilian Impacted River

Cytome analysis (micronuclei and nuclear anomalies) in bioindication of environmental pollution in animals with nuclear erythrocytes

Assessment of cytogenetic homeostasis of indicator animals is of great importance in ecological monitoring. The simplest method of its study is micronucleus analysis. Animals with nuclear erythrocytes are often used as indicator animals. In addition to the micronuclei usually recorded, a wide range of cytological nuclear and cellular abnormalities (cytomic analysis) is encountered when assessing the spontaneous level and under the influence of anthropogenic factors. Spontaneous frequency of cytogenetic disorders in 36 species of fish, amphibians, reptiles and birds was studied. Ecological monitoring of territories of Kazakhstan with different types of pollution (radiation, petrochemical, pesticide, heavy metals, due to rocket and space activities) was carried out with the help of separate species of animals. The results of the study include comparative descriptions, schematics and microphotographs clearly demonstrating a wide range of cytological anomalies of nuclear erythrocytes of animals of different classes. The greatest spectrum of nuclear anomalies in the studied animals was registered at petrochemical and pesticide contamination of territories. Depending on the tasks and climatic-geographical conditions, all investigated species can be used as bioindicators. Testudo horsfieldii is an exception for desert regions due to high spontaneous micronuclei level in this species. A review of the names of the main nuclear anomalies is carried out and variants of its ordering are proposed.

Erythrocyte Recovery in Oreochromis niloticus Fish Exposed to Urban Effluents

Urban activities pollute aquatic ecosystems, and the integrity of organisms such as fish. The use of cytological techniques, such as the analysis of blood cellular integrity using the Micronucleus test, can help detect mutagenic damage as a result to urban effluents exposure. In this context, this study aimed to evaluate the frequency of micronucleus and other nuclear abnormalities in Oreochromis niloticus fish environmentally exposed to urban effluents in relation to their erythrocyte recovery capacity when exposed to clean water (30 and 45 days). The results indicated high copper, dissolved iron, nickel, and thermotolerant coliform levels in the urban stream. There was no difference in the frequency of micronuclei. In contrast, cells with nuclear nuclei, binucleates, kidney-shaped nuclei, notched nuclei, lobed nuclei, and segmented nuclei decreased according to the time the fish were exposed to clean water. When exposed to clean water, we conclude that urban fish recover from genotoxic and cytotoxic damage.

Genotoxicity of surface waters in Brazil

Brazil has abundant surface water resources, huge aquatic biodiversity and is home to 213 million people. Genotoxicity assays are sensitive tools to detect the effects of contaminants in surface waters and wastewaters, as well as to determine potential risks of contaminated waters to aquatic organisms and human health. This work aimed to survey the articles published in 2000-2021 that evaluated the genotoxicity of surface waters within Brazilian territory to unveil the profile and trends of this topic over time. In our searches, we considered articles focused on assessing aquatic biota, articles that conducted experiments with caged organisms or standardized tests in the aquatic sites, as well as articles that transported water or sediment samples from aquatic sites to the laboratory, where exposures were performed with organisms or standardized tests. We retrieved geographical information on the aquatic sites evaluated, the genotoxicity assays used, the percentage of genotoxicity detected, and, when possible, the causative agent of aquatic pollution. A total of 248 articles were identified. There was a trend of increase in the number of publications and annual diversity of hydrographic regions evaluated over time. Most articles focused on rivers from large metropolises. A very low number of articles were conducted on coastal and marine ecosystems. Water genotoxicity was detected in most articles, regardless of methodological approach, even in little-studied hydrographic regions. The micronucleus test and the alkaline comet assay were widely applied with blood samples, mainly derived from fish. Allium and Salmonella tests were the most frequently used standard protocols. Despite most articles did not confirm polluting sources and genotoxic agents, the detection of genotoxicity provides useful information for the management of water pollution. We discuss key points to be assessed to reach a more complete picture of the genotoxicity of surface waters in Brazil.

Genotoxicity biomarkers on native fish species from the Araguari River (Amazon biome)

The Araguari River, one of the most important waterways in the Brazilian state of Amapá, is ecologically relevant and essential for the conservation of Amazonian fish biodiversity. Our previous studies demonstrated contamination of water and fish by metals. In particular, water samples showed genotoxic damage in Danio rerio. Here, we extended our studies of potential genotoxic damage to native fish from sampling sites located in the Araguari River lower section. To accomplish this, we collected samples of fish with different feeding behaviors, but in the same sampling sites, and evaluated the same genotoxicity biomarkers in erythrocytes. All eleven species of fish collected in the Araguari River lower section showed profiles and frequencies of genotoxic damage similar to those previously observed in tests with D. rerio, confirming that genotoxic pollutants present in these waters are also causing damage to native fish species.

Bioaccumulation, genotoxicity, and risks to native fish species from inorganic contaminants in the Pantanal Sul-Mato-Grossense, Brazil

The Aquidauana River is one of the most important rivers in the Pantanal region, Brazil. However, its waters have been contaminated by nearby anthropogenic activities, threatening native fish species. In this study, our objectives were: 1) to determine the concentrations of Al, As, Cd, Cu, Fe, Mn, Ni, Pb, and Zn in water and sediment samples from the Aquidauana River and to assess the risks posed to aquatic biota; 2) to quantify the concentration of these elements in muscle and liver tissue samples from four native fish species; 3) to evaluate the potential bioaccumulation of inorganic elements in the muscles and liver; and 4) to investigate genotoxicity biomarkers and their association with the inorganic element concentrations present in the muscle tissue. Water and fish samples were collected in November 2020. The concentrations of Al, As, Cd, Cu, Fe, and Pb in the water samples were in disagreement with the Brazilian legislation and presented risks to the aquatic biota. In terms of mixtures of inorganic elements, there was a great increase in the risk to biota. The As concentration did not meet the Brazilian standard for sediments in the sample collected at sampling site 6. The concentrations of Cd and Pb in the muscle tissue of Hypostomus regani, Prochilodus lineatus, Brycon hilarii, and Mylossoma duriventre exceeded the Brazilian standards for human consumption. H. regani showed greater genotoxic damage, and the higher the Al and Fe concentrations in the muscle tissue, the higher the frequencies of lobulated nuclei and nuclear invaginations. Together, our results demonstrate the negative impacts on native fish species from the Aquidauana River contamination and indicate risks to Pantanal biodiversity.

High concentrations of metals in the waters from Araguari River lower section (Amazon biome): Relationship with land use and cover, ecotoxicological effects and risks to aquatic biota

The Araguari River is one of the most important water body in the Brazilian state of Amapá. However, the quality of its waters has been deteriorating and, recently, high concentrations of metals were found in water samples collected from its lower section. Overall, we aimed to evaluate land use and cover around three sampling sites located in the Araguari River lower section and its contribution to water pollution by metals; correlate land use pattern with detected metal concentrations; assess acute toxicity using the Daphnia similis test and genotoxicity using the Danio rerio bioassay of water samples from the three sampling sites; and investigate the risks arising from metals present in waters to aquatic biota. Riparian forest around all sampling sites is fragmented owing to the expansion of pasture areas, which showed a significant positive correlation (p < 0.05) with the concentrations of Hg and Cu in water samples. Water samples from sampling sites 2 and 3 presented acute toxicity for D. similis, and the D. rerio bioassay confirmed the presence of genotoxic pollutants in the waters from all sampling sites. Our preliminary risk assessment showed that individual concentrations and the mixture of metals posed a high risk to aquatic biota. Taken together, our results demonstrate that the conversion of native forest to pastureland contributes to water contamination by metals, which contributes to the risks to aquatic biota.

Genotoxic effects of urban pollution in the Iguaçu River on two fish populations

Environmental impacts on water resources and discharges of pollutants are some of the main problems of aquatic ecosystems. Currently, the Iguaçu River is considered the second most polluted river in Brazil, therefore, given the importance of understanding the effects of water pollution on living organisms, this study aimed to analyze the possible genotoxic effects in Astyanax bifasciatus (Characiformes; Characidae) and Geophagus brasiliensis (Perciformes: Cichlidae) in response to the water quality of the Iguaçu River. Four sampling points were determined on the Iguaçu River, with different levels of environmental impact. The micronuclei and nuclear abnormalities were quantified by counting 2000 erythrocytes from each specimen. There was a statistical difference in the frequency of nuclear abnormalities both for A. bifasciatus (Kruskal-Wallis _3;30 = 10.9; p = 0.01) and for G. brasiliensis (Kruskal-Wallis _3;26 = 12.27; p = 0.006), with point 1 (critically degraded) showing a higher frequency of nuclear abnormalities and point 4 (moderately degraded) showing a lower frequency of nuclear abnormalities for both species, showing genotoxic potential in fish erythrocytes. This result demonstrates the need for further discussion on the conservation of the Iguaçu River as well as broadening the discussion on its potability.

Toxicogenetic effects on fish species in two sub-basins of the upper Paraguay river, Southern Pantanal - Brazil

This study aimed to evaluate water quality using limnological parameters in two sub-basins of the Negro and Apa Rivers, along with the composition and structure of the landscape around the locations sampled in the two sub-basins and their possible contribution to the loss of water quality. We also set out to identify the genotoxic effects on the erythrocytes of Prochilodus lineatus and Leporinus friderici. In particular, we quantified total Cr, Ni and Pb in the muscle of these fish species to determine which genotoxic changes are related to the concentration of metals detected in the fish from these two sub-basins of the Paraguay River Basin. The sub-basin of the Apa River presented a greater proportion of surrounding pastureland in relation to the basin of the Negro River. The erythrocytes of P. lineatus showed a significant difference between the sub-basins for nuclear pyknosis, binucleated cells and lobed nuclei (p < 0.05). In L. friderici, vacuolated nuclei, nuclear pyknosis and lobed nuclei alterations also showed a significant difference between the sub-basins (p < 0.05). The genotoxicity index of the Apa River sub-basin presented higher frequencies of nuclear alterations in P. lineatus and L. friderici (p < 0.05), compared to the Negro River sub-basin. The concentration of total Cr, Ni and Pb in the muscles of P. lineatus and L. friderici in the Negro River sub-basin leads to genotoxic damage, mainly from the induction of lobed nuclei. Based on our results, it can be concluded that toxicogenetic effects in native fish species are an important source of environmental diagnosis in the Upper Paraguay River Basin.

Micronuclei in Fish Erythrocytes as Genotoxic Biomarkers of Water Pollution: An Overview

Freshwater and marine water bodies receive chemical contaminants from industrial, agricultural, urban, and domestic wastes. Eco-genotoxicity assays are useful tools to assess the cumulative genotoxicity of these pollutants. Fish are suitable indicators for biomonitoring of mutagenic and carcinogenic pollution.In this review, we present a complete overview of the studies performed so far using the micronucleus test in peripheral erythrocytes of fish exposed to polluted water. We have listed all the species of fish used and the geographical distribution of the investigations. We have analyzed and discussed all technical aspects of using this test in fish, as well as the advantages and disadvantages of the different experimental protocols. We have reported the results of all studies. This assay has become, for years, one of the simplest, fastest, and most cost-effective for assessing genotoxic risk in aquatic environments. However, there are still several factors influencing the variability of the results. Therefore, we have given indications and suggestions to achieve a standardization of experimental procedures and ensure uniformity of future investigations.

Bioaccumulation of metal in liver tissue of fish in response to water toxicity of the Araguari-Amazon River, Brazil

This study aimed to determine the concentration of metals in the water and in the liver tissue of fish (Anodus orinocensis, Hemiodus unimaculatus, Curimata vittata, and Plagioscion squamosissimus) in the lower Araguari River. Steps were also taken to estimate any difference in metal bioaccumulation in the liver of fish species at different trophic levels, determine any correlations between metals found in hepatic tissue of fish species relative to that found in river water, and evaluate the bioaccumulation factor. The metals analyzed in the water in the lower Araguari River (Cd, Pb, Fe, Hg, Cu, and Zn) exceeded the limits considered safe for aquatic life. We found a significant difference only in the bioaccumulation of Pb between A. orinocensis and C. vittata (F = 4.65, p = 0.005) and Cr between A. orinocensis and H. unimaculatus (F = 3.12, p = 0.03). Species of distinct trophic levels showed differences in metal concentration in liver. Cd and Cu showed bioaccumulation factor above 100, especially Cu with a relatively high value, for all fish species. The bioaccumulation of metals in the liver of fish species showed a positive correlation with the metals detected in the water of the Araguari River. In this sense, the lower course of the Araguari River is undergoing some type of environmental stress, making this study of additional valuable in diagnosing environmental quality pursuant to the development of environmental monitoring projects in order to guarantee the safety and maintenance of aquatic life.

Comparative metal accumulation and toxicogenetic damage induction in three neotropical fish species with distinct foraging habits and feeding preferences

Environmental pollutants affect fish species differently because their routes of exposure make them more critical to a specific group regarding foraging habits or food preferences. However, the association between local problems and environmental conditions makes a particular species more suitable for use in monitoring programs. Thus, this study compared muscle accumulation of metals (Al, Ba, Cr, Cu, Fe, Mn, Ti and Zn) and toxicogenetic damage to three neotropical species from the Itapemirim River Basin (Brazil) with distinct foraging habits and feeding preferences: Geophagus brasiliensis (benthopelagic - omnivorous); Harttia sp. (benthic - detritivorous); and Leporinus copellandii (pelagic - omnivorous). There was seasonal influence on muscle metal concentrations: Ba and Mn concentrations in G. brasiliensis, Cr in Harttia sp. and Zn, Al and Fe in L. copellandii increased during the rainy season. G. brasiliensis was the most sensitive species, since it had a statistically higher prevalence of erythrocytic nuclear abnormalities, which was influenced by seasonality. This result might be an effect of its benthopelagic habits, which favors contact with a larger group of contaminants due to its interaction with both water column and sediment. The present study showed the differential sensitivity of fish species and that the combination of chemical analysis of pollutants with evaluation of toxicogenetic responses helps to choose the best species for field studies.

Water temperature and acid pH influence the cytotoxic and genotoxic effects of aluminum in the freshwater teleost Astyanax altiparanae (Teleostei: Characidae)

The toxicity of metals, including aluminum (Al), can be potentiated by temperature and acid pH, a concern in view of the current global warming scenario. The aim of this study was to evaluate the bioconcentration of Al in the testes and semen of Astyanax altiparanae and the potential of this metal, at different environmental temperatures and acid pH, to cause cytotoxicity and genotocixity in erythrocytes and spermatozoa. A. altiparanae males were divided into nine experimental groups: at each of three different water temperatures (20, 25 and 30 °C), the fish were exposed to a neutral pH, an acid pH and acidic water containing Al (0.5 mg.L^-1). The fish were subjected to subacute, semi-static exposure and sampled at 24 and 96 h. After each exposure period the comet assay (blood and semen) and micronucleus test (blood) were performed. Bioconcentration of Al was evaluated in the testes and semen. Exposure time and temperature influenced the Al bioconcentration pattern in the testes. Al concentration in the semen was higher in fish exposed at 20 and 25 °C (24 h). The DNA fragmentation score for the semen and blood was higher in fish exposed to Al at 20 (24 h) and 30 °C (96 h). The frequency of nuclear abnormalities in erythrocytes was higher in the group exposed to Al at 30 °C (96 h). It was concluded that Al bioconcentrates in the testes and semen of A. altiparanae at different temperatures and is potentially cytotoxic and genotoxic to erythrocytes and spermatozoa in this species.

The Response of Neotropical Fish Species (Brazil) on the Water Pollution: Metal Bioaccumulation and Genotoxicity

The streams and rivers of the Upper Paraná River Basin have been seriously affected by impacts of high population density around the basin area. Fishes are widely used as models to assess the health of aquatic ecosystems, being considered as bioindicators of environmental pollution. In this context, our objective was to assess the potential genotoxic and mutagenic effects of the polluted water in three native fish species (Astyanax lacustris, Hypostomus ancistroides, and Rhamdia quelen) from Tarumã Microbasin, Upper Paraná River, Brazil. We also investigated the concentration of metals in water and in fish muscle to verify bioavailability and bioaccumulation of metals. For both less impacted sites (LI) and impacted sites (IMP) of the microbasin, the concentrations of metals were above the maximum limit allowed by Brazilian legislation (Resolution CONAMA 357/2005), except for Pb, total Cr, and Cu at LI sites and total Cr at IMP sites. A. lacustris showed a higher frequency of micronuclei (MN) at IMP sites compared with LI sites (p < 0.0001). We found no significant differences in MN frequency between site classes for H. ancistroides and R. quelen (p > 0.05). There were no significant differences between site classes regarding to nuclear abnormalities in erythrocytes frequencies (p > 0.05). A. lacustris from IMP sites had higher concentrations of Pb, Cu, Fe, Zn, and Ni in muscle tissue (p < 0.05), whereas H. ancistroides from IMP sites had higher concentration of Cr, Cu, and Ni (p < 0.0001) and R. quelen showed higher concentration of Cd, Fe, and Ni at these sites (p < 0.0001). So, the chosen biomarkers are able to identify the environmental risk of the water pollution.

Erythrocyte Nuclear Abnormalities in Astyanax lacustris in Response to Landscape Characteristics in Two Neotropical Streams

The objective of this research was to evaluate land use and occupation in the landscape surrounding two neotropical streams of the Upper Paraná River in Brazil and to investigate if the water from these streams induces erythrocyte nuclear abnormalities in Astyanax lacustris. We observed that the areas surrounding the streams are predominantly used for agricultural purposes (73.46% of the total area), followed by buildings (15.21%). Only 8.78% of the area consisted of forest fragments. We observed higher frequencies of micronuclei in erythrocytes of A. lacustris exposed to water from impacted sites (IMP) compared with less impacted sites and the negative control (NC) (p < 0.05). Analysis of nuclear alterations in A. lacrustis erythrocytes showed significant differences in the frequency of notched nuclei and nuclear pyknosis only between the NC and the IMP sites (p < 0.05). Our results indicate that water from the most impacted sites of the microbasin can induce mutagenic and genotoxic effects in A. lacustris.

In situ monitoring of the Sinos River, southern Brazil: water quality parameters, biomarkers, and metal bioaccumulation in fish

The Sinos River is an important water supply in Southern Brazil and receives industrial, agricultural, and domestic effluents which may affect aquatic biota. Water physicochemical and microbiological analyses, biomarker responses (scaled mass index (SMI), gill histopathology, and micronucleus and nuclear abnormality (MN and NA) frequencies), and metal bioaccumulation in muscle were assessed in the fish species Bryconamericus iheringii (Characidae) captured at three sampling sites (S1, S2, and S3) in four sampling periods. The mean values of five parameters (total phosphorus, thermotolerant coliforms, aluminum, iron, and lead) exceeded the limits established by the Brazilian legislation at the three sampling sites. Although physicochemical analysis indicated higher impacts at S3, in some samples, significantly higher MN frequencies and bioaccumulation of manganese in fish muscle were observed at S1, whereas low SMI and higher concentrations of aluminum and zinc in fish muscle were found at S2. Histopathological alterations in gills were observed in fish collected at the three sampling sites; however, no spatial differences were observed, indicating similar environmental conditions with respect to this biomarker. Moreover, temporal variation of biomarker responses and metal bioaccumulation were found at all sampling sites. Furthermore, the consumption of fish from the Sinos River should be avoided given the concentrations of chromium (all samples), cadmium, and lead in fish muscle above the threshold for safe human consumption.

Water quality parameters, biomarkers and metal bioaccumulation in native fish captured in the Ilha River, southern Brazil

The Ilha River is one of the main tributaries of the Sinos River, southern Brazil, and it is located in an area characterized by low population density and presence of agricultural activities. Thus, this study aimed to assess the water quality of two sites of the Ilha River (source and mouth, S1 and S2 respectively) in five sampling periods using water physicochemical and microbiological analyses, biomarkers, such as condition factor, micronucleus test, gill histopathological analysis, and metal bioaccumulation in the native fish Bryconamericus iheringii. Mean values of BOD₅, thermotolerant coliforms, aluminum, iron and lead exceeded the limits established by the Brazilian legislation for surface waters at both sampling sites. Significant higher micronucleus, nuclear abnormalities and mucous cells frequencies were found at S2 in, at least, one sampling period, whereas fish from S1 presented significant lower condition factor, higher frequencies of lamellar alterations and higher concentrations of chromium and nickel in muscle. Additionally, concentrations of cadmium, chromium and lead in fish muscle exceeded the limits considered safe for human consumption at both sites in at least one sampling period. Data from our study evidenced the mouth of the Ilha River suffers from point genotoxic effects, whereas the source is also contaminated by metals, despite being located in an area under minor anthropic activities.

Mutagenic and genotoxic effects and metal contaminations in fish of the Amambai River, Upper Paraná River, Brazil

The present study evaluated mutagenic and genotoxic effects and metal accumulation in the liver and musculature of Pterygoplichthys ambrosetti and Prochilodus lineatus in the Amambai River, a tributary of the Upper Paraná River in Brazil. We also evaluated the potential for these fish species as environmental bioindicators and performed risk assessment for conservation purposes. We found that P. ambrosetti had a higher frequency of micronuclei compared to P. lineatus (p < 0.0001). There were no significant differences between species in other erythrocyte nuclear abnormalities (ENA) (p > 0.05). For both species, the liver contained a higher concentration of metals (Cd, Pb, Cr, Cu, Fe, Zn, and Ni) than the musculature did (p < 0.0001). Of the two species, P. ambrosetti was more suitable to evaluate mutagenic and genotoxic effects and metal accumulation in the liver and musculature, likely due to its resident behavior; hence, we highlight the potential of this species for use as an environmental bioindicator. The concentrations of non-essential metals observed in the fish confirm conditions of environmental stress in the Amambai River, possibly related to the discharge of pollutants and exacerbated by lack of native vegetation cover along the watercourse.