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Two of the largest water reservoirs in the Metropolitan Region of São Paulo, Brazil (MRSP), named Billings and Guarapiranga, are facing high levels of anthropic impact. This is evidenced by the presence of contaminants and pollutants, which are deteriorating their water quality. Therefore, this study evaluated antioxidant defense enzymes, lipoperoxidation and genotoxicity, in adult females of a native species, Astyanax altiparanae from the Guarapiranga and Billings reservoirs. The study also aimed to evaluate these biomarkers during two different periods of the year, the rainy (summer) and dry (winter) seasons. The oxidative stress was evaluated by the activity of enzymes such as glutathione peroxidase, glutathione S-transferases, superoxide dismutase, and catalase in the gills and liver, and the occurrence of lipoperoxidation was also evaluated in both organs. The genotoxicity was assessed by performing comet assay, micronucleus, and nuclear abnormality tests on blood samples. The results showed that fish from both reservoirs are subjected to oxidative stress and genotoxic damage, mainly during winter, but fish living in Billings showed greater alterations than fish from Guarapiranga. Likewise, the results of the principal component analysis suggested that caffeine, nitrogenous compounds, and some metals might be triggering these toxic effects in fish.

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Ivermectin (IVM) is one of the most widely used antiparasitics worldwide. It is a potent and effective drug for treatment and prevention of internal and external parasitic infections of livestock and humans. IVM is excreted unchanged in manure of treated animals. Thus, residues of IVM may reach aquatic systems, affecting non-target organisms such as fish. Although the presence of IVM in aquatic environments has been reported, a multilevel approach (from cellular to behavioral responses) is necessary to determine the health of exposed organisms and the environmental risks associated. The aim of the present study was to investigate the response of the Neotropical fish Prochilodus lineatus, one of the main target species of South American freshwater fisheries, exposed to environmental concentrations of IVM: low (0.5 µg L-1) and high (1.5 µg L-1). Behavioral responses were assessed in juvenile fish and included water column use, routine swimming, total distance travelled, total activity time and Maximum swimming speed achieved during the escape response. Biochemical/oxidative stress responses assessed included brain acetylcholinesterase (AChE), catalase (CAT) and glutathione S-transferase (GST) activities; total antioxidant competence against peroxyl radicals (ACAP) and lipid oxidative damage (TBARs). Hematological biomarker responses included blood glucose levels, hematocrit, hemoglobin concentration, mean corpuscular hemoglobin, mean corpuscular hemoglobin concentration, and mean corpuscular volume. Condition factor and hepatosomatic index were also calculated. The lowest IVM concentration caused a significant decrease in GST activity and maximum swimming speed during the escape response. Multivariate analysis with biochemical/stress and behavioral data revealed overall effects of IVM treatments. This multilevel analysis shows detrimental effects related to swimming behavior and predator avoidance which could affect population size and size-structure of P. lineatus. To our knowledge this is the first attempt to assess the effects of IVM on Neotropical fishes using an integrative approach based on biomarkers from different levels of biological organization.

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Melano-macrophage centers (MMCs) are nodular clusters of pigmented macrophages, implicated in homeostasis and destruction and recycling of endogenous and exogenous material. They can increase in size and/or frequency under environmental stress resulting in immunohistological biomarkers of water quality. Fluoxetine (FLX), a commonly prescribed antidepressant, can cause neuroendocrine, behavioral and reproductive alterations in teleost fish. In the present study, we analyzed the effects of a 2-week 50 µg/L FLX exposure on MMCs in histological sections of spleen and head-kidney (HK) of the cichlid fish Cichlasoma dimerus. In the spleen, FLX caused an increase in the area and a decrease in the number of MMCs. An increase in the proportion of the HK occupied by MMCs was observed in FLX-exposed fish, due to an increase in their number but not their area. The deposition rate of MMCs varies according to the hemolymphopoietic organ and would be the result of a differential response to FLX on homeostatic functions (elimination of cellular debris, iron processing and immune response).

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Persistent organic pollutants reach aquatic ecosystems during application and can bioconcentrate/biomagnify because of their lipophilic nature. Toxicological studies focus almost exclusively on the active ingredients of pesticides, instead of commercial formulations, whose toxicity can differ as a result of nonspecified ingredients. The intensive use of endosulfan as a wide-ranging insecticide over the last few decades makes it one of the most frequently detected contaminants in the aquatic environment, even after it has been restricted worldwide. The aim of the present study was to evaluate the bioaccumulation and organ distribution of waterborne endosulfan in the freshwater fish Cichlasoma dimerus, comparing the active ingredient and a commercial formulation. Males were exposed to 0.7 µg/L endosulfan for 2 wk, which was quantified (gas chromatography with an electron capture detector) in the liver, testes, gills, brain, and muscle. The results suggest rapid metabolism of α-endosulfan and ß-endosulfan isomers to endosulfan sulfate (endosulfan-S) in tissues. Isomer levels were highest in gills, indicative of recent uptake. Levels of endosulfan-S were highest in liver and testes for the active ingredient and testes and brain for the commercial formulation. For the active ingredient, endosulfan-S levels showed a positive correlation with organ-lipid percentage. No correlation was evident for the commercial formulation, indicating that the presence of adjuvants alters endosulfan distribution because gills and liver showed a higher uptake and mobilization of ß-endosulfan. These differences in organ distribution may alter tissue-specific toxicity; therefore, additives cannot be considered inactive even if nontoxic. Environ Toxicol Chem 2020;39:604-611. © 2019 SETAC.

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Teleostei present great plasticity regarding sex change. During sex reversal, the whole gonad including the germinal epithelium undergoes significant changes, remodeling, and neoformation. However, there is no information on the changes that occur within the interstitial compartment. Considering the lack of information, especially on the role played by metalloproteinases (MMPs) in fish gonadal remodeling, the aim of this study was to evaluate the action of MMPs on gonads of sex reversed females of Synbranchus marmoratus, a fresh water protogynic diandric fish. Gonads were processed for light microscopy and blood samples were used for the determination of plasma sex steroid levels. During sex reversal, degeneration of the ovaries occurred and were gradually replaced by the germinal tissue of the male. The action of the MMPs induces significant changes in the interstitial compartment, allowing the reorganization of germinal epithelium. Leydig cells also showed an important role in female to male reversion. The gonadal transition coincides with changes in circulating sex steroid levels throughout sex reversion. The action of the MMPs, in the gonadal remodeling, especially on the basement membrane, is essential for the establishment of a new functional germinal epithelium.

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The organochlorine insecticide endosulfan (ES) is widely used despite its high toxicity to fish (96-h LC(50) median value of 2.6 µg L(-1)). This study aimed to assess the acute toxicity, histological and physiological parameters after exposure to 0; 0.25; 1; 2; 3; 4 and 16 µg L(-1) ES for 96 h under semi-static conditions in a freshwater perciform fish, Cichlasoma dimerus. Prior to death, fish exhibited behavior indicative of neurotoxicity. No difference was found in brain AChE activity. A decrease in erythrocyte mean corpuscular volume, mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration in exposed fish suggests a state of anemia. Histological alterations observed in exposed fish included hyperplasia of the interlamellar epithelium, blood congestion in secondary lamellae, and mucous cells hyperplasia and hypertrophy in gills; pycnotic nuclei and hydropic degeneration in liver; testicular damage. These moderate pathological responses in major organs could become crucial during reproduction and under prolonged exposure periods.

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