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Pesticides are one of the main sources of pollution on the planet, affecting different environments. The aim of the study was to evaluate the chronic effect of atrazine (ATZ) on brain, gill, and liver histology and the clinical signs of intoxication in Hyphessobrycon eques fish and to determine the effect on the expression of proteins related to proliferation, damage, death, and cellular stress pathways. The chronic toxicity test was performed during 30 days of exposure to ATZ. Concentrations of 0.57, 1.14, 5.74, and 11.50 mg L−1 were applied and there was a control. Aquariums with a capacity of 5 L of water were used with aeration pumps containing 5 animals per replica, weighing between 1.0 ± 0.2 g per organism. At the end of the chronic toxicity tests of ATZ for H. eques, samples of the gills, brain, and liver were collected for histological analysis. The same organs were collected and stored in cryogen tubes in liquid nitrogen until the moment of extraction and then massaged mechanically for the Western-blot technique. In the histopathological analyses, the gills showed the greatest changes in relation to the other organs, such as the loss of support of the secondary lamellae, and the fish also showed a loss of swim bladder capacity. In conclusion, ATZ in the environment, in long-term exposure, can cause histological and biochemical effects, affecting the survival and proliferation of cell pathways. [ABSTRACT FROM AUTHOR]

Chlorpyrifos (CPF) is an organophosphorus insecticide detected in aquatic environments considered harmful to living beings. The aim of this research was to evaluate the ecotoxicity of CPF for neotropical aquatic organisms of distinct trophic levels (Lemna minor, Azolla caroliniana, and Wolffia brasiliensis macrophytes; Pomacea canaliculata snail; Macrobrachium acanthurus shrimp; Xiphophorus maculatus and Hyphessobrycon eques fish), to verify the risk of environmental poisoning for each organism, and to determine the best bioindicator species of aquatic contamination by the insecticide. Ecotoxicological assays were carried out with different concentrations of CPF under controlled laboratory conditions standardized for each species. IC50;7d, LC50;7d, EC50;48h, and LC50;48h values were calculated using the Trimmed Spearman Karber software with 95% confidence limits. The toxicity data were used to classify the CPF according to the ecotoxicity categories for aquatic organisms. The risk of CPF environmental poisoning was determined by the quotient method considering different environmental scenarios. The sensitivity order of neotropical aquatic organisms to chlorpyrifos was Macrobrachium acanthurus (0.002 mg L−1) > Xiphophorus maculatus (0.07 mg L−1) > Hyphessobrycon eques (1.65 mg L−1) > Pomacea canaliculata (30.66 mg L−1) > Azolla caroliniana (849.72 mg L−1) > Wolffia brasiliensis (1271.63 mg L−1) = Lemna minor (1299.60 mg L−1). The risk of poisoning by chlorpyriphos may vary according to the environmental concentration of the insecticide and the exposed trophic level. The best bioindicator and with the greatest risk of environmental poisoning was shrimp. The difference in CPF ecotoxicity for distinct aquatic trophic levels shows the relevance of evaluating the effects of contaminants considering food chains and highlights the importance of studying these levels in environmental monitoring programs. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate histological changes in targeted tilapia organs exposed to sublethal concentrations of carbofuran. Fishes with an average weight of 67.5 ± 2.0 g were exposed to sublethal concentrations (0.0044, 0.0088, 0.0440, and 0.0880 mg L−1) of carbofuran for 7 days. In the end of the experiment, the gill, the liver, and the kidney samples were collected for histological evaluation. In gills exposed to 0.0044 mg L−1 of carbofuran, an increase in interlayer epithelium and disruption of the secondary lamella was observed, while in other concentrations (0.0088, 0.0440, and 0.0880 mg L−1), only blood congestion in the secondary lamellae occurred. In the liver samples of exposed tilapias, all carbofuran concentrations caused hepatocyte hypertrophy with the nuclei displaced to the cell periphery, stasis within the sinusoid capillaries, and necrosis points. All sublethal concentrations tested caused detachment of the glomerular capsule, necrosis in the proximal and distal tubules, and absence of intercellular space in the kidney of exposed tilapia. The presence of carbofuran in aquatic environments at concentrations from 0.0044 mg L−1 and exposure periods longer than 7 days alters the gill, the liver, and the kidney histology and consequently compromising the fish's health. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate changes in hematological parameters of O. niloticus exposed to sublethal concentrations of the imidacloprid in order to utilize these parameters as biomarkers of exposure. Fish with an average weight of 68.5 ± 2.0 g were exposed to sublethal concentrations of imidacloprid (1.405, 2.810, 14.050, and 28.1 mg L−1) for 7 days. Blood samples were collected by puncture of the tail vein. Blood samples were used to determine the number of erythrocytes, hemoglobin level, hematocrit number, total plasma protein concentration, total and differential leukocytes count, and thrombocytes number. All tested concentrations caused changes in fish leukogram. Concentrations from 14.050 mg L−1 reduced the number of erythrocytes and total plasma proteins. The tilapia exposed to 28.1 mg L−1 had a significant increase in the number of thrombocytes. Although considered slightly toxic to fish, sublethal concentrations of imidacloprid in aquatic environments, even if it does not cause immediate death, may compromise the health and long-term survival of these animals. The sublethal responses adopted for evaluation toxicity in this study were sensitive and adequate to show the extent to which pesticide can affect non-target organisms. This study recommends the use of blood parameters as biomarkers of exposure of fish to pesticides. [ABSTRACT FROM AUTHOR]

Diflubenzuron (DFB) is a larvicide widely used to control Aedes aegypti populations as an alternative to organophosphates (OPs), with a specific mechanism of action for insects by inhibiting their chitin synthesis. However, DFB is used extensively in urban and rural environments, having the aquatic environment as the major receptor. Thus, the present study aimed to investigate the toxicity of DFB-based formulation and compare it with the toxicity of the OP temephos (TMP)-based formulation, a larvicide still used to control A. aegypti, on freshwater fishes Oreochromis niloticus and Hyphessobrycon eques. Organisms were submitted to acute (48 h) and prolonged (7 days) exposures, in the presence and absence of organic sediment, seeking interactions between chemical and sediment. Histopathological analyses were performed on O. niloticus gills and liver. According to 48-h median lethal concentration (LC50), DFB- and TMP-based formulations were classified as harmful and toxic to fish, respectively, following the Globally Harmonized System of Classification (GHS). After prolonged exposure to sublethal concentrations, DFB-based formulation decreased H. eques body weight at concentrations 272-fold lower than its LC50. Ultrastructural responses of O. niloticus indicated edemas and aneurisms on gills, and hepatocyte hypertrophy and vascular congestion of the liver. TMP-based formulation also induced pyknotic nuclei, which may lead to irreversible necrosis. The addition of organic sediment did not alter the larvicide toxicity, suggesting that larvicides remained available to the organisms. Altogether, these results suggest that as an insect-specific pesticide, DFB still induces mortality and tissue damage in fishes; thus, both larvicides pose risks to fishes. [ABSTRACT FROM AUTHOR]