Impact of antiparasitic used in livestock: effects of ivermectin spiked sediment in Prochilodus lineatus, an inland fishery species of South America.

Ivermectin (IVM) is a widely used antiparasitic. Concerns have been raised about its environmental effects in the wetlands of Río de la Plata basin where cattle have been treated with IVM for years. This study investigated the sublethal effects of environmentally relevant IVM concentrations in sediments on the Neotropical fish Prochilodus lineatus. Juvenile P. lineatus were exposed to IVM-spiked sediments (2 and 20 µg/Kg) for 14 days, alongside a control sediment treatment without IVM. Biochemical and oxidative stress responses were assessed in brain, gills, and liver tissues, including lipid damage, glutathione levels, enzyme activities, and antioxidant competence. Muscle and brain acetylcholinesterase activity (AChE) and stable isotopes of 13C and 15N in muscle were also measured. The lowest IVM treatment resulted in an increase in brain lipid peroxidation, as measured by thiobarbituric acid reactive substances (TBARs), decreased levels of reduced glutathione (GSH) in gills and liver, increased catalase activity (CAT) in the liver, and decreased antioxidant capacity against peroxyl radicals (ACAP) in gills and liver. The highest IVM treatment significantly reduced GSH in the liver. Muscle (AChE) was decreased in both treatments. Multivariate analysis showed significant overall effects in the liver tissue, followed by gills and brain. These findings demonstrate the sublethal effects of IVM in P. lineatus, emphasizing the importance of considering sediment contamination and trophic habits in realistic exposure scenarios.

Multibiomarker responses and bioaccumulation of fipronil in Prochilodus lineatus exposed to spiked sediments: Oxidative stress and antioxidant defenses.

Fipronil is a current use pesticide, widely used in many crops, commonly adsorbed to sediments of aquatic environments. The purpose of this study was to evaluate the biomarker responses and fipronil distribution pattern in different matrixes (fish, sediment and water) after juveniles P. lineatus exposure at two environmental concentrations (5.5 and 82 µg kg--1) of fipronil-spiked sediments. The levels of oxidized proteins (PO), lipid peroxidation (LPO), and enzymatic activity of superoxide dismutase (SOD), reduced glutathione content (GSH), antioxidant capacity against peroxyls (ACAP) and acetylcholinesterase (AChE) were evaluated in liver, gills and brain. Concentrations of fipronil and its metabolites (f. desulfinyl, f sulphpHide and f. sulfone) were quantified by GC-ECD. F. desulfinyl was the major metabolite found in all matrixes, followed by f. sulphide in sediments, while f. sulfone was mainly accumulated in fish. Fipronil promoted oxidative stress in P. lineatus, as evidenced by the increases in LPO and PO levels and the decrease brain AChE activity. Fish exposed at both concentrations showed significant decrease in antioxidant capacity. Alterations in the antioxidant defenses system was evidenced in all organs. These results suggest that the occurrence of fipronil in aquatic environments can generate oxidative stress at different levels in P. lineatus, showing that this species is highly sensitive to the deleterious effects of fipronil and metabolites.

Nanosilver and Silver Nitrate Toxicity in Ex Vivo-Exposed Gills of Fish and Mitigation by Humic Acids.

Silver nanoparticles (AgNP) are unique because of their biocide properties. Once released to environment, AgNP interact with the natural organic matter which impact on their fate, dispersion, and ultimate toxicity. We carried out an ex vivo exposure of gill of Corydoras paleatus fish to 100 µg L-1 of AgNP or AgNO3, alone and in combination with 10 mg L-1 of humic acids (HA), with the aim to evaluate the potential mitigation of HA on AgNP toxic effects. We analyzed Ag accumulation and oxidative stress biomarkers. The results showed high bioaccumulation after the AgNO3+HA exposure. An inhibition of glutathione-S-transferase enzymatic activity and depletion of reduced glutathione levels were registered after the AgNO3 exposure, and increased lipid peroxidation levels in the case of AgNP one. Oxidative responses were mitigated when the HA were present in the media. Overall, the knowledge about the fate of this emergent pollutant was deepened through this study.

Exposure to environmental concentrations of fipronil induces biochemical changes on a neotropical freshwater fish.

Fipronil is a broad-use insecticide with severe toxicity to fish. Biomarkers responses and bioaccumulation were evaluated on Prochilodus lineatus after exposure to environmentally relevant concentrations of fipronil (0.5 µg L-1, 9 µg L-1, and 100 µg L-1) in a prolonged flow-through assay and ex vivo gills short-term exposition. Lipid peroxidation (LPO), oxidatively modified proteins (PO), the activity of superoxide dismutase (SOD), the content of reduced glutathione (GSH), antioxidant capacity against peroxyles (ACAP), and acetylcholinesterase (AChE) were evaluated. Besides, levels of fipronil and metabolites were analyzed by GC-ECD. At the end of the flow-through assay, fipronil, Fp. sulfone and Fp. desulfinyl were detected in fish, being liver the target organ. Fipronil prolonged exposition promoted oxidative damage in lipids and proteins, alterations in the defense system and low-antioxidant capacity in organs of P. lineatus. The brain AChE activity was affected after prolonged exposition. Ex vivo gills exposition to fipronil promoted changes in antioxidant capacity and damage to lipids, providing a fast and suitable test to assess the pesticide exposure in fish. The results revealed that fipronil at environmental concentrations would be an inducer of oxidative stress in this fish, becoming a vulnerable species to the effects of fipronil in aquatic environments.

Mitigation of silver nanoparticle toxicity by humic acids in gills of Piaractus mesopotamicus fish.

Silver nanoparticles (AgNPs) are one of the most produced nanoproducts due to their unique biocide properties. The natural organic matter has an important impact on nanoparticle's dispersion as it may alter their fate and transport, as well as their bioavailability and toxicity. Therefore, this study aimed to evaluate the mitigatory effect of humic acids (HAs) on AgNP toxicity. For this purpose, we carried out an ex vivo exposure of gill of Piaractus mesopotamicus fish to 100 µg L-1 of AgNPs or AgNO3, alone and in combination with 10 mg L-1 of HAs. In parallel, a complete AgNP characterization in the media, including the presence of HAs, was provided, and the Ag+ release was measured. We analyzed Ag bioaccumulation, antioxidant enzymes activities, lipid peroxidation, antioxidant capacity against peroxyl radicals, and reduced glutathione levels in fish tissue. Our results indicated the Ag+ release from AgNPs decreased 28% when the HAs were present in the media. The Ag accumulation in gill tissue exposed to AgNPs alone was higher than the AgNO3 exposure, and sixfold higher than the treatment with the HA addition. Moreover, after both Ag forms, the catalase enzyme augmented its activity. However, those responses were mitigated when the HAs were present in the media. Then, our results suggested the mitigation by HAs under the exposure to both Ag forms, providing valuable information about the fate and behavior of this emergent pollutant.

Assessment of the pollution impact on biomarkers of effect of a freshwater fish.

Changes in biomarkers of fish captured from stressed environments may represent a reliable tool in revealing sublethal effects of the pollutants found in aquatic ecosystems. The response patterns of selected biochemical and morphological variables biomarkers of effect were assessed in adult females of an indigenous teleost Cnesterodon decemmaculatus, caught at a polluted site (San Francisco) of the Reconquista river (Buenos Aires, Argentina). Combined field-caging experiments with controlled laboratory exposure to clean media were performed. The biochemical parameters measured were specific activities of gill (Na+ + K+)-ATPase, liver AlaAT and AspAT, and brain AChE; LSI and CF were also calculated. The changes in gill (Na+ + K+)-ATPase and liver AlaAT activities of fish captured in the field in most cases were reversible after transfer to clean media. The results were interpreted in association with the physicochemical profile of the water samples taken simultaneously with the capture of the fish. Results suggested the suitability of the test species used as tools in environmental monitoring programs of risk assessment.

Biomarkers of a native fish species (Cnesterodon decemmaculatus) application to the water toxicity assessment of a peri-urban polluted river of Argentina.

Environmental monitoring by means of biomarker parameters assessed in different species is a useful tool. It has the advantage of providing a quantitative response as well as valuable information of ecological relevance on the chronic adverse effects caused by water pollution. The aim of this study was to assess the response of biochemical and physiological parameters of Cnesterodon decemmaculatus, a native teleost, simultaneously caught in two sites of Reconquista river, a highly polluted peri-urban river. This study compared the measured parameters with that of specimens of the same species captured in an unpolluted body water, and correlated the detected changes with the physicochemical profile of the water at each site. A comparison was made of selected parameters of gill, brain and liver and of somatic indices of fish collected from polluted and reference sites. The main parameters whose changes allowed to discriminate between sampling sites were gill (Na(+),K(+))-ATPase, brain acetylcholinesterase (AChE) and liver aminotransaminases activities; tissues' protein content and liver somatic index (LSI) were also sensitive biomarkers in brain and liver, respectively. The results showed that the response of the measured biomarkers allowed for the differentiation of sampling sites according to their water quality and confirmed that Cnesterodon decemmaculatus may be a useful test organism for the biomonitoring of freshwater environments. In addition, the simultaneous measurement of the physicochemical parameters of the water samples showed a good correspondence between the biomarkers responses and the environmental chemical stress conditions.