Glyphosate is a broad-spectrum organophosphate (OP) herbicide, highly soluble in water, and when applied in terrestrial systems it penetrates into soil, eventually reaching the aquatic community and affecting nontarget organisms. The aim of this study was to evaluate the toxicity of glyphosate on ovaries of zebrafish (Danio rerio). Ovaries (n = 18 per triplicate) were exposed to 65 μg/L of glyphosate [N-(phosphonomethyl) glycine] for 15 d. This concentration was determined according to Resolution 357/2005/CONAMA/Brazil, which establishes the permissible concentration of glyphosate in Brazilian inland waters. Nonexposed ovaries (n = 18 per triplicate) were used as control. Subsequently, morphology and expression of steroidogenic factor-1 (SF-1) of exposed and nonexposed ovaries was determined. No apparent changes were noted in general morphology of exposed and nonexposed ovaries. However, a significant increase in diameter of oocytes was observed after exposure to glyphosate. When ovarian ultrastructure was examined the presence of concentric membranes, appearing as myelin-like structures, associated with the external membranes of mitochondria and with yolk granules was found. After glyphosate exposure, immunohistochemistry and immunoblotting revealed greater expression of SF-1 in the oocytes, which suggests a relationship between oocyte growth and SF-1 expression. These subtle adverse effects of glyphosate on oocytes raised a potential concern for fish reproduction. These results contribute to understanding glyphosate-induced toxicity to nontarget organisms, showing subcellular and molecular impairments that may affect reproduction in +female fish.

Changes in aquatic environments are potentially large, and effects on biota are highly variable. In Santa Catarina State, Brazil, the main sources of pollution in headwaters are wastewater, pesticides, and animal waste, which contain chemical and organic additives, and there is little knowledge about their effects on aquatic organisms. This study was aimed at investigating the possible genotoxic effects of the waters of the Engano River through the micronucleus (MN) test in Astyanax bimaculatus erythrocytes. Samplings were performed at two sites on the river, and there were six temporal repetitions with collection of blood from six individuals per site/repetition. For the negative-control treatment, we used fish from organic culture; cyclophosphamide was inoculated to constitute the positive-control treatment. MN was obtained in 3,000 erythrocytes/individual. Kruskal-Wallis analysis of variance, Scott-Knott test, and Spearman correlation were employed for data analysis. We found 124 MN in fish from the river, with 70 and 54 MN, respectively, for each site and 16 and 59 MN in negative and positive controls, respectively. The results showed a statistical difference for the formation of MN between river fish and fish in the positive-control treatment. Considering the average MN, we found the formation of three distinct groups: (1) fish from site no. 1 and those in the negative-control group, (2) fish from site no. 2, and (3) fish in the positive-control group. The greater values of chromosomal damage were found during periods of lower rainfall. The test used indicated the presence in the water of substances likely to cause clastogenic and aneugenic effects.

Os herbicidas são muito utilizados na agricultura por substituírem a mão-de-obra na capina, diminuindo consequentemente o esforço exigido pelo trabalho, e otimizando o tempo dos agricultores, mas em uma concentração elevada pode trazer malefícios para organismos aquáticos podendo provocar alterações moleculares e celulares que afetarão a morfologia, fisiologia e bioquímica dos tecidos. Dentre os agrotóxicos, o organofosforado glifosato é um dos herbicidas mais usados no Brasil e no mundo. Considerando a importância de reconhecer as alterações macroscópicas e mutagênicas na avaliação da toxicidade do herbicida glifosato, amplamente utilizado na agricultura, foi utilizado neste estudo, como modelo experimental, o peixe Danio rerio. O estudo teve como objetivo avaliar os efeitos subletais de toxicidade do herbicida glifosato sobre a morfologia nos ovários de D. rerio e analisar o percentual de micronúcleo nos peixes expostos às concentrações de glifosato. Os peixes foram divididos em dois grupos, sendo um exposto ao herbicida a uma concentração 65 µg/L diluído em água, determinado pela Resolução do Conselho Nacional do Meio Ambiente (CONAMA) Nº 357, de 17 de março de 2005, que estabelece a concentração de 65 µg/L de glifosato em águas dos rios no Brasil. O outro grupo de peixes foi utilizado como controle, mantidos em água isenta de herbicida. Verificou-se um aumento significativo na massa dos ovários, bem como um aumento significativo no índice gonadossomático (IGS) em ovários de peixes expostos ao glifosato por um período de 15 dias. Em relação ao percentual de micronúcleo dos eritrócitos os grupos não diferiram estatisticamente entre si. Mesmo na concentração de glifosato regulamentada para os rios do Brasil, efeitos subletais tóxicos foram identificados nos ovários. Desta forma, sugere-se a realização de testes toxicológicos para avaliação de parâmetros reprodutivos. Os efeitos adversos do glifosato sobre os ovários demonstradas aqui representam um importante risco para a reprodução de peixes.