The use of multiple biomarkers has been shown to be an efficient method for evaluating environmental contamination. In this work, we evaluate neurotoxic effects and the antioxidant system responses of the R. branneri collected in two streams of lower Iguazu River basin, relating them with different percentage of vegetation coverture, presence of pesticides and fall and winter seasons. The biological samples were collected in March and August of 2015, from two streams that belong to the lower Iguazu River basin (Brazil): the Manoel Gomes River and the Arquimedes Stream. Soil analyses were performed, and the results showed the presence of the following organophosphates in the Manoel Gomes River and the Arquimedes Stream: disulfoton, methyl parathion, and ronnel. The present study detected inhibition of cholinesterase activity in the brain and muscle of fish samples during the fall from the Manoel Gomes River and the Arquimedes Stream. In the Manoel Gomes River, elevated lipoperoxidation was also observed during the fall. It was observed that the increase or decrease of biomarkers was related to temporal variation and, possibly, to the exposure of animals to agrochemicals. Although the Manoel Gomes River and the Arquimedes Stream are located in regions with large areas of vegetation, the soil analyses show that agrochemical residues are able to reach these locations, which suggests that the fauna are in contact with oxidant and anti-cholinesterase agents during the fall, in addition to respond differently during each season.

多种生物标志物的使用已被证明是评估环境污染的有效方法。在这项工作中，我们评估了R. branneri的神经毒性作用和抗氧化系统反应收集在伊瓜苏河下游的两条河流中，这与植被覆盖率的不同，农药的存在以及秋冬季节有关。2015年3月和2015年8月，从属于伊瓜苏河下游流域（巴西）的两条溪流中采集了生物样本：Manoel Gomes河和Arquimedes溪流。进行了土壤分析，结果表明，在Manoel Gomes河和Arquimedes河中存在以下有机磷酸盐：双硫丹，甲基对硫磷和罗纳尔。本研究检测到从Manoel Gomes河和Arquimedes河跌落时鱼样本的大脑和肌肉中的胆碱酯酶活性受到抑制。在马诺埃尔·戈麦斯河（Manoel Gomes River），秋天还观察到较高的脂过氧化。观察到生物标志物的增加或减少与时间变化有关，可能与动物对农用化学品的接触有关。尽管Manoel Gomes河和Arquimedes河位于植被大面积的地区，但土壤分析表明，农药残留物能够到达这些位置，这表明该动物在接触过程中与氧化剂和抗胆碱酯酶物质接触。秋天，除了每个季节的反应不同。