Avaliação da toxicidade de pesticidas sobre o crescimento e biomarcadores de estresse oxidativo em oligoquetas (Eisenia andrei)

Abstract

In Brazil, herbicides and fungicides are the most widely used classes of pesticides. Of these products, the 3 most commercialized are the herbicides Glyphosate (GLY) and 2,4- Dichlorophenoxyacetic Acid (2,4-D), and the fungicide Mancozeb (MZ). Due to their permanence in the environment and their potential to cause damage to environmental and human health, knowing their effects on organisms in the edaphic environment can help to elucidate their mechanisms of action in non-target living beings, such as earthworms. However, the oxidative effects of glyphosate, 2,4-D and mancozeb on earthworms still need to be studied, given the ecological role of these organisms. Therefore, the aim of this study was to analyze whether exposure to glyphosate, 2,4-D and mancozeb harms the health of earthworms. To this end, three studies were conducted. In the first, the effects of glyphosate on earthworms and the consequences for the edaphic environment were investigated through a literature review. We found that the effects of exposure to glyphosate are diverse, varying according to the species of earthworm, the formulation and dose of glyphosate, exposure time and soil type. The second and third studies were experimental, in which we assessed whether exposure to sublethal doses of 2,4-D and MZ induced changes in growth and biochemical markers of oxidative stress in earthworms of the Eisenia andrei species. To this end, the worms were subjected to concentrations of 250, 500, 750 and 1000 µg a.i. Kg-1 (of 2,4-D and MZ) for a period of 21 days. Growth rate, levels of reactive oxygen species (ROS), antioxidant capacity against peroxides (ACAP), lipid peroxidation (TBARS), content of non-protein thiols (NPSH), activity of the enzymes glutathione-S-transferase (GST), superoxide dismutase (SOD), catalase (CAT) and acetylcholinesterase (AChE) were evaluated. The results showed that both pesticides induced a reduction in growth, changes in redox status and neuromuscular damage, compromising the animals' health. Taken together, our results indicate that the changes observed in the set of antioxidant enzymes and cell damage markers show that oxidative stress may be a common outcome of the toxicity of the three pesticides in earthworms. From the changes at biochemical and cellular level, we infer that this observed imbalance can lead to damage to the earthworms' metabolism and tissues, compromising their survival and, as a consequence of these effects on the earthworms, can affect the edaphic environment, given the ecological importance of these animals.