Efeitos combinados de microplásticos e Glifosato nas brânquias de Tilápia(Oreochromis niloticus).

Abstract

Microplastics are becoming the most common contaminants in all aquatic environments, causing ecotoxicological and sometimes deleterious effects on aquatic organisms. Likewise, the herbicide glyphosate has been widely used to combat weeds that grow around agricultural production. It is known that both contaminants can be available in the aquatic environment and can associate causing combined effects. The aim of this work was to evaluate the sublethal effects of the association of plastic microparticles of polyethylene and glyphosate on tilapia (Oreochromis niloticus) gills, using different toxicity biomarkers. The bioassay was performed acutely (96 h), in which the animals were randomly divided into aquariums, with a control (CG) and the others containing 5 mg L-1 of polyethylene microplastic (MPG); 5 mg L-1 of glyphosate (GG) and one with both associated contaminants (AG), at the same concentrations as the isolated groups. After exposure, a blood sample was collected via caudal puncture, for physiological biomarkers and then the animals were euthanized to remove the gills. Gill samples were used for histopathological, enzymatic and osmoregulatory biomarkers. There was an increase in mean corpuscular hemoglobin in AG compared to control and MPG, evidencing a physiological stress that indicates hyperchromia. In MPG there was thrombocytosis, suggesting an inflammatory process. Such processes may be related to the histopathological alterations found in gills, which demonstrate circulatory alterations in the GG, hypertrophy and proliferation of mitochondria-rich cells (MRCs) in the GG and AG, in addition to epithelial ruptures in all exposed groups. Such pathophysiological findings did not compromise the functioning of the organ, however, the osmoregulatory biomarkers showed that there was an osmo-ionic imbalance, which was adjusted by the animal with the proliferation of MRCs at the end of 96 h of exposure. The sublethal concentrations of this study, easily present in the aquatic environment, are not lethal to fish, however, they indicate stress induction and the need for physiological adjustments so that the organisms are in homeostasis. The gills of O. niloticus are sensitive to environmental changes and respond, in an integrated way, to the combined effects of multiple xenobiotics in the ecosystem.