Histopatologia hepática do jundiá Rhamdia quelen como ferramenta de monitoramento ambiental em afluentes do Rio Iguaçu

Abstract

The Iguaçu River is heavily affected by the dumping of urban waste and agrochemicals, and is considered one of the most polluted rivers in Brazil. These anthropogenic activities, such as the use of pesticides and the discharge of effluents, affect the flora, fauna, and functioning of the aquatic system. Continuous monitoring of the environmental quality of the Iguaçu River basin is essential. For this purpose, fish can be used as bioindicators. The ichthyofauna of this river has an endemism rate equal to or greater than 70%, which reinforces the importance of its preservation. This study aimed to evaluate the histopathological effects on the liver of the fish Rhamdia quelen (jundiá) as a tool for environmental monitoring in tributaries of the Iguaçu River. Samples were collected in areas with different land uses, including urban, agricultural, and environmental preservation zones, covering points along the basin. The collected livers were processed histologically and analyzed for pathological alterations based on the Bernet Index, which considers the extent and importance of lesions. Significant differences were observed among sampling points for the Bernet Index (ANOVA; F(3,33)=10.473; p=0.00005), indicating that land use influences hepatic alterations. The riparian forest site showed the highest Bernet and IBR values, while the Iguaçu National Park exhibited the lowest. The most frequent lesions were melanomacrophage centers, free macrophages, and vacuolar degeneration. These results suggest that even areas considered preserved may be subject to diffuse contamination and confirm the use of Rhamdia quelen as an effective bioindicator of environmental quality in the Iguaçu River basin. For future studies, it is recommended to include complementary biomarkers to deepen the understanding of pollutant dynamics in the basin.