Histopathological changes in Lithobates catesbeianus tadpoles used as biomarkers of pesticide poisoning

The use of biological indicators has increased in recent years with the aim of investigating environmental pollution in aquatic environments that are vulnerable to the constant use of pesticides. Some biomarkers can help assess the health status, indicating physical, metabolic, and behavioral changes under acute and sublethal poisoning. The mixture of the active ingredients cyproconazole and picoxystrobin is a widely used fungicide for the control of pests in cotton, rice, coffee, sugarcane, corn, soybean, and wheat. The objective of this study was to verify the occurrence of possible histopathological lesions in the liver and kidneys of bullfrog tadpoles (Lithobates catesbeianus) caused by a fungicide commercial formula composed of picoxystrobin and cyproconazole. The animals were subjected to different concentrations of the fungicide to determine the median lethal concentration (LC50-96h = 0.05 mg L-1), that is, the lethal dose for 50% of the animals in 96 h. After determining the value of LC50-96h, the animals were subjected to three sublethal concentrations (LC50-96h/2, LC50-96h/10, and LC50-96h/100). Through histological biomarkers, it was verified that this fungicide changed the morphology of the animals' kidney and liver tissues in a chronic way, impairing the functioning of organs that are essential for their survival and metamorphosis, which can result in an imbalance in the biodiversity of aquatic ecosystems.