Toxicidade do inseticida tiametoxam para peixes tilápia-do-nilo (Oreochromis niloticus) e pacamã (Lophiosilurus alexandri)

Abstract

The thiamethoxam is a neonicotinoid insecticide used in different cultures and classified as dangerous for the environment. The objective of this research was to study the toxicity of an insecticide thiamethoxam (Actara 250WG®) for Nile tilapia (Oreochromis niloticus) and Pacamã (Lophiosilurus alexandri). Therefore, we conducted three experiments, the first was the determination of LC50 for tilapia Nile, the second evaluated the sublethal toxicity (10% LC50) for tilapia juveniles through histopathological aspects of the liver and changes in serum biochemistry. In the third experiment evaluated the acute and chronic toxicity to pacamã through histopathological aspects of the liver.The methodology used in the first experiment was the exposure of fingerling tilapia to five different concentrations (150, 300 , 450, 600 and 750 mg / L) of the insecticide for a total period of 96 hours, and a control group , with quantification of mortality every 24 hours. In the second experiment juvenile tilapia were exposed to 32 mg / L ( 10 % LC50) and a control group for 360 hours , 4 sampling periods (24, 96, 168 and 360 hours), to which were made the blood samples for biochemical analysis and liver tissue fragments for histopathology and histomorphometry. In the third experiment were used fingerling pacama submitted to five different concentrations of insecticide (30, 60 , 120, 240 and 480 mg / L) and a control group for 15 days , divided into two sample days, 96 hours and 15 days, these periods were executed collections of liver tissue for histopathology. As a result, it was determined LC50 of Actara 250WG® to Nile tilapia fingerling of 322.08 mg / L. In exposure to 10% of LC50, juvenile tilapia demonstrated decrease total protein and increase in serum triglycerides and greater severity of liver and pancreatic necrosis in exposed animals. For pacama LC50 was determined as more than 100 mg / L and liver necrosis was evident in exposed animals with increasing occurrence after 15 day exposure. For both species , thiamethoxam showed hepatotoxicity.