Avaliação da Toxicidade do Endosulfan Sulfato sobre Juvenis de Danio Rerio (Cypriniformes, Cyprinidae)

Evaluation of toxicity endosulfan sulfate on Danio rerio juvenilis (Cypriniformes, Cyprinidae) The objective of this work was to evaluate the toxicity of endosulfan sulfate toxicity (the most persistent form) in Danio rerio juveniles, considering the mortalities, in exposition of 96 hours, and survive and microscopic gill morphology in toxicity test partial chronic (7 days) in concentrations of 0.003 µg L ‐1 , 0.3 µg L ‐1 and 3.0 µg L ‐1 , near the levels detected in the upper Jacare-Guacu river basin (Sao Paulo, Brazil). The result of the mortality was detected CL50, 96 h of the 7.29 µg L ‐1 . Considering the survival, only the higher concentration (3 µg L ‐1 ) promoted toxicity to the test organisms. However, the histological analyses revealed gill changes such as hyperplasia, fusion between some secondary lamellae and thickening of the apex of some secondary lamellae. These alterations compromised the gases exchange and consequently the vital functions of the biological system. The obtained alterations were of first and second level, but these changes can either to return to normal conditions when chemistry conditions improve, or to progress to a third stage degree, which are irreversible, provoking the death of the individual. This results prove the importance of the histology as a tool to evaluate toxicity of chemical products, giving evidences that endosulfan sulfate is toxic to this fish specie at concentrations found in aquatic environments.