Acute toxicity of endosulfan to the fish Hyphessobrycon bifasciatus and Brachydanio rerio

Acute toxicity of endosulfan to zebra fish (Brachydanio rerio ) and yellow tetra (Hyphessobrycon bifasciatus ) was determined by semi-static bioassay. The 24-h LC50 values were 2.6 (2.3-2.9) and 1.6 (1.3-2.1) mu g/L for Hyphessobrycon bifasciatus and Brachydanio rerio , respectively. Behavioral changes including hyperactivity, erratic swimming and convulsions were observed at the highest exposure levels. Histological studies showed predominant acute effects in the gills, with inflammatory infiltration necrosis and separation of respiratory gill epithelium. Degradation studies with endosulfan showed that both alpha - and beta -isomers were very unstable under the test conditions, presenting half-lives of approximately 24 h.