Acute and chronic toxicity of copper on aquatic insect Chironomus ramosus from Assam, India.

Acute toxicity of copper (Cu) on Chironomus ramosus was determined by exposing third-instar larvae to graded concentrations of copper sulphate (CuSO4 x 5H2O). Median lethal concentrations (LC50) of Cu as CuSO4 at 24, 48, 72 and 96 hr were determined as 3280, 1073.33,780 and 183 microg l(-1), respectively. For determining the effects of chronic toxicity, small first-instar larvae were individually exposed to sublethal concentrations of copper sulphate (1.0-18.0 microg l(-1)) for a period of 21 days. Discoloration and thinning of body were detected at 1 microg l(-1) and ventilation movements, pupation and adult emergence were significantly affected at 1.8 microg l(-1). At 10 microg l(-1) CuSO4 concentration, growth and tube-building activities of the larva were significantly different from the control.