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. 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 μg 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 μg l-1) for a period of 21 days. Discoloration and thinning of body were detected at 1 μg l-1 and ventilation movements, pupation and adult emergence were significantly affected at 1.8 μg l-1. At 10 μg l-1 CuSO 4 concentration, growth and tube-building activities of the larva were significantly different from the control.

Acute toxicity of endosulfan and malathion on Chironomus ramosus (Insecta : Diptera : Chironomidae) from north Cachar hills, Assam, India.

Acute toxicity tests for the pesticides endosulfan and malathion on the larvae of Chironomus ramosus were conducted. Median Lethal Concentration (LC50 ) values of endosulfan were 0.55 x 10-2, 0.16 x 10-2, 0.089 x 10-2 and 0.036 x 10-2 ppb respectively, while those for malathion were 0.139 x 10-2, 0.054 x 10-2, 0.019 x 10-2 and 0.0032 x 10-2 ppb respectively, at 24 , 48, 72 and 96 hr. Thus Chironomus ramosus larvae were more sensitive to malathion at all hours of toxicity tests than endosulfan.