Chronic effects of Cu on reproduction of Polypedilum nubifer (Chironomidae) through water and food.

The effects of Cu on the reproduction of Polypedilum nubifer (Chironomid) through water and food were examined in a flowthrough aquarium by Cu exposure from the egg stage. The emergence success decreased to 74, 38, 16, and 2% of the control at 10, 20, 30, and 40 micrograms Cu/liter, respectively. However, the oviposition success (No. of egg clusters/female) remained at 64% of the control value even at 30 micrograms Cu/liter. From these results and the acute toxicity test, it was suggested that a decrease in emergence success was caused mainly by mortality in the early instar stage, when Cu sensitivity is high. There were no significant effects of Cu on the emergence success, oviposition success, and hatchability of the oviposited eggs in the midge which had been given food contaminated with about 330 micrograms Cu/g (dry weight). However, emergence success and hatchability of the oviposited eggs decreased to 30 and 40% of the control in the midge which had been fed food accumulating 1770 micrograms Cu/g, although the oviposition success was not impaired compared to the control. Emergence did not occur from the aquaria fed food accumulating 5200 micrograms Cu/g.