Effect of long-term exposure to copper on survival and development of two successive generations of Culex pipiens (Diptera, Culicidae)

Aquatic invertebrates can be exposed to copper from various sources, including agricultural applications. For example, concentrations up to 1000 mu g L-1 are found within rice fields, where copper-containing formulations are used as fungicides and algaecides. We conducted toxicity tests to study lethal and sublethal effects of copper sulfate pentahydrate on all immature stages across two generations of Culex pipiens mosquitoes as our model organism. Mortality was dose-dependent at concentrations of 500 mu g L-1 and above in the first generation, and 125 mu g L-1 and above in the second generation. The median lethal concentrations (LC50) of copper sulfate pentahydrate for larval Cx. pipiens were 476 +/- 30.60 mu g L-1 and 348.67 +/- 23.20 mu g L-1 for the first and second generations, respectively. Generation one pupation decreased from 96% in controls to 48% at 500 mu g L-1, while the second-generation pupation decreased from 96% in controls to 17.5% at 500 mu g L-1. Mortality during the pupal stage varied from 2 to 10% at 500 mu g L-1 of first and second generations, respectively. Higher levels also delayed development to adulthood in both generations. The duration of the immature period was 14.8 days in controls in both generations, but when exposed at 500 mu g L-1 it increased to 18.8 days in the first generation and to 20.5 days in the second generation. The chronic, multi-generation exposures in this study showed greater toxicity than reported for shorter exposures of Cx. pipiens, and confamilial taxa like Culex hortensis and Anopheles hispaniola.

Automated summary

Toxicity tests on Culex pipiens mosquitoes exposed to copper sulfate pentahydrate revealed lethal and sublethal effects at concentrations of 500μg/L and above. Sensitivity to copper varied slightly between generations, with prolonged developmental periods observed in both larval and pupal stages under exposure.