Toxicological Effects of Some Heavy Metal Ions on Culex pipiens L. (Diptera: Culicidae)

Different concentrations of selected heavy metals in the form of cadmium chloride (CdCl2), copper sulphate (CuSO4), lead nitrate (Pb (NO3)2) and mercuric nitrate (Hg (NO3)2) were tested against immature and mature stage of C. pipiens to assess the toxicity, LC50, total carbohydrate and lipid content. The survival potential of 2 instar larvae was highly affected by the contamination with the tested heavy metals. On the basis of LC50, Cd was the most toxic metal against the larval stage followed by Hg, Cu and Pb. The late toxicity of heavy metals tested on the adult females resulted from larvae treated with the LC50 of each heavy metal decreased significantly the number of eggs laid by female. The fecundity recorded 81.7±5.03, 90.3±2.52, 92.7±3.5 and 78.6±1.52 eggs/♀ for females resulted from larvae treated with the LC50 of CdCl2, CuSO4, Pb (NO3)2 and Hg (NO3)2; respectively, compared to 186±4 eggs/♀ for control females. The hatchability percent of eggs laid with the LC50 of CdCl2, CuSO4, Pb(NO3)2 and Hg (NO3)2 was significantly decreased to 37, 73, 80 and 39 %; respectively, compared to 97 % for eggs laid by untreated females. A significant decrease in total carbohydrate content in the whole body of males and females, C. pipiens resulted from larvae treated with the LC50 of CdCl2 or the LC50 of Hg (NO3)2 was observed. Also, the present study showed a significant decrease in total lipid content of females by the LC50 CuSO4 and the LC50 of Hg (NO3)2, while in males a significant increased was caused by the LC50 CuSO4 and the LC50 of Pb(NO3)2. It is clear from the results obtained in this study that the presence of such elements in the environmental system of the mosquito C. pipiens water as possible to contribute to the reduction of mosquito breeding.