Effects of heavy metals - Cu, Hg, Cd - on three species of mosquitoes larvae (Diptera : Culicidae)

The effects of three heavy metals (Cu, Hg, Cd) on the development of Anophe les hispaniola, a potential vector of malaria, Culex pipiens and Culex hort ensis have been studied in oued N'fis near Agadir Tachraft, in the Marrakec h (Morocco) experimental wastewater treatment lagoons and in a pond used to rear frogs. The effects varied with the species, related to instar stage, metal type an d concentration. The LA stage of A. hispaniola is more sensitive to Cu, Hg and Cd, with 24hr LC50 values of 3.78, 1.52 and 4.81 mg.L-1 respectively, i n comparison with the lower LC50 values for C. hortensis (5.02, 3.1 and 9.9 1 mg.L-1) and C. pipiens (5.91, 4.43 and 17.48 mg.L-1). However, sensitivit y to Cd is not significantly different in the L2 instar of A. hispaniola an d C. hortensis based on a the Newman - Keuls test. This study shows that A. hispaniola, which has a relatively short life cycl e and is easy to rear in the laboratory, is twice as sensitive to mercury, 3.4 times as sensitive to cadmium and 8.6 times as sensitive to copper in c omparison with Aedes aegypti. This latter species has been suggested as a t est species for the same parameters to study the biological effects of heav y metals on aquatic insects.