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The ability of mosquito larvae to tolerate toxic compounds (temephos, Bacillus thuringiensis var. israelensis, toxic vegetable leaf litter) was examined on a laboratory larval strain of Aedes aegypti L. Bioassays and detoxifying enzyme activity measurements were performed to compare tolerance/resistance capacities. The possibility of a functional plasticity of detoxifying equipment was investigated through experimental determination of the inductive effect of each xenobiotic within a given generation. In the same way, the selective effect of a toxic leaf litter was also investigated along successive generations. Results revealed that differential cytochrome P450 monooxygenase, esterase, and glutathione S-transferase activity levels correlated with the bioassay results. Both induction and selection increased larval tolerance to the xenobiotics used and increased the levels of larval detoxifying enzyme activities. [ABSTRACT FROM AUTHOR]

The larvicidal properties of the dietary leaf litter originating from the vegetation surrounding the subalpine mosquito breeding sites were investigated by using 10-month decomposed alder leaf litter against different field collections of culicine taxa of various ecological origin (Aedes cantans, Aedes caspius, Aedes cataphylla, Aedes detritus, Aedes punctor, Aedes pullatus, Aedes rusticus, Anopheles claviger,Culex hortensis, Culex pipiens, Culiseta morsitans). Larvae originating from sites with polyphenol-poor vegetation appeared more sensitive to ingested leaf litter than those originating from sites with polyphenol-rich vegetation. Within a given taxon (e.g., A. rusticus, A. cataphylla, C. hortensis), the overall levels of cytochrome P450 monooxygenase and esterase activities appeared higher in larvae able to feed on leaf litter than in pupae and adults unable to feed on leaf litter. This suggests the involvement of these enzymes in the detoxification mechanisms responsible for larval tolerance to polyphenols of the dietary leaf litter. Such a tolerance of the larval stage thus appears as fundamental in the ecotoxicological adaptation of mosquito taxa to the polyphenolic profiles of the riparian vegetation. [ABSTRACT FROM AUTHOR]