Toxicity and perturbation of the metabolite contents by a chitin synthesis inhibitor in the mosquito larvae of Culiseta longiareolata

Abstract

Novaluron is an IGR of the benzoyl urea family, acting as a chitin synthesis inhibitor. The activity of a commercial formulation of Novaluron (10% EC) was tested, at different concentrations, ranging between 0.2 and 1.6 µg/l, against third and fourth-instar larvae of Culiseta longiareolata. (Diptera: Culicidae). The technical material showed a high level of activity with mortality recorded for both treated and following stages and happened after incomplete development. The LC50 values were 0.51 and 0.91 µg/l active ingredient for third and fourth instar larvae; and LC90 values were 2.32 and 4.30 µg/l respectively. In other experiments the compound was applied at LC50 and LC90 against the fourth instars larvae and its effects investigated on biochemical composition of larval body. Metabolite analyzes showed that novaluron affected significantly the amount of carbohydrates, lipids and proteins of fourth instars larvae starting from the day three following treatment. The carbohydrate and lipid amounts increased significantly whereas those of proteins decreased as compared with control series. For the same treated series a significant decrease was also recorded in the body weight with a decrease in development time. In the presence of chitin synthesis inhibitors, the last step of the chitin biosynthesis pathway is inhibited and the precursor is not converted in to chitin. It may either act on the hormonal level in the haemolymph to announce the synthesis, degradation or the inhibition of the metabolites. Than carbohydrates, lipids, proteins are under endocrine control and the exposure of the larvae to this xenobiotic product can modify the synthesis of these metabolites. The data obtained were discussed according to the mode of action of this insect growth regulator and the metabolism of lipids carbohydrates and proteins.