Abstract

Volatile oils of Microlobius foetidus were used for the evaluation of mortality, trypsin, chymotrypsin and acetylcholine inhibition and Aedes aegypti morphology. Bioassays were made with different concentrations (25, 50 and 100 μg/ml) and alterations in the gut of 4th stage larvae were observed. Volatile oils affected larvae in all stages, with 100% mortality for the 100 μg/ml concentration (LD₅₀ >33.02). The acute toxic unit (2.7 μg/ml), chronic toxic unit (32.68 μg/ml) and toxic load (2.7 μg/ml) confirm the sensibility of the 4th stage larvae. These larvae and 3rd presented a lesser trypsin (0.176 μmol/min), chymotrypsin (0.110 μmol/min) and acetylcholinesterase (0.172 μmol/min) synthesis. Larvae of the 4th stage also had their internal morphology observed, and the main alterations were discontinuity of the peritrophic epithelium, thickening of the peritrophic membrane, decrease/increase of the subjacent epithelium and decrease of endoperitrophic space were observed in the mid gut. The results show the repellent activity of the volatile oils of M. foetidus, with a retardation of overall growth, that are associated with the inhibition of the trypsin and chymotrypsin synthesis. Mortality and enzymatic inhibition in all developmental stages confirm the insecticide potential of M. foetidus.

Key words: Dengue fever, digestive system, biological control agents, natural products.