Effects of cashew nut shell liquid (CNSL) component upon Aedes aegypti Lin. (Diptera: Culicidae) larvae’s midgut

Abstract

aegypti Lin. (Diptera: Culicidae) larvae’s midgut The cashew nut shell liquid (CNSL) has been associated with a number of biological activities. The aim of this study was to evaluate the insecticidal potential caused by CNSL from Anacardium occidentalle L. (Anacardiaceae) upon Aedes aegypti and verify histomorphological alterations in the larval midgut. The experiments were carried out using third instar A. aegypti larvae, exposed to CNSL at  different concentrations. After 24 h, the larvae were treated and stained with hematoxylin-eosin (HE). Morphometric analyzes were performed on the A. aegypti larvae midgut and registered by photomicroscopy. Anacardic acid was identified in CNSL by high performance liquid chromatography (HPLC) and showed 69% purity. The minimum concentration of CNSL that promoted mortality of A. aegypti larvae (LC₁₀) was 0.01 mg mL^-1; the LC₉₀ was 0.139 mg mL^-1 and the LC₅₀ was 0.07 mg mL^-1. Changes in the midgut were severe in larvae treated with CNSL, especially at concentrations of 1.0 to 0.01 mg mL-1; degeneration of the lining, hypersecretion of epithelial cells, increased vacuoles, and separation of the epithelial cells from the basal membrane, and disintegration of the brush border and damage of the peritrophic membrane occurred. CNSL caused damage to the midgut of 3rd instars of A. aegypti by irreversibly disrupting their complete larval development.
 
Key words: Dengue fever, bioinsecticids from plants, morfology of midgut