Effect of Croton tetradenius essential oil on larval viability, pupal viability, and wing geometric morphometrics of Aedes aegypti

Abstract

Plant-derived insecticides, such as the essential oils of Croton species, can be an effective alternative to replace synthetic chemical insecticides against Aedes aegypti. This study aimed to evaluate the effect of the essential oil from the aerial part of Croton tetradenius on larval and pupal viability and the wing geometric morphometrics (WGM) of Ae. aegypti. The essential oil of C. tetradenius was extracted using an industrial Clevenger apparatus. To evaluate the larvicidal activity, 3rd and 4th instar larvae of Ae. aegypti were submitted to bioassays with essential oil using six concentrations and five repetitions. The WGM analyses were performed for the surviving larvae and pupae. For the morphometric analysis, 417 left wings of the adult mosquitoes were photographed and scanned. The essential oil of C. tetradenius showed larvicidal activity (LC50 = 4.71 and LC90 = 6.03 mg mL-1) after 24 h of exposure. Larval viability at the lowest concentrations (0.062 and 0.031 mg mL-1) was 96.67 and 95.55%, differing from the control group (97.78%). Differences were observed for the pupal viability for the concentration of 0.031 mg mL-1 when compared to the control. Geometric morphometry through canonical variables revealed an 82.46% difference between the groups studied. The principal component analysis also showed cumulative variance among the groups (28.32, 41.84, 54.61, 65.27, and 74.31%). Therefore, the essential oil of C. tetradenius was toxic to the Ae. aegypti mosquito larvae, and affected the larval and pupal viability, sex ratio, and wing geometric morphometrics of the mosquitoes.