In recent years, lectins have been identified as alternative agents against Aedes aegypti during the aquatic phases of its life cycle. For example, chitin-binding lectin from Myracrodruon urundeuva leaf (MuLL) can function as a larvicide. In this study, we investigated whether MuLL can also act as an ovicide against this insect. Aedes aegypti eggs were incubated with MuLL for 72 h to determine the concentration at which the hatching rate reduces by 50% (EC50). The effects of MuLL on the egg surface structure were evaluated using scanning electron microscopy (SEM), and the possible interaction of MuLL with the internal structures of eggs and embryos was investigated using MuLL-fluorescein isothiocyanate (FITC) conjugate. MuLL acted as an ovicidal agent with an EC50 of 0.88 mg/mL. The SEM analysis revealed that eggs treated with MuLL for 24 and 48 h no longer had tubercles and did not show a well-defined exochorionic network. In addition, deformation and degeneration of the surface were observed after 72 h. Fluorescence microscopy showed that MuLL penetrated the eggs 48 h after incubation and was detected in the upper portion of the embryo's gut. After 72 h, MuLL was observed in the serosal cuticle and digestive tract. In conclusion, MuLL can function as an ovicidal agent against A. aegypti through damage to the surface and internal structures of the eggs.
Keywords: Chitin-binding proteins; Dengue mosquito; Egg structures; Insecticidal activity.
© King Abdulaziz City for Science and Technology 2022.