Abstract:
Aedes aegypti, the principal global vector of arboviral diseases and previously considered to oviposit
and undergo preimaginal development only in fresh water, has recently been shown to be capable of
developing in coastal brackish water containing up to 15 g/L salt. We investigated surface changes in
eggs and larval cuticles by atomic force and scanning electron microscopy, and larval susceptibility
to two widely-used larvicides, temephos and Bacillus thuringiensis, in brackish water-adapted Ae.
aegypti. Compared to freshwater forms, salinity-tolerant Ae. aegypti had rougher and less elastic
egg surfaces, eggs that hatched better in brackish water, rougher larval cuticle surfaces, and larvae
more resistant to the organophosphate insecticide temephos. Larval cuticle and egg surface changes
in salinity-tolerant Ae. aegypti are proposed to respectively contribute to the increased temephos
resistance and egg hatchability in brackish water. The findings highlight the importance of extending
Aedes vector larval source reduction efforts to brackish water habitats and monitoring the efficacy of
larvicides in coastal areas worldwide.
