Effect of salinity on the behavior of Aedes aegypti populations from the coast and plateau of southeastern Brazil.

BACKGROUND & OBJECTIVES: Mosquito larvae can develop in fresh, salty and brackish water. The larvae of Aedes aegypti develop in fresh water. However, in laboratory studies, tolerance of this species for oviposition and hatching in brackish water was observed. Immature forms of Ae. aegypti have also been found developing in brackish water in coastal areas. The purpose of the study was to compare the effects of salt on the biological cycle of Ae. aegypti populations from coastal and plateau areas of southeastern Brazil.

METHODS

Aedes aegypti were collected from plateau (Taubaté) and coastal (São Sebastião) municipalities to establish colonies. Specimens of the F1 generation were exposed to five salt concentrations (3.5, 7, 10.5, 14 and 17.5%) to assess the oviposition and cycle development from egg hatching to adult eclosion. Deionized water was used in the control groups.

RESULTS

Both Taubaté and São Sebastião populations oviposited in all salt concentrations tested; however, development occurred in all except in the 17.5% concentration. Significant differences in development and adult size were observed at intermediate concentrations (São Sebastião from 10.5% and Taubaté from 7%, for both variables) between the two populations.

INTERPRETATION & CONCLUSION: The results of this study showed different response patterns to salinity between the two populations, suggesting better adaptive adjustment of the coastal population to the metabolic constraints exerted by salt. The implications of this adaptation are discussed, and additional studies are suggested to evaluate the mechanisms that determinate the adaptive processes of Ae. aegypti in brackish water and the implications to its vectorial capacity.