Adaptive larval thermotolerance and induced cross-tolerance to propoxur insecticide in mosquitoes Anopheles stephensi and Aedes aegypti.

Fourth-instar larvae of mosquitoes Anopheles stephensi and Aedes aegypti normally died within 90 min at 43 degrees C. Pre-exposure to high but sublethal temperatures conferred adaptive thermotolerance, dependent on the temperature and the duration of pre-exposure. Adaptive cross-tolerance to propoxur (a carbamate insecticide) was also induced in larvae by pre-exposing them to sublethal temperatures. Pre-exposure to sublethal concentrations of propoxur was found to confer cross-thermotolerance to a lower extent. These results suggest that the shock proteins (e.g. heat shock proteins) induced by unrelated stress factors play an important role in the development of adaptive cross-protection (stress response) to other stress conditions.