Temperature limits for winter development of Aedes aegypti under natural conditions in a temperate region.

FISCHER, SYLVIA; DE MAJO, MARÍA SOL; MONTINI, PEDRO

Buenos Aires

Simposio; 8°th International Symposium on the Environmental Physiology of Ectotherms and Plants; 2019

Species of tropical origin are limited in their persistence in temperate regions if they lack the ability to survive the low winter temperatures. Most studies on the thermal biology of the mosquito Aedes aegypti (Diptera: Culicidae) have focused on populations from tropical and subtropical regions with low emphasis on the lower temperature limits for development. In recent decades this tropical species has invaded many temperate regions, where it survives the winter season in the egg stage. In Buenos Aires, a temperate climate city, recent studies demonstrated its ability to complete immature development during the winter season. In this study we aimed to assess the mortality of immature stages in response to the low temperature conditions they experience during the winter. The experiment consisted in the rearing of larval cohorts under natural thermal conditions throughout the winter season. Daily mortality of larvae and pupae were calculated, and their association to thermal conditions analyzed. The daily mortality was generally low (less than 1%), and a few high mortality events were recorded, the most important (5.6% during 3 consecutive days affecting especially the pupae) occurred after seven days of low temperatures (minima below 7°C). The mortality showed a closer association to minimum temperatures than to mean or maximum temperatures. The mortality peaks occurred with a delay of 6 days from the beginning of the periods of low temperatures. The results suggest that cold fronts may represent a risk for the immature stages survival during the winter, and that the effects are sublethal, only causing mortality a certain time later if temperatures do not increase enough to allow for the recovery. The higher tolerance to low temperatures compared with other studies suggest that the local population might be adapting to winter conditions.