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

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

Buenos Aires

Simposio; 8th International Symposium of the environmental physiology of ectotherms and plants; 2019

Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires

Species of tropicalorigin are limited in their persistence in temperate regions if they lack theability to survive the low winter temperatures. Most studies on the thermalbiology of the mosquito Aedes aegypti(Diptera: Culicidae) have focused on populations from tropical and subtropicalregions with low emphasis on the lower temperature limits for development. Inrecent decades this tropical species has invaded many temperate regions, whereit survives the winter season in the egg stage. In Buenos Aires, a temperateclimate city, recent studies demonstrated its ability to complete immaturedevelopment during the winter season. In this study we aimed to assess themortality of immature stages in response to the low temperature conditions theyexperience during the winter. The experiment consisted in the rearing of larval cohorts under natural thermal conditionsthroughout the winter season. Daily mortality of larvae and pupae werecalculated, and their association to thermal conditions analyzed. The dailymortality was generally low (less than 1%), and a few high mortality eventswere recorded, the most important (5.6% during 3 consecutive days affectingespecially the pupae) occurred after seven days of low temperatures (minimabelow 7°C). The mortality showed a closer association to minimum temperaturesthan to mean or maximum temperatures. The mortality peaks occurred with a delayof 6 days from the beginning of the periods of low temperatures. The resultssuggest that cold fronts may represent a risk for the immature stages survivalduring the winter, and that the effects are sublethal, only causing mortality acertain time later if temperatures do not increase enough to allow for therecovery. The higher tolerance to low temperatures compared with other studiessuggest that the local population might be adapting to winter conditions.