Comparison between summer and autumn eggs of an Aedes aegypti (Diptera: Culicidae) population in temperate Argentina

Abstract

In temperate regions, the survival of Aedes (Stegomyia) aegypti (L.) populations during the unfavourable cold season depends on the ability of eggs to overwinter and produce viable larvae the following spring. This strategy would involve changes in egg traits depending on when they are laid. The present study aimed to assess differences in some traits of eggs laid in the field in summer and autumn in the temperate region of Argentina. The traits compared were egg survival, spontaneous hatching, hatching response, developmental time until adult emergence and wing length of emerged adults. Eggs laid in summer and autumn were collected in the field and stored under constant temperature (15°C) and photoperiod (12L:12D) for 124 days (storage period). All eggs were 2–9 days old at the time of storage. At the end of the storage period, eggs were immersed for hatching at constant temperature (23°C) and photoperiod (12L:12D). After hatching, larvae were reared until adult emergence in a thermal bath at constant temperature (23°C) and photoperiod (12L:12D), and fed ad libitum. Eggs laid in autumn showed higher survival, lower proportion of spontaneous hatching and lower hatching response than did eggs laid in summer. Adults from eggs laid in autumn had longer wings and shorter developmental time than those from eggs laid in summer. Our results suggest that in Ae. aegypti the strategy to deal with seasonality affects various offspring traits.