Temperature and photoperiod differentially impact maternal phenotypes in diapause egg-laying Aedes albopictus mosquitoes

Abstract

BackgroundAedes albopictus (Skuse 1894) mosquitoes can transmit deadly arboviruses and are globally invasive due to their ability to survive in both tropical and temperate climates. Although adults cannot survive harsh winters, females are capable of anticipating seasonal change and producing overwintering diapause (DP) eggs that remain in a state of arrested development over the winter and hatch when favorable conditions return in the spring. Previous work has shown that shortening photoperiod (day length) alone is sufficient for DP induction. While decreasing temperatures can facilitate DP entry, temperature signals alone are not sufficient to induce DP. Methodology/Principal FindingsTo identify maternal phenotypes predictive of DP egg production, we characterized aspects of maternal physiology and behavior to identify those that correlate with DP egg production and changes in photoperiod, versus changes in temperature. Neither changes in temperature nor photoperiod impacted protein preference, blood meal consumption, or total number of eggs produced per female. Egg retention and oviposition timing were influenced by temperature, independent of DP egg production. However, females housed under short photoperiod conditions showed increased starvation resistance, despite showing similar levels of locomotor activity and internal stores of triacylglycerols, glucose, glycogen, and trehalose compared to females housed in long photoperiods. Conclusions/SignificanceThese results suggest that temperature and photoperiod differentially affect maternal phenotypes and identify starvation resistance as a maternal phenotype that is influenced by photoperiod and can be used to predict DP egg status. AUTHOR SUMMARYAedes albopictus mosquitoes can survive in temperate climates because females are able to detect changes in temperature and day length in the autumn to produce "diapause" eggs that are provisioned with extra nutrients to survive harsh winters by remaining in a state of arrest and hatching in the spring. Although temperature and day length normally change in concert with each other throughout the year, studies have shown that day length is the most important cue used by female mosquitoes to initiate diapause egg production. In this study, the authors examined aspects of feeding and reproduction to determine which of these correlated with day length. Many aspects of reproduction were influenced by temperature; however, housing female mosquitoes under autumn-like short day conditions led to increased starvation resistance. Surprisingly these females survive longer even though they do not appear to expend less energy compared to females housed in spring-like long day conditions at the same temperature. This suggests that the mosquito mothers undergo changes in their metabolism that can be used predict whether she will produce eggs that can survive the winter. This new knowledge may lead to new targets to disrupt seasonal reproduction in mosquitoes and limit the parts of the world where they can survive.