Abstract
The Asian tiger mosquito, Aedes albopictus, is a highly invasive mosquito species that transmits chikungunya and dengue. This species overwinters as diapausing eggs in temperate climates. Early diapause termination may be a beneficial strategy for winter mosquito control; however, a mechanism to terminate the diapause process using chemicals is not known. We tested the hypothesis that a hormonal imbalance caused by the administration of juvenile hormone analog would terminate egg diapause in A. albopictus. We tested the insect growth regulator pyriproxyfen on all developmental stages to identify a susceptible stage for diapause termination. We found that pyriproxyfen treatment of mosquito eggs terminated embryonic diapause. The highest rates of diapause termination were recorded in newly deposited (78.9%) and fully embryonated (74.7%) eggs at 0.1 and 1 ppm, respectively. Hatching was completed earlier in newly deposited eggs (25–30 days) compared to fully embryonated eggs (71–80 days). The combined mortality from premature diapause termination and ovicidal activity was 98.2% in newly deposited and >98.9% in fully embryonated eggs at 1 ppm. The control diapause eggs did not hatch under diapausing conditions. Pyriproxyfen exposure to larvae, pupae and adults did not prevent the females from ovipositing diapausing eggs. There was no effect of pyriproxyfen on diapausing egg embryonic developmental time. We also observed mortality in diapausing eggs laid by females exposed to pyriproxyfen immediately after blood feeding. There was no mortality in eggs laid by females that survived larval and pupal exposures. In conclusion, diapausing eggs were the more susceptible to pyriproxyfen diapause termination compared to other life stages. This is the first report of diapause termination in A. albopictus with a juvenile hormone analog. We believe our findings will be useful in developing a new control strategy against overwintering mosquito populations.
Highlights
The Asian tiger mosquito, Aedes albopictus, is one of the world’s worst invasive species [1]
Aedes albopictus eggs from a laboratory colony maintained under non-diapausing conditions (26 ± 2°C, 65% RH and 16L:8D photoperiod) [28], were hatched in dechlorinated tap water in 2L enamel trays
Eggs in diapause are not expected hatch under diapausing conditions (8L:16D photoperiod and 21°C); if we observed eggs hatching under these conditions we considered them to have experienced diapause termination
Summary
The Asian tiger mosquito, Aedes albopictus, is one of the world’s worst invasive species [1]. This mosquito is prevalent worldwide and transmits chikungunya and dengue viruses in Asian, African and European countries [2,3,4]. One factor contributing to A. albopictus establishment into new areas is a specialized egg with a thick eggshell that is desiccation tolerant [8,9] and ability to enter diapause [10]. The ability of diapause eggs to survive harsh temperate conditions may have facilitated A. albopictus range expansion [14,15,16]
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