Study of Aedes albopictus Hatching Rate by Low-Temperature Stress

Abstract

Aedes albopictus overwinters as eggs and lays diapause eggs under conditions of low temperatures, low humidity, and short photoperiods. We compared the hatchability of diapause and nondiapause eggs in response to cold stress. Nondiapause eggs were acquired at 27°C ± 1°C, 70% ± 5% humidity, and 16:8 (L:D) photoperiod, and diapause eggs were acquired at 21°C ± 1°C, 40% ± 5% humidity, and 8:16 (L:D) photoperiod. The obtained eggs were dried under the same conditions and then exposed to low-temperature stress for each temperature and time. After that, eggs were transferred to a thermostat to induce hatching at room temperature, and the hatching rate and the time required for hatching were measured and analyzed by two-way ANOVA and multiple regression analyses. When exposed to low temperatures for 1–24 h at a temperature of 0°C to −10°C, the diapause eggs had a hatching rate higher than that of nondiapause eggs in all sections. The difference in hatching rate according to temperature, exposure time, and diapause status was all considered significant at −6°C or less (two-way ANOVA). A significant regression equation was calculated to estimate the hatching rate, a dependent variable (R² = 0.439, p < 0.000). We found a significant difference in hatching rates for low-temperature stress between diapause eggs and nondiapause eggs of Ae. albopictus, which may explain why Ae. albopictus spreads in high-latitude regions. The morphological differences between diapause and nondiapause and variables such as dryness and light intensity should be studied to understand the overwintering of Ae. albopictus.