Adaptation and Carry Over Effects of Extreme Sporadic Heat Stress in Culex Mosquitoes

Mosquitoes, as temperature-sensitive ectothermic vectors, exhibit temperature-dependent traits like reproduction and survival. This study investigates Culex pallens (Cx. pallens) mosquito responses to abrupt temperature increases and their implications for mosquito control programs. Cx. pallens first instar larvae (24hr post hatching) and newly enclosed adults (24hr post emergence) were separately exposed to heat shock regimes of 33℃, 37℃, and 42℃ for 3 days alongside a control temperature of 27℃. Results showed that mortality was triggered at 42℃ within a day. Newly enclosed males were less tolerant to all temperatures than larvae and females (p < 0.05. Heat exposure significantly decreased larvae’s development time, growth and adult emergency (p < 0.05). Reproductive fitness was significantly reduced (p < 0.05) in males emerging from larvae exposed to 37℃. Life table parameters showed significantly increased mortality rate, kill power and decreased life expectancy at the embryonic stage (p < 0.05). Sporadic heat deactivated the Transient receptor protein ankyrin 1 at 37℃ (p < 0.05) in larvae but not adults. Calmodium, Heat shock protein 90, and small heat shock protein expression was significantly decreased in larvae at 37℃ (p < 0.05) as compared to larvae raised at 33℃ and 27℃. In conclusion, we classified the heat waves into three categories: adaptable (33℃), critical (37℃), and fatal (42℃). Prolonged exposure of Cx. pallens larvae to heat affects the male reproductive output. These findings may serve as an important reference for forecasting vector and pest dynamics. They can be used to tailor mosquito prevention and control measures.