Ella Girard

Abstract Humidity levels, like light and temperature, fluctuate daily yet are less predictable; however, whether humidity can entrain circadian clocks and synchronize animal behaviors with environmental variations remains unknown. Here, we investigate the circadian humidity entrainment in various insects across multiple orders. Insect species respond to humidity cycles with distinct patterns, some active during wet periods or at the arid-humid transition. When the humidity cue is removed, most species continue to show rhythmic activity associated with the previous arid-humid (AH) cycles. Fruit flies shift their activity accordingly when humidity cycles are altered and remain in the new rhythms under the following free-running conditions (FRC; constant humidity, HH). Moreover, Drosophila clock and hygrosensation mutants lack rhythmic activity during (AH) and after humidity entrainment (FRC with HH), indicating that core clock components and hygrosensors are essential for circadian entrainment. Our findings provide strong evidence that humidity is likely to serve as a potential zeitgeber for circadian entrainment in most, but not all, insect systems and will likely have broad applicability and importance across animal systems. While light and temperature act as the primary zeitgebers, understanding the mechanisms of humidity entrainment will help us better interpret the behavioral patterns of terrestrial animals, particularly those susceptible to dehydration. One Sentence Summary: Humidity entrainment of the circadian clock synchronizes insect activity to environmental changes.

Abstract Mosquito-borne diseases have caused more than one million deaths each year. There is an urgent need to develop an effective way to reduce mosquito-host interaction to mitigate disease transmission. Sugar diets have long been linked to abnormal physiology in animals, making them potential candidates for mosquito control. Here, we show the impact of sugar diets on humidity preference and survival in Aedes aegypti and Culex pipiens . With two-choice assays between 100% and 75% relative humidity (RH), we demonstrate that the effect of sugar diets on humidity preference is species-specific where Ae. aegypti showed significant differences and the reduced effects were noted in Cx. pipiens . Among the sugar diets, arabinose significantly reduced the survival rate of mosquitoes even at low concentrations. Moreover, we found that host landing was not impacted by feeding on different sugar types. Our study suggests that specific sugar treatments could be applied to mosquito control by dampening their humidity preference and reducing their lifespan, thus reducing mosquito-borne disease transmission.

Mosquito-borne diseases have caused more than 1 million deaths each year. There is an urgent need to develop an effective way to reduce mosquito-host interaction to mitigate disease transmission. Sugar diets have long been linked to abnormal physiology in animals, making them potential candidates for mosquito control. Here, we show the impact of sugar diets on humidity preference and survival in Aedes aegypti (Gainesville) and Culex pipiens (Buckeye). Two-choice assays with high and low relative humidity (80% and 50% RH) show that the impact of sugar diets on humidity preference is species-specific. In comparison to Cx. pipiens, various sugar diets resulted in marked reductions in humidity avidity and preference in Ae. aegypti, which exhibited significant differences. Among the sugar diets, arabinose significantly reduced the survival rate of mosquitoes at low concentrations. Moreover, we found that host landing was not impacted by feeding on different sugar types. Our study suggests that specific sugar treatments could be applied to mosquito control by dampening their humidity preference and reducing their lifespan, thus reducing mosquito-borne disease transmission.