Intra-species quantification reveals differences in activity and sleep levels in the yellow fever mosquito, Aedes aegypti.

Aedes aegypti is an important mosquito vector of human disease with a wide distribution across the globe. Climatic conditions and ecological pressure drive differences in the biology of several populations of this mosquito species, including blood-feeding behaviour and vector competence. However, no study has compared activity and/or sleep among different populations/lineages of Ae. aegypti. Having recently established sleep-like states in three mosquito species with observable differences in timing and amount of sleep among species, we investigated differences in activity and sleep levels among 17 Ae. aegypti lines drawn from both its native range in Africa and its invasive range across the global tropics. Activity monitoring indicates that all the lines show consistent diurnal activity, but significant differences in activity level, sleep amount, number of sleep bouts and bout duration were observed among the lines. The variation in day activity was associated with differences in host preference and ancestry for the lineages collected in Africa. This study provides evidence that the diurnal sleep and activity profiles for Ae. aegypti are consistent, but there are significant population differences for Ae. aegypti sleep and activity levels and interactions with host species may significantly impact mosquito activity.

Humidity as a zeitgeber for circadian entrainment of insect systems.

Humidity levels, like light and temperature, fluctuate daily yet are less predictable; however, whether humidity entrains circadian clocks and enables animals to synchronize behaviors to environmental variations remains unknown. Here, we investigate the circadian humidity entrainment in various insects. Multiple species robustly respond to humidity cycles, and when the humidity cue is removed, their rhythmic behaviors continue, suggesting that humidity-associated rhythmic activities are under circadian control. Moreover, the Drosophila clock and hygrosensation mutants lack rhythmic activities during and after humidity entrainment, indicating that the core clock components and hygrosensors are essential to circadian entrainment. Our findings identify that humidity serves as a novel zeitgeber for circadian entrainment for insects that could have broad applicability and importance among animal systems. One Sentence Summary: Humidity entrainment of the circadian clock enables the synchronization of insect behaviors to environments.