Role of circadian rhythms in the host seeking initiation and feeding behaviour of day and night biting mosquitos-a brief review

Mosquitoes exhibit daily rhythms in their host-seeking and feeding behaviours that are driven by internal circadian clocks. This review examines how circadian clock genes and their molecular outputs regulate the timing of host-seeking flights and the duration of blood-feeding bouts, comparing night-biting vs. day-biting mosquito species. Mosquito species exhibit diverse circadian activity patterns, including diurnal, nocturnal, and distinctly crepuscular behaviours, reflecting adaptations to specific ecological and physiological constraints. Underlying these differences are circadian oscillators composed of clock genes (including clock, cycle bmal1, period, timeless, and cryptochrome variants) that drive daily rhythms in behaviour and physiology. We discussed evidence that night-biting mosquitoes have circadian peaks in clock gene protein levels (such as PERIOD) at dusk, aligning with nocturnal activity, whereas day-biters show anti-phasic peaks around dawn, aligning with diurnal feeding times. These molecular rhythms influence sensory physiology (e.g. olfactory sensitivity) and motivation to seek hosts, thereby gating feeding to optimal times of day. Circadian control may also affect the duration of feeding bouts: day-biting mosquitoes often take shorter, more frequent blood meals (due to host defences and physiological drive), whereas nocturnal mosquitoes feed to repletion in one bout on a sleeping host. We highlight recent studies showing that genetic disruption of clock components (e.g. cycle or neuropeptide pigment-dispersing factor (PDF)) alters the daily timing and persistence of host-seeking and biting behaviour. Understanding how internal clocks regulate mosquito feeding provides insight into vector–host interactions and suggests novel avenues for mosquito control by targeting circadian processes.