Do Mosquitoes Sleep?

Abstract

Sleep is a phenomenon conserved across the animal kingdom, where studies on Drosophila melanogaster have revealed that sleep phenotypes and molecular underpinnings are similar to those in mammals. However, little is known about sleep in blood-feeding arthropods, which have a critical role in public health as disease vectors. Specifically, sleep studies in mosquitoes are lacking despite considerable focus on how circadian processes, which have a central role in regulating sleep/wake cycles, impact activity, feeding, and immunity. Here, we review observations which suggest that sleep-like states likely occur in mosquitoes and discuss the potential role of sleep in relation to mosquito biology and their ability to function as disease vectors.

Keywords: circadian rhythms; mosquito biology; mosquitoes; sleep; vectorial capacity.

Figure 1.. Resting (sleep-like) and active (awake) states are associated with stereotypical postures.

(A) Illustration of posture changes associated with resting (Left) and active states (Right) in 5-day-old Aedes aegypti females. The angular differences between the main body axis (red line) and the main axis of the tarsomeres (blue line) were quantified in Fiji (NIH-NIAID). (B) Principal component analysis of posture metrics (elevation of the tip of the hind legs, hind leg - abdomen angle, distance between the thorax and the substrate), revealed a clear clustering of resting (blue) and active (orange) postures, classified according to [23] (Fuzzy clustering analysis, Dunn-coefficient = 0.85). Protocols for analyses are included in the supplemental Box S1.

Figure 2.. Identification of putative resting/sleep-like state genes in mosquitoes.

(A) Orthology analysis between mosquito genes sets and those associated with sleep processed in Drosophila. (B) Re-analysis of previous circadian rhythm expressional studies in heads of Aedes aegypti [24] and Anopheles gambiae based correlation in expression profiles to periods of high and low activity [25]. Scale in red is high correlation and blue is low correlation. Full comparative analyses are found in supplemental Figure S1 and Figure S2. Details on the protocols used in analyses and complete module assignments are included in the supplemental Box S2.

Figure 3.. Summary of factors indicative that the resting period is likely a sleep-like state in Aedes aegypti based on previous studies and our novel interpretation.

Front four legs are not included to emphasize positional changes in body and rear legs and details based on [–25].