Circadian Rhythms Could Control Malarial Mosquitoes

Mosquitoes, like all animals, show daily rhythms in behavior and physiology. The rhythmic behaviors of Anopheles gambiae - the mosquito species that transmits the malaria parasite from person to person - include dusk mating swarms, nocturnal flight activity and feeding on sugar and blood-meal hosts and egg-laying.

Now, Notre Dame researchers, led by principal investigator Duffield, have undertaken a gene expression analysis of adult female Anopheles gambiae, which were sampled every four hours over a 48-hour period under both environmental light-dark cycles and under constant dark conditions.

A total of 2,095 genes were discovered to be rhythmic in either the mosquito head or body and under diel - a regulation controlled by the daily alternating light-dark cycle - and/or circadian control - daily 24-hour rhythmic cycles regulated by an organism's internal molecular clock.

Interestingly, it was found that circadian control amounts to nearly 16 percent of the Anopheles gambiae geneome.

Their data on rhythms of the mosquito's immune system highlight the likelihood for Anopheles gambiae to exhibit rhythms in sensitivity to chemical insecticides, such as pyrethroids and DDT, which is an important finding for maximizing exposure of the mosquito to insecticides in relation to the time of day when they may be most susceptible.

These rhythms, can also contribute to the time-of-day specific host-seeking behavior of Anopheles mosquitoes, and raises the possibility that mosquitoes may not bite humans during the daylight hours simply because they do not detect their presence during this time.

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The study has been published in the Proceedings of the National Academy of Sciences.

Source-ANI