Mosquito species have clear biting times. The US Centers for Disease Control and Prevention notes that, “Most Anopheles mosquitoes are crepuscular (active at dusk or dawn) or nocturnal (active at night).” Das and Dimopoulos studied one of the most common malaria vectors in Africa and explain that, “Anopheles gambiae mosquitoes exhibit an endophilic (after blood feeding, prefer to rest indoors), nocturnal blood feeding behavior. CDC says that insecticide treated bednets are especially helpful in reducing bites from these night time feeders.
But can mosquitoes tell time? Foster and Kreitzman have written in the Rhythms of Life and “describe how organisms measure different intervals of time, how they are adapted to various cycles, and how light coordinates the time within to the external world.” They review the implications of the ‘biological clock’ for humans but also explain that, “it has played an essential role in evolution and … continues to play a vitally important role in all living organisms.”
In reviewing Rhythms of Life, Harman describes how an understanding of the genetics of time works: “a clock can be constructed of a gene that codes for a protein which acts to inhibit its own production, and a second protein that delays this self-inhibition by a reliable amount of time.” Harman explains that, “the light/dark cycle, provid(es)the crucial link between inner (genetic) and outer worlds,” or an organism.
Das and Dimopoulos studied night time mosquito feeding behavior after exposure to light pulses. They found that “The temporary feeding inhibition after short light pulses may reflect a masking effect of light, an unknown mechanism which is known to superimpose on the true circadian regulation. Nonetheless, the shorter light pulses resulted in the differential regulation of a variety of genes including those implicated in the circadian control, suggesting that light induced masking effects also involve clock components. Light pulses (both short and long) also regulated genes implicated in feeding …”
What can be done with the finding that shows “that the mosquitoâ€™s feeding behavior is under circadian control?” Bringing light pulses to the rural Africans may not be feasible, but understanding the genetics behind feeding behavior can have important implications for the development of future mosquito control technologies. As we’ve mentioned many times before, research is continually needed to understand all aspects of malaria transmission since it is not safe to rely on only one tool to eliminate malaria. More funding for malaria research would certainly make 2009 a ‘happy’ new year.