Mosquitoes routinely risk their lives to feed on human blood. However, it is more than just a mechanic, instinctive impulse that drives this behavior. Mosquitos love the taste of human blood so much that neurons connected to its syringe-like tongue explode like fireworks. The behavior is also exclusive to females, and it is driven by the need to nourish their eggs as they develop. When they are not nurturing their eggs, they will feed on flower nectar.
In order to better understand why mosquitoes feed on human blood, scientists used a genetically modified genus of the Aedes aegypti mosquito species, whose taste-related neurons emit fluorescent lighting whenever they are activated. Using fluorescent microscopy, the researchers were then able to detect which neurons were firing as the mosquitoes fed on human blood and other liquids.
Scientists who research the behavior of mosquitoes will usually allow the mosquitoes to bite them. However, for this study, the researchers used a device known as a biteOscope, which was designed by another team, and which consists of a small open platform that has a membrane over several pockets that have liquid inside them. The biteOscope basically mimics a skin-covered host and it allows scientists to collect data on mosquito feeding behavior without having to use humans as subjects in the tests.
By using this device and the genetically modified mosquitoes, scientists were able to observe the neuronal activity in the mosquito beaks as the insects approached blood, nectar, and a blood-like solution made from sodium bicarbonate, sodium chloride and glucose, in concentrations that mimicked the blood values of vertebrate species. The blood-like solution also contained adenosine triphosphate (ATP) which is a chemical compound that is found in blood, and which transfers energy to the cells through which the blood travels. Previous studies have shown that ATP is attractive to mosquitoes.
Interestingly, the neuron’s in the mosquito’s stylet flared up only in the presence of blood and the lab-made blood-like substance. Scientists were still not certain what blood tasted like to mosquitoes however. Is it sweet, is it salty? This is because ATP has no taste to us, and that is the component that attracts mosquitoes to our blood.
While we do not share the mosquitoes attraction to ATP, both our species have an appreciation for salty tastes. We perceive the salt flavour of the chemical sodium chloride, which is present in our blood and the synthetic blood used during the experiment.
Understanding why human blood is so attractive to mosquitoes could be the first step in developing products that reduce our appeal to mosquitoes. It could also help scientists stop the spread of diseases such as Zika and dengue, which mosquitoes transmit by feeding on people who have been infected. On a global scale, this could lead to a considerable decrease in mortality and, not to mention, suffering. Of course, if we could remove the nuisance of being bitten by a mosquito, it would be a nice, little extra
