Mosquitoes are not only annoying, but also dangerous. They can spread deadly diseases such as malaria, yellow fever, dengue, Zika and West Nile through their bites. But how do they find their victims and what makes them prefer some people over others?
Mosquitos can ruin a nice picnic in the park, camping out with your friends, even your own humble abode!
Now Vosshall and her colleagues have discovered what turns on this powerful blood pump. In a study published in Neuron, the team describes a unique group of neurons in the female mosquito’s syringe-like stylet that don’t seem to care about simple tastes like sweet or salty. Rather, they activate only when sugar, salt, and other components of blood are all present at once.
“These neurons break the rules of traditional taste coding, thought to be conserved from flies to humans,” says Veronica Jové, a graduate student in Vosshall’s lab who led the study. “We knew that the female stylet was unique, but nobody had ever asked what its neurons like to taste.”
The researchers tracked the activity of sensory neurons in the insects’ blood-feeding appendage, called the stylet. They found that stylet neurons start to fire in the presence of blood but not when exposed to sugars found only in nectar, such as fructose. The team’s experiments showed that the blood-responsive stylet neurons also become active when exposed to a mixture of four blood ingredients: sodium chloride, glucose, the energy-carrying molecule ATP and blood’s main pH regulator, sodium bicarbonate.
To see what’s special about the combination of these four ingredients, the researchers first tested how mosquito stylets responded to each component. “There are two neat rows of sensory neurons on both sides of the stylet,” Jové says. “We delivered just the tiniest microfluidic drop to the tip of the stylet, and recorded which neurons responded.”
But why do some people attract more mosquitoes than others? One factor is the amount of skin bacteria, which produce body odor. Female mosquitoes are more attracted to people with more skin bacteria, which may indicate a larger or warmer body.
When a mosquito bites, it not only sucks blood but secretes saliva. This saliva enters your blood and causes an allergic reaction that results in itching and swelling. The mosquito saliva also contains anticoagulants that prevent blood clotting and facilitate feeding.
Mosquitoes are not always bloodthirsty, though. Both male and female mosquitoes feed on nectar, plant juices and sugary fluids, but only female mosquitoes need blood for egg production.
So next time you encounter a mosquito, remember that it may be looking for a sweet treat or a protein-rich meal. And if you want to avoid being bitten, try to reduce your skin bacteria and body odor, or use repellents that mask your scent.
Relevant articles:
– TIL that both male and female mosquitoes feed on nectar, plant juices and sugary fluids. The female mosquitoes that feed on human blood are attracted to persons with an abundance of skin bacteria., Reddit, 6 minutes ago
– Taste test: how mosquitoes tell nectar from human blood, Nature, 13 October 2020
– Mosquito Bites: What They Look Like, Why They Itch & Treatment, Cleveland Clinic, no date
– Mosquito ‘tongue’ neurons ignite like fireworks at taste of human blood, Live Science, 15 October 2020.