You Can Teach Mosquitoes to Fear Your Smell so They Will Avoid You

  

It had been clear that mosquitoes don’t decide whom to bite at random. They show obvious preferences for some people over others. They are also known to alternate hosts seasonally, feeding on birds in the summer and mammals and birds during other parts of the year, for instance. Riffell and his colleagues wanted to find out more about how learning might influence mosquitoes’ biting preferences.

As a first step, they trained mosquitoes by pairing the odor of a particular person or animal species (a rat versus a chicken) with a mechanical shock. For the mechanical shock, they used a vortexer machine to simulate the vibrations and accelerations a mosquito might experience when a person tried to swat them. The insects quickly learned the association between the host odor and the mechanical shock and used that information in deciding which direction to fly. (Interestingly, they couldn’t learn to avoid the smell of a chicken.)

Learning in many animals, from honeybees to humans, depends on dopamine in the brain. Additional study showed that dopamine is also essential in mosquito learning. Genetically modified mosquitoes lacking dopamine receptors lost the ability to learn.

The researchers also glued mosquitoes to a custom 3D-printed holder that allowed the insects to still fly in place while the activity of neurons in the olfactory center of their brains was recorded. Those experiments showed that without dopamine, those neurons were less likely to fire. As a result, mosquitoes became less able to process and learn from odor information.

The findings may have important implications for mosquito control and the transmission of mosquito-borne diseases, according to the researchers.

“By understanding how mosquitoes are making decisions on whom to bite, and how learning influences those behaviors, we can better understand the genes and neuronal bases of the behaviors,” Riffell says. “This could lead to more effective tools for mosquito control.”

With this new understanding of how mosquitos learn to avoid certain hosts, the researchers say they are now exploring mosquitoes ability learn and remember favored hosts. “In both cases, we think dopamine is a critical component,” Riffell says.

Researchers acknowledge the support of the Air Force Office of Sponsored Research, the National Institutes of Health, the National Science Foundation, UC Riverside, MaxMind, an Endowed Professorship for Excellence in Biology, the University of Washington Institute for Neuroengineering, and the Human Frontiers in Science Program.

Contacts and sources:
Joseph Caputo
Cell Press