Mosquitoes have clever neurological wiring to detect humans

I’m told that mosquitoes initially detect humans by the carbon dioxide emitted from their mouths. When you blow a waft of carbon dioxide over mosquitoes in a container, they go wild and start buzzing around trying to target a human which they zone in on by their body odour. And the conclusion of recent research published in the journal Cell and conducted by Margot Herre and Meg Younger , a neuroscientist at Boston University and a co-author of the study (and colleagues), is that mosquitoes have clever neurological wiring which appears to be more advanced than that of mice and fruit flies.

Meg Younger, a neuroscientist at Boston University, and her colleagues discovered that a mosquito's sense of smell is more complex than we'd thought.
Meg Younger, a neuroscientist at Boston University, and her colleagues discovered that a mosquito’s sense of smell is more complex than we’d thought. Photo: Ari Daniel/NPR.

In the words of the scientists:

“Mosquitoes are intensely attracted to body odor and carbon dioxide, which they detect using ionotropic chemosensory receptors encoded by three large multi-gene families.”

Most of what scientists know about the neuroscience of smell comes from research on mice in fruit flies in which the neurological wiring is quite simple. Each neuron in the nose or antenna has one kind of receptor which detects a single kind of odour.

The researchers found that if they chemically knocked out the smell receptors that spotted humans, the mosquitoes were still able to rapidly detect them. Meg Younger said that the reason for this is because: “The same neuron can respond to different odours. If you remove one receptor, the neuron still responds to the odours that the other receptor detects”.

Mosquitoes have clever wiring to detect humans
Mosquitoes have clever wiring to detect humans. Image: the study referred to at the base of the page.

In the language of the scientists:

“We discovered that Ae. aegypti uses a different organizational principle, with many neurons co-expressing multiple chemosensory receptor genes.”

In short, they have failsafe systems to back up their standard systems. Like I said it’s cleverer than the odour detecting systems of fruit flies. Margot Herre said: “We were really curious about what are the neurons and the parts of the brain that mosquitoes use to smell people. As we started to dig in more, we quickly realised that the mosquito smell system is not playing by the rules that the smell systems have in more well studied organisms.”

As I understand it, the underlying reason for their research was to protect people from mosquito bites by knocking out their odour detecting systems. They’ve currently failed for the reason stated. Mosquitoes spread malaria and dengue and as we know have an enormously negative impact on humans in many countries.

Josefina del Marmol, a molecular neurobiologist at the Harvard Medical School who was not involved in the research applauded the finding and said: “It really does change a lot about what we know of how insects perceive the world. It’s a lot more complex than we thought.”

Study title: Non-canonical odor coding in the mosquito.

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Post Category: Insects