The extreme sensitivity of some mosquito species when chasing humans may be due to their sophisticated olfactory system with built-in support for detecting human odors.
Mosquitoes can detect carbon dioxide or sweat released from humans using unique chemical receptors on their antennae and mandibles, which are an elaborate sensory accessory for insects.
A new study led by researchers at Boston University and Rockefeller University explains why mosquitoes are so good at sensing us, even though the researchers genetically disabled human chemical receptors.
According to the study, at least one species of mosquito, Aedes aegypti, has a completely different way of regulating its olfactory system than most animals.
Using CRISPR as a gene editing tool, researchers have developed mosquitoes whose olfactory neurons can express fluorescent proteins and glow under the microscope when certain odors are nearby. This allowed the researchers to see how different scents stimulate the olfactory system.
It turns out that A. aegypti connects multiple olfactory sensory receptors to a single neuron, a process called co-expression.
According to the team, this ignores a basic principle of the science of olfaction, which states that each neuron has only one chemical receptor attached to it.
“It was surprisingly strange, not what we expected,” said Boston University neuroscientist and lead author Meg Younger.
“The central dogma of the sense of smell for us is that the sensory neurons in our nose express some type of olfactory receptor,” says Younger.
This axiom applies to honey bees (Apis mellifera), tobacco hornworms (Manduca sexta) and fruit flies (Drosophila melanogaster), all of which contain about the same number of chemosensory receptors as olfactory glomeruli. (Glomeri are spherical structures in the brain that receive olfactory signals.)
The researchers write that A. aegypti has at least twice as many receptors as glomeruli, a “stunning mismatch”.
The results indicate the existence of an atypical olfactory system containing multiple sensory receptors on individual neurons.
“The redundancy provided by the olfactory system may increase the robustness of the mosquitoes’ olfactory system and may explain our long-term inability to impair mosquito detection by humans,” the authors wrote.
The long-term goal of the research is to create an advanced mosquito repellent that generates attractants that effectively mask human odor or repel mosquitoes from their food.
This article was published in: Cell.
Source: Science Alert
Source: Arabic RT
