from the too-late-for-agent-pleakley dept.
Common wisdom is that mosquitoes use multiple methods to home in on their prey, including Carbon Dioxide in respiration and detection of body heat. Now, in a paper published in the journal Science, researchers describe the underlying temperature detection mechanism used, and interestingly it isn't a heat-seeking mechanism, but rather a cold-avoiding one.
[...] Last year, [professor of biology Paul Garrity, Ph.D.] and several colleagues published a paper in the journal Neuron that upended the conventional thinking about the temperature-sensing receptors at the tip of flies' antennas.
Traditionally, these receptors were thought to act like thermometers, taking the temperature of the surroundings to let the fly know if the environment is hot or cold. Instead, Garrity and his colleagues found that the receptors only detected whether the temperature was changing, letting the fly know if things were getting hotter or colder.
For this reason, Garrity renamed these temperature sensors the Cooling Cells and Heating Cells. They're so sensitive they can detect a few hundredths of a degree change in temperature per second.
Mosquitoes, who are close evolutionary relatives of flies, also have Cooling Cells and Heating Cells.
While it would seem to make sense to look at the insects' heating cells to understand what draws them to human warmth, Garrity's group considered an alternative —- and counterintuitive —- hypothesis. Maybe it wasn't that the insects were flying toward the heat; maybe they were flying away from the cold. This would mean the Cooling Cells would be the ones to focus on.
The specific Cooling Cells Garrity and his fellow scientists studied for their paper in Science rely on a molecular receptor called IR21a. IR stands for ionotropic receptor, a group of proteins that help neurons to transmit signals. IR21a facilitates the transmission of a signal that the temperature around the insect is falling.
Here is a YouTube video comparing the ability of mosquitoes with and without the IR21a receptor to find a human temperature surface.
According to Garrity, the IR21a receptor is activated whenever mosquitoes move toward a cooler temperature. Since humans are usually warmer than their surroundings, this means that as a mosquito is approaching a human, IR21a is silent. But if the animal should deviate from its course and start to move away from its warm-blooded prey, IR21a becomes activated, only shutting off once the insect course-corrects.
Garrity said IR21a seems to act like "an annoying alarm. It goes off whenever the female mosquito heads towards cooler climes. When they are seeking humans, they seem to be driven to do whatever it takes to turn down the sound."
Now let's figure out how to hit 'snooze'.