Carbon dioxide lovers

Scientists have determined what mosquitoes love in humans

Biologists had to study the small malaria mosquito more carefully than many mammals. After all, this insect is one of the main enemies of humanity, and without it, our lives would be much safer. But it turns out that even in the structure of this long-time acquaintance it is sometimes possible to detect “white spots”. Specialists from the American University of Vanderbilt (Tennessee) managed to determine the mechanism of operation of the sensors with which mosquitoes find their prey.

In fact, insects in general and mosquitoes in particular have quite a lot of sense organs. For example, olfactory antennae located on the front of the head or a proboscis, which can detect both smells and taste. There are also maxillary tentacles, which researchers paid attention to. It is they, according to the study, who recognize the “aroma” of a person. There are three types of sensory cells on the tentacles: some detect the presence of carbon dioxide, others are responsible for octenol (a special substance contained in human sweat), and others are used to improve the olfactory picture.

Apparently, octenol is one of the main signals that allows mosquitoes to determine the direction to the victim. A similar pattern was previously found in another species of mosquito, Aedes aegypti. These insects carry rarer, but no less serious diseases - yellow fever and dengue fever. It has been suggested that understanding how mosquitoes' targeting systems work could help fight infections. Perhaps in the future it will be possible to develop powerful repellents that act specifically on this part of the insects' sense of smell. But this is still a long way off.

However, mosquitoes are not the only living carbon dioxide detectors. For example, fruit flies, using such sensors, are also able to find the most attractive food for themselves. This property was discovered by scientists from the University of California at Berkeley. The smell (or in this case, rather the taste) of carbon dioxide signals insects that there is decaying organic material nearby for yeast to work with. These microorganisms, which trigger the fermentation process, release carbon monoxide into the air.

In fact, insects sense not only carbon dioxide, but also ordinary sugar. And, as the Berkeley researchers note, carbon dioxide is most likely used by flies as a “flavor enhancer.” And in order to prove sensitivity to carbon monoxide, the experimental program had to “turn on” and “turn off” the corresponding sensors for a long time.

The researchers paid attention to neurons of the E409 class, located on the upper lip of flies. They were believed to be responsible for sweet or bitter taste. However, it turned out that the signal from them goes to other parts of the insects’ brain. Then experiments were started with various substances, after which it turned out that neurons react more actively to those substances that contain a lot of carbon monoxide. Thus, nervous excitement increased sharply in the presence of beer, yeast, and even plain carbonated water. There was no such reaction on substances without carbon dioxide. Finally, it turned out that if these neurons in flies are completely “turned off,” then solutions with carbon dioxide lose their attractiveness to insects.

It is very interesting that with carbon dioxide in fruit flies, everything happens according to the well-known joke: they love to eat it, but they don’t. The fact is that they do not like the smell of carbon monoxide, and high concentrations of this gas in the air scare them away. But its presence in food, on the contrary, is clearly attractive to flies.

Mikhail MANSKOY