Biology: Mites live and die in the pores of the face

The little creatures live so isolated and incestuous on their faces that they “approach permanent existence with humans”. A study by an international research team with the participation of the University of Vienna was published in the journal Molecular Biology and Evolution.

Due to their very special way of life in human facial skin, microscopically small mites “Demodex folliculorum” have developed into such simplified organisms that they could soon become one with humans, claims a research team led by Alejandro Manzano Marin of the Center. for Microbiology and Environmental Sciences of the University of Vienna in the show. With an international team, he sequenced and analyzed the genome of small animals.

“Become active at night for mating”

Unlike “normal parasites”, human skin animals do not have to find new hosts because mothers reliably transmit them to their children. “I think it happens when you breastfeed because the temperature and humidity are elevated,” says Marin. Almost everyone wears such mites and feeds them with their sebum, which the cells on the face and nipples secrete into the pores.

Close the pores of the face with mites

University of Reading

Close-up of mites in human facial pores

“They become active at night to mate,” said the research team. They are awakened by the human sleep hormone melatonin, which is released into the skin at dusk and makes small invertebrates like these mites nocturnal. They can no longer produce it on their own because they have lost the gene for it, as well as the one that could wake them up in daylight. The latter is an advantage because they also do not have UV protection.

Mites stick to facial hair during sex

This “genetic reduction” is probably a consequence of their isolated existence in human pores, where they are not exposed to any external threat, do not have to compete with other parasites and do not encounter other mites with which they could exchange genes, ie. biologists explain. Thus, they became extremely simple organisms with tiny legs that move only three single-celled muscles.

The undiminished mite genes ensure that the male’s penis protrudes upwards, which means that they must be placed under the female during mating and both hold on to human hair during sexual intercourse, Viennese researchers report their observations. Oral organs that protrude especially strongly make it easier for them to eat.

A man’s regular guest

The study also refutes the previous assumption of colleagues that mites have no way out for digestive waste (anus) and accumulate feces in the body until they are released after death, causing skin inflammation. “A new study confirms that they have an anus and are therefore wrongly considered responsible for many skin diseases,” the scientists write.

According to Viennese researchers, small animals are currently likely on an evolutionary step from parasites to “harmless, permanent symbionts” that may or may not offer humans any benefits. If the connection fails, it would be fatal for the type of mite. Lack of contact with potential partners, which could bring new genes to their offspring, would bring the mites to an evolutionary impasse, at the end of which there is a danger of extinction.

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