At night, skin mites mating on our faces gradually merge with humans

If you are reading this, you are probably not alone.

Most people on earth are mites, and they spend most of their short lives head to head, in hair follicles, primarily on the surface. In fact, it is the only living environment for people Demodex folliculorum. They are born in us, feed us, kill us, and die with us.

Their entire life cycle revolves around eating dead skin cells until they kick a tiny little bucket.

I am addicted D. folliculorum New research has shown that microscopic mites have a beneficial relationship with the internal symbiont of the ectoparasite and its owners (that is, we) in the process of evolution.

In other words, these mites gradually enter our bodies and now live permanently inside us.

Researchers have now listed the genomes of these tiny predators, and the results show that their human-oriented lives could cause changes not seen in other types of mites.

Alejandra Perotti, an invertebrate biologist at the University of Reading in the United Kingdom, said:

“These changes in their DNA have led to unusual features and behaviors in the body.”

D. folliculorum is visible in the preparation of potassium hydroxide of human skin. (KV Santosh / Flickr, CC BY 2.0)

D. folliculorum is a really interesting little creature. Detritus of the human skin is his only source of nourishment, and he spends most of his two-week life chasing it.

Individuals emerge at night, only in the dark, and gently crawl through the skin to find a mate, mating before returning to the safe darkness of the follicle.

Their tiny bodies are about a third of a millimeter long, and their long, sausage-like bodies have small legs and mouths at one end – perfect for lowering human hair follicles.

A study of the tick genome by Marin and Gilbert Smith, a geneticist at the University of Bangor in the United Kingdom, revealed some interesting genetic features that contributed to this way of life.

Because their lives are so cruel – they have no natural predators, no competition, and no contact with other mites – their genomes have been reduced to just what they need.

The legs are made up of three, single-celled muscles, and their bodies have an absolute minimum number of proteins necessary for life. This is the lowest number ever seen in a wide group of related species.

This is some reason for the genome below the wall D. folliculorumThe other strange Peccadilloes too. For example, because it only comes out at night. Among the missing genes are those responsible for protecting against ultraviolet radiation and those that wake animals during the day.

They are also unable to produce the hormone melatonin, which is found in most living organisms and performs various functions; In humans, melatonin is important for regulating the sleep cycle, but in small invertebrates, it stimulates mobility and reproduction.

This was not an obstacle D. folliculorum, but the; it can collect melatonin released from the host’s skin in the twilight.

demodex folliculorum posterior genitaliaThis is not convenient. (Smith et al., Mol. Biol. Evolution., 2022)

Unlike other mites, their reproductive organs D. folliculorum The genitals of male ticks move from the back to the front of the body, facing forward and upward. This means it has to be placed under the female, as they sit dangerously on top of the hair to mate, which they do all night in an AC / DC style (presumably).

However, while mating is very important, the potential gene pool is very small: there is very little opportunity to expand genetic diversity. This could indicate that the mites are in an evolutionary deadlock.

Interestingly, the team also found that mites had the largest number of cells in their bodies during the nymph stage of development between the larva and the adult. When they reach adulthood, they lose their cells – the first step in evolution, the transition of arthropods to a symbiotic way of life.

People may wonder how they can benefit from these special animals; Another thing that researchers have found may indicate a partial response. For many years, scientists have thought so D. folliculorum When the anus dies, the tick instead accumulates debris in the body and explodes, causing skin diseases.

demodex folliculorum anusThe arrow points to the tick’s anus, and you’re probably on some observation list. (University of Education)

The team found that this was simply not the case. Ticks have small holes; Your face may not be filled with the dung of a tick that is expelled after death.

Henk Braig, a zoologist at Bangor University and the National University of San Juan in Argentina, said the councils were to blame for many things. “Prolonged contact with people shows that they can have simple but important beneficial roles, such as turning off pores on our faces.”

The study was published Molecular biology and evolution.

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