The skin mites that merge on our faces at night are slowly merging with humans

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

Most people on Earth are mite habitats that spend most of their short lives buried in hair follicles, primarily on the face. In fact, humans are the only habitat for Demodec folliculorum. They are born on us, feed on us, mate on us and die on us.

Their entire life cycle revolves around chewing your dead skin cells before they hit a small bucket.

That’s how he relies D. folliculorum to humans for their survival, new research suggests that microscopic mites are in the process of evolving from ectoparasites to an internal symbiote – and one that shares a mutually beneficial relationship with its hosts (that’s us).

In other words, these mites are gradually merging with our bodies so that they now live permanently in us.

Scientists have now sequenced the genomes of these ubiquitous small beasts, and the results show that their human-centered existence could cause changes not seen in other mite species.

“We found that these mites have a different arrangement of body parts genes than other similar species because they adapt to protected life inside the pores,” explained invertebrate biologist Alejandra Perotti of the University of Reading in the UK.

“These changes in their DNA have led to some unusual characteristics of the body and behavior.

D. folliculorum seen in the preparation of potassium hydroxide on human skin. (KV Santosh / Flickr, CC BI 2.0)

D. folliculorum is actually a fascinating little creature. Human skin detritus is his only source of food and he spends most of his two-week life searching for it.

The individuals appear only at night, under the cover of darkness, to painfully slowly crawl on the skin to find a partner and, hopefully, mate before returning to the safe darkness of the follicles.

Their tiny bodies are only one-third of a millimeter long, with a set of tiny legs and a sausage-shaped mouth at one end of the long body – just enough to push human hair follicles to get delicious noms in them.

Work on the mite genome, co-led by Marin and geneticist Gilbert Smith of Bangor University in the UK, has revealed some of the fascinating genetic traits that drive this lifestyle.

Because their lives are so crucial – they have no natural predators, no competition, no exposure to other mites – their genome has been reduced to the most basic.

Their legs are powered by three single-celled muscles, and their bodies have an absolute minimum of protein, just what it takes to survive. This is the smallest number ever seen in its wider group of related species.

This reduced genome is the reason for some of D. folliculorum‘s another weird pekadilo, too. For example, the reason why he only goes out at night. Among the lost genes are those responsible for protection from UV radiation, and those that keep animals in daylight.

They are also unable to produce the hormone melatonin, which is found in most living organisms, with different functions; in humans, melatonin is important in regulating the sleep cycle, but in small invertebrates it causes motility and reproduction.

This doesn’t seem to bother me D. folliculorum, However; can collect melatonin secreted by its host’s skin at dusk.

demodec folliculorum dorsal penisThis is not convenient. (Smith et al., Mol. Biol. Evol., 2022)

Unlike other mites, their reproductive organs are D. folliculorum they moved to the front of the body, with the mite’s penises pointing forward and upward from their backs. This means that it must be placed under the female while sitting insecurely on the coat for mating, which they do all night, in AC / DC style (probably).

But although mating is quite important, the potential gene pool is very small: there are very few opportunities to expand genetic diversity. This could mean that mites are on their way to an evolutionary impasse.

Interestingly, the team also found that, in the nymph development phase, between the larva and the adult, mites have the largest number of cells in their body. When they enter the adult phase, they lose cells – the first evolutionary step, the researchers said, in the march of the arthropod species towards a symbiotic way of life.

One might wonder what benefits humans can derive from these unusual animals; something else the researchers found could partially suggest an answer. For years, scientists have thought so D. folliculorum it has no anus, instead it accumulates waste in its body to explode when the mite dies, thus causing skin diseases.

demodec folliculorum anusThe arrow points to the anus mite and now you are probably on some watch list. (University of Reading)

The team found that this was simply not the case. Mites do have small holes; your face is probably not full of excrement from mites expelled posthumously.

“Many things are to blame for the mites,” said zoologist Hank Braig of the University of Bangor and the National University of San Juan in Argentina. “Long socializing with people may suggest that they could also have simple but important useful roles, for example, in keeping the pores on our face uncluttered.

The research was published in Molecular biology and evolution.

#skin #mites #merge #faces #night #slowly #merging #humans