Skin Mites That Mate on Our Faces at Night Are Slowly Merging With Humans

The majority of humans on Earth are homes for mites, which spend the most of their brief lives burrowed, head-first, in our hair follicles, particularly those of the face. Demodex folliculorum does not actually have a home outside of people. They are created on us, sustain themselves off of us, breed with us, and pass away on us.

Prior to passing away, they spend their entire life cycle devouring your dead skin cells.

According to current study, D. folliculorum is so dependent on people for existence that the tiny mites may be in the process of changing from ectoparasites to internal symbionts, which have a mutually beneficial connection with their hosts (that would be us).

In other words, these mites are slowly fusing with our bodies and are now permanently residing inside of us.

These ubiquitous tiny creatures have now had their genomes sequenced, and the findings indicate that their human-centered existence may be causing modifications that are not seen in other mite species.

"We found these mites have a different arrangement of body part genes to other similar species due to them adapting to a sheltered life inside pores," stated professor Alejandra Perotti of the University of Reading in the UK, an invertebrate biologist.

"These changes to their DNA have resulted in some unusual body features and behaviors." 

Actually a lovely tiny species, D. folliculorum. Its only food source is human skin debris, and it spends the majority of its two-week existence searching for it.

Only at night, under cover of darkness, do the individuals come out to meticulously and slowly move across the skin in search of a mate and, perhaps, copulate before retreating to the secure darkness of a follicle.

They have a mouth and a cluster of tiny legs at one end of a long, sausage-shaped body that is precisely the correct size for scooching into human hair follicles to get at the yummy noms within. Their small bodies are only a third of a millimeter long.

Some of the remarkable genetic traits that underlie this way of living were discovered as a result of the study on the mite's genome that Marin and geneticist Gilbert Smith of Bangor University in the UK co-led.

Their DNA has been reduced to the bare minimum because of how simple their lives are—they have no natural predators, no rivals, and no contact with other mites.

Their bodies contain the bare minimum of proteins, just enough for existence, and their legs are propelled by three single-cell muscles. In the larger group of closely related species, it is the least number ever recorded.

Some of D. folliculorum's other peculiar quirks are also caused by its condensed genome. For instance, the explanation for why it only appears at night. The genes that guard against UV rays and those that awaken animals at dawn are among those that have been lost.

They are also unable to generate the hormone melatonin, which is present in most living things and has a variety of roles, including regulating sleep in humans and promoting movement and reproduction in tiny invertebrates.

However, D. folliculorum still appears to be able to collect melatonin from its host's skin at nightfall, despite this.

Unlike other mites, their reproductive organs of D. folliculorum have moved towards the front of their bodies, with male mites' penises pointing forwards and upwards from their backs. This requires him to position himself behind the female as they precariously hang on a hair for mating, which they perform all night long in the style of AC/DC (presumably).

Although mating is significant, there is relatively little possibility to increase genetic diversity since the prospective gene pool is so limited. This could indicate that the mites are headed for an evolutionary stalemate.

Intriguingly, the research team discovered that the mites have the most cells in their bodies while they are at the nymph stage of development, which occurs between larva and adult. The first evolutionary step in an arthropod species' transition to a symbiotic existence, according to the researchers, is the loss of cells as they advance to the adult stage.

One would ask what advantages these odd animals might provide for humans; nevertheless, another discovery made by the researchers may provide a partial solution. It has long been believed by experts that D. folliculorum lacks an anus and instead builds up waste inside its body that explodes when the mite dies, resulting in skin disorders.

You're presumably now on a watch list because the arrow points to the mite's anus.

This is clearly not the case, the researchers discovered. Your face is probably not covered in postmortem mite excrement; nevertheless, the mites do have tiny little buttholes.

"Mites have been blamed for a lot of things," remarked Henk Braig, a biologist from the National University of San Juan in Argentina and the University of Bangor. "The long association with humans might suggest that they also could have simple but important beneficial roles, for example, in keeping the pores in our face unplugged." 

The research has been published in Molecular Biology and Evolution.