Microscopic mites having sex on our faces at night may be evolutionarily forgotten, scientists say Science and technology news

If you think giant pandas were faring badly, think of the tiny parasitic mites that live in the pores of the skin on our faces, which a new analysis of their DNA suggests may be destined for an evolutionary dead end.

More than 90% of us harbor the 0.3mm long mites in the oily creases of our face, most living in the pores near our nose and eyelashes.

It’s probably the closest relationship with another animal that most of us never knew we had.

The mite, Demodex follicularum, spends its entire life in our skin follicles. During the day they feed on our oily skin secretions, at night they leave the pore to find mates and find new follicles in which to have sex and lay their eggs.

If the thought makes you want to wash your face, forget it. You’ve carried the mites since birth – they’re passed from mother to baby during breastfeeding – and live too deep in your pores to wash out. And besides, we need them, says Dr. Alejandra Perotti from the University of Reading, who co-authored the study.

“We should love them because they are the only animals that live on our bodies our entire lives, and we should cherish them because they clean our pores.”

“Plus, they’re cute,” says Dr. Perotti.

Maybe not everyone would agree. The mites have four pairs of stubby legs, each with two claws. In addition, a long, worm-like body that sometimes protrudes from our hair follicles under the microscope.

But this latest study, published in the journal Molecular Biology and Evolution, has revealed just how incredibly intimate her relationship with humans has become.

The researchers analyzed the mite’s genome and found that it contained the fewest number of functional genes of any arthropod (insect, arachnid and crustacean).

The animals have become so dependent on their human host that their genome is being “eroded” – reduced to the bare minimum of genes needed for survival, the researchers conclude.

They found that the gene that normally regulates waking and sleeping in arthropods has been lost. Instead, the organism recognizes changes in the level of the hormone melatonin in our skin secretions. It goes up when we sleep, telling Demodex to get up, and going down when we wake up – her cue to go back into our oily pores for dinner.

They’ve also lost the gene that protects their bodies from UV light – what’s the point of only coming out at night? Even their physique is minimalistic – each leg is powered by just a single muscle cell.

Their ecology, so closely synchronized with that of humans, shows that the species is on the way from a parasite to a symbiote – an organism that depends entirely on another for its survival. In this case we.

As their genetic diversity shrinks, and with it their ability to leave their host and find new mates, they are also at risk of eventual extinction, either at the hands of humans or as a result of a significant change in their environment.

Demodex was previously believed to be a cause of common skin conditions, but in healthy people, Demodex actually helps prevent problems like acne by unclogging pores.

But that’s not the only reason we should take care of them, says Dr. Perotti:

“We live in a world where we should protect biodiversity – and these are our own animals.”