Scientists say microscopic mites that have sex on our faces at night could face evolutionary oblivion | Science & Technology News

According to a new analysis of their DNA, if you think giant pandas did it badly, look out for the tiny parasitic mites that live in the pores of our facial skin, they may be destined for an evolutionary dead end, according to a new analysis of their DNA.

Over 90% of us possess 0.3mm long mites in the oily folds of our faces, most of which live in the pores near our nose and eyelashes.

It is perhaps 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 secretions from our oily skin, at night they leave their pores to find a mate and find new follicles to copulate and lay eggs.

If that thought makes you want to wash your face, forget it. You’ve been carrying ticks since birth – they’re passed from mother to baby during breastfeeding – and live too deep in your pores to be washed away. And besides, we need them, said Dr Alejandra Perotti of the University of Reading, co-author of the study.

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

Dr. Perotti said: “Also, they are very cute.

Perhaps not everyone will agree. Ticks have four pairs of stout legs, each with a pair of claws. In addition, a worm as long as the body, under the microscope, can sometimes be seen protruding from our hair follicles.

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

The researchers analyzed the tick’s genome and found it had the smallest number of functional genes of any arthropod (insects, spiders and crustaceans).

The researchers concluded that the animals had become so dependent on human hosts that their genomes were being “eroded” – eliminating the bare minimum of genes needed to survive. the researchers concluded.

They found that genes for normal wakefulness and sleep in arthropods were lost. Instead, this organism detects changes in the levels of the hormone melatonin in our skin secretions. It goes up when we sleep, tells Demodex to wake up, and drops when we wake up – their cue to get back into our greasy pores for dinner.

They’ve also lost the gene that protects the body from UV rays – what good is it when you only go out at night? Even their body plan is minimalistic – each leg is powered by only a single muscle cell.

Their ecology becoming so closely synchronized with humans suggests that the species is on its way from being an external parasite to an internal symbiont – one that is completely dependent on us for survival.

As their genetic diversity shrinks, and their ability to leave their hosts and find new mates, they are also at risk of eventual extinction – either by humans or by some dramatic change. to their environment.

It was once believed that Demodex was the cause of common skin conditions, but in healthy people, evidence is that Demodex actually helps prevent problems like acne by unclogging pores.

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

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

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