If you think giant pandas were bad, consider the tiny parasitic mites that live in the pores of the skin on our faces, which could be destined for an evolutionary impasse, according to a new analysis of their DNA.
More than 90% of us have mites 0.3 mm long in greasy wrinkles on the face, most of which live in pores near the nose and eyelashes.
It is probably the closest relationship with another animal that most of us never knew we had.
The mite, Demodec follicularum, spends its entire life living in our skin follicles. During the day, they feed on our oily skin secretions, at night they leave the pores to find a mate, and find new follicles in which to have sex and lay eggs.
If that thought makes you wash your face, forget it. You carry mites from birth – they are passed from mother to baby during breastfeeding – and live too deep in the pores to wash off. In addition, we need them, says Dr. Alejandra Perotti from the University of Reading, who is the 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.
“Besides, they’re cute,” says Dr. Perotti.
Maybe not everyone would agree. Mites have four pairs of broken legs, each with a pair of claws. In addition, a long body like a worm that can sometimes be seen under a microscope protruding from our hair follicles.
But this latest study, published in the journal Molecular Biology and Evolution, showed how incredibly close their relationship with humans has become.
Researchers analyzed the mite genome and found that it has the fewest functional genes of all arthropods (insects, spiders and crabs).
Animals have become so dependent on their human host that their genome “erodes” – to a minimum the genes needed for survival, the researchers conclude.
They found that a gene that normally regulates waking and sleeping in arthropods has been lost. Instead, the body detects changes in the level of the hormone melatonin in our skin secretions. It increases when we sleep, telling Demodec to get up, and decreases when we wake up – their sign to go back through our oily pores for dinner.
They’ve also lost a gene that protects their body from UV light – what’s the point of going out at night? Even their body plan is minimalist – each leg is driven by only one muscle cell.
Their ecology, which is becoming so closely synchronized with humans, shows that the species is on the way from a parasite to a symbiote – an organism that completely depends on another for its survival. In this case, we.
As their genetic diversity decreases, and with it their ability to leave their host and find new pairs, they are also at potential risk of extinction – either when people do so or as a result of a significant change in their environment.
Demodex was once believed to be the cause of common skin conditions, but in healthy people, the evidence is that demodex actually helps prevent acne-like problems by unblocking pores.
But that is not the only reason why 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.
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