If you think giant pandas were bad, think of the small parasitic mites that live in the pores of our faces’ skin, which may be destined for an evolutionary dead end, according to a new analysis of their DNA.
More than 90% of us contain 0.3 mm long mites in the greasy folds of our faces, most live in the pores near the nose and eyelashes.
This is probably the closest relationship to another animal that most of us didn’t know 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 pores to find halves 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 have been carrying mites since you were born – they are passed from mother to baby during breastfeeding – and live too deep in the pores to be washed. We also need them, says Dr Alejandra Perotti of the University of Reading, who co-authored the study.
“We have to love them because they are the only animals that live on our bodies all our lives, and we have to appreciate them because they clean our pores.”
“They’re also cute,” says Dr. Perotti.
Maybe not everyone would agree. Mites have four pairs of slender legs, each with a pair of claws. Beyond this long body like a worm, which under a microscope can sometimes be seen protruding from our hair follicles.
But this latest study, published in the journal Molecular Biology and Evolution, showed how incredibly intimate their relationships with humans have become.
The researchers analyzed the mite’s genome and found that it had the smallest number of functional genes of all arthropods (insects, arachnids and crustaceans).
Animals have become so dependent on their human host that their genome is “eroded” – to a minimum of genes necessary for survival, the researchers concluded.
They found that the gene that normally regulates arthropods’ awakening and sleep is lost. Instead, the body detects changes in the levels of the hormone melatonin in our skin secretions. It rises when we sleep, telling Demodex to get up, and decreases when we wake up – their sign to return to our oily pores for dinner.
They have also lost the 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 fed by only one muscle cell.
Their ecology, which is becoming so closely synchronized with humans, shows that the species is on its way from a parasite to a symbiote – an organism completely dependent on another for its survival. In this case we.
As their genetic diversity shrinks, and so does their ability to leave their host and find new partners, they are also at potential risk of eventually disappearing – either when people do, or as a result of some significant change. in the environment.
Demodex was once thought to be the cause of common skin conditions, but in healthy people, the evidence is that Demodex actually helps prevent problems such as 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 have to protect biodiversity – and these are our own animals.
Add Comment