The mites that copulate on our face at night have a serious problem

Ian Parodi

The mites 'Demodex folliculorum' lead a full life on the face of almost all human beings without our being aware of their symbiotic existence, which, far from being a mere existence, do not deprive themselves of their sexual life when night comes. However, these intimate encounters on the surface of our skin could have their days numbered.

The organisms in question are about 0.3 millimeters long and live in the hair follicles, also in those of the eyelashes and nipples, feeding on the sebum that the pores release naturally. They are 'nocturnal animals' that copulate by clinging to human hair, but apparently they are already facing extinction.

A new study published in the journal Molecular Biology and Evolution, the first to sequence the genome of this species, found that the number of genes in Demodex folliculorum mites is minimal and, in fact, the lowest ever seen in them and related species.
A mite 'Demodex folliculorum'.Gettyimages

The loss of genes coincides with the drastic reduction in cell numbers. Coupled with extreme inbreeding due to their isolated existence, the lack of DNA repair genes may have put these mites on a path to their end.

"The loss of essential DNA repair genes and lack of exposure to potential mates that could add new genes to their offspring may have set 'D. folliculorum' on an evolutionary dead end and possible extinction," explained Spanish researcher Andrés Moya of the University of Valencia, one of the study's authors. "While these phenomena were already known to occur in symbiont bacteria, the study demonstrates it for the first time in animal eukaryotes," he added.

The reason why the mites are active precisely at night lies in the lack of ultraviolet protection, which forces them to hide in our pores in broad daylight, and the loss of the gene responsible for the animals to react to the sun and wake up.

In addition, they are not able to produce melatonin and to fuel their important reproductive tasks during nighttime sessions they use the melatonin secreted by human skin at dusk. This chemical compound is necessary for many nocturnal animals to stay awake during the night.

Another of the scientists' discoveries was to confirm that mites have an anus, even though it was previously assumed that they did not. This fact relieves them of the responsibility for some of our skin irritations that used to be attributed to them, since it was believed that they carried their feces throughout their lives and when they released them at the time of death, they caused inflammations.

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