The secret life of mites in the skin of our faces

The secret life of mites in the skin of our faces

Image showing the Demodex folliculorum mite on the skin under a Hirox microscope. Credit: University of Reading

Microscopic mites, which live in human pores and mate on our faces at night, are becoming so simple organisms because of their unusual lifestyles that they may soon become one with humans, new research has found.

IN mites are transmitted during childbirth and are worn by almost everyone, with their number peaking in adults as the pores enlarge. They are about 0.3 mm long, are found in the hair follicles of the face and nipples, including the eyelashes, and eat sebum, naturally released from the cells in the pores. They become active at night and move between the follicles, looking to mate.

The first study to sequence the genome of the D. folliculorum mite found that their isolated existence and the resulting inbreeding led them to secrete unnecessary genes and cells and move to external parasites to internal symbionts.

Dr Alejandra Perotti, associate professor of invertebrate biology at the University of Reading, who led the study, said: in the pores “These changes in their DNA have led to some unusual characteristics and behavior of the body.”

Mite Demodex folliculorum under a walking microscope. Credit: University of Reading

An in-depth DNA study of Demodex folliculorum revealed:

  • Due to their isolated existence, no exposure to external threats, no competition for host infections and no encounters with other mites with different genes, genetic reduction has led them to become extremely simple organisms with small legs, powered by only 3 unicellular muscles. They survive with a minimal repertoire of proteins – the lowest number ever seen in this and related species.
  • This reduction in the gene is also the reason for their nocturnal behavior. Mites lack UV protection and have lost the gene that causes animals to wake up in daylight. They have also been left unable to produce melatonin – a compound that makes young invertebrates active at night – but they are able to nourish their mating sessions overnight using melatonin secreted by human skin at dusk.
  • Their unique genetic arrangement also leads to unusual mating habits. Their reproductive organs have moved forward, and males have a penis that protrudes upward from the front of their body, which means they have to position themselves below the female when mating and mate while both cling to human hair.
  • One of their genes has been reversed, giving them a special arrangement of the appendages of the mouth, which are particularly prominent for food collection. This helps them survive at a young age.
  • Mites have many more cells at a young age than in adulthood. This takes into account the previous assumption that parasitic animals reduce their cell numbers at the beginning of development. Researchers say this is the first step towards turning mites into symbionts.
  • The lack of exposure to potential partners that could add new genes to their offspring may have put the mites at an evolutionary impasse and potential extinction. This has been seen in bacteria that have lived in cells before, but never in an animal.
  • Some researchers have suggested that mites do not have an anus and should therefore accumulate all of their feces throughout their lives before releasing them when they die, causing skin inflammation. However, a new study has confirmed that they have an anus and have therefore been unfairly blamed for many skin conditions.
  • The secret life of mites in the skin of our faces

    The image shows an unusually positioned penis of the mite Demodex folliculorum. Credit: University of Reading

  • The secret life of mites in the skin of our faces

    Microscopic image of the posterior end of the anus of the mite Demodex folliculorum. The presence of the anus of this mite was mistakenly ignored by some earlier, but this study confirmed its presence. Credit: University of Reading

The study was led by the University of Bangor and the University of Reading, in collaboration with the University of Valencia, the University of Vienna and the National University of San Juan. It was published in the magazine Molecular biology and evolution.

Dr Hank Braig, co-author of Bangor University and San Juan National University, said: “Mites have been blamed for many things. Long-term relationships with people may suggest that they may also have simple but important useful roles, such as keeping the pores of your face unclogged. ”

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More info:
Gilbert Smith et al., Human follicular mites: Ectoparasites become symbionts, Molecular biology and evolution (2022). DOI: 10.1093 / molbev / msac125

Quote: The Secret Life of Mites in the Skin of Our Faces (2022, June 21), retrieved on June 21, 2022 from

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