A new study has found that microscopic mites that live in human pores and mate on our faces at night have become streamlined organisms that, due to their unusual lifestyles, may soon become one with humans.
The moths Transmitted during childbirth and transmitted by nearly every human, numbers peak in adults as the follicles enlarge. They are about 0.3 mm long, are found in the hair follicles on the face and nipples, including the eyelashes, and feed on lipids that are naturally secreted by cells in the follicles. They become active at night and move between follicles looking to mate.
Dr Alejandra Perotti, Associate Professor of Invertebrate Biology at the University of Reading, who co-led the research, said, “We found that these mites have a different arrangement of body parts genes than other similar species due to their adaptation to a sheltered life inside the pores. These changes resulted in In the DNA are some of the body’s unusual traits and behaviours.”
The in-depth study of Demodex folliculorum DNA revealed:
- Due to their solitary existence, with no exposure to external threats, no competition to infect hosts and no encounters with other moths of different genes, genetic reduction has caused them to become very simple, small-legged organisms supported by only three unicellular muscles. They live with a minimal repertoire of proteins – the lowest number seen in this and related species.
- This genetic decline is the reason for their nocturnal behavior as well. The mites lack protection from UV rays and have lost the gene that causes animals to wake up in daylight. They were also left unable to produce melatonin – a compound that makes small invertebrates active at night – however they are able to fuel all-night mating sessions with melatonin secreted by human skin at dusk.
- The unique genetic arrangement also leads to the unusual mating habits of the moths. Their genitals have moved forward, males have a penis that protrudes upward from the front of their bodies which means they have to position themselves under the female when mating, and to mate as both cling to human hair.
- One of their genes was flipped, giving them a specific arrangement of oral appendages that are particularly prominent for food gathering. This helps them to stay young.
- Mites have more cells at a young age than in adulthood. This conflicts with the previous assumption that parasitic animals reduce their cell numbers early in development. The researchers argue that this is the first step toward the mites becoming commensal.
- The lack of exposure to potential pairs who could add new genes to their offspring may have set the moths on an evolutionary impasse, and possible extinction. This has been observed in bacteria that live inside cells before, but not in an animal.
- Some researchers have hypothesized that the moth does not have an anus, and thus must accumulate all of its faeces throughout its life before releasing it when it dies, causing dermatitis. However, the new study confirmed that they do have anus and have therefore been unfairly blamed for several skin diseases.
The research was led by Bangor University and the University of Reading, in collaboration with the University of Valencia, the University of Vienna and San Juan National University. It was published in the magazine Molecular biology and evolution.
Dr. Henk Bragg, co-lead author from Bangor University and the National University of San Juan, said, “Moths have been blamed for many things. Their long association with humans may suggest that they could also have simple but important beneficial roles, for example , in keeping the facial pores disconnected.”
Gilbert Smith et al, Human follicular mites: ectoparasites become commensal, Molecular biology and evolution (2022). DOI: 10.1093/molbev/msac125
University of Reading
the quote: The Secret Life of Moths in the Skin of Our Faces (2022, June 21) Retrieved June 22, 2022 from https://phys.org/news/2022-06-secret-mites-skin.html
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