Jun 22, 2022 19:00:00

Demodex folliculorum parasitizing the human face is evolving from a parasite to a symbiotic organism

Many human faces are infested with mites called '

Demodex folliculorum '. This Demodex folliculorum spends its entire life on human skin, but research results show that genetic information is changing toward 'coexisting with humans' due to generational changes in an environment that is too isolated. it was done.

Human follicular mites: Ectoparasites becoming symbionts | Molecular Biology and Evolution | Oxford Academic
https://doi.org/10.1093/molbev/msac125

The secret lives of mites in the skin of our faces
https://phys.org/news/2022-06-secret-mites-skin.html

Demodex folliculorum is a mite that parasitizes the skin of mammals, and in the case of humans, it is also called 'face mite' because it parasitizes the skin of the face in particular. This Demodex folliculorum parasitizes the inside of human pores at the time of birth and lives on the sebum released from human pores as a nutrient source. Demodex folliculorum reproductive at night, and newly born Demodex folliculorum also parasitizes inside human pores.

Demodex folliculorum parasitizes the inside of the pores and ends its life, so it is not much affected by foreign enemies. For this reason, it was speculated that Demodex folliculorum evolved in a direction that disregarded defense from foreign enemies. As a result of detailed analysis of the DNA of such Demodex folliculorum, the following characteristics were clarified.

・ Demodex folliculorum's legs move with only 3 muscle cells
・ The types of proteins that make up the body of Demodex folliculorum are the fewest among similar organisms.
・ Demodex folliculorum lacks 'genes that awaken in response to sunlight'
・ Demodex folliculorum uses melatonin secreted by humans at night to activate reproductive activity at night.

In addition, it is generally said that parasites reduce the number of cells in the early stage of development, but it was confirmed that Demodex folliculorum has a larger number of cells in the early stage of development than in the adult stage. From these research results, the research team points out that 'Demodex folliculorum is changing from a parasite to a symbiotic organism.'

Furthermore, it has been said that Demodex folliculorum 'does not have an anus, so waste products accumulate in the body and cause inflammation in the skin of the host', but as a result of detailed analysis, it is said that demodex folliculorum has an anus. It was found to have less effect on skin inflammation. 'Demodex folliculorum has been criticized by many factors, but the long relationship between Demodex folliculorum and humans may have given it a beneficial role,' said Henk Braig, a member of the research team. ..