(ORDO NEWS) — A group of British biologists from the University of Reading have been able to sequence the DNA of the blackhead, a tiny mite that lives in the skin of almost everyone on the planet. Scientific observer Nikolai Grinko talks about the lifestyle of these arthropods and the results of the study of their genome.
First, the bad news: with a 90% chance, tiny mites of the genus Demodex live on your face right now, feeding on the secretions of the sebaceous glands. They come to the surface at night to mate and return to your hair follicles in the morning.
Now the news is a little better: you are not alone. Acne gland (sometimes also called facial or eyelash mite) is found in almost all people of any skin color, gender and origin. They populate the follicles of almost everyone throughout life: newborns do not yet have them, and in people at the age of 70 they occur with a probability of 100%.
The population of ticks on one representative can reach 1-2 million individuals, but under normal conditions we do not notice anything. Their transparent bodies, 0.3–0.4 mm long, do not cause us any inconvenience.
Only sometimes Demodex cause inflammation, which is quite easily treated. Finally, the good news is that many biologists believe that iron glands are useful – they help unclog oily pores and remove dead skin cells.
Almost all mammals have skin mites. There are about 150 described species in this genus, each with its own specific host. For example, Demodex canis is found on domestic dogs, while folliculorum and brevis are specific to humans. As a person grows, their pores enlarge and more mites can live in them.
Most often they concentrate on the face, but they also occur in hair follicles on the nipples, eyelashes, ears, nose and genitals.
Until recently, surprisingly little was known about these mites, although they were first described as early as 1842. But now scientists have been able to decipher their DNA and learned a lot.
Deciphering or at least isolating the genome of these arthropods is quite difficult: due to their microscopic size and lifestyle, the resulting material always contains a lot of “pieces” of human and bacterial DNA. But a team of biologists managed to collect and isolate about 250 ticks for research.
Having deciphered DNA, scientists were surprised to find that acne glands lose genes. It turned out that long-term adaptation to life in the pores of the skin made many of the functions of their organisms unnecessary.
For example, mites no longer need protection from solar ultraviolet radiation, since during the day they are deep under the epidermis. Therefore, the gene encoding protection from UV radiation simply fell out of the DNA as unnecessary.
Similarly, Demodex stopped producing the sleep hormone melatonin because it is obtained directly from human skin, and there are many such examples. All this suggests that ticks live on humans for so long that this period was enough for the regressive evolution of the species.
Most surprisingly, such a vast reduction in the genome means a transition from parasitism on our bodies to symbiosis – a dense constant interaction of two different species on favorable terms for both.
There are many such examples in nature – clownfish and sea anemones, pollinating insects and flowering plants, green algae in the fur of sloths, ants and aphids. All these species closely cooperate with each other, and sometimes they cannot exist at all separately.
By the way, symbionts already live in the human body – these are gastric and intestinal bacteria, without which digestion would be impossible. The researchers say that Demodex, which has been a constant companion of man for thousands of years, will soon become an integral part of us.
People can only change their squeamish attitude towards them to gratitude for the work of cleansing the body. It is not so difficult. Although…
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