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You probably don’t know it, but right now dozens of microscopic creatures are hiding in the pores of the skin on your face, feeding on the sebum they give off. And at night, while you sleep, something even more disturbing happens: they pursue and mate by clinging to your hair follicles, including your eyelashes. If you just happened to think his bedroom was a boring wasteland where nothing ever happens, he has no idea what nightly ‘party’ he’s missing, including unorthodox sexual habits.
These mites, just 0.3 mm long, are transmitted during birth and are carried by almost everyone, especially in adulthood, as the pores enlarge.
But this particular form of life, so hidden and isolated, is taking its toll on them, according to a study published in the specialized journal ‘Molecular Biology and Evolution’. The investigation has also discovered some aspects of the strange body of these beings: for example, the peculiar disposition of the penis of the males and that they are endowed with an anus.
But the most important thing revealed by the sequencing of the genome of Demodex follicular -scientific name of these small beings-, is that they are becoming so simplified organisms that they could soon become one with humans. Their isolated and protected existence inside the pores and the resulting inbreeding are causing unnecessary genes and cells to shed and move towards a transition from external parasites to internal symbionts.
“We found that these mites have a different arrangement of body part genes than other similar species. These changes in their DNA have resulted in some unusual body characteristics and behaviors,” says Alejandra Perotti, a professor at the University of Reading in England.
Due to their isolated existence, no exposure to external threats, no competition to infest hosts, and no encounters with other mites with different genes, genetic reduction has turned them into extremely simple organisms with tiny legs powered by just three single-celled muscles. They survive with the minimum repertoire of proteins, the lowest number ever seen in this and related species.
This gene reduction is also the reason for their nocturnal behavior. The mites lack UV protection and have lost the gene that makes animals wake up in daylight. They also haven’t been able to produce melatonin, a compound that makes small invertebrates active at night. However, they can fuel their mating sessions throughout the night using the melatonin secreted by human skin at dusk.
unusual mating
Their unique genetic makeup also results in unusual mating habits. Their reproductive organs have moved, and the males have a penis that protrudes upwards from the front of their body, meaning they have to get under the female when they mate and copulate while both hold on to human hair.
Also, one of their genes has been inverted, giving them a particular arrangement of mouthparts that protrude more to gather food. This helps their survival at a young age.
On the other hand, mites have many more cells at a young age compared to their adult stage. This contradicts the earlier assumption that parasitic animals reduce their cell numbers early in development. The researchers argue that this is the first step for mites to become symbionts.
Lack of exposure to potential mates who could add new genes to their offspring may have put the mites on the path to an evolutionary dead end and a possible extinction. This has been seen before in bacteria that live inside cells, but never in an animal.
they have anus
Some researchers had assumed that mites do not have anus and therefore must accumulate all of their feces throughout their lives before releasing it when they die, causing skin inflammation. However, the new study confirmed that they do, and thus have been unfairly blamed for many skin conditions.
“Mites have been blamed for many things. The long association with humans could suggest that they could also have simple but important beneficial roles, for example in keeping the pores on our face unclogged,” says Henk Braig of Bangor University in Wales.
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