Mites that live and reproduce on your face have anus, according to a genome study

Scientists have finally revealed the genetic secrets of humanity’s most welcoming roommates: Demodex folliculorum, also known as the skin mite. Among other things, the findings confirm that these mites actually have anus, contrary to previous speculations. They also indicate that microscopic animals may not be as potentially harmful as is commonly thought, and that they are evolving into codependent symbiotic creatures that may provide us with some benefits.

D. folliculorum is actually one of two species of mites that call us home, along with Demodex brevis. Both species are arachnids — more closely related to ticks than spiders — but D. folliculorum mites are the ones that usually reside (and mate) on our face. These worm-shaped critters live for two to three weeks, all the time embedded in our pores, cling to the hair follicles and feed primarily on our sebum, the fatty substance that our body provides to protect and hydrate. the skin.

Although virtually everyone in the world has their own collection of mites, there are still many things we don’t understand about them. But in a new study published Tuesday in the journal Molecular Biology and Evolution, researchers in Europe say they have now completely sequenced the genome of D. folliculorum, an achievement that could answer some persistent questions about its internal functioning.

Some researchers have argued, for example, that these mites have no anus. Without anus, according to the theory, their fecal waste simply accumulates inside them during their short useful life and is only released at the same time when they die. Some have also speculated that an overabundance of mites can cause a skin disease known as rosacea, perhaps due to bacteria being released from this poop blast after the death of a mite. Other research has questioned this claim, however, and the researchers behind the new study say they have confirmed that the mites do have an anus.

The author of the study, Alejandra Perotti, a researcher at the University of Reading in the United Kingdom, points out that the increased presence of mites in people who develop rosacea and other skin conditions may well be a consequence of the disease. not its real cause. And if mites don’t leave large amounts of poop behind when they die, there’s a less clear reason why they would make us sick in the first place. Other studies, worthwhile, have continued to find a link between mites and rosacea, although they may only be one of the many triggers involved.

“It’s easier and faster to just blame the mites,” he said in an email to Gizmodo.

Other findings from the team show that these mites have evolved to become incredibly lazy, genetically speaking, as a result of sticking their cart to humans. They have a very simple genome compared to other related species, and they seem to survive with the minimum number of cells and proteins needed to function (even their leg pairs are fed by a single muscle cell each). They have lost the ability to survive exposure to ultraviolet light, which explains why they sink into our pores and only move and mate at night, and they no longer seem to produce their own melatonin, as many animals do. instead, they seem to be making fun of us. They are also transmitted from mother to child, often through breastfeeding, meaning that populations have relatively low genetic diversity. And its lack of natural predators, host competition, and generally protected existence suggests that mites can only lose more genes over time.

Researchers theorize that these trends could one day lead to the end of D. folliculorum mites as a different entity, a process that has been observed with bacteria but never with an animal, they say. Finally, it is possible that mites no longer live externally on our skin as parasites, but become fully internal symbiotes. If so, we may be seeing the beginnings of this transition now, though this transformation is unlikely to be over for long.

Regardless of the future fate of these mites, scientists say they may be doing us some good now. They can help cleanse the skin of excess dead cells and other materials, for example, at least when their populations are kept under control. Perotti also hopes that his research will provide people with “adequate knowledge of these permanent peers, who have been to blame for our skin problems for too long.”

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