The mites that live and breed on your face have anus, genome study finds

An illustration of Demodex folliculorum.

an illustration of Demodex folliculi.
Photograph: shutterstock (shutterstock)

Scientists have finally unlocked the genetic secrets of humanity’s coziest roommates: follicular demodex, also known as the skin mite. Among other things, the findings confirm that these mites do indeed have anuses, contrary to previous speculation. They also indicate that microscopic animals may not be as potentially harmful as is thought and that they are evolving into co-dependent symbiotic creatures that may provide us with some benefits.

follicular D. actually it’s one of the two mite species that call us home, along with abbreviated demodex Both species are arachnids – more closely related to ticks than spiders – but follicular D. mites are the ones that usually reside (and mate) on our faces. These stubby, worm-like creatures live for two to three weeks, all the time embedded in our pores, clinging to hair follicles and feeding mainly on our sebum, the oily substance provided by our bodies to protect and moisturize our skin. .

Despite the fact that virtually everyone in the world has their own collection of mites, there is still a lot we don’t understand about them. But in a new study published On Tuesday, in the journal Molecular Biology and Evolution, researchers in Europe say they have now completely sequenced the genome of follicular D.— an accomplishment that may answer some lingering questions about your inner workings.

Some researchers have argued, for example, that these mites do not have anus. Without an anus, the theory goes, their fecal waste simply accumulates inside them during their brief life and is only released in one go when they die. Some have also speculated that an overabundance of mites could cause a skin condition known as rosacea, perhaps due to bacteria released from this poop explosion after a mite dies. Other research has cast doubt on that claim, and the researchers behind the new study say they have confirmed that mites do indeed have an anus.

Study author Alejandra Perotti, a researcher at the University of Reading in the UK, notes that the increased presence of mites in people who develop rosacea and other skin conditions may well be a consequence of the condition rather than its actual cause. And if mites aren’t leaving behind huge amounts of poop behind when they die, then there’s less clear-cut logic to how they would make us sick in the first place. Other studies, it is worthwhile, have continuous find a link between dust mites and rosacea, although they may be just one of the many triggers involved.

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

The team’s other findings show that these mites have evolved to become incredibly lazy, genetically speaking, as a result of harnessing their wagon to humans. They have a very simple genome compared to other related species, and appear to be surviving on the bare minimum of cells and proteins needed to function (their pairs of legs are powered by a single muscle cell each). They’ve lost the ability to survive exposure to ultraviolet light, which explains why they crouch deep in our pores and only move and mate at night, and they don’t even seem to produce their own melatonin anymore, as many animals do… in instead, they seem to take it away from us. They are also passed from mother to child, often through breastfeeding, meaning populations have relatively low genetic diversity. And their lack of natural predators, host competition and generally protected existence suggests that mites are likely to lose more genes over time.

Researchers theorize that these trends may one day lead to the end of follicular D. mites as a distinct entity — a process that has been observed with bacteria but never with an animal, they say. Eventually, mites can no longer live externally on our skin as parasites, but become fully internal symbiotes. In this case, we may be seeing this transition taking place now, although this transformation will likely not be complete for a long time.

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

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