“Eating tallow and pooping regularly? It’s not much, but it’s honest work,” – D. folliculorum, 2022. Image credit: University of Reading
Almost all human faces harbor mites that gorge themselves on the sebum released by the cells. They sneak into our hair follicles for marathons of nocturnal mating, and now new research has shed light on the peculiar effect their humble lives have had on their genetics.
Face mites (Demodex folliculorum) are microscopic, but with the help of a serious approach and genome sequencing, a paper published in Molecular Biology and Evolution reports just how simplistic these animals have become. They live almost entirely alone on our faces, rarely encountering competing parasites, and since they only mate with genetically similar mites, their body plans aren’t very important.
“We found that these mites have a different arrangement of body part genes than other similar species because they are adapted to a protected life within the pores,” Dr. Alejandra Perotti, an associate professor of biology, said in a statement. invertebrates at the University of Reading, who co-led the research.
“These changes to their DNA have resulted in some unusual bodily characteristics and behaviors.”
Each 0.3mm-long mite has tiny legs powered by just three single-celled muscles and is composed of the least amount of protein of any known related species. Their genotype is so simple, in fact, that they’ve lost the gene that makes them wake up in response to daylight, which is why our face eaters are nocturnal creatures.
A good thing too, since they lack any form of protection against ultraviolet light. D. folliculorum it is able to steal something that its human hosts lack, since despite not having the necessary genes to produce melatonin, they can search for it by nibbling on the melatonin that our skin secretes every night.
Male mite penises are not in the easiest places. Image credit: University of Reading
The mite’s sex life has also taken a turn in the face of declining genetics, with male penises forced into such a position (pointing upward from the front of their body, like a rhino’s horn) that the only way they can copulate is by standing under a female while both hold on to a human hair.
Interestingly, mites actually have a greater diversity of cells on their bodies when they are young, but this number decreases as they age. This could indicate that they are becoming symbionts, a form of mutualism in which something lives on another, but both benefit from each other.
In the case of face mites, that benefit could be eating away at clogged pores.
The vindication of the mites of the face arrived since it was verified that they do have an anus. Image credit: University of Reading
Years were thought to be something else. D. folliculorum they lacked, but simply ate and accumulated feces until they died and released all of it, presumably causing inflammation of the skin. However, this latest research found that they are, in fact, years old and therefore not to blame for the explosive death poop-induced inflammation.
“Mites have been blamed for a lot of things,” said Dr. Henk Braig, co-senior author from Bangor University and San Juan National University. “The long association with humans might suggest that they might also have simple but important beneficial roles, for example in keeping the pores on our face unclogged.”