This episode is sponsored by Squarespace.

Go to Squarespace.com/microcosmos to save 10% off your first purchase of a website or domain. A lot happened in the year 2022.

Economies shifted, reigns ended, wars began. So it is okay if you missed out on this little bit of we think very important news: Demodex have buttholes. Now perhaps you have never thought to wonder about this.

Perhaps you have never even heard of a Demodex before and you’re just slowly putting together that it must be related to the creature that we are watching right now. Yeah, the one that looks like a tardigrade but weirder, which says a lot given that tardigrades already look pretty weird to us. So you might wonder why we would care if a Demodex has a butthole or not.

Well, we care because they live on our face. Demodex are a genus of tiny mites that build their lives around the hair follicles of various animals. And there are two species that are found on humans: Demodex folliculorum and Demodex brevis.

They each have their own preferred nooks on our faces, with Demodex folliculorum preferring hair follicles, and Demodex brevis preferring our sebaceous glands. The mites we are looking at had the distinction of coming straight from the face of our master of microscopes, James, who saw a little black dot on his forehead and was curious what was going on inside. So he simply scraped the spot with the side of a microscope slide and took a look.

But these mites don’t always localize themselves in neat little dots, so sometimes scientists have to turn to other measures to study them. In one NPR interview, a scientist described applying glue to a microscope slide and then sticking it to a person’s forehead so as they peeled the slide off, the mites would peel off too. And look, we get it.

Learning that there are little animals crawling around your face, it might be a little unsettling. Even James, who spends just about every day thinking about microbes, found himself initially repulsed by what he found on his skin. But then he realized that they look like tardigrades with big butts.

And if we can all collectively love tardigrades the way that we seem to, perhaps we can find some space in our hearts for these mites. They’re even cute under the harsh glare of our UV light! The mites are tiny, less than a millimeter in length.

And you can see two distinct halves to their body. At one end—the tardigrade end, as we like to call it in a purely unscientific way—are eight stubby legs waving behind the Demodex’s mouth. At the other end are their gastrointestinal organs and their genitals.

Those spherical droplets in their body are oil droplets, the digested remains of the sebum and moisturizer that Demodex like to eat from our skin. Now, if at this moment, your mind is conjuring up images of the demodex wandering your face in search of oil to eat, you can rest easy. Well, for now at least.

They’re probably not wandering, they're just chilling out inside your pores. At night though, Demodex do like to party. They emerge from your pores in search of each other, looking for other mites to mate with.

And when they are done, they head back to your pores to lay their eggs. An adult Demodex folliculorum lays around 20-24 eggs in your hair follicles. Within three to four days, the young Demodex will hatch, emerging with only six legs weirdly enough.

As they develop into adulthood, the other two legs will develop as well. Their life span will end a few weeks later, at which point the dead mites will decompose in your follicles or sebaceous glands, turning the tiny little pockets of your skin into little mite graveyards. It's a lot, I know.

We keep trying to say that Demodex are cute actually, but then we talk about little mite mating parties and mite graveyards on your skin, and none of that is cute. But here’s the thing: we pretty much all have them. If you’re watching this video, you probably have Demodex living in your face.

And if you don't now, you will eventually. Now they usually spread through physical contact, though a 2015 study found that we tend to primarily pass them on via close contact with our family members rather than strangers. And when they have found your face, they’ll probably stick around, hiding in your pores and other spaces that make them hard to scrub out.

Generally, that’s fine. Demodex don’t wreak much havoc on your skin. They can become too abundant, creating a distinctive white sheen that dermatologists call Demodectic frost.

That excess of mites is usually connected to a decline in the immune system. But these cases are very rare. For a time, there was a theory that Demodex could cause rosacea, because they were thought to not have a butthole.

What do those things have in common with each other? Well the idea was that without an anus, the Demodex couldn’t poop. Instead, the Demodex would spend their short lives accumulating waste in large cells in their body, and storing it away.

And when they died, the feces would burst from their bodies, releasing bacteria that could then cause rosacea. There are enough correlations between Demodex and the occurrence of rosacea to leave us considering that there could be a connection between the two. But we are here to vindicate the mites a little.

Because that mechanism is based on an idea that would turn out to be very wrong, the idea that Demodex don’t have an anus. In 2022, scientists were studying the genes within Demodex. And among their results are some microscopy images and these words, which we hope will become a classic in the history of butthole science: There have been several reports that Demodex does not have an anus, and when Demodex dies, the accumulated waste spills into the pores of the skin and leads to inflammation; this is not correct.

We’ve talked before about just how mysterious and confusing the history of anus evolution is, and so we were excited to hear this news. But the other results of the scientist’s genetic study of the Demodex are also worth learning more about because they reveal just how strange our relationship with these creatures is. In particular, the scientists found that the Demodex are surprisingly simple, relying on a small number of proteins to survive.

This likely drives their nocturnal behavior, because they lack the compounds that allow their relatives to survive at all in the daytime. And this might be the result of just how lonely the Demodex mites are, in an ecosystem built out of our skin where they face few threats and little competition. They’re doing so well that they may require less than they once did to survive.

And that has been pushing them—at least according to these scientists—to a future where they might be symbionts with us, much like bacterial endosymbionts that have become fully embedded in their hosts. That is, for now, just a hypothesis. If there comes a day when the hypothesis is fulfilled, well what do we do then?

Do we consider them weird and creepy, and maybe even a little rude? Or do we accept them as part of us, as inevitable as every other cell in our body? Or perhaps it is both, as nuanced as any other experience we have with our bodies.

Wonderful and terrible, all at once. Thank you for coming on this journey with us as we explore the unseen world that surrounds us. And thank you to Squarespace for sponsoring this episode.

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And you can do all of this on one easy-to-use platform. So go to Squarespace.com to sign up for a free trial, and when you’re ready to launch, go to squarespace.com/microcosmos to save 10% off your first purchase of a website or domain. One thing that you've got to know, as a Patreon patron of Journey to the Microcosmos, is you don't know where the next episode is going.

But you trust us, to go in the direction that we want to go in to discover what we can discover by not looking big but looking small. The people on the screen right now, they are our Patreon patrons, and they are the reason that we can do this. If you would like to join them, you can go to Patreon.com/JourneytoMicro.

If you want to see more from our master of microscopes, James Weiss, check out Jam and Germs on Instagram. And if you want to see more from us, there's always a subscribe button somewhere nearby.