This episode is sponsored by Blinkist. Blinkist takes all of the need-to-know
information from thousands of nonfiction books
and condenses it down to just 15 minutes and you can go to blinkist.com/microcosmos to learn more.
One of the most frequent questions we get asked on Journey to the Microcosmos is how James,
our master of microscopes, stays safe while gathering and studying samples.
After all, as beautiful as the microcosmos is, there are plenty of parasites and pathogens in
there that we’d prefer to keep under the microscope and out of our bodies.
But while James has simple and effective guidelines to protect his health—like
making sure he always washes his hands before and after handling samples, and never venturing into
a pond with an open wound—there are times when those measures don’t quite cut it.
These are the times when no matter how much you protect yourself outside or inside,
the microcosmos gets the best of you. These are the times of the dust mite.
Now we don’t usually start these videos with a warning, but we’re going to do that today.
While working on this video, at least 4 members of the Journey to the Microcosmos team
found themselves having a bit of a crisis about how clean their homes were.
If you’ve found yourself sneezing and wheezing and
running around miserable with a runny nose because of dust, this arachnid
is probably the culprit—though perhaps not in the way you would expect.
Dust mites are small in the grand scheme of things, but large in the microcosmos, hitting just
around 300 micrometers in length. Their bodies are decked out with four pairs of legs ending in feet
that act like suction cups as they wander in their quest for three things: water, food, and darkness.
Dust mites love humidity because their lives depend on it. They don’t drink water
so much as they osmosis it into them, relying on a salt-filled gland near their mouth to absorb
water vapor from the air around them. So if their surroundings become more arid, an adult dust mite
will wither away until it eventually dies. This is a challenge for dust mites that live
in places with seasons, where wet and rainy falls give way to dry winters. To survive those shifts,
they rely on the resilience of their younger brethren—the nymphs—whose
forms are able to withstand the lack of moisture. The seasons of the dust mite’s life was one of the
important clues that helped scientists in the 20th century understand their role in dust allergies.
Scientists identified dust as the source of some kind of allergen in the 1920s, but they were not
sure what it was exactly about dust that did it. They just knew that people all over the globe
suffered from dust allergies, and that these allergies were often seasonal, peaking in the
autumn, particularly after warm, humid summers2. And other possible sources, like animal dander
or mold, just didn’t quite fit right with the seasonality of the allergy. But in the 1960s,
scientists in the Netherlands and Japan realized that the dust mite might be the culprit.
They’re found in large numbers in the dust that lines the unwashed and untouched corners of our
homes, their populations peaking in time with the runny noses and bleary eyes of dust allergies.
But while experiments confirmed that mites really were the source of people’s sensitivities
to house dust, it wasn’t clear what made them so special. So, we’ll get to that in a bit...
James often finds dust mites in the humidity chambers he uses to keep his microbes alive.
These chambers are made up of a dish lined with wet toilet paper,
which is just about all a dust mite needs to feel right at home—especially when there’s potentially
some delicious microbes to munch on. So to keep those other microbes from becoming a mite meal,
James has to regularly clean out and disinfect the humidity chamber.
Now, that cleaning might get rid of the dust mites in the humidity chamber, but
the problem is that our houses are full of food for them because our houses are full of
us—of flakes from our skin that shed and gather all around and sustain the invisible mite.
And this is a problem not just because it means the mite can thrive in our homes.
It’s a problem because food means poop. Over the course of its life, a mite will produce
about 1000 pieces of poop that are roughly the size of a grain of pollen. Inside those bits of
fecal matter are enzymes that help the dust mite eat its own poop and get nutrients that it might
not have gotten the first time around. But should the dust mite choose to not
revisit its prior meals, the feces will float around the room, attached to other particles
until eventually they settle down—perhaps on a pillow, or on a pet’s bed, or a car seat.
It’s like we’re living in a gigantic snow globe, except that the snow... is dust mite feces.
In 1981, researchers confirmed the bad news about this animal’s poop— people are allergic to it.
To be more specific, they confirmed that dust mite poop contains specific
proteins that many people are allergic to. So if you’re airing out some sheets and you start
sneezing, what you might actually be reacting to is dust mite feces flying around the air.
Now, we apologize for this mental image but it is reality, and it has embedded in our heads,
so we have to share it with you as well. But we can offer what might be a small comfort:
there is another allergen from dust mites that has nothing to do with poop.
Dust mites have a fairly lengthy mating process, sometimes taking up to two days to finish—this
is a pretty lengthy time for any organism, but especially for an animal that’s only got about
100 total days to live. Over the course of their life, the female dust mite will lay up to 80 eggs,
which hatch into larvae that then go through several different stages of development
before becoming adults With each passing stage,
the dust mite sheds its exoskeleton, leaving behind its youth. And that exoskeleton provides
some of the other allergens for people react to. But though that is something people are sometimes
allergic to, it really is mostly just the poop that sets off people’s allergies. So I guess there
really wasn’t that much comfort there after all. And even for a trained and cautious
microbiologist, dust mites can become an unwelcome surprise.
Once, James brought home some samples taken from a water dish that his neighbor left outside for
their cat. The surface was covered in tiny round things, and James thought they might be rotifers.
But when he looked at the surface of the scum under the microscope, there were no charming
rotifers to be found. It was mites, just hundreds of them crawling around the slide.
It was so unpleasant that James immediately bleached the slide.
Now, he’s not sure if that sample is the reason, but for days after, James kept sneezing and
having to deal with a runny nose, all of which pointed to a potential mite invasion.
Fortunately though, our homes are not a utopia for dust mites. What they really need is dark,
which is why they prefer to dig themselves deep into carpets and other soft things that give them
space to burrow4. Dust mites have a harder time with materials like suede that are difficult to
hide themselves in5, and they usually avoid hard surfaces that are exposed to light.
So for James, his weapons against the mite invasion were clear:
a vacuum, a mattress cleaner, and a strong UV light bulb. It is one of the more ignoble
ends to one of our organisms. We don’t like to hurt them, unless they are hurting us.
But I am sure there’s a dust mite somewhere in our homes right now, settling into a soft, dark abode
of its own, with hardly a care in the world for the battle that was waged to bring you this video.
Thank you for coming on this journey with us as we explore the unseen world that surrounds us.
And we would like to thank Blinkist for sponsoring today’s episode.
Blinkist is an app that takes the best insights and need-to-know information from over 4,000
nonfiction books and condenses them down into just 15 minutes that you can read or listen to.
Maybe you have an idea for a podcast that you just haven’t been able to get off the ground yet?
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It’s a funny and inspiring, hands-on guide
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And if you’re one of the first 100 people to sign up today using Blinkist.com/microcosmos,
you can get free unlimited access for 7 days and you’ll also get 25% off if you decide to
get a full membership. Check out the link in the description to start your free 7-day trial.
It might be that your name is coming up on the screen right now. And if that is the case,
I just want to say “Thank you!” These are all the names of our Patreon patrons.
They are the people who make this project possible and without them, we would not be able to continue
exploring all of the nooks and crannies and ins and outs of the tiny world that surrounds us.
So, thank you all, to all of our patrons, and if you would like to become one of them,
you can go to Patreon.com/journeytomicro. If you want to see more from our Master
of Microscopes James Weiss, you can check out Jam and Germs on Instagram or TikTok.
And if you want to see more from us, there’s always a subscribe button somewhere nearby.
There's a tickle in my nose.
Oh god!