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Go to squarespace.com/microcosmos to get a free trial and 10% off your first purchase of a website or domain. We don’t know how many rites of passage there are institutionalized among amateur microscopists.

But we do have to imagine, that as people find themselves navigating the microcosmos for the first time, they’re often on the lookout for tardigrades. Their funny appearance and legendary resistance have made tardigrades icons of the microscopic world, and who doesn’t love an icon? Recently, our master of microscopes James decided to try out a new way to gather tardigrades.

The method is simple, and the results quite astounding. All you need is some mesh, water, and a little bit of patience. James has a little patch of moss next to his trash bins.

So when he takes his trash out, he’ll sometimes collect bits of the moss to look for microbes later. And we have seen tardigrades from these bits of moss before. The question is, though, how to easily and efficiently get the tardigrades to emerge from the moss so that James can watch them under the microscope.

Recently, James was inspired to try out something called the Baermann funnel, which he’d found in a book. This technique goes back to at least 1917, when it was first described by a Dutch physician named Gustav Karl Theodor Friedrich Baermann. He invented the method when he was in Java, looking for nematodes that live in soils— particularly parasitic hookworms.

And since then, the tool has become one of several that nematode researchers use to gather their research subjects, in part because it is just so easy to set up. Here we can see just how simple James’ version is. To make one of your own, start by placing some soil or moss on a mesh fabric.

There’s a number of things you can use for the mesh, including tea bags, a pair of tights, or a cheesecloth. Then place the mesh/moss combination into a funnel and carefully add water until only just part of the moss is dipped in the water. Make sure to seal off the bottom of the funnel— in James’ case, he used a piece of rubber tube.

The next day, you can return to see what organisms have gone through the mesh and are now settled at the bottom of the funnel. The Baermann funnel has proven to be a lasting tool for nematologists to find worms buried in soil. They begin with the soil sample above the mesh, and with the addition of water, the worms are released from the soil.

This sets them free to travel to the mesh and then through it, ultimately settling at the bottom of the funnel. And after anywhere from 16-72 hours, the nematologist can return to find a bundle of microscopic worms at the bottom. But this doesn’t necessarily work for all nematodes.

Nematodes that live in plants can take longer to come out, while other species will travel away from the bottom of the funnel. So when James decided to try this technique out to find tardigrades, there was no guarantee that it would actually work. He returned the day after setting up his tardigrade-trapping apparatus and had to just hope for the best.

He collected a drop of water from the bottom of the funnel and prepared a slide. What he saw was incredible. He counted 196 tardigrades on his very first slide.

That is a lot of tardigrades! If you try the Baermann funnel out and find that your tardigrades are a bit hard to see because bits of sediment or other things floating in your sample, don’t worry, James had this same issue too. They’re kind of hard to make out here because there’s just so much stuff for them to hide in.

He just washed the tardigrades a bit to make them a little more presentable for us, carefully pipetting drops of water until there was minimal debris to obscure our view. And one of the cool things about having caught so many tardigrades at once is that you can see how much variety there is to them. Like here we have a few tardigrades that look like giants crawling in a variety pack of miniature tardigrades.

You can also catch tardigrades in some funny situations, like this tardigrade that’s using its clawed feet to walk along the glass slide. Tardigrades cannot swim, but they will use their claws to walk around underwater. And glass is a tough surface for this one at the moment, but over time, it will get better— though not because of anything the glass or tardigrade does.

Over time, those little dots of bacteria you see across the screen will accumulate. And as the number of bacterias grow and spread across the glass, their bodies will create friction along the surface, which means the tardigrade will be better equipped to walk across it. James also found this tardigrade who looks trapped in a bag.

In reality, she’s stuck to her cuticle, which is full of eggs that will one day hatch and replenish the world of tardigrades. So the Baermann funnel helped James find a ton of tardigrades without much fuss. But there’s one major thing he did have to keep in mind: oxygen.

When he first added the moss to the funnel, the tardigrades were in their resting tun state, their entire being temporarily on pause so they could survive the desiccated conditions. And when James added water and created more favorable conditions, the tardigrades emerged from the tuns and began walking around. So ideally, you will give the tardigrades enough time to unfreeze themselves.

But if you wait too long, then the water in the funnel begins to form an oxygen gradient. The surface will have more oxygen, while the bottom will have less. And that’s a problem because that bottom region is where the tardigrades end up settling as we collect them through the mesh.

As more and more tardigrades accumulate in that bottom area, they will have to compete with each other for oxygen. And sadly, the oxygen concentration can change very rapidly, killing the tardigrades before they can even return to their protective tuns. But there are a few ways to prevent the death of your tardigrades.

Try and collect the tardigrades from the funnel sooner rather than later. It may take some trial and error to find the right timing, but James says to try and avoid waiting longer than a day. And when James does collect his tardigrades, he provides them with fresh water to replace the oxygen-deficient water they're living in.

He also adds some algae from his pond samples into the slides and keeps them in transparent humidity chambers under a light source. The light helps the algae reproduce, providing

tardigrades with both food and oxygen. These are the refinements that James has made to the Baermann funnel to make it work for his tardigrades.

And depending on what materials you have available to you and the samples you’re collecting, you might have to make your own creative adaptations. The joy of the microcosmos is that it is all around us, but it can also take time and practice to figure out the best ways to actually find its inhabitants. So we hope this technique helps you all on your own journey.

And if you try the Baermann funnel out on your hunt for nematodes and tardigrades, make sure to share what you find with us. 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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They're the people who make it all work here at Journey to the Microcosmos, so that we can continue finding new ways to interact with our world and sharing those ways with you. I'm really excited to see if anybody else goes ahead and builds a Baermann funnel to capture hundreds of tardigrades. If you want to become one of these people, you can do that at 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. And if you want to see more from us, there's always a subscribe button somewhere nearby.