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This week, the microcosmos meet the cosmos as we explore even more fascinating things about our friend, the tardigrade. We'll discuss their weird weird mouths, how we take care of our tardigrades, and what's going to happen to those tardigrades that crashed into the moon.

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We don’t know about you, but here on the Microcosmos team, we find it hard not to smile as we watch tardigrades with their cute, pitch-black eyes and little feet ambling across the smooth glass surface of the microscope slide.

Moss piglets, water bears—whatever you call them, they’re fascinating to watch, and even more fascinating to try and understand. They are a puzzle, and we humans are the puzzler.

And so we figured, sure, we’ve already focused on tardigrades in a previous episode. But we cannot possibly leave it there. After all, like the microscopic world around them, tardigrades always have more to show us.

Our water bears are collected from ponds and growing moss, environments that give them the water and food they need to thrive. And so, behind the scenes, we like to give them a bit of attention, making sure that they are well fed and comfortable in their slides. After all, a drop of water is barely anything to us, but to a tardigrade, a thing so tiny and so good at surviving, that drop can be everything.

Tardigrades of course live their lives, absent of any kind of intention to teach us anything. They don’t even know we’re here. But watching is a form of interaction, and one that reveals the interface between the micro, the macro, and even the cosmic.

So let’s start with a part of the tardigrade body whose weirdness we haven’t had the chance to fully appreciate here yet: their mouths. The opening of the tardigrade mouth is a distinct ring, giving way to a tube that connects to the pharyngeal bulb, which helps the tardigrade suction out the juicy contents of its meal. But to get to the juice, the tardigrade first needs to pierce its target, relying on a pair of stylets that poke out of the mouth ring when it comes time to feed.

When the tardigrade molts, they shed their stylets and replace them with a new pair. Tardigrades are omnivorous, they’re open to eating bacteria, plants, and animals. For some species, their meal might even be another tardigrade.

But for the species here, our samples contain plenty of algae and plant matter for them to dine on, collected from the same watery and earthy worlds as the tardigrades these bits of organic matter keep them well fed like a built-in buffet. But there are other times where bearing witness to the microcosmos takes a little more adaptation on our part. Recently, we found a water bear with its half-shed cuticle filled with eggs, still attached to its body in what amounts to parenting in the microcosmos.

As you might imagine, we were more than a little curious to watch these eggs develop. But if you keep a slide on a microscope for too long, the water will evaporate, taking with it the moisture the tardigrade needs to exist outside of its desiccated, dormant state. So we kept these slides in humidity chambers and took extra care to make sure the coverslip wouldn’t crush the developing tardigrades.

And then…we watched. The tardigrade though was still. This video is from our sixth day of observation, the only sign of life being the absence of decomposition.

Three days later, we can see the eggs are developing, and there are even little tardigrade heads appearing. The mother still seems the same, attached to her eggs and seemingly still alive despite her complete stillness. When it comes time to hatch, the embryos will use their stylets and pharyngeal pump to make their way out, sucking in water to increase the pressure on the egg from the inside until the shell breaks.

But…we’re still waiting for that day to come with this tardigrade brood. Embryonic development in tardigrade can last from 5 days to more than 100, varying by species and dependent on environmental factors like temperature. The thing with biology, no matter what scale of creature you’re looking at, is that you’re always on their schedule, not the other way around.

Food and birth probably seem a bit domestic compared to some of the more recent tardigradian exploits you may have heard about. Earlier in 2019, Israel sent a spacecraft called Beresheet to the moon, taking with it, among many things, a digital archive of almost the entirety of English Wikipedia and also thousands of tardigrades, dried out in their ball-like tun form and ready for lift off. Seconds before Beresheet was supposed to land, however, it lost contact with Mission control and crashed instead, leaving one very obvious question: what will happen to those thousands of tardigrades, potentially spilled across the surface of the moon.

Our seeming penchant for sending tardigrades into space has taught us that they’re able to tolerate vacuums. Without liquid water, of course, the tardigrades will remain in their dormant state. Maybe if someone is able to return to that crash site decades from now, they might manage to find tardigrades that survived that crash, and there’s a chance that with a little water, they could come back to life.

We’re still working to understand all of the tricks of tardigrade survival, how does it play out in their DNA and proteins, and why some tardigrade species seem to be better than others. This is part of the fun of tardigrades and our collective fascination with them. We’re all learning together here on planet earth, like a giant science classroom, asking important questions like, “Is that round thing the mouth?” and “What does happen when you put a tardigrade on the moon?” Maybe this is our 21st century remix of Apollo, a conversation between microcosmos and good old-fashioned cosmos.

Science is ultimately a mix of deliberate and accidental questions, taking on many forms to suit our available tools. Sometimes science is a detailed study, and sometimes it’s a crash landing. It can be a collector of microbes and a master of microscopes, carefully tending to samples to meet the needs of their invisible residents.

And sometimes it’s you, watching along, making your own observations, maybe even thinking of new questions that no one has ever thought to ask before. Thank you for coming on this journey with us as we explore the unseen world that surrounds us. And thank you to all of these patrons.

All of these wonderful people who it possible for us to take care of our microscopic friends and bring you these videos once a week here on Journey to the Microcosmos. If you want to see more from our Master of Microscopes, James, check out Jam and Germs on Instagram. And if you want to see more from us, we've got a lot of videos up now.

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