Hello, everyone, and welcome back to the second half of our tardigrade reproduction spectacular.

In our last episode, we got a very close look, though I suppose all of our looks are pretty close, at the various biological intimacies exchanged by tardigrades as they mate. Multiple males contended for the heart, or at least the unfertilized eggs, of a female tardigrade by poking endlessly at her exuvia.

It was really quite dramatic, and if you haven't watched it yet, you should. It’s great. There’s poop.

But now, it is time for the thrilling conclusion to all of that mating: the babies. This tardigrade has been lugging her future offspring in a sack made up of her exuvia, which is her shedded exoskeleton. Like a spare room that's been converted into a baby nursery, the same exuvia that started as the mother's own cuticle before it became the site of courtship, has now undergone another renovation to become a handy, portable egg nursery.

The ways that tardigrades deal with their eggs may look different for different species. While this water bear carries her exuvia at the end of her body, some species carry it more towards the front. Some don't lay eggs in exuvia at all, while another species has been seen depositing their eggs in the exuvia of water fleas.

Why our species has evolved or chosen this method is unknown to us. Maybe it allows her to provide them protection, or perhaps she can ensure they hatch in the best possible location this way. We just don't know.

But we did very much want to observe this mother-to-be. And so for three days, we followed her, doing our best to also take good care of her. Now, the biggest concern was making sure she wouldn't get too dry, so we had to keep her away from the edges of the slide.

To do this we used only the most advanced techniques: we poked her with the fine hair from a brush to push her towards the more watery regions of the slide. We even set an alarm to remind us to add a drop of water to the slide every four hours. Yes, even at night.

That’s a lot of alarms. Now, you might be thinking--aren't tardigrades supposed to be the hardiest creatures on Earth? Able to withstand extreme conditions, hypothetical apocalypses, and maybe even crash landings on the moon?

Surely they do not require this level of helicopter parenting (or I guess it’s grandparenting?). Well, we do care a lot for all of our microscopic organisms, and so it could be that this watery vigil is just an abundance of caution on our part. But we've seen with our own eyes that no matter how tough tardigrades may be, the microcosmos is tougher.

Sometimes things just...happen, and not in the way you might hope. You might remember this tardigrade from a previous episode. We were pretty excited about her because we could see all of those eggs just ready to be hatched.

But the mother was completely still. She hadn't moved at all, which would usually be worrisome. But she wasn't decomposing, so we thought maybe she was still alive, just biding the time until her eggs hatched.

And so while she waited, so did we. Gestation in tardigrades can vary quite a bit, not just by species, but with temperature and just plain old chance. It generally takes a few days, but it can take months.

We kept her in a humidity chamber and checked in to make sure the coverslip wasn't crushing her. But the inactive tardigrade never became active again. Eventually, her body did begin to decompose, as did the eggs inside her.

And so, this tardigrade family was not meant to be. We don't know what killed this tardigrade, but it's hard not to feel responsible for the organisms we film. Sure, they're unaware of our existence, but they are in our care, and like the animals and humans we come to feel connected to, it's sad to be reminded that endings can come for even the mightiest creatures among us, even if they're also among the smallest.

That's why, when we later found the impending tardigrade mother that started this episode, we took so much care to keep her alive. It was nerve-wracking because we didn't want to lose another brood, hence the 4 hour alarms and the brush hair. So you might be able to imagine our combined excitement and relief when after 4 days of this intensive care, we saw a tardigrade cuticle that was no longer full of eggs--it was full of egg shells and baby tardigrades!

Now unfortunately, it turned out that getting footage of the actual hatching during this moment was challenging. The eggs would roll around in the cuticle while also being dragged by the mother. But you can see the baby tardigrades clawing their way through the mass of eggs.

Eventually though, the mother finally completely shed her cuticle. You can see it here, it almost looks like a tardigrade ghost chasing behind her. This moment was particularly fortuitous for us because as the tardigrade rid herself of the exuvia that had housed her future children, one unhatched egg came out as well.

It's weird to look at this and realize that in a few moments, out will come a tardigrade. Just an oval with some lines in it, a formed thing packed away. That arrow-shaped thing that's pumping away is the tardigrade's stylets, a part of their mouth that pokes out when it comes time to eat and it helps the tardigrade suction out the meatiness of the microbes that it feeds on.

But before they can get to eating, the stylets have an important task: helping the baby tardigrade get out of their shell. After two hours of struggling, the stylets of the tardigrade begin to move more repetitively until finally, it's able to poke holes in the egg. These holes allow water into the egg, increasing the pressure inside until the egg just pops and out comes a little moss piglet.

And with it, a new generation is born, adding to a lineage of mighty microscopic animals stretching back hundreds of millions of years. If you heard a sigh just then, it's a sigh of relief and joy from all of us at the Microcosmos team. When we set out to track and record a tardigrade birth, we didn't know that it would lead to both heartbreak and excitement.

But it's all worth it for this little buddy among many. We hope to see them all again, perhaps creating their own brood. But for now, paddle away, our little friend, the whole microcosmos awaits.

Thank you for coming on this journey with us as we explore the unseen world that surrounds us. Journey to the Microcosmos is produced by Complexly. If you want to keep imagining the world complexly with us, you can check out Animal Wonders, a YouTube channel hosted by Jessi Knudsen Castañeda.

Animal Wonders is an animal rescue and education facility that cares for close to 100 exotic animals and non-releasable wildlife. Every week on the Animal Wonders YouTube channel, Jessi features a different animal and shares what it’s like to keep them happy and healthy. Recently, Jessi and the Animal Wonders team took in Tigli the arctic fox.

If you’d like to learn all about Tigli’s story and find out how he’s getting along with the other foxes at Animal Wonders, there’s a link in the description to a video all about that. And here is a list of all of the people who support us on Patreon. Thank you so much to all of them for allowing us to go on this journey and allowing us to take so many other people along with us.

You can be one of those people and get some really cool perks, just go and check out patreon.com/journeytomicro. Thanks to our Master of Microscopes James for all of his amazing work and skill. If you’d like to see more of what he does, you can check out Jam & Germs on Instagram.

And if you’d like to see more of what we do, just go to youtube.com/microcosmos where you can find our entire first season of videos and also click on that subscribe button so you can find a new video every single week. Ok. Bye