This episode is sponsored by Squarespace.

Go to Squarespace.com/microcosmos to save 10% off your first purchase of a website or domain. If you clicked on this video, we assume it’s because you read the title, “We fed our microbes blood so you don’t have to,” and immediately asked the question everyone asks when a youtuber says they did something so you don’t have to: but why?

Well, it all comes down to some worm pieces, a cat, and one very gruesome way of eating. Our master of microscopes, James, is often on the hunt for rare anaerobic ciliates, like our friend Legendrea here. But of course the trouble with rare organisms is that they are rare, which makes hunting them down very challenging.

So recently, James set up a trap. He took a little tube and filled it with pieces of worms, covered it with a mesh, and then buried the tube in sediment where his targets tend to live. But when he went back to check the trap, he did not find his rare ciliates.

Instead, he found a whole bunch of ciliates like these coleps, also drawn to the pieces of worms. It turns out that life as a master of microscopes is not all thrilling pond excursions and glamorous microscopy footage. Sometimes it’s burying pieces of worm in the sand, and still not finding what you intended to find.

So why did James think his trap was going to work? And why were these other ciliates so drawn to it? And most importantly, when does the blood happen?

Well, James created his trap with the idea that his rare anaerobic ciliates might show some degree of what’s called histophagy, meaning they like to eat the tissue of dying organisms. But those rare ciliates are not the only creatures that might do this. In fact, histophagy has shown up in a number of different ciliate families.

When James mentioned his histophagous ciliate trap to his fellow microscope master Professor Genoveva Esteban, she mentioned knowing of several scientists who would feed ciliates with blood, often using their own. Which is really, you know, quite a personal contribution to science. So, James decided to try this out… and then completely forgot.

Fortunately, one day James’ cat got excited by a bird flying around outside, and in the process of launching his way onto the windowsill, he scratched James. And that gave James a perfect little drop of blood to add to his slide. Because the blood is so dilute in our slide, you can only see James’ red blood cells as small, transparent circles in the background of this image.

As the ciliates mow their way through a lawn of blood cells, the ingested cells turn their body red. These histophagous ciliates are drawn to their targets through chemical signals in the water, which tell them where to find their food. But free-floating blood is one thing— and honestly, probably not the main thing either for these microbes.

Their real specialty is this. Yes, that pack of tetrahymena have excavated their way into a dying tardigrade, burrowing their way past the animal’s cuticle and into its body so they can get direct access to the tissue that sustains them. Histophagous ciliates often attack in groups like this, and they can clear out a body within an hour.

In this case, all they’ve left behind is the outline of what used to be an organism with a reputation for resilience. And according to James, some of those individuals probably weren’t even there when the group first entered. They might be the product of some of those earlier tetrahymena dividing while buried inside their meal.

Histophagous ciliates typically seek out organisms that are alive but injured, with wounds that release chemical signals drawing them in. And when the ciliate arrives, it can use those wounds as an entrance This ophryoglena, for example, is trying to burrow into the cuticle of a rotifer so that it can eat the animal from the inside out. You can see the insides of the rotifers squirming and squishing about as the ophryoglena continues its work.

We’re watching histophagous ciliates take on blood cells and microbial animals. But some species have even bigger fish to fry. And by “bigger fish,” what we really mean is just “fish.” The disease tetrahymenosis is a disease in fish caused by roughly 10 tetrahymena species.

Symptoms of which include whitish patches and lesions on the body. It’s a macroscopic view of the behavior we are seeing here in the microcosmos. But it doesn’t always go so great for the histophagous ciliates.

Sometimes they eat too much, or they sustain damage while eating. And we think that both of those happened to this holophrya here. Most likely, this little fellow was trying to bite off a little more than it could chew, and instead, the dead nematode in its vicinity went through the cell.

And again, this is taking a very educated guess, but we think that the ciliate got damaged and repaired itself around the nematode, effectively trapping itself like a shishkebab. And in the end, even a histophagous ciliate has its predators. We have seen them buried in the bodies of other organisms that they’re trying to eat.

But eventually, they might just end up buried in a body that is eating them. Thank you for coming on this journey with us as we explore the unseen world that surrounds us. And thank you also to Squarespace for sponsoring this episode.

Squarespace gives people a powerful and beautiful online platform from which to create their website. So whether you’re looking to create an online portfolio, start a blog, or open an online store, Squarespace can help you out. Maybe it’s time for you to take your Bookstagram to the next level by starting a whole book-review blog!

Well, Squarespace has the tools you need. They make it super simple to categorize, schedule and share your blog posts. And with Squarespace, you can interact with your community of fellow book lovers through threaded comments and replies.

And if you decide you want to start selling custom bookmarks and book sleeves, Squarespace can help you out there as well. Squarespace is already a powerful ecommerce platform, but you can even go the extra mile and add third-party extensions to help you manage inventory, streamline bookkeeping, and ship products across the world. 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. There's a bunch of names on the screen right now. And they are the names of real human people in the world who decided that they wanted this thing to exist.

They wanted to pay for it so that it could exist for everybody. So that James could capture the feeding of his own blood to microbes. Thank you so much to all of the people who have been Patreon patrons of Journey to the Microcosmos.

We appreciate you so much. And we love that you like what we do here. If you want to see more from our master of microscopes, James Weiss, you can check out Jam and Germs on Instagram.

And you really, really should. And if you want to see more from us, there's probably a subscribe button somewhere nearby.