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The family Spathidiidae is made up of around 20 genera, which encompass around 250 known species. And there’s a lot of variety in the Spathidiid family to sort through.

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The first 100 people who click on the link in the description will get 25% off a Fabulous subscription. The little ciliate you see swimming through the field of debris on your screen right now has a fun name.

It’s called Rhinothrix porculus. The first part of the name, Rhinothrix, combines the Greek words “rhino”, for nose, and “thrix”, for hair. No, the name is not an ode to nose hair.

Rather, the name is a reference to the hair-like cilia around the organism, and the fact that up there at one end, is what looks like a teeny tiny nose. The second part of the organism’s name, ”porculus”, translates to pig. And that makes sense because Rhinothrix porculus likes to live in mud.

This little organism belongs to the family Spathidiidae, though we’ll just call them by their common name Spathidiids. Spathidiids are found in freshwater and marine habitats, but they’re also often found in soil. And some time ago, James, our master of microscopes, received 60 soil samples from a far away forest on the eastern edge of Poland, storing them in plastic bottles in his bathroom.

And every so often, like a force of nature gathering over a woodland, James adds water to those samples and watches the organisms go wild. And wild do they go. This is a recording of one of their feeding frenzies, which we think involves a horde of Spathidiids wreaking havoc on a population of ciliates called colpodids.

It’s chaos in microbial form and if you’re having trouble making out exactly what’s going on, don’t worry, that’s kind of the Spathidiid experience for you. The family Spathidiidae is made up of around 20 genera, which encompass around 250 known species. And there’s a lot of variety in the Spathidiid family to sort through.

For example, he largest species is about 35 times larger than the smallest. And as far as shape goes, well, their name is a callback to the origins of the word “spatula,” and you can see that spatula shape in some of the species when the broadness of its front end comes into view. But that is not universal.

Some species are more round, others more cylindrical. And others take on shapes that require words like “botuliform” and “lunate” and “turbinate” to describe them. And all Spathidiids are fairly flexible, which helps them bend and wiggle around whatever obstacle the microcosmos throws their way.

They can glide along mud particles, but in water, they can also swim, by spinning around. Some Spathidiids though put their flexibility to work in other forms of movement, like this species ducking in and out of the substrate in motions that look more like a worm than the spinning ciliate we saw earlier. As diverse as Spathidiids are, there are a few helpful features they all have in common.

One is that large circle you see at the back of their body. That’s the contractile vacuole, which helps control the amount of fluid inside the organism. As they swim through the water, the Spathidiids accumulate water and other fluid in their bodies.

And while water is, you know, essential, if there is too much, the Spathidiid will burst. So to avoid that, watery explosion, they rely on those large contractile vacuoles to gather excess fluid and then expel it back out into the world. So in a way, what you’re looking at is the Spathidiid equivalent of a bladder, taking up a large amount of space so that the ciliate can do its own version of peeing.

Spathidiids are colorless, but as you can see here, they sometimes take on some green coloring. That’s not their own pigments though—they take on the verdant hue thanks to algae that have either taken up residence as a symbiont, or that have had the misfortune to be eaten. In some cases, like with our Rhinothrix from earlier, you can also see bright, shimmering lights glowing from within.

Some of those are crystalline parts of the organism, while others are sugars that refract beautifully under our microscope’s light. To hunt down their food, Spathidiids rely on the toxicysts lining their mouths to immobilize their prey. And from there, some species will swallow their meals whole, while others use chemicals released by their toxicysts to mash up their meals outside their body, like a little protist smoothie they can just slurp up.

Now for all the distinctive traits of these different species, they’re quite difficult to identify by just looking at them under a microscope. Many of the traits that differentiate them are subtle, rooted in features that don’t immediately reveal themselves to us. Instead, scientists have to turn to other methods to bring those traits to light.

Take this species, for example, which we’re pretty sure belongs to the genus Protospathidium. One way for us to know for sure is to look for a specific part unique to the genus, but we can’t see it without killing the organisms and adding stains that highlight that part. So that’s why so much of our Spathidiid footage is so vaguely labeled, it's hard to figure out exactly what they are without killing them, and we don’t really want to do that.

But that doesn’t mean we can’t enjoy digging through their lives. And there are a few species that we have been able to identify a bit further, like this moving ball of fuzz, which James is pretty sure belongs to the genus Penardiella. In fact, it might even be completely new.

When James first saw it under the microscope, he thought it must be a damaged cell. But he was shocked to find many more like it on his slide, so now he’s collecting more data to see whether or not it really is a new species. For comparison, this is another member of the Penardiella genus that we think is Penardiella undulata.

If we’re correct, this would be the first time someone has documented the species in almost 90 years! This species belongs to the genus Perispira, but there’s not much known about it except that its mouth spirals around its body, which is definitely a helpful trait when it comes to identifying the species. And James is doing more molecular work with this species to see if he can unravel more of its mysteries.

But until then, the Spathidiids remain just about as murky and opaque as the mud they come from, though perhaps just a little bit more beautiful to look at. Thank you for coming on this journey with us as we explore the unseen world that surrounds us. We’re going to be taking the next couple of weeks off from uploading so we can catch up on some stuff, but we will be back on March 28th with a brand new episode.

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These are a bunch of human beings who wiggled out of the mud one day and decided they wanted to see some very peculiar kinds of content on That content is the thing you are watching right now, Journey to the Microcosmos, and these are our patrons. And I’m sorry that I said they wiggled out of the mud, though I don’t think that they’d mind.

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If you want to see more from our master of microscopes, James Weiss, check out Jam and Germ on Instagram. And if you want to see more from us, there’s always a subscribe button somewhere nearby.