Thanks to Brilliant for supporting this episode of Journey to the Microcosmos.

Go to Brilliant.org/microcosmos check out their Scientific Thinking course and get 20% off an annual premium subscription. When you’re in the business of hunting for microbes, sometimes you have to send some weird emails.

That is why James, our master of microscopes, sat down one day to send his own strange request to the people at Coralaxy, a coral farm in Germany. The job of coral farms like Coralaxy is to cultivate corals for people to fill their aquariums with, protecting natural reefs from collection in the process. And while farming might make it sound like they’re growing plants, corals are actually animals colonies made up of marine invertebrates that form spectacular structures painted with vibrant colors.

So you can imagine that there are lots of beautiful things to seek out from coral farms. But James was not emailing to ask about corals. James wanted something a little more unusual and a little less desirable.

He wanted to know if Coralaxy could check their filter systems and send him some of the scum that deposits there. After all, we’ve found fascinating organisms in fish tanks and in sink drains, why not combine the two? Fortunately, the people at Coralaxy were also very curious about what their reef tanks might reveal when put under the microscope, so, of course, they sent James a bunch of stuff.

In addition to corals, which we’ll get to in a future episode, the generous team at Coralaxy put together two bags of sediment and gravel from their tanks, three large bottles of plankton cultures, some macroalgae, and most exciting of all to James, a concrete brick. Yes. You heard me correctly.

It just so happened that this brick had been placed in many of their tanks. So when James got his hands on it, he was delighted to find all sorts of interesting creatures growing on the brick. Some of the organisms he found were completely new to him, like this weird living hybrid of spikes and puff.

Understandably, when James first saw it, he wasn’t sure what to make of it. But then when he zoomed in on those tiny pointy bits, he could make out the needle-like structures called spicules that belong to sponges. Sponges are sort of like corals in that they are invertebrates that don’t move around.

But they’re also much more simple than corals. This particular sponge is known either as a pineapple sponge or a q-tip sponge, both of which are excellent names. They’re found in marine waters all around the world, but they also often hitchhike their way into aquariums.

James also got the chance to record some ciliates that he hadn’t recorded before, like the Peritromus you see here wheeling itself across the slide. And from even closer up, you can see those individual cilia at work as they push the organism around in circles. One of the fascinating parts of looking at organisms that have come from aquariums is getting to see them make homes out of structures we don’t usually get to see in our normal pond samples.

Like these worm-like ciliates called trachelocercids, which are stretching in and out of a shell they found. There are several of them inside there, turning the shell into its own little trachelocercid commune. Which makes you wonder how they all found the shell to begin with, and how they all decided to gather there.

And then there’s this ciliate swimming in the remains of a crustacean’s carapace or shell, looking just a teeny bit lost. The structures in the carapace make for a harsh landscape under the microscope, like columns of icy rocks that the ciliate has to make its way through. From other angles, the landscape shifts into a surreal crystal palace, one that seems to have temporarily trapped the ciliate in its confines.

But the carapaces that now have formed chiseled boundaries around the ciliate were once part of a living, breathing animal, a crustacean. So where did that crustacean go? Well we don’t know for certain.

But perhaps they got eaten by this flatworm. You can see the remains of a crustacean taking up space, static in the otherwise very wiggly body of the flatworm. Zoom in closer and you can see the remains of the crustacean surrounded by a mixture of yellow and brown that looks like Dijon mustard.

Of course, it’s not like the flatworm has made a tasty mustard crustacean dish for itself. Those bits of brown are actually endosymbiotic dinoflagellates that live inside the flatworm in exchange for providing nutrients to the worm. This relationship mirrors the mutualism that corals and algae exhibit as well, with corals providing protection and photosynthesis supplies to the algae, and the algae providing nutrients and waste-removal services in return.

Unfortunately, not all creatures are turning to algae for a mutually beneficial relationship. Some just like to use algae for food. Like this ciliate called Chlamydodon, whose body is filled with its dinoflagellate dinners.

And inside the sediment samples that James studied were many gorgeous algae-eating foraminifera. Those hard exteriors are home to amoebas, which use their false feet to poke out and grab food. But they’re also an integral part of marine food webs because animals like fish will come along and eat them.

In addition to the microbial worlds that James got to explore in these samples, there were also plenty of creatures who are, by our standards, on the large side. Like this snail spinning around in circles. We can’t speak to what these snails are up to, but it’s not surprising to find them here.

Snails eat debris and plant matter, which makes them useful living vacuum cleaners to help clear up aquariums. Plus, they’re just cool to watch, this one has an “alien crawling across the empty night sky” vibe that makes it hard to look away. And in addition to the snails, there were bristle worms in these samples that we were very excited to see, but we’re going to save that excitement for the next episode.

For all the things we know in these samples, there were also some mysteries as well. For example, we think this creature might be a flatworm, cause it kind of looks like a flatworm. It certainly moves like a worm.

But this is the microcosmos we’re talking about, a place where appearances are often deceptive. And since we can’t identify the species we’re looking at, we’re not actually sure if it is a flatworm. With higher magnification, you can see these rod structures inside of it, like a bunch of tiny little worms nested within the body of this maybe-worm.

Except we have no idea what those structures are. So if any of you know what this creature is or what those structures are, please let us know in the comments. What has stood out to us as we’ve looked through all of these samples is just how many different types of creatures there are.

Some resemble life we’ve found in other bodies of water, and some are things we may not have gotten a chance to see if James had not taken the step to send a strange email to a coral farm. It should hardly be surprising given that corals support such an incredible breadth of life in the wild. But it is still beautiful to explore that breadth of life, to see its smallest forms thriving because to them, even a farm is wild.

Thank you for coming on this journey with us as we explore the unseen world that surrounds us. And thank you to Brilliant for sponsoring this episode. Brilliant features hands-on, interactive courses in science, engineering, computer science, and math.

And Brilliant has recently upped the interactivity in their courses. In their Scientific Thinking course, you’ll dive into the world of scientific principles by exploring the laws of physics and principles of engineering. Along the way you’ll gain the understanding and insight needed to start looking at the world in a different way.

The courses are designed for people of all levels, so you can jump in at any point and work your way to mastery. And Brilliant courses are also available offline using their iOS and Android app. So if you’re traveling or have a spotty internet connection, you’ll be able to keep learning.

If you’re interested in learning more, you can get 20% off an annual premium subscription at Brilliant.org/microcosmos. The folks whose names you are seeing come up on the screen right now, you know who they are. They are the people who make it possible for us to send a weird email to a coral farm and get a bunch of stuff mailed to us so that we can show you the beautiful diversity of all that is going on inside of a brick!

What a cool thing we are all doing together. Thank you so much for your support, and if you’re interested in that you can check it out at Patreon.com/JourneytoMicro If you want to see more from our master of Microscopes, James Weiss, and why wouldn't you, you can check out Jam & Germ on Instagram. And if you want to see more from us.

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