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We’ve spent most of our journey through the microcosmos seeking out the organisms that are too small to see with just the human eye. The bacteria, the ciliates, the tardigrades. Part of what makes them so exciting to find is that they are so tiny. Every moment we spend with one of these organisms is a peek into something exceptional in our experience of the world, and it’s the result of how much work James, our master of microscopes, has put into hunting down as many microbes as he can.

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Go to   to start streaming thousands of  documentaries and non fiction TV shows. We’ve spent most of our journey through the  microcosmos seeking out the organisms that   are too small to see with the human eye.  The bacteria, the ciliates, the tardigrades.   And Part of what makes them so  exciting to find is that they are   so tiny.

Every moment we spend with one of  these organisms is a peek into something   exceptional in our experience of the world,  and it’s the result of how much work James,   our master of microscopes, has to put into  hunting down as many microbes as he can. And sometimes, that effort  requires a lot of persistence. Take the creature we’re going to  focus on today: the bristle worm.   This has been one of the white whales for our  channel for some time.

And as you watch it,   you can perhaps understand  why we have been searching   so hard for it. It’s got the body of a pipe  cleaner with the head of a cartoon dragon. And maybe you also understand  that just because we’ve been   wanting to find one of these worms, that doesn’t  mean we are guaranteed anything.

After all,   one of the things you have to  accept about the microcosmos,   and microbe hunting, is that it is a big world full of tiny creatures,  and it can take a while to find some of them. The fact that we are showing you  one of those bristle worms right now   spoils the twist we would usually build  into, but, surprise, we found a bristle worm! The real twist is that this was  not the first bristleworm we found.

This was the first bristle worm we found.  Twenty centimeters of segments and bristles   climbing up the side of a tank before  burrowing back beneath the sand. Unfortunately, that’s just about all the video  we got of that bristle worm. James spent so much time trying to  find this bristle worm again that he started to feel a connection to it.

So  he decided to give it a name: Gunther. James spent hours trying to catch it  without hurting the worm. But Gunther   has hundreds of appendages  that can grab onto sand,   and James didn’t want to accidentally  snap the worm in half with his tweezers.   So instead of showing all the features of Gunther  that we wanted to show, we’re going to show clips   of this bristle worm instead because it kind  of resembles Gunther, except a lot tinier.

Gunther is hopefully still somewhere in that  tank, living a nice life in the burrow it dug   for itself. But it’s hard to know exactly where  in the tank Gunther made its home because it   would only show activity in the dark. The moment  James tried to turn the lights on and watch the   worm in motion, it would vanish again under the  sand.

And as it became harder and harder to find,   James kept hoping that one day, something  would bring another bristle worm to him. And then, one day, James received a  package from a coral farm containing   sediments and other things that might  contain some interesting organisms.   We talked about some of those organisms  that James found in our last episode. But in addition to all of those  organisms, James found several   species of his long sought after bristle worm.

Bristle worms are also known as polychaetes,   and they’re part of the segmented  worm phylum known as Annelids. The name “polychaete” translates in Greek to  “many hairs.” Those stiff hairs are called   setae, and for most polychaetes,  they’re attached to paddle-like   appendages called the parapodia that  branch off each segment of the worm. Our giant friend Gunther most likely  belongs to the order Eunicida,   but its microscopic look-alike is more unknown  to us.

But we can imagine that it spends its   life crawling around the sand and feeding on  algae, or whatever else it can take a bite out of.  You can see this one moving its mouth in  slow motion, like a weird pair of pincers   inside clamping down on something, and the  movement is even more dramatic in full speed. This probably looks like a bunch of  tiny individual orange worms tangled   together. But it is, in fact, a worm belonging  to the genus Cirratulus that can get to around   12 centimeters in length.

And along with  its distinctive color, the worm is easy   to spot in wet sandy mud because of those  threads you see waving across your screen.   Some of these threads are tentacles,  but others are actually gills. And in the water, those threads seem to float  serenely. But this effect is lost on land.   In a paper from the beginning of the 20th  century titled “Notes on the Ecology of   Cirratulus tentaculatus,” the author  wrote, “When withdrawn from the mud   Cirratulus presents an exceeding  limp and bedraggled appearance.” This worm has a more imposing appearance  but also a funnier name.

It belongs to the   terebellid order, but it’s known as a spaghetti  worm. These tropical worms live in sand,   building tubes out of gravel and limestone to  live in. Their tentacles spill out from the tube,   sometimes extending as far as a meter to gather  building materials and food for the worm.

To reproduce, spaghetti worms will release their  eggs and sperm into the water, but only at night   and sometimes even without other males or females  around. They seem to do this on a lunar cycle,   with a limited two week window for these  gametes to release and find each other. That   seems like an extraordinarily chance-y way to  reproduce, but it seems to work for this worm.

These are the bristle worms we were able  to find from our coral farm samples. And   so it seems like our hunt for  this white whale might be over. Except, the more we’ve been reading about  bristle worms, the more we wish we could find   even more.

Because these are an animal whose  existence seems designed to inspire lists   of fun facts and bizarre trivia. There  are thousands of species of polychaetes,   and they all seem to have something  remarkable or weird about them.  Some spend their lives in tubes that stick up  from the sand, using their parapodia to paddle   water through the burrow. Others have managed  to carve out lives near hydrothermal vents.   Some sound like they’re straight out of a horror  novel, growing up to ten feet long or dining on   the bones of decomposing animals.

And some  even have eyes on both ends of their bodies. So knowing that all of these  different species are out there,   how could we ever end our quest  for the bristle worm? Thank you for coming on this journey with us as  we explore the unseen world that surrounds us.

This episode has been brought to you by Curiosity  Stream, a subscription streaming service that   offers thousands of documentaries and non­fiction  TV shows from some of the world's best filmmakers,   including award winning exclusives & originals. They cover topics like history, nature, science,   food, technology, travel, and more! And to balance out all of the creepy   crawlies you’ve been watching throughout this  episode, this week we’re going to recommend   checking out The Science of Cute on Curiosity  Stream.

Not only will you get to see a bunch   of super cute puppies, but you’ll also learn  about the domestication of dogs and how their   behavior and anatomy has changed over time to  make them just the cute little things ever. You can stream CuriosityStream’s library,  including their collections of curated programs   handpicked by their experts, to any  device for viewing anytime, anywhere,   and if you go to  and use the code “Microcosmos” to sign up,   it will only cost you $14.99 for an entire year! The people whose names are on your screen right  now, they are our Patreon patrons.

We are so happy   and excited to be able to continue our search  of the microcosmos doing weird things like   writing to coral companies and having them send us  samples. I think that’s just the beginning of some   of the cool stuff we can do, and these patrons  are the reason that we can do it. So thank you   so much to all of them, and if you want to become  a patron you can go to

If you want to see more from our  master of microscopes, James Weiss,   and why wouldn’t you, check  out Jam & Germs on Instagram,   and if you want to see more from us, there is  always a subscribe button somewhere nearby.