This episode is sponsored by Squarespace.

Go to squarespace.com/microcosmos to get a free trial and 10% off your first purchase of a website or domain. If you’re like a big stentor fan, it’s probably surprising to hear that what we are currently looking at is a stentor.

It looks more like a green cloud propped at just the right angle to look like, maybe like a rabbit's head. But stentors are famously built more like trumpets, not weird distorted bunnies. So what happened here?

Well, we did. Yes, what you are currently looking at is James, our master of microscopes, using a microscopy slide as a cutting board. This is not our usual approach to stentor care.

Usually, he gets his stentors from a nearby park, brings them home, and pampers them with a drop or two of milk. Within a day, they grow so big that they are visible to the naked eye. Stentors are single-celled eukaryotes, so the fact that they can get so large has always made them quite striking to us.

And they are always fun to watch. The cilia around their oral apparatus are always buzzing and gathering food, and the stripes lining their bodies can be filled with pigments that make these giants even more vivid against the rest of the microcosmos. And we’ve always been intrigued by the famous capacity for stentors to regenerate.

So we wanted to spend today watching a stentor put itself back together. Now usually, we try to avoid hurting our microbial friends. In this case, though, we made an exception because, as we will see, stentors can handle it.

Our stentor friend from the beginning of the episode was a casualty of this goal, and as we can see, it’s still a ways from looking like an actual stentor. We can see a little more definition to the shape, but not by much. It turns out that slicing up a stentor took a bit more work than we originally thought it would.

At first, James tried to be precise and use a razor blade to take on individual stentors in his sample. But with each movement of the blade, the surface tension of the water would move the stentor away. So instead, he went for the much less precise strategy, chopping away at the slide so that he ended with a bunch of individual stentors.

Then he used a pipette to grab individual pieces of stentors and transfer them over to a new drop of water so he could investigate them more closely. Now it might help to take a quick look at a healthy stentor to remember exactly what they’re supposed to look like. Obviously, things change from species to species, but there’s the general trumpet shape we’ve mentioned before.

And at the broader end of the stentor is its oral apparatus, fringed with cilia buzzing around to help the stentor gather food from its surroundings. So when we return to our regenerating buddy, it’s starting to look like a stentor you might quickly scribble on a napkin, perhaps when you’re telling your friend about the really cool Journey to the Microcosmos video you just watched. And examining the other diced up stentors from James’ samples shows us just how many different injuries they’ve sustained.

There’s headlessness…. Then there are these. It’s not even clear if we should be calling these stentors anymore.

They’re fragments, remnants of something that was once a stentor. And yet these organisms are remarkably capable of repairing themselves, even from these tiny fragments. Our stentor friend, for example, is looking practically refreshed.

As it turns through the microcosmos, the light reveals the striations down its body, and it looks like there was hardly a wound there at all. If we look closer at another stentor in the midst of patching itself up, we can see a much better view of those stripes that make them up. In this stentor, the parts without the stripes are the damaged part of the stentor’s cell membrane.

And if you zoom in closer, you can see the pigment granules that make up those stripes. When you see just how many granules there are, not to mention how neat and orderly the pattern formed from them is, the feat that stentors are performing in their regeneration becomes even more incredible to comprehend. Like sure, yes, it’s incredible to see our stentor look more and more like a stentor from this distance.

But it’s almost like looking at a piece of art: you may not notice all the details that make it a masterpiece, but they are there and they are vital. Scientists have been studying stentor regeneration for decades, chopping them up— often with a bit more precision than we exhibited here— so that we can watch a stentor reassemble its oral apparatus or whatever body part they’re interested in. Those experiments have taught us quite a bit about how stentors regenerate.

For example, the primary requirement for regeneration is that the stentor fragment contains part of the macronucleus— the large nucleus that extends throughout the stentor— because the macronucleus contains many, many copies of the stentor’s genome. So even with a tiny bit of the macronucleus, the stentor has all the instructions it needs to remake itself. And this process can be done in a couple of hours.

The molecular mechanisms that make stentors able to coordinate the many, many steps needed to rebuild themselves remain a mystery. But however mysterious, we can see those processes at work. Every time we return to our stentor, it’s like it manages to look more and more like a stentor, even if we can’t pinpoint all the specific changes that refine that appearance.

And this is where we will leave our friend, repaired and wandering around the microcosmos. Perhaps one day, it’ll run into another stentor, remade from another fragment of that original stentor. But by that point, I suppose, they will be two new entities entirely, like two ships passing in the night, not knowing that they were built with the scrap of the same old ship.

Thank you for coming on this journey with us as we explore the unseen world that surrounds us. And thank you to Squarespace for sponsoring this episode. Squarespace gives people a powerful and beautiful online platform from which to create their website.

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Now, maybe some of them aren't going to be super happy about how we treated our Stentors today. So I don't want to say that they are technically responsible for the content of this episode, but without them, this channel would not exist at all. So we are super grateful for them.

And if you would like to become a patron of Journey to the Microcosmos, you can go to Patreon.com/JoruneytoMicro. If you want to see more from our Master of Microscopes, James Weiss, you can check out Jam and Germs on Instagram. And if you want to see more from us, there is probably a subscribe button somewhere nearby.