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This goofy little guy is called a planarian.
Sure, it’s just a flatworm at the bottom of a pond.
But it has a very special superpower, one that scientists would love to harness.
To show you … well, it’s going to get a little bit slasher movie here.
OK, don’t worry.
It’s going...
To be...
OK.
Seriously.
I promise.
It doesn’t even hurt.
That would be curtains for most organisms.
I mean, this piece here is just a chunk, with no head and no tail.
But watch.
You can see under a microscope that overnight its wound heals closed.
OK, maybe we could do that – more slowly, of course.
But then it starts to regenerate, growing new tissue.
It’s that white part, called the blastema.
In a week … See those tiny little spots?
They’re new eyes grown from scratch.
But the planarian – can I call it that yet? – it still kind of looks like a blob.
By Day 12, it’s starting to look like a proper planarian.
It’s got a head – an entirely new one.
And a new tail.
And it’s doing its regular planarian things, like, uh, pooping.
That’s because one of the first things it started regrowing was a tube called the pharynx,
which is how things go in and out.
It sucks up food, like this beef liver that scientists are feeding it.
After three weeks, it looks totally normal.
From that one planarian, you get four.
Other animals, like this newt, can regrow a toe or a tail.
But planarians are practically the only animal that can regrow a head.
So why can’t we do that?
Well, it all comes down to powerful cells known as stem cells.
They’re the green dots here.
And they make up one fifth of a planarian’s body.
They can turn into different kinds of cells and make every new body part.
We only have stem cells that act like these when we’re embryos.
Once we grow up, we pretty much lose this ability.
Though doctors have been able to get us to grow back a fingertip.
But what if we could grow ourselves anew?
A whole arm, or a liver?
Scientists are trying to figure out exactly how planarians do it, and maybe one day these
humble flatworms could inspire new ways to heal our injuries.
Hi, it’s Lauren again.
This kind of planarian is from San Francisco.
Those aren’t ears; they’re auricles.
It uses them to feel around.
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