Two-Headed Space Worms : Wow in the World What in the world are Planarian Flatworms? Why in the world did scientists send them on a mission to outer space? And where in the world are their mouths if not on their heads?! Join Guy Raz and Mindy Thomas for a tale of two one body. It's the latest who, what, when, where, why, how, and WOW in the world of WORMSTRONAUTS!
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Two-Headed Space Worms

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Two-Headed Space Worms

Two-Headed Space Worms

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THE POP UPS: Stay seated. Three, two, one. Ignition.

Get ready for an adventure of magnificent proportions.

(Singing) I don't know what you've been told, but we're in a golden age. So many discoveries that are jumping off the page. Wow in the world. Wow in the world. Wow in the world. Wow in the world. Wow in the world. Wow in the world. Wow in the world. Wow in the world. Wow in the world.

With Guy and Mindy.

We're on our way, Houston.



Hi, Mindy.


Good morning, Guy Raz. Are you ready to attack this day with vim and vigor - or yes?

RAZ: I just had the longest, craziest, most confusing dream.

THOMAS: Did you say dream?

RAZ: Yeah, I've got to tell you all about this dream.

THOMAS: (Imitating sound of static). Bad connection. (Imitating sound of static). Can't hear you talk about your crazy, long dream.

RAZ: That's weird. Everything sounds fine on my end.

THOMAS: Ah. (Imitating sound of static). Ooh.

RAZ: You know what, Mindy? I'll just come over and tell you all about my dream in person. It's too long to share over the phone, anyway. I'll be right over.


THOMAS: Bad connection.

RAZ: Mindy, open the door. I know you're in there.


THOMAS: Good morning, Guy Raz. You're looking bright-eyed and bushy-tailed this morning.

RAZ: OK, now back to my long, crazy dream...

THOMAS: Ah, this is going to take all day.

RAZ: So I was in outer space, but it didn't look like regular outer space. And I just stumbled upon the International Space Station - only, it looked like a gas station. It was mixed with shooting stars, and they were spraying from the pumps.

And then there was a slug lord that ruled all of the astronauts, but the astronauts were actually hermit crabs. And they were dressed in pink flamingo spacesuits. And there was space junk flying everywhere. And then a robot space worm lost its head. And - but when I turned around, two heads had grown back in its place.

THOMAS: Wait, what'd you just say?

RAZ: I went to outer space. I saw a worm lose its head.


RAZ: And then I saw that same worm grow two heads back in the same place.

THOMAS: OK, Guy Raz, what if I told you that at least part of your dream came true?

RAZ: Astronaut hermit crabs in flamingo spacesuits?

THOMAS: No, going to outer space and coming back with two heads.

RAZ: Mindy, what are you talking about?

THOMAS: So you've heard of flatworms before, haven't you?

RAZ: Yeah.

THOMAS: OK, so there is this one type of flatworm called the planarian flatworm. And they're - are these super flat, tiny, little worms with kind of triangle-shaped heads. And you could usually find them in certain bodies of water.

RAZ: Oh, yeah. I've never actually seen one, but I've heard that they're some of the most resilient creatures on earth, that when they get knocked down, they get back up again.

THOMAS: Well, yeah, that's one way to look at it. I mean, you can chop them up, and chop them up, and chop them up, and those chopped-up little worm bits will not only survive, but they'll regenerate and regrow to create entirely new, whole flatworms.

RAZ: You mean that if a flatworm's head become separated from its body, the head will grow a new body?

THOMAS: Yup. And the body will grow a new head, and even new eyes and a new brain.

RAZ: Hey, that's a little like a starfish or a lizard. You know how a lizard can regrow its tail even if it gets pulled off?

THOMAS: Yeah. And all sorts of amphibians can regenerate their body parts too, like newts, and axolotls and salamanders. Oh, and there's even an African spiny mouse that can regrow its skin if it gets bitten off.

RAZ: Ooogh (ph), well, I guess studying these animals must be really important for medical scientists, especially the kinds of scientists who, you know, who study people who've lost arms and legs.

THOMAS: Exactarinos (ph).

RAZ: Gosh, I wish I could see one of those planarian flatworms in person.

THOMAS: Oh, well, in that case, why don't you just step this way, Guy Raz?

RAZ: Where are you taking me?

THOMAS: Now open this mysterious screen door to the backyard. Watch out for the cats.

RAZ: Whoa.

THOMAS: Right?

RAZ: Mindy, what is that?

THOMAS: Guy Raz, feast your eyes on my flatworm petting farm.

RAZ: Ugh.

THOMAS: And it's open for business.

RAZ: Mindy, you filled an entire baby pool with...

THOMAS: ...The world's largest personal collection of flatworms. Go ahead, check one out.

RAZ: No, thank you. I would not want to hurt it.

THOMAS: Hurt it? Guy Raz, you could literally chop these things up into little pieces, and they will still survive and regrow themselves.

RAZ: Well, I don't know, Mindy. They look like little aliens.

THOMAS: Go ahead, it's fine. Here, put these on. You can see them a little bit closer if you're wearing magnifying goggles.


THOMAS: But you're smart to be careful because some flatworms really are dangerous. So generally speaking, unless it's me inviting you to my flatworm petting farm, you should probably just not touch them.

RAZ: OK, I got.

THOMAS: Go ahead. Pick one up, and hold it like a baby.

RAZ: Hi, there, little guy.

THOMAS: Yeah, he is a little one, that for sure, even smaller than a grain of rice. His sister over there is twice his size.

RAZ: Mindy, I think he likes me.


RAZ: Hey, it looks like you might need some glasses, buddy, don't you?

THOMAS: Oh, yeah. The other thing about flatworms is that, for some reason, a bunch of them have googly (ph) eyes, which makes it hard for them to drive cars, and to shoot bows and arrows.

RAZ: What?

THOMAS: And while this guy and his buddies are cross-eyed, there are some species of flatworms that have a bunch of eyes spread all over their bodies, and some with only one eye and even some with no eyes at all.

RAZ: Well, then, how would they see?

THOMAS: Well, they don't, really. In fact, none of them do.

RAZ: But this little guy's got two googly (ph) eyes.

THOMAS: Well, besides being there to make him look adorable, those googly (ph) eyes are there to help them detect light so that he can squirm away from the light into the darkness to escape predators.

RAZ: So you're saying that after seeing me look at him through these magnifying goggles, he wouldn't even be able to recognize my face.

THOMAS: To him, Guy Raz, you and I might as well be the same person.

RAZ: Well, it is true that all humans are 99.5 percent identical, based on our DNA sequence.

THOMAS: Oh, boy.

RAZ: Wow, these are interesting creatures, Mindy.

THOMAS: Right?

RAZ: Aren't you interesting, you little creature?


THOMAS: Oh, boy.

RAZ: Aren't you? Yes, you are.

THOMAS: Oh, and he can't hear you, Guy Raz.

RAZ: What?

THOMAS: I said, he can't hear you, Guy Raz.

RAZ: I can hear you. I can hear you, Mindy. It's just that if he can't hear me, then why does he have these cute little ears on his head?

THOMAS: Oh, so those little ear-looking things are actually not used for hearing sound.

RAZ: But...

THOMAS: They're used for detecting chemicals.

RAZ: So they taste and smell with their ears.

THOMAS: Well, yeah, kind of. Crazy, right?

RAZ: Yeah, I'll say. So where's his mouth? Or does he eat with his ears too?

THOMAS: Guy Raz, how many times do I have to tell you that food does not belong in your ears?

RAZ: I believe I was the one to tell you that when you tried to store your chewed bubble...


RAZ: But then how does this little flatworm eat? I mean, I don't see a mouth on his little googly-eyed head.

THOMAS: Oh, that's because his mouth is not on his head.

RAZ: What?

THOMAS: ...Because it's on his belly.

RAZ: His mouth is on his belly and not his face? Is it this tiny tube on the underside of his body, here?

THOMAS: Yep, that little tube is called a pharynx, and it's attached to his mouth.

RAZ: So what does he eat?

THOMAS: Well, if you look over on that table by the fence over there, you will feast your eyes on an all-you-can-eat buffet that I have laid out especially for my flatworm petting farm

RAZ: Wow, that's really impressive and cute - so many tiny foods.

THOMAS: I know.

RAZ: Let's see what you've got here. Let me see through the magnifying goggles.

THOMAS: Here you go.

RAZ: Ugh, are those water fleas?

THOMAS: Water flea tacos. I added the taco part.

RAZ: Do they like eating flea tacos?

THOMAS: Oh, yeah - beats the alternative when sometimes, they eat each other.

RAZ: Ugh.

THOMAS: It's terrible.

RAZ: So how do their little tube-like mouths work?

THOMAS: Well, let's watch.

RAZ: Oh, perfect. Here comes a flea.

THOMAS: OK, so it looks like he spots his prey.

RAZ: He's going in for it. Oh, now he's wrapping himself around the flea.

THOMAS: ...Just like a Boa constrictor snake.

RAZ: And now he's devouring that flea through his mouth and tube.

THOMAS: Poor flea - didn't even see it coming.

RAZ: Look at him just sucking the flea through that thing.

THOMAS: Now, I should also note that besides his mouth and the pharynx tube attached, there is no other opening in his body.

RAZ: But Mindy, what goes in must come out.

THOMAS: Yeah, so this part's a little gross.

RAZ: Uh-oh, don't tell me.

THOMAS: Yeah, so he - you....

RAZ: Don't - don't say it, Mindy.

THOMAS: So since he doesn't have a butt...

RAZ: No, no, no, no, no, no, no, no, no, no, no, no, no.

THOMAS: He poops out of his mouth.

RAZ: Ah.

THOMAS: He poops out of his mouth, Guy Raz. Can you believe...

UNIDENTIFIED WOMAN #1: We interrupt this program for a brief barf break. WOW IN THE WORLD will return in three, two, one.

THOMAS: Here, buddy, just wipe it up with this.

RAZ: Ah, that's my tweed blazer.

THOMAS: So back your dream, Guy Raz...

RAZ: Yeah, great idea. I'm just going to go home, go back to bed and forget I ever, ever saw your mouth-pooping worm farm. I'm just going to...

THOMAS: Guy Raz, what if I told you that some of these flatworms were astronauts.

RAZ: I'm listening.

THOMAS: Now imagine this - a little group of wormstronauts (ph) wearing teeny, tiny spacesuits and helmets launch into outer space on a mission.

RAZ: Are you making this up, Mindy?

THOMAS: Only some of it.

RAZ: Ah, OK. What was the mission?

THOMAS: OK, that part is real. So Michael Levin, a professor of biology at Tufts University in Massachusetts, sent these flatworms on a mission to the International Space Station in low Earth orbit.

RAZ: He sent worms on this mission? I mean, I know a lot of humans, including me, who would be more than willing to do this.

THOMAS: Guy Raz, their mission was to show scientists here on Earth how microgravity or weightlessness in space might affect the way these flatworms are able to regenerate and regrow.

RAZ: So why did professor Levin and these other scientists want to find this out?

THOMAS: Well, they were curious to see how living in space for long periods of time might affect the cells, or the tiny building blocks of life inside human bodies.

RAZ: So earlier, you mentioned that if these flatworms were to, say, come apart...

THOMAS: You mean get chopped up?

RAZ: Yeah, so if they were chopped up, they'd be able to regenerate or regrow into multiple whole flatworms.


RAZ: So I have to ask - were these wormstronauts (ph) whole or, you know...

THOMAS: Chopped up.

RAZ: ...Or chopped up when they went to space.

THOMAS: Glad you asked, Guy Raz. So some of the worms were whole, but 15 of them were not.

RAZ: Ugh.

THOMAS: Since these scientists were so curious about the flatworm's ability to regenerate in space, they sent up a bunch of headless, tailless three-part worm fragments - or wiggling nuggets, or bits of chopped up, living worm bites, or...

RAZ: I get it, I get it. So how long were they up there?

THOMAS: Well, their footloose and fancy-free space station vacation lasted for a whopping five weeks.

RAZ: Oh, that must've been nice.

THOMAS: But after that, the party was over, and it was back to lab for another 20 months.

RAZ: Well, why so long?

THOMAS: Oh, because the scientists needed time to study them and to take note if they did anything weird.

RAZ: Weird compared to what?

THOMAS: Weird compared to another group of flatworms that stayed here on earth and did not go on an all-expenses-paid space station vacation.

RAZ: So what did they discover?

THOMAS: Well, for one, when they surprised all of the flatworms with a little petri dish pool party, the wormstronauts (ph) freaked out, curled up into little balls and basically just forgot how to squiggle and swim for like two hours.

RAZ: And do these scientists have any idea why?

THOMAS: Well, it's pretty complicated. But let's just say that some important things changed inside their bodies that caused them to grow differently.

RAZ: Interesting.

THOMAS: Oh, and remember how I said that their eyes were used more for detecting light than for seeing?

RAZ: Yeah.

THOMAS: Well, the scientists tried a little experiment where they shined a light on one part of the flatworms' little petri dish pool.

RAZ: But you said that these worms used their eyes to help them move away from light.

THOMAS: And they do, here on Earth.

RAZ: But after spending a few weeks in space...

THOMAS: After spending a few weeks in space, they no longer seem bothered by the light. They didn't even try to get away from it.

RAZ: And Mindy, you mentioned earlier that fragments, or parts of these flatworms, were sent to space. Were they able to regrow themselves like they would here on Earth?

THOMAS: OK, so, this is where it gets really crazy.

RAZ: Oh, boy.

THOMAS: Guy Raz, out of all of the flatworms and flatworm fragments that were sent to the space station, one of them came back with...

RAZ: Came back with what?

THOMAS: Wait for it.

RAZ: What?

THOMAS: Wait for it.

RAZ: Mindy.

THOMAS: Two heads.

RAZ: What?

THOMAS: Two heads - one on each end of its body.

RAZ: Just like the robot worm in my dream.

THOMAS: Just like in your dream.

RAZ: But two heads - I mean, is that normal?

THOMAS: No, it's definitely not normal. I mean, this kind of thing almost never happens to flatworms here on Earth. Oh, and it gets even weirder.

RAZ: How could this get any weirder?

THOMAS: So then the scientists chopped off both of its heads.

RAZ: Ah.

THOMAS: Oh, don't worry, Guy Raz. Flatworms do not feel pain the way we do, so...

RAZ: But still, I - OK, what happened when they chopped both heads off?

THOMAS: Well, the middle part of the body just grew two new heads - one on the top, one on the bottom. And over the course of the year, these scientists snipped off its heads two more times. And every single time...

RAZ: The two heads would regenerate or grow back again.

THOMAS: You got it.

RAZ: Unbelievable. So spending time in outer space really changed something within these worms. I mean, do the scientists know what caused the changes?

THOMAS: Well, it seems to be a combination of a bunch of different things.

RAZ: ...Like I guess loss of gravity, or weightlessness and extreme G-forces from takeoff.

THOMAS: Yup, just like those G-forces on that roller coaster ride we took.

RAZ: And I'd imagine just the trip alone would have an effect.

THOMAS: Oh, for sure. The vibrations from the travel, the stress of takeoff and landing....

RAZ: Wait a minute, I experience that kind of stress every time we take a trip on your carrier pigeon, Reggie (ph).

THOMAS: Not the same thing, Guy Raz.

RAZ: Yeah, fair enough - but do we know how these things cause this worm to sprout two heads?

THOMAS: Well, that's what these scientists are studying now. And one of the things they're hoping is that by understanding what happened with the flatworms in space, they'll have a better idea of how to help our human bodies regenerate and heal after injuries here on Earth.

RAZ: And I imagine this might give them a better idea of how long periods of time in space might affect our human bodies as well.

THOMAS: Indubitably. And studying these wormstronauts (ph) might give scientists more ideas on how to safely send humans to space for long periods of time.

RAZ: ...And maybe even lead to new inventions like flatworm-inspired, regenerative space robots, like in my dream last night.

THOMAS: Sky's the limit, Guy Raz.

RAZ: Well, actually...

THOMAS: Actually, if there's anything we've learned from this story, it's that there is no limit.

RAZ: I mean, just look at this pool of flatworms, Mindy.

THOMAS: Yeah - kind of hoping that one of them will grow arms, or a tail or something.

RAZ: Hey, there, little guy.


THOMAS: Careful - not too close.

RAZ: Oh, you little flatworm - my buddy, my pal, the future hope for all mankind.

THOMAS: What - um...

RAZ: Mindy, I knew he'd recognized me.

THOMAS: Yeah, Guy Raz, that's a different one.


THE POP UPS: (Singing) Wow in the world.


THOMAS: Earlier this week, for just a few short minutes, day became night as the great total solar eclipse swept across America - the first eclipse of its kind in almost a century. We asked Wowsers (ph) from coast to coast to send us your experiences watching this historical event, and boy, did you. We received hundreds of sky witness reports from all over the country. And we have loved reading, and seeing and listening to each and every one of them. We wanted to take a few minutes now to share some of those sky witness reports with you. Let's que the tape.


THOMAS: Hi, thanks for calling WOW IN THE WORLD. After the beep, get ready to record.


ARIANA: Hi, Mindy and Guy Raz. Our names are Ariana (ph)...

STUART: ...And Stuart (ph).

ARIANA: And we are 9.

STUART: ...And 7.

ARIANA: And we live in White Plains, N.Y. And our wow in the world is that on the solar eclipse day, we thought it would be dark, but it was light. And after, we made a lemonade stand, and it had a solar eclipse special - a mix of lemonade and iced tea.


JOAQUIN: Hi, my name's Joaquin (ph). I live in Austin, Texas. I saw the solar eclipse with my whole school today, and it was awesome. Bye.


TABITHA: Hello, my name's Tabitha (ph). I am from Beavercreek, Ohio. I saw a full solar eclipse today. There was a cool sun ring around it, and the moon was blocking most of the light. And the crickets came out.


BOBBY: Hi, I'm Bobby (ph), and I'm from Braswell, Ga. And I'm 6.

ELLIE: I'm Ellie (ph), and I'm 4.

BOBBY: We went to a Tallulah Gorge to see totality for the eclipse, and it's awesome. Bye, we love your show.


CAMORA: Hello, my name is Camora (ph). I live in Kansas City. Something that I liked seeing from the eclipse was how the sun streamed. And I like how the sky was light, and then it went to dark.


GREYSON: Hi, my name's Greyson (ph) and Adam (ph) and Jackson (ph). When the solar eclipse happened, all the shadows were crescents. It's like it was magic. Bye Mindy, Guy Raz. And don't give up the good work you're doing.


BRIAN: Hi, Guy Raz. Hi, Mindy. I'm Brian (ph), and I live in Delaware. And when I went to the solar eclipse, I had a big party. Bye.


ELLIS: Hello, my name is Ellis (ph). I'm 5-year-old - I'm from Charleston, S.C. When the solar eclipse is happening, it was dark, dark, and then it got, like, darker than nighttime. And it was thunder and lightning during the solar eclipse. It was awesome. Bye.


UNIDENTIFIED WOMAN #2: End of messages.

THOMAS: Hey, guys. Thank you so much for checking out this Thursday edition of WOW IN THE WORLD. Grown-ups, to keep the conversation going, we've posted some fun questions on our website, And we love hearing from you. Grown-ups, you can find us on Facebook, Twitter and Instagram - @wowintheworld. And our email address is Today's show was written by me and Guy Raz, and produced by Jed Anderson. Say hello, Jed.


THOMAS: Our theme song is written and performed by The Pop Ups. You can find more of their awesome music at Finally, we've loved hearing what's been wowing you. Thanks so much for sending in your voicemails. We listen to each and every one of them.

For a chance to be featured on an upcoming episode, have your grown-ups help you share something that's recently wowed you by dialing 1-888-7-WOW-WOW. Thanks again for subscribing and telling your friends about our show. We'll be back on Monday with a brand new episode. Until then, go forth, and find your own wow in the world.


THE POP UPS: (Singing) Wow in the world. Wow in the world. Wow in the world. Wow in the world. Wow in the world. Wow in the world.

UNIDENTIFIED CHILD: WOW IN THE WORLD was made by Tinkercast and sent to you by NPR.

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