The Most Charismatic Single Cell You’ll Meet Today

IRA FLATOW: This is Science Friday. I’m Ira Flatow. And now, it’s time for our very first Charismatic Creature Corner.

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Sorry, some of that [INAUDIBLE]– it’s going to be a fun segment, some of our favorite stories about creatures, bees, bats, birds, even the bacteria in your gut. Well, and starting this week, we’ll be featuring one charismatic creature a month. And by creature, we mean anything– animals, viruses, carnivorous plants. You name it.

And by charismatic, we really mean intriguing, charming, worthy of your curiosity. But we’ll let you decide if a creature makes the cut. Making the case for today’s creature is our Charismatic Creature Correspondent, Science Friday’s own Elah Feder. Hi.

ELAH FEDER: Hey. Hey, Ira, sorry about all that alliteration. So we asked our listeners on the Science Friday VoxPop app for suggestions for creatures. And they had a lot.

AUDIENCE: Yes, please, talk a lot more about the tardigrades.

AUDIENCE: I’d like to learn more about tardigrades.

AUDIENCE: Pangolins.

AUDIENCE: Narwhals.

AUDIENCE: Tardigrades.

AUDIENCE: I would like to know more about the emperor penguin.

AUDIENCE: Four-legged snake.

AUDIENCE: The wolverine.

AUDIENCE: Dumbo octopus.

AUDIENCE: Also I think known as the water bears.

AUDIENCE: Musk turtles.

AUDIENCE: Brown Japanese marmorated stink bug.

AUDIENCE: Thank you.

AUDIENCE: Thank you.

ELAH FEDER: So first, thank you to everybody who submitted suggestions. You can still submit them on the Science Friday VoxPop app at the end of this segment. So a lot of people were hoping for narwhals or penguins. Or tardigrades were really popular, and I totally get that. I really like them too.

But these creatures would not be particularly challenging for our very first Charismatic Creature Corner, because they are undeniably oozing with charm.

IRA FLATOW: I get it.

ELAH FEDER: And speaking of oozing– [LAUGHS] that’s my segue. That’s for you. We did get this message from Ronnie in Coudersport, Pennsylvania.

RONNIE: I am curious about slime molds. I have heard that they solve mazes. And I’d like to know more about creatures who do problem solving without having a brain.

ELAH FEDER: So Ira, today, I am here to you to convince you that slime molds are charismatic creatures. I’m going to have some help from two researchers. I’m going to talk to you about one slime mold in particular.

IRA FLATOW: OK, but first, you have to tell me what exactly is a slime mold.

ELAH FEDER: What is a– OK, I’m going to start by telling you what is not a slime mold, or what a slime mold is not. It’s not a mold, actually. That’s a misnomer. It’s not a plant or an animal or a bacterium or any kind of fungus. It is a protist, which actually does not mean a lot. The kingdom Protista is kind of like a junkyard for the natural world. It’s where we stick all of those creatures that are really hard to classify.

So slime molds are kind of a blobby thing. You can find them in leaf litter, growing under logs, inside rotting wood. There are a lot of different species with delightful names like dog vomit and wolf’s milk. But today, we’re going to talk about one species called Physarum polycephalum, which is the many-headed slime mold.

But to learn more about them, I actually called up a researcher in Sydney earlier this week, Tanya Latty. She studies collective intelligence. And just to paint a picture for our listeners, here’s Tanya explaining what these look like.

TANYA LATTY: So they’re yellow. They’re really mucousy and sticky. And I mean, if you touch them, they just kind of goop up your hands, really. It’s not something you really want to be touching at all.

They move so slowly you can’t quite see them moving. They have what I think is a lovely floral smell but everyone else tells me is gross. So yeah, they basically just look like mucus. That’s really what a slime mold looks like, like patterned mucus.

IRA FLATOW: Hm.

ELAH FEDER: [LAUGHS] So it doesn’t sound great. They can actually be really, really beautiful. We have some pictures up at sciencefriday.com/slimemold.

IRA FLATOW: So they look like patterned mucus– so far, so good. I hear they’re getting trendy as pets in France. Is that right? What do you need to know to have them as a pet?

ELAH FEDER: Yeah, that’s what I heard from a researcher in France, that they’re the new Tamagotchi pet. OK, so if you’re going to have a pet, which I do, slime molds like darkness, moisture. They also really like rolled oats, apparently. They really go wild for these.

No one knows why. I hear the American strain really likes the Quaker brand for some reason. So if you give them a rolled oat, they will slime over to it, engulf it, and pulse, which is apparently something they do when they really like their food.

IRA FLATOW: And what don’t they like? What do you have to avoid with them?

ELAH FEDER: You want to avoid light and dryness. So they like it dark and moist. So like our listener Ronnie mentioned, these goopy, mucousy things can do really incredible things like solve mazes.

But here is the truly astounding part. These creatures, organisms, if you want to call them, they are just one cell. They are one cell with a lot of nuclei.

TANYA LATTY: All the yellow goo, even when you see them and they’re like half a meter across in size, all of that goo is one single cell. It’s a unicellular organism. And it can get to those sizes because it has these millions of nuclei that just keep dividing inside of the same membrane. So you wind up with this enormous creature. But because they’re all sharing a single sort of envelope, it’s still technically one cell.

ELAH FEDER: So as you know, most cells are actually invisible to the naked eye. You need a microscope to see them. The ones in Tanya’s lab get up to about 12 inches in diameter. And there is one slime mold species that allegedly– this needs to be independently verified– but allegedly, it could cover 10 square feet and weigh as much as 44 pounds.

IRA FLATOW: Get out.

ELAH FEDER: Allegedly. [LAUGHS]

IRA FLATOW: 44 pounds square, that’s pretty cool.

ELAH FEDER: I mean, it’s one cell. That’s astounding. So this is where, I think, it gets truly interesting. Slime molds, for one giant goopy cell, are way smarter than they have any business being. And actually, it took people a long time to notice.

They were used as model organisms in labs for decades. But really, just to study cell mechanics, they’re really handy because, one, they’re, as we mentioned, visible. You can also cut them up into little pieces, and then each of those little pieces becomes its own independent slime mold.

And people weren’t really thinking about things like, well, what can a slime mold do? How do they behave? Until a Japanese researcher in 2000 changed all that. So to tell us more, we have Simon Garnier. He’s an associate professor at the New Jersey Institute of Technology, and he works on swarm intelligence. Simon, welcome to the show.

SIMON GARNIER: Hi, how are you?

ELAH FEDER: Good, how are you?

IRA FLATOW: Hey there, welcome.

SIMON GARNIER: Pretty good, thank you.

ELAH FEDER: So just– yeah.

SIMON GARNIER: No, no, go ahead.

ELAH FEDER: OK. To start us off, what did this Japanese researcher, Toshiyuki Nakagaki, what did he do in 2000 that got people so excited?

SIMON GARNIER: Well, he published a paper in Nature, I believe, that showed that slime mold was capable of solving a maze, right? So I don’t know. In newspapers, sometimes you have these little games which you have to go from one end of a maze to another and finding the shortest possible path. And that’s a complicated task to do, even for a human adult. But the slime mold was capable of doing that task in what seems like a very short amount of time for a slime mold.

IRA FLATOW: Now, I heard about them recreating the Tokyo railway network. Tell us about that.

SIMON GARNIER: Yeah, so imagine you’re the mayor of New York. And you’re trying to redesign the subway of New York City, which you know is necessary, I think. You are going to face a big challenge. The challenge is you’re going to have to build a network that’s both usable and robust to any form of disturbances.

So imagine like when the L train stops working, you need to be able to route the users through different routes. But at the same time, you want it to be cheap. So you don’t want to build too many lines. But you want enough connection between the lines so that people can go around.

So that’s a problem that is very complicated to solve. But Nakagaki in 2010 published this paper where he showed that slime mold is capable of finding the sweet spot, the right balance, between building a network that is very robust, very capable, but at the same time is relatively to be cheap to build. And this paper was done by comparing the property of the network built by slime mold to the property of the actual subway network in Tokyo.

ELAH FEDER: So I find this really impressive, although I think I find their ability to learn even more impressive. Maybe you could tell us a bit about that.

SIMON GARNIER: Yeah, so the beauty of optimizing things is something that is common to a lot of organisms. But the ability to learn is not necessarily present, at least that we know of, in all organisms on the planet. And so for a long time, it wasn’t clear whether slime mold was capable of learning and was capable of encoding information and use that information for later use.

And quite recently, actually, there’s been a number of studies that have showed that it’s capable of, for instance, anticipating events, which means that you have to learn when an event is likely to come. But there’s also other studies that show that slime mold is capable of learning that a bad stimulus actually has no consequence. So it’s a phenomenon that we call habituation. I don’t know if I should explain habituation is here.

ELAH FEDER: Yeah, please do.

SIMON GARNIER: Yeah. Yeah, habituation is a simple thing. If you are at a cocktail party and there’s some annoying voice in the background of someone singing bad music, the beginning is going to be extremely annoying to you. But as this sort of stimulus keeps being repeated, at some point, you’re going to habituate. Your reaction to that stimulus is going to decrease over time, allowing you to still function properly in an environment, even though there is annoying stimuli around.

And so that experiment that was done by– I’m guessing that’s the French researcher you talked to. [INAUDIBLE] showed that slime mold doesn’t like salty environment. If it has to cross a salty environment to find food, it will over time learn that it’s OK to cross these dangerous salty places in order to get access to food. So it will habituate to this negative stimulus in order to get access to a resource.

IRA FLATOW: Well, you’re sort of winning me over. Anything else you can tell me about the [INAUDIBLE]?

ELAH FEDER: We’re making the case here. If we want to convince Ira that slime molds are charismatic, is there anything else that he should know or think about?

SIMON GARNIER: Well, I think, for me, what’s absolutely fascinating with that organism is, as Tanya described it, it has the consistency of snot, essentially. It is bright yellow, which is not a very serious color. It doesn’t smell very good. It tastes even worse, just like old salad.

ELAH FEDER: Wait, pause.

IRA FLATOW: You’ve tasted them?

SIMON GARNIER: Oh, yeah, of course. You have to. If you’re a biologist, you have to taste what you’re working on at some point.

ELAH FEDER: Do you?

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SIMON GARNIER: Well, as long as it’s not going to kill you. You should probably try at least once. But yeah, so this organism is nothing impressive. When you look at it, when you see it for the first time, it doesn’t seem to be moving or doing anything impressive.

But then if you start posing a problem to that organism, you see that it’s capable of solving these problems in ways that are very close to the way our best algorithms are capable of solving these same problems. So for me, that’s the impressive part of it is that it’s probably the least sexy organism to look at. And in same time, it’s extremely, extremely smart, given the fact that, again, it’s just a sac of lipid and proteins that is blubbing around in the environment.

IRA FLATOW: There you go. I’m Ira Flatow. This is Science Friday from WNYC Studios, talking about slime mold with Elah Feder.

ELAH FEDER: So I had a question for you. I think it was earlier this week. Our video producer, Luke Groskin gave me a little slime mold, dehydrated, to keep as my own pet. It’s now the office pet. And I brought it into the studio today.

IRA FLATOW: It’s a yellow little streak. And you fed it an oatmeal flake.

ELAH FEDER: So I started by adding a little bit of water. I didn’t add enough because it dried back up. But today, I added more. It got really slimy. Can you see this, Ira?

IRA FLATOW: I can absolutely. Absolutely, it’s grown in size since earlier in the day.

ELAH FEDER: It’s all veiny, and yeah, slime moldy. And so we’re wondering if you had any tips for successfully raising our new– unnamed, yet unnamed. And we’ll take suggestions from listeners for the name as well.

SIMON GARNIER: Yeah, I mean, it’s an organism that’s actually fairly easy to grow. It likes humidity, right? If it’s not humid enough, it’s going to dry out. But actually, the good thing is, even when it’s dry, you can resuscitate– oh, it’s a complicated word for me. You can make it back, come to life, with just a little bit of water. So it needs a humid environment.

IRA FLATOW: Where do you get one? Where do you get one from?

SIMON GARNIER: Oh, you can get one in any of the woods around New York City or New Jersey. You can also order it online. There’s a number of companies that will ship you a kit of slime mold for– I don’t know– maybe $10 or $15.

IRA FLATOW: There you go.

SIMON GARNIER: So it’s very, very easy to get access to. And once you have it, if you find the right condition, you can grow it indefinitely, essentially.

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ELAH FEDER: I can not wait.

SIMON GARNIER: So a little bit of humidity, it likes warmer climates. So somewhere around 78, 80 degrees, it’s a good temperature for it, and then a lot of oatmeal.

ELAH FEDER: I’ve given it a single flake so far. So we’re just about out of time. We’ve only scratched the surface for slime molds. There’s a lot more. And if you want to go to sciencefriday.com/slimemold, you’ll learn more. I think that’s about it. I hope I’ve convinced you, Ira.

IRA FLATOW: Thank you. Thank you very much. Thank you for bringing all your guests on this show.

ELAH FEDER: Yeah, I wanted to thank you, Simon, for coming on. Simon Garnier–

SIMON GARNIER: Thanks for having me.

ELAH FEDER: –is associate professor at the New Jersey Institute of Technology. And also, a special thanks to Tanya Latty from the University of Sydney.

IRA FLATOW: Thank you both for joining us today. And we want to ask our listeners. What do you think? Are slime molds charismatic? You got something even better? If you have a creature you think that would make a great contender, send us a tweet @SciFri or leave a voice memo on our Science Friday VoxPop app.

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