Speaker 1: The fungus known as Ohio cortceps may be the most
Speaker 1: famous fungus in pop culture right now. I know it's
Speaker 1: a lobar, but still it's pretty cool. The Girl with
Speaker 1: All the Gifts, The Last of Us and a host
Speaker 1: of other books, movies, and video games feature this behavior
Speaker 1: manipulating fungal pathogen. But what does it really do? How
Speaker 1: do the zombie ants behave? And what do we know
Speaker 1: about how the fungus hijacks ant behavior? And Yes, at
Speaker 1: the end of the episode, I'll speculate on whether Ofio
Speaker 1: coort aceps could jump from ants to humans hijacking or
Speaker 1: behavior along the way. Welcome to Daniel and Kelly's Manipulated Universe.
Speaker 2: Hi. I'm Daniel. I'm a particle physicist, and I like
Speaker 2: to think of myself as a fun guy.
Speaker 1: You know, Daniel, you have made that joke before.
Speaker 2: It's too good?
Speaker 1: It is, It is good, It's good. I'm Kelly Wider Smith,
Speaker 1: and I'm a fun gal.
Speaker 2: And today we're talking about how funguses make us friends,
Speaker 2: or make us more fun no, or make us whact
Speaker 2: weird and climbed to the tops of.
Speaker 1: Things or something else entirely Yes, how ants get manipulated
Speaker 1: by a fungal pathogen, but probably well, wait till the end,
Speaker 1: we'll see what we think about people.
Speaker 2: I do like the idea that some of our weird
Speaker 2: behavior can be attributed to some part of us that's
Speaker 2: not really part of us. You know, that you can say, oh,
Speaker 2: that's just the fungus in my brain.
Speaker 1: Yeah. Absolutely. So. When I started my PhD, I was
Speaker 1: studying why organisms behave the way they do, so I
Speaker 1: was into animal behavior and I came across the Toxoplasma
Speaker 1: Gandhi literature, where that parasite that lives in our brains
Speaker 1: is a sociated with weird behaviors. And I got absolutely
Speaker 1: hooked on this idea that not all of our behaviors
Speaker 1: are attributable to our decisions, that maybe it's like a
Speaker 1: group effort the person who we end up being, and
Speaker 1: that you know, the microbes in our gut influence our
Speaker 1: behavior and the parasites in our brain influence our behavior.
Speaker 1: And I find this topic totally fascinating.
Speaker 2: But in some sense that's frame because it tells you, oh,
Speaker 2: it don't make all my decisions. In another sense that's
Speaker 2: terrifying because it's like, oh my gosh, I don't make
Speaker 2: all my decisions, and Katrina would probably be like, no,
Speaker 2: that is who you are. Your microbes are part of you.
Speaker 1: Yeah, No, I tind of agree with that take. But
Speaker 1: one thing that I think is fun is that one
Speaker 1: of the big names in the field that studies how
Speaker 1: Toxoplasma gandhia impacts human behavior, his name is Yaroslav Flagger.
Speaker 1: Apologies for my you know, forever bad pronunciations. He got
Speaker 1: into this because he was like, you know, I act
Speaker 1: kind of weird, sort of like not like other people.
Speaker 1: I wonder if I have a brain infecting parasite. And
Speaker 1: he gave himself a test and he did, and this
Speaker 1: set him off on the path of like wondering about
Speaker 1: how toxoplasmosis is associated with human behavior. It's an interesting question.
Speaker 2: Is it possible to have a fungus in your brain
Speaker 2: that makes you eat cookies too late at night? Can
Speaker 2: I blame that on somebody?
Speaker 1: Daniel? That is you? No, that's you, Daniel, that's you.
Speaker 1: And just for clarification, Toxoplasma gandhia is not a fungus,
Speaker 1: but there are a variety of different parasites that can
Speaker 1: live in human brains.
Speaker 2: Unfortunately, so if I do have a parasite, it's probably,
Speaker 2: like Daniel, stop eating cookies. Those are bad for you
Speaker 2: and bad for us.
Speaker 1: Yeah.
Speaker 2: Maybe, Wow, I'm overruling them.
Speaker 1: I don't know that cookie consumption as an implication of
Speaker 1: brain parasites has been studied thoroughly, So I don't want
Speaker 1: to go on the record.
Speaker 2: It's so easy to get to the edge of knowledge
Speaker 2: in biology. Wow.
Speaker 1: Yeah, we're not asking the right questions.
Speaker 2: Why does mainstream biology want to shut this question down?
Speaker 2: Kelly hmm.
Speaker 1: Yeah, I don't know, Daniel, not a great question, But
Speaker 1: you know, what is a great question?
Speaker 2: Give us a transition?
Speaker 1: Yeah, what is a great question is the question we
Speaker 1: asked our listeners.
Speaker 2: What was that?
Speaker 1: That was? What is summit disease? And if you would
Speaker 1: like to answer questions for us, send us at an
Speaker 1: email at questions at Danielinkelly dot org and we'll add
Speaker 1: you to our list. So let's hear what our listeners
Speaker 1: had to say in response to what is summit disease?
Speaker 2: Summit disease is an affliction that occurs when you can't
Speaker 2: stop hiking to the top of mountains, and it causes
Speaker 2: you to neglect the rest of your life. I think
Speaker 2: it's a brain disorder that makes you way at dead
Speaker 2: bodies on the way up Nepalese mountains. The sickness individuals
Speaker 2: get when they are at a high altitude and climbing mountains,
Speaker 2: for example.
Speaker 3: I think you're referring to high altitude sickness. Mountain climbers,
Speaker 3: when they go up above a certain elevation, can get
Speaker 3: lack of oxygen, pulmonary edema, cerebral edema, et cetera. No bueno,
Speaker 3: this is a disease a similar to OCD. You have
Speaker 3: to walk around adding things together.
Speaker 2: I could be mistaken, but I believe it is when
Speaker 2: an avid climber gets the impulsive need to tell the
Speaker 2: people around them all of the mountains that they have summitted.
Speaker 3: It seems like summer disease could be when I go
Speaker 3: on top of a mountain and my fingers swell up
Speaker 3: and I get tired.
Speaker 2: Easier except for way way worse.
Speaker 3: Summit disease is when you, after a really long climb,
Speaker 3: get to the summit, and then the mountain gods invade
Speaker 3: your brain make you do bad stuff.
Speaker 2: I don't know.
Speaker 3: When you reach the summit of a mountain and you
Speaker 3: can't stop throwing up because you're so sick of looking
Speaker 3: at mountains.
Speaker 2: I think that's when you're hiking and you've each an
Speaker 2: altitude or an elevation where the air gets dinner and
Speaker 2: you start to get headaches and funauseous and stuff like that.
Speaker 2: So I also would have guessed something that happens to
Speaker 2: you at the top of Mount Everest.
Speaker 1: Yeah, that is a totally reasonable answer. We have a
Speaker 1: very smart audience, but actually this is something that happens
Speaker 1: to insects and not to humans. And I'll also note
Speaker 1: that I laughed out loud at the uh you have
Speaker 1: to walk around adding things together. It took me a
Speaker 1: second to put that together and be like, oh, some
Speaker 1: it some it adding, and I laughed out loud. So anyway,
Speaker 1: thank you for that moment of revelation there.
Speaker 2: Well, I love this opportunity to dig into the real
Speaker 2: science that's sort of underlying some Hollywood myths. You know,
Speaker 2: there are these fun stories you hear sometimes in science fiction,
Speaker 2: but often these are inspired by actual and really fascinating
Speaker 2: on their own stories of what's going on out there
Speaker 2: in nature. So tell us, Kelly, what is the story
Speaker 2: that inspires all these Hollywood tropes?
Speaker 1: Well, So let's start with what is summit disease. And
Speaker 1: Summit disease is a thing that happens to a lot
Speaker 1: of different insects that are infected by fungus or by viruses.
Speaker 1: And the deal is that either the fungus or the
Speaker 1: virus gets an insect to climb high, and then it
Speaker 1: gets the insect to stay there instead of like coming
Speaker 1: down for the night. And then they like cling in
Speaker 1: some way and they stay up high and from that
Speaker 1: location they then die and they rain infectious particles down
Speaker 1: on their other insects below.
Speaker 2: They like explode.
Speaker 1: Uh you know, explode might be over selling it a little,
Speaker 1: but like, so, for example, there's a virus that infects caterpillars,
Speaker 1: and caterpillars go up during the day to like eat leaves,
Speaker 1: and then at night they usually come down and they
Speaker 1: like hide. But this when they're infected by this virus,
Speaker 1: they climb up and they stay there and then they
Speaker 1: die and they sort of liquefy and they rain virus
Speaker 1: particles down on the caterpillars that are below.
Speaker 2: They drip guey infected caterpillar down they do.
Speaker 1: Yeah, what a weather forecast that's oh yeah, cloudy with
Speaker 1: the chance of virus soup caterpillar bits. That's right, gross,
Speaker 1: But this also happens. There are like quote unquote zombie
Speaker 1: flies that are infected by a fungus and they'll climb
Speaker 1: up and they'll even like they'll climb up and then
Speaker 1: they'll spread their wings out to the side so that
Speaker 1: when they die, the fungus can come out of their
Speaker 1: back and their wings don't get in the way. And
Speaker 1: that one does it sort of like shoots like cannonballs
Speaker 1: out of their back down at the like flies below.
Speaker 1: And so, oh my gosh, this is a pretty common
Speaker 1: strategy you see in viruses and fungus that infect insects
Speaker 1: that want to go on to infect more insects.
Speaker 2: It's fascinating because you say it does this so that
Speaker 2: this other thing happens, which implies that there's some sort
Speaker 2: of high level decision making. But I know it's all
Speaker 2: like low level mechanistic blind evolution. So I'm curious to
Speaker 2: hear how all that comes together and how the whole
Speaker 2: process comes together. You know, it's one of these examples
Speaker 2: of like a complicated thing where you need lots of
Speaker 2: pieces all together to accrue the benefit, which always makes
Speaker 2: me wonder how it came together in the intermediate stages.
Speaker 1: Yeah, and this is why the zombie ant system is
Speaker 1: one of my favorite systems to study. So this phenomenon
Speaker 1: where some parasite or pathogen hijacks the behavior of its
Speaker 1: host so that the host is doing something that benefits
Speaker 1: the parasite, we call this manipulation, and it's really tempting,
Speaker 1: and we've talked about this in other episodes. It's really
Speaker 1: tempting when you see a host behaving weirdly to be like, oh,
Speaker 1: that's a manipulation that must benefit the parasite in some way.
Speaker 1: But while it's easy to come up with a story,
Speaker 1: it's harder to test that. And every once in a
Speaker 1: while we'll have a story where it sounds like the
Speaker 1: pathogen was benefiting, but when you look into it, it's
Speaker 1: not so. Mosquitos when they're infected by malaria, right after
Speaker 1: they get infected by malaria, they bite less, and there's
Speaker 1: a period where after the mosquito takes a blood meal
Speaker 1: that has malaria, that malaria is sort of maturing and
Speaker 1: can't transmit yet. So if the mosquito took a blood
Speaker 1: meal and got slept by a hand, then the malaria
Speaker 1: would die, and so that wouldn't be good. You know,
Speaker 1: in a very anthropomorphic way, the malaria quote unquote doesn't
Speaker 1: want the mosquito to get killed or to take blood
Speaker 1: meals at that point.
Speaker 2: While it's still developing and preparing.
Speaker 1: That's right. But once it's ready, once it's in the
Speaker 1: mosquito salivary glands and could transmit to a human, those
Speaker 1: mosquitos start biting even more. So this was thought of
Speaker 1: as manipulation. The parasite is protecting the mosquito and itself
Speaker 1: until it can transmit, and then once it transmits, it
Speaker 1: gets the mosquito to bite a lot more. And that
Speaker 1: really sounds like it would be good for the mosquito.
Speaker 1: It's a good story, it's a great story. But it
Speaker 1: turns out that if you activate the mosquito's immune response
Speaker 1: by for example, killing bacteria and then putting those dead
Speaker 1: bacteria into the mosquito, it will do the same thing.
Speaker 2: Even though it doesn't benefit that bacteria.
Speaker 1: That's right. Where Yeah, the bacteria are dead, they're just
Speaker 1: making the mosquito's immune system activate, and this is what
Speaker 1: the mosquito does. So it could be like when the
Speaker 1: mosquito's immune system is activated, it just kind of wants
Speaker 1: to hunker down. It's not as fast, it's feeling kind
Speaker 1: of crummy. It's just taking a nap before it's ready
Speaker 1: to go again. And so that's probably not manipulation. It
Speaker 1: doesn't look like the malaria is doing that. That's something
Speaker 1: that's driven by the mosquito.
Speaker 2: Could still be in response to the malaria. Right when
Speaker 2: it gets infected, it does this, and the malaria can
Speaker 2: benefit from it. You're just saying it's not something that
Speaker 2: the malaria has specifically engineered to benefit itself. It's something
Speaker 2: the mosquito is already doing or would otherwise have done.
Speaker 2: Fascinating exactly.
Speaker 1: Yeah, So trying to figure out who's driving the change
Speaker 1: in the behavior and how it actually benefits is much
Speaker 1: harder than coming up with the initial story. Yeah, and
Speaker 1: so what I love about the zombie ants is that
Speaker 1: this system has been studied in quite a bit of detail,
Speaker 1: and so we're actually starting to nail down the various
Speaker 1: pieces of what's happening here.
Speaker 2: Well, that reminds me of our conversation with Capo hen
Speaker 2: and when we were talking about science and storytelling and
Speaker 2: how much of science is storytelling is saying this happens
Speaker 2: because of that, because of this other thing, and sometimes
Speaker 2: the statistics or the mechanics of it don't always support that.
Speaker 2: It's just we are trying to extract stories because stories
Speaker 2: make sense to us.
Speaker 1: Yeah, and I think sometimes we get a little carried
Speaker 1: away with our stories and we don't necessarily have facts
Speaker 1: to support every piece of the story. And so this
Speaker 1: system is nice because almost every piece of the story
Speaker 1: has been dug into to some degree.
Speaker 2: All right, then carry us away to a story, Kelly
Speaker 2: tell us about manipulation of ants.
Speaker 1: Okay, you are a little ant walking around on the
Speaker 1: forest floor. Unbeknownst to you, you have stepped on a
Speaker 1: fungal spore. The fungus gets in between the cuticles and
Speaker 1: invades the body.
Speaker 2: Wait, I'm a little ant and I have cuticles still exoskeleton.
Speaker 1: I think they call that cuticle. I don't study ants.
Speaker 2: Man. What's the name of my aunt? Am I Dantiel?
Speaker 1: Yes, yes, you're Danchel.
Speaker 2: Walking around the forest with my little cuticles.
Speaker 1: Okay, so poor Danchel has picked up a fungus. Danchel
Speaker 1: doesn't realize that he's infected. Actually, if you're a forger,
Speaker 1: you're probably a female. So this anyway, this is not
Speaker 1: working great. But anyway, so the little ants, the little
Speaker 1: ant has gotten infected, doesn't realize it. It goes back
Speaker 1: to its nest. The nest mates don't seem to realize
Speaker 1: that it's infected either. But a couple weeks after it
Speaker 1: initially gets infected, it starts walking out of the nest.
Speaker 1: And this nest is up in a tree, and it
Speaker 1: starts rumbling down. We call it a drunk walk. So
Speaker 1: it sort of starts stumbling down the tree and then
Speaker 1: it walks along the forest floor and it climbs up
Speaker 1: a stalk and this is in the tropics. It climbs
Speaker 1: up a stalk or a stem of something to about
Speaker 1: twenty plus or minus two centimeters. This is happening at
Speaker 1: solar noon and on the north northwest side of the plant.
Speaker 1: It goes underneath a leaf, bites down with its mandibles.
Speaker 1: These are like the pinsy mouth parts it has, and
Speaker 1: then it will never move again and it dies.
Speaker 2: Wow. So it has to go all the way down
Speaker 2: the tree just to find the stalk to climb up.
Speaker 1: Yes, yep, just to find the stock to climb up.
Speaker 2: Fascinating.
Speaker 1: And then the ant dies and a stalk comes out
Speaker 1: of the side of its neck and it forms a
Speaker 1: ball at the sort of like top ish part of
Speaker 1: the stalk, and then fungal spores rained down on the
Speaker 1: forest floor and the cycle starts again.
Speaker 2: The stalk is not from the plant, it's some like
Speaker 2: weird fungal thing.
Speaker 1: Yeah, it's the fungus makes it so the fungus, now
Speaker 1: that the ant is dead, it starts using all of
Speaker 1: the ant's internal body parts and converting it into fungus
Speaker 1: and makes this stalk that rains fungal spores down, and
Speaker 1: the cycle starts again.
Speaker 2: This sounds like a science fiction horror movie. You're telling
Speaker 2: me this is happening on our planet all the time.
Speaker 1: Oh my it is. And okay, so what blows my
Speaker 1: mind is that that is so specific. Like one of
Speaker 1: one of Zach's gripes about me as a human being
Speaker 1: is that I am really bad at estimating distances, and
Speaker 1: like He'll be like, well, what's you know? Do it
Speaker 1: about two feet from here, and I'll be like, I
Speaker 1: have no idea what you mean, Like, I just I
Speaker 1: can't do that. Whereas this fungus by remote control is
Speaker 1: getting the ant to about twenty five centimeters plus or
Speaker 1: minus like two and a half centimeters. I think earlier
Speaker 1: I said it was twenty but it's more like twenty five,
Speaker 1: which is very specific. And so how does that happen.
Speaker 1: We're gonna get to our best guess right now at
Speaker 1: how that happens a little bit later in the show.
Speaker 1: But it's amazingly specific.
Speaker 2: Wow.
Speaker 1: But now it's worth mentioning that. Okay, that is a
Speaker 1: story from O fio cordus steps unilateralis And just to
Speaker 1: complete the.
Speaker 2: Loop, it rains it down on the forest floor and
Speaker 2: then the next ant can come along and pick it
Speaker 2: up in there goals and that's how it completes the cycle.
Speaker 1: Danchel, the she ants does pick up dante l Yeah, Dantel,
Speaker 1: that's right, picks up the fungus and the cycle starts again.
Speaker 2: Wow, all right, okay, And so the name of this
Speaker 2: fungus is some crazy Latin phrase. Yeah.
Speaker 1: So Ofio cordyceps unilateralis. The unilaterallysis refers to the fact
Speaker 1: that the stalk comes out of one side of the
Speaker 1: ant's head. And so opio coortceps is a genus. So
Speaker 1: there's a lot of different fungus species that are very
Speaker 1: closely related, and they infect different ant species, so they
Speaker 1: seem to specialize on different species. So there's actually a
Speaker 1: bunch of ants all over the world that are infected
Speaker 1: by this fungus in slightly different ways. So the story
Speaker 1: isn't the same for all of them. The story I
Speaker 1: gave you is a story that I'd initially read for
Speaker 1: Ophagio Cordyceps unilateralis infecting an ant species in the tropics.
Speaker 1: But yeah, there's a lot of this happening in our world, and.
Speaker 2: Within this species of ant and this species of fungus.
Speaker 2: You're saying, there's not a lot of variation in the
Speaker 2: behavior of ants. They like basically all do the same
Speaker 2: march to death and then brain.
Speaker 1: Explosion, brain explosion or you.
Speaker 2: Know, fungal stock extrusion or what.
Speaker 1: Yeah. Yeah, So we are going to talk about how
Speaker 1: they differ a little bit. The details can differ depending
Speaker 1: on where you are, but the story is generally the same.
Speaker 1: That they find a way to be up above the
Speaker 1: areas where the foragers usually go so that they can
Speaker 1: rain the spores back down.
Speaker 2: Again. Wow, amazing, So tell us how it works.
Speaker 1: So first, I want to note we call these zombie ants,
Speaker 1: and I often get people in the field grumpy with
Speaker 1: me for calling them zombies because they're like people are
Speaker 1: gonna think they come back from the dead. Dear listener,
Speaker 1: I don't think that you think that ants come back
Speaker 1: from the dead. But just to be clear, the zombie
Speaker 1: ants do not come back from the dead. They are
Speaker 1: their behavior is getting hijacked while they're alive, and then
Speaker 1: they die in a very particular position that benefits the fungus.
Speaker 2: So you're saying they're not zombies because the ants haven't died.
Speaker 2: They're just in some sort of like controlled state where
Speaker 2: they're not really acting the way they would if they
Speaker 2: were normal ants. They're like drunk or they're hallucinating or something.
Speaker 1: Something like that, and yet it looks like their circadian
Speaker 1: rhythms are getting messed with. So Terarissa de Becker's lab
Speaker 1: has looked at how a big part of the manipulation
Speaker 1: seems to be them doing kind of normal behaviors but
Speaker 1: at abnormal times.
Speaker 2: So that seems to me a very technical definition of zombie.
Speaker 2: I mean, if humans, for example, were infected by something
Speaker 2: which made them stagger around and want to eat brains,
Speaker 2: but weren't technically dead, would you be there being like,
Speaker 2: excuse me, you're not a zombie.
Speaker 1: Sir, No, Because I love fiction in all of its forms,
Speaker 1: and as long as the rules are consistent in the
Speaker 1: world that's created, I don't care. So when I use
Speaker 1: the word zombie, I basically just mean an organism where
Speaker 1: a significant amount of its behaviors seem to be under
Speaker 1: the control of another critter, and those behaviors are good
Speaker 1: for the parasite but usually bad for the host.
Speaker 2: All right, well, let's take a break because I definitely
Speaker 2: need one, and come back and hear all about the
Speaker 2: details of how this fungus controls this an. Okay, we're back,
Speaker 2: and we're talking about the name of a fungus that
Speaker 2: I cannot pronounce but is amazingly adept at manipulating ants.
Speaker 1: This is a really nice like turn of the tables.
Speaker 1: Usually I'm the one who can't pronounce things. We've got
Speaker 1: to do more episodes with like complex latinate names. But okay,
Speaker 1: So one of the first things I think is so
Speaker 1: amazing about this system is that it evades the social
Speaker 1: immune system that ants have. So ants are very genetically
Speaker 1: related to one another, and they work together for this
Speaker 1: common goal of like helping the queen create more offspring
Speaker 1: and stuff like that.
Speaker 2: And they have complex fractional relationships, right, It's not just
Speaker 2: like you have kids that are half you. You're like
Speaker 2: related by a quarter or a sixth or a third
Speaker 2: or something complicated. Right.
Speaker 1: I think it's like three quarters. Like you're way more
Speaker 1: closely related than like, you know, my brother and I
Speaker 1: would be, for example, typical siblings, and so they're like,
Speaker 1: you know, pretty close to you genetically. And so this
Speaker 1: tends to result in what look like ultruistic behaviors. And
Speaker 1: so if one of the ants comes into the colony
Speaker 1: and is clearly infected with something, the nest has a
Speaker 1: like social immune response where other nestmates will be like, oh,
Speaker 1: you can't bring that in here, man, and they will
Speaker 1: in some cases kill that ant and then go put
Speaker 1: it in like a graveyard somewhere far away from the
Speaker 1: nest so that it can't infect the rest of the.
Speaker 2: Nest based just on the behavior. It's not like it's
Speaker 2: giving off some pheromones or something.
Speaker 1: I think in a lot of cases we don't know
Speaker 1: exactly how the nest mats can tell. It's probably some
Speaker 1: combination of behaviors. And then ants are a species that
Speaker 1: in particular tends to communicate a lot with chemical cues.
Speaker 1: So it could be that they sort of smell or
Speaker 1: whatever taste and nestmate and they're like, no, that's it's weird.
Speaker 1: We're kicking you out, Daniel.
Speaker 2: You taste funny. We're killing you.
Speaker 1: Yeah, that's right, that's right, Daniel. It's not how your
Speaker 1: forehead is supposed to taste. And I licked it and
Speaker 1: now you can't live here anymore. Danchel, danchel. And so anyway,
Speaker 1: so usually when an infected nest mate comes back, it
Speaker 1: gets picked up on and they get killed and kicked out.
Speaker 2: Brutal but fair.
Speaker 1: Brutal but fair. And this is a pathogen that you
Speaker 1: would want to put a stop to. So you know,
Speaker 1: if they don't capture this individual and kill it, it
Speaker 1: is going to create essentially like a stock of infectious
Speaker 1: propagules nearby. So anyway, there should be selective pressure for
Speaker 1: this part.
Speaker 2: And so how does it evade this selective pressure? Why
Speaker 2: can't the other ants tell?
Speaker 1: So we don't have a great handle on why the
Speaker 1: other ants can't tell. Part of it seems to be
Speaker 1: that in at least some systems. So I'm going to
Speaker 1: be talking about this system like every system acts the
Speaker 1: same way, but just sort of like with the tartar grades.
Speaker 1: Some questions have been asked in one ophiocordycep species infecting
Speaker 1: one ant species. Some questions been asked in other systems,
Speaker 1: but we're going to mix and match for the purpose
Speaker 1: of this show. But there's the disclaimer. So some ants,
Speaker 1: the timing of their behavior changes and they interact with
Speaker 1: nestmates less often, and so part of the story might
Speaker 1: be that instead of just like blindly going into the
Speaker 1: nest and then getting found out, these ants that are
Speaker 1: infected are avoiding nest mates so they never get found out,
Speaker 1: they never get their forehead licked, and so so they're
Speaker 1: able to escape in that way. It could also be
Speaker 1: like the scent of the fungus is being masked in
Speaker 1: some way, but through mechanisms we don't understand, it manages
Speaker 1: to evade the social immunity of the nest.
Speaker 2: Wow.
Speaker 1: Amazing, Yeah, pretty cool. All right, So now you've got
Speaker 1: this ant that's infected. It's nest mates haven't killed it
Speaker 1: like they probably should have, and then at some point
Speaker 1: it's does that Drunkard's walk, and we don't really understand
Speaker 1: why that drunkard's walk happens. But there is a chemical
Speaker 1: that's produced by the ant that is associated with something
Speaker 1: that causes like staggering and seizures and other insects. And
Speaker 1: so we think that it's going out there and it's
Speaker 1: starting to do this staggering thing because of some chemicals
Speaker 1: produced by the fungus. It gets down to the forest floor,
Speaker 1: and now the interesting question is how does it know
Speaker 1: where to go? So this is the Summit disease part.
Speaker 1: It starts climbing up, but we're trying to figure out
Speaker 1: how does it know where to stop? How does it
Speaker 1: know where a good spot is.
Speaker 2: Well, it's very confusing to me that the behavior is
Speaker 2: so complex that it includes climbing down and then climbing up,
Speaker 2: Like I could see it somehow is pulling on some
Speaker 2: lever inside the brain to make it go up, to
Speaker 2: make it go down, but to make it go down
Speaker 2: and then up like that's really amazing.
Speaker 1: That is really amazing. I mean, I think part of
Speaker 1: the selection pressure there. And this is just me telling
Speaker 1: a story. I haven't I don't know that we've tested this,
Speaker 1: but if the ant had gone down, it's probably one
Speaker 1: going down a big trunk, and they tend to attach
Speaker 1: to like thin stems, and we'll get into that in
Speaker 1: a second. But also if it just kind of clung
Speaker 1: in an area where foraging ants would be going up
Speaker 1: and down. Anyway, if a four ant sees a dead
Speaker 1: ant with a stalk coming out of its neck, that
Speaker 1: it is going to throw over into the trash can,
Speaker 1: and so that would be the end for the fungus too.
Speaker 2: So that tells us why that strategy, the simpler strategy
Speaker 2: wouldn't work of just like clinging to the tree. But
Speaker 2: it leaves us still impressed with this complex strategy of
Speaker 2: climbing down and then climbing up.
Speaker 1: Right, And so let me go ahead and jump ahead
Speaker 1: a little bit to the benefit of climbing back up again.
Speaker 1: So there's been an experiment done where they took ants
Speaker 1: that had like settled in at a particular location and
Speaker 1: they cut the leaf off that the ant was on
Speaker 1: and they moved it up. And when you move it up,
Speaker 1: the temperature and the humidity are no longer good for
Speaker 1: the fungus, and the fungus can't make that stalk and
Speaker 1: it can't make the infectious propagules that rain down on
Speaker 1: the other foragers, and so there is this like kind
Speaker 1: of narrow band that the fungus needs to be in
Speaker 1: in order to complete its development. And so you know,
Speaker 1: it takes some work to find exactly the right spot.
Speaker 2: And it's fascinating to me to imagine all the evolutionary
Speaker 2: dead ends. You know, ants that just went down and
Speaker 2: never climbed up, ants that climbed up the tree instead
Speaker 2: and didn't propagate. It's incredible that this whole thing came together.
Speaker 1: Yeah, yeah, it really is well, and I'm sure that
Speaker 1: a lot of times when researchers go out to study
Speaker 1: this kind of stuff, like you know, if you're too low,
Speaker 1: then spiders and other scavengers come along and they'll eat
Speaker 1: the zombie ant. And so there's probably some instances where
Speaker 1: the ant dies and the wrong spot, but the researchers
Speaker 1: never find it because something is eating it and it's gone.
Speaker 1: So you know, you do the best you can with
Speaker 1: the data you've got.
Speaker 2: So tell us about this climbing up. How does it
Speaker 2: know where to stop that it gets this right height? Like,
Speaker 2: do we understand the mechanisms for how it knows how
Speaker 2: high it is. It's not like doing GPS or something.
Speaker 1: So we think it's queuing in on light, which is
Speaker 1: amazing to me because it's inside the body of an ant,
Speaker 1: and so how is it getting information about light? So
Speaker 1: what they did was they found what's called ant graveyards,
Speaker 1: So the ants tend to accumulate in certain areas of
Speaker 1: the and so they're like, Okay, we know this is
Speaker 1: an area that's good because the fungus have chosen to
Speaker 1: be here before. And then they put a little bit
Speaker 1: of a light shade over the zombie graveyard and so
Speaker 1: now that area is getting a little bit less light
Speaker 1: than it was getting before. And what they found was
Speaker 1: that if you go back in future weeks, that area
Speaker 1: doesn't get as many new ants as nearby areas that
Speaker 1: have more light. So it looks like the fungus is
Speaker 1: driving the ants towards areas that have certain amounts of light.
Speaker 1: And then they looked there were still some newly infected
Speaker 1: ants that went into the areas with the shades, and
Speaker 1: if you followed what was happening with that fungus, overtime,
Speaker 1: the fungus was less able to produce those stalks and
Speaker 1: produce I'm just gonna call them baby fungus because no
Speaker 1: one wants to hear me try to say propagule again.
Speaker 1: So less baby fungus gets made in areas where you've
Speaker 1: got these shades, I see.
Speaker 2: And so the ants are using the light as a
Speaker 2: queue for where to go. Is the light important in
Speaker 2: making the baby funguses or is it just like a
Speaker 2: signal to the fungus of when the ant has crawled
Speaker 2: up to the right height.
Speaker 1: I think that the light is used as a proxy
Speaker 1: for information about temperature and humidity. And it could be
Speaker 1: that the light is important for some way too. I
Speaker 1: don't a fungus. I don't know, but nature's complicated, but
Speaker 1: it does look like things like temperature and humidity and
Speaker 1: light are all important for the way the fungus is
Speaker 1: able to develop.
Speaker 2: Wow. Fascinating.
Speaker 1: And this is the part that you see another insects too.
Speaker 1: We I talked about those zombie flies and those caterpillars.
Speaker 1: This climbing up thing happens in a lot of insects systems.
Speaker 2: And then you said they also bite down, they like
Speaker 2: clamp onto this plant. Why is that part important? Is
Speaker 2: it because the ant's going to die and you want
Speaker 2: it to stay there.
Speaker 1: Yeah, so you want the ant to stay put. And
Speaker 1: so in the tropics, what happens is they find a leaf,
Speaker 1: they crawl along the bottom of the leaf, along the
Speaker 1: major leaf veanes, and the ants will clamp down with
Speaker 1: their mandibles. They've got these pincers and their muscles will
Speaker 1: like hyper contract, so though like really strongly bite down,
Speaker 1: and then the ants will never be able to open
Speaker 1: their mandibles again and they will die there.
Speaker 3: Wow.
Speaker 1: And so that's how they hold on. And this is
Speaker 1: called the death grip. And one of the things that's
Speaker 1: interesting is that depending on where you are in the world,
Speaker 1: the death grip will look a little bit different. So
Speaker 1: in the tropics they tend to bite down on leaves,
Speaker 1: but if you go to like North Carolina, for example,
Speaker 1: instead of biting down on leaves, they'll bite down on stems,
Speaker 1: and they'll also wrap their legs around them, and so
Speaker 1: they'll hold on with their legs and with their pincy parts.
Speaker 1: And we think that the reason that they hang out
Speaker 1: on stems instead of leaves in areas that are farther
Speaker 1: north like North Carolina, is because in the tropics, leaves
Speaker 1: really never fall off the trees, or they at least
Speaker 1: don't have a seasonal pattern of falling off in the winter,
Speaker 1: whereas farther north, if you bite down on a leaf,
Speaker 1: you've got until like I don't know, August, September, or
Speaker 1: October before those leaves start to fall off. But if
Speaker 1: you're on the stem, then you can stay up there
Speaker 1: for longer, raining fire down upon the other ants. And
Speaker 1: so it looks like there have been four different instances
Speaker 1: where you've gotten this evolutionary transition from biting down on
Speaker 1: leaves to biting down on things like stems.
Speaker 2: This is fascinating. I love these moments in science when
Speaker 2: you can look at what's going on and unravel it
Speaker 2: and tell a story. I remember Hazel summarizing all of
Speaker 2: science once. She says, like, stuff happened and we figured
Speaker 2: out why, And I'm like, yeah, that's pretty much the
Speaker 2: whole idea. Yes, So by looking at this pattern of
Speaker 2: how things evolve differently in different parts of the world
Speaker 2: where the conditions are slightly different, we start to get
Speaker 2: a sense for how this all came together. That's incredible.
Speaker 1: Yeah, it's really incredible. And I got to see one
Speaker 1: in North Carolina. I'll put a picture on this online
Speaker 1: when it comes out. But we found one in North Carolina,
Speaker 1: and Andrew Turner found it. I was out looking for
Speaker 1: snakes and salamanders. And Andrew Turner, a friend of mine,
Speaker 1: was like, is that a zombie at And I freaked out.
Speaker 1: Anyone in like a one mile radius probably her me
Speaker 1: screamed because I didn't think I was going to get
Speaker 1: to see a zombie ant. So anyway, I've seen them
Speaker 1: in North Carolina. And then Andrew Turner put one in
Speaker 1: like a resin for me, and so I've got it
Speaker 1: on my desk and it is my favorite.
Speaker 2: And what are we looking at?
Speaker 1: We are looking at this is a bit of stem
Speaker 1: and on the bottom there's an ant that's got its
Speaker 1: legs wrapped around the stem. It's biting down with its mandibles.
Speaker 1: You can see it's got a big stalk coming out
Speaker 1: of the side of its head. The spore that the
Speaker 1: fungus would come out of is kind of small. It's
Speaker 1: hard to see, but it's about maybe three quarters of
Speaker 1: the way up the stem. Best thing I own.
Speaker 2: You have children too, don't for care.
Speaker 1: I don't own them. You know, they could choose to
Speaker 1: leave at one point, but this will never leave.
Speaker 2: It's a special place in your heart. It is all right.
Speaker 1: So the ant bites down. And one of the cool
Speaker 1: things about this, what we call a death grip, is
Speaker 1: that it leaves a very distinctive mark. So if you
Speaker 1: find leaves, you'll see the they've got. It looks like,
Speaker 1: you know, like scissors cut on either side of the veins.
Speaker 1: And there are forty eight million year old leaf fossils
Speaker 1: from Germany that have these little scissor cuts in them,
Speaker 1: and we think that these are like essentially fossil records
Speaker 1: of behavior showing that like around the time a bunch
Speaker 1: of the different mammalian species we're sort of evolving into existence,
Speaker 1: this manipulation was already happening. And you know, you can't
Speaker 1: be one hundred percent sure the ants weren't still attached
Speaker 1: or anything like that, but it's indirect evidence that this
Speaker 1: is sort of an ancient association and a manipulation that's
Speaker 1: been going on for longer than humans have been on
Speaker 1: this planet.
Speaker 2: And so when the ant mandibles do this hyper contraction,
Speaker 2: they make a special sort of pattern that they can't
Speaker 2: otherwise make because it's just the ant mandible, right, It's
Speaker 2: not like, how is this pattern different from a normal
Speaker 2: ant chomp.
Speaker 1: So, first of all, a lot of ants don't chomp
Speaker 1: around leaf veans like this, So you might be thinking
Speaker 1: about leaf cutter ants, and leaf cutter ants will cut
Speaker 1: out like chunks of leaves and bring them back to
Speaker 1: their net so that they can they feed them to fungus,
Speaker 1: and that they're sort of like a farming situation. But anyway,
Speaker 1: ants don't usually just go and like chomp down on
Speaker 1: leafs around the veins and then do nothing else with it.
Speaker 2: I see. So it's also the location of the chump.
Speaker 1: Yeah, it's also the location of the chump. Wow, amazing, Yeah,
Speaker 1: pretty cool. And so you tend to get aggregations in
Speaker 1: these good parts of the forest where the conditions are
Speaker 1: good for fungal growth, and so you end up with
Speaker 1: these ant graveyards where you've got a bunch of these
Speaker 1: zombified ants hanging on the underside of stems or leaves,
Speaker 1: raining fungal spores down on their nest mates below.
Speaker 2: And does the fungus actually kill the ant or does
Speaker 2: this sort of death march end up exhausting the ant
Speaker 2: or why does the ant die?
Speaker 1: I don't know if the ant dies, because once it
Speaker 1: bites down, it can't use its mandibles again. I don't
Speaker 1: know if it just eventually dies because it runs out
Speaker 1: of energy, or if the fungus kills it, but I
Speaker 1: do know that pretty soon after it bites down, the
Speaker 1: fungus starts consuming the inside of the ant to make
Speaker 1: more fungal tissue instead.
Speaker 2: And how long is it like spraying propagules.
Speaker 1: For That really depends on where you are. I think
Speaker 1: in some parts of the world it happens for like
Speaker 1: just a couple months. I think in some areas, I
Speaker 1: think it can happen for like a year. That really
Speaker 1: depends on the environment that you're in.
Speaker 2: All Right, and let's take a break, and when we
Speaker 2: come back, we'll hear about how this benefits the fungus
Speaker 2: and how the ant manages to pull this all off. Okay,
Speaker 2: we're back, and we're talking about the death march of
Speaker 2: zombie ants. Kelly, tell us why the fungus makes this happen.
Speaker 2: Why can't the fungus just find some other friendlier way
Speaker 2: to spread itself.
Speaker 1: I don't know why it doesn't find a friendlier way
Speaker 1: to do it, but we do know that this method
Speaker 1: seems to work for the fungus. As we sort of
Speaker 1: hinted at earlier. It's actually pretty easy to move these
Speaker 1: ants to different places to test out, like where would
Speaker 1: the best place be for these ants to have settled down,
Speaker 1: so you can cut off a leaf, And if you
Speaker 1: move it up too high, as we mentioned earlier, the
Speaker 1: temperature and humidity and lightning conditions are just not good
Speaker 1: and the fungus will essentially never be able to produce
Speaker 1: that stock that makes the spores. And so that's the
Speaker 1: end of the line for the fungus. Not great. And
Speaker 1: if you move it down too low, it gets found
Speaker 1: by scavengers. And so unlike a lot of other examples
Speaker 1: where we have a nice story, here we've been able
Speaker 1: to manipulate the system a little bit and say, you know, look,
Speaker 1: if you do something different than what we're seeing, the
Speaker 1: fungus is quite clearly doing less well. The fungus either
Speaker 1: gets eaten and killed or it can't make babies.
Speaker 2: I'm still sort of amazed that this whole thing works,
Speaker 2: Like I can imagine a fungus infecting an and and
Speaker 2: it makes a small change in the ant's behavior, and
Speaker 2: maybe that benefits it a little bit, But this benefit
Speaker 2: requires such complex behavior for the antigodam and then across
Speaker 2: and then up and then bite and all this stuff.
Speaker 2: All these pieces have to basically fall into place due
Speaker 2: to random mutation. So how do you get all the
Speaker 2: way to this complex behavior when none of the individual
Speaker 2: pieces on their own are going to benefit the fungus.
Speaker 1: Yeah, that's a great question. So one thing that's worth
Speaker 1: noting is that, you know, as we've mentioned earlier, this
Speaker 1: summoning disease thing happens pretty often. So it suggests that
Speaker 1: there's something about insects where it's not too hard to
Speaker 1: manipulate their ability to go up or stay up. And
Speaker 1: so a number of different kinds of parasites and pathogens
Speaker 1: have found the switch. I can't say I'm an expert
Speaker 1: on what that switch is, but there's a couple of
Speaker 1: different routes to up and stay there. But you can
Speaker 1: imagine that this happened, you know, step by step. So
Speaker 1: maybe the first thing that happened was that ants that
Speaker 1: were starting to show signs of being infected by the
Speaker 1: fungus left the nest so that the nestmates didn't kill them,
Speaker 1: and maybe they died on the forest floor. And then
Speaker 1: there happens to be an ant that climbed up a
Speaker 1: little bit before it died, and that helped the fungus
Speaker 1: relative just dying on the floor. And so you can,
Speaker 1: you know, imagine how each step could have happened first
Speaker 1: and then been honed over time. But this is definitely
Speaker 1: one of those things where we have to tell a
Speaker 1: story and we can't be exactly sure what happened in
Speaker 1: what order. I mean, maybe what happened first is that
Speaker 1: the ants that are infected by a fungus would die
Speaker 1: high up and they'd never go back to their nest.
Speaker 1: And maybe the nest stuff came later by some ant
Speaker 1: that happened to wander back but wasn't discovered for whatever reason.
Speaker 1: And so you know, each step there's selective pressure for
Speaker 1: whatever benefits the fungus more. But the exact path that
Speaker 1: this took. I think the best we can do is speculate.
Speaker 2: I see. But it's plausible to string these complex behaviors
Speaker 2: together because each individual one already does benefit the fungus.
Speaker 2: So that, yeah, that makes sense. I wonder what in
Speaker 2: one hundred million years, this fungus will have this ants doing, like, oh,
Speaker 2: it turns out if they do the macarena before they
Speaker 2: bite down.
Speaker 1: Yeah, yeah, it could be. I mean I would imagine that, like,
Speaker 1: as climate is changing across the planet, the exact location
Speaker 1: where biting down is the most beneficial might change. So
Speaker 1: there might be selection to like tinker with exactly where
Speaker 1: the ants end up so you keep getting the right
Speaker 1: temperature in humidity, and maybe that will be like you know,
Speaker 1: you should go to areas with even less light because
Speaker 1: everything is getting too warm and too hot, and so
Speaker 1: less light will be a little cooler and the temperatures
Speaker 1: will be right anyway, So I can imagine that happening.
Speaker 1: But part of understanding the steps is probably understanding the mechanisms,
Speaker 1: because that gives you some insights.
Speaker 2: Yeah, like what's going on inside the ant that lets
Speaker 2: the fungus? What are these levers that the fungus is pushing?
Speaker 1: Yeah, so first let me just talk briefly about how
Speaker 1: we start answering these questions. So, as we've discussed, there's
Speaker 1: a bunch of different steps here that the fungus is doing,
Speaker 1: and so the answer for how does the fungus manipulate
Speaker 1: behavior probably differs depending on what step you're talking.
Speaker 2: About different ants, different answer.
Speaker 1: Do I tell you often enough? How much I like
Speaker 1: working with you, Daniel, because I really do.
Speaker 2: I'm just going for the easy puns because somebody has to.
Speaker 1: I know, the dad jokes, the amazing dad jokes. So
Speaker 1: the way that you know, for example, if you're trying
Speaker 1: to figure out what differs between an ant that gets
Speaker 1: ignored by its nest mates and an ant that gets dumped,
Speaker 1: well you can, for example, infect some ants with ofio
Speaker 1: cordyceps and other ants with a different kind of fungus
Speaker 1: and send them both into a nest and see how
Speaker 1: they interact differently with their nest mates, how the nestmates
Speaker 1: interact differently with them, And then you can look at
Speaker 1: the different chemical profiles and say, like this one is
Speaker 1: emitting these chemicals and this one is emitting these chemicals,
Speaker 1: and then try to figure out, you know, is the
Speaker 1: fungus is ofio cord aceps producing some chemicals that the
Speaker 1: other fungus doesn't produce, and then start looking into those
Speaker 1: as candidates for what's happening there.
Speaker 2: Do you need an IRB for these kinds of experiments
Speaker 2: or can we just experiment willy nilly on ants? Do
Speaker 2: ants have any rights?
Speaker 1: That's a good question. So IRBs are almost exclusively for humans,
Speaker 1: so you don't need an You.
Speaker 2: Can't just experiment on dogs and chimps and rats, right,
Speaker 2: there's some ethics there, yep.
Speaker 1: For dogs and chimps and rats, you need an institutional
Speaker 1: Animal Care and Use Committee protocol and you have to
Speaker 1: jump through many hoops to make that happen, which which
Speaker 1: we'll talk about on another episode. But for invertebrates like ants,
Speaker 1: you don't need to do those kinds of protocols. But
Speaker 1: I will say that everyone who I've ever talked to
Speaker 1: who works with animals, even just little ants, gets pretty
Speaker 1: emotionally attached to them, and they do worry about, like
Speaker 1: how do I euthanize this ant to get my data
Speaker 1: in the way that will like make it fastest. And
Speaker 1: you know, I don't think we really know if ants
Speaker 1: feel pain or not, but like, if they do, how
Speaker 1: could we do it so that they'll feel the least
Speaker 1: amount of pain?
Speaker 2: So nobody's just callously grinding up ants. They're like shedding
Speaker 2: a tear while grinding up ants. That's nice.
Speaker 1: Yeah, let's move on.
Speaker 2: All right, No, but I mean jokes aside. You're saying
Speaker 2: that scientists involved understand the costs here in terms of
Speaker 2: lives and the appearances even of the little ants, and
Speaker 2: that's nice.
Speaker 1: Yes, no, they do, and I think they try to
Speaker 1: make the ants lives as natural and as nice as
Speaker 1: possible before these experiments happen. But so mostly the point
Speaker 1: I wanted to make was how we do these different
Speaker 1: comparisons to get a handle on what might be happening.
Speaker 1: And the answer is, you know, at very similar time points,
Speaker 1: you look at ants that are uninfected, ants that are
Speaker 1: infected by opiel cordyceps, and ants that are infected by
Speaker 1: other fungus that are bad for the ant, but we
Speaker 1: don't think they manipulate behavior in any way. And by
Speaker 1: looking to see what's happening differently in the bodies and
Speaker 1: the behavior of the ants in those three different categories,
Speaker 1: we can start getting some like candidate molecules for you know,
Speaker 1: this might be the thing that's getting produced by the
Speaker 1: fungus to change the behavior. And so they found a
Speaker 1: lot of stuff that differs, and that's not too surprising
Speaker 1: because the ants are doing complicated behaviors. There's a lot
Speaker 1: of behaviors. I feel like what we really want as
Speaker 1: humans is that the answer is there's this one molecule
Speaker 1: that tells you everything, and that's fascinating, but really it
Speaker 1: ends up being like hundreds of molecules that are being
Speaker 1: produced that we think are important in every single different step.
Speaker 1: So there's not like a really nice, easy to tell story.
Speaker 1: But a couple things that pop out is that interra
Speaker 1: toxins seem like they're important. These are toxins that are
Speaker 1: released by things like bacteria like E. Coli. We're not
Speaker 1: totally sure what the toxin is doing to the ants,
Speaker 1: but it might be playing a role in breaking down
Speaker 1: ant muscles at particular times. So maybe after the ant
Speaker 1: bites down, those muscles get broken down so the ant
Speaker 1: can't leave, and that might be what the toxin is
Speaker 1: doing when it's released at that point.
Speaker 2: I think it's great to try to dig into the
Speaker 2: details and understand the mechanisms to make sure the story
Speaker 2: that we're telling is the real story, and also because
Speaker 2: you could discover surprising things when you dig into the details.
Speaker 2: But what else could we learn by doing this. Is
Speaker 2: there the possibility here of a surprise that we discover, Oh,
Speaker 2: it's not actually working the way that we expected.
Speaker 1: Yeah, So a lot of people think of the behavior
Speaker 1: manipulating parasites and pathogens as like evolutionary neuroscientists. So they've
Speaker 1: been interacting with their host for you know, in this case,
Speaker 1: it looks like more than forty eight million years, and
Speaker 1: through the process of natural selection, they've maybe happened upon
Speaker 1: solutions for changing the ants behavior. And so by looking
Speaker 1: to see what is the fungus making, if it's a
Speaker 1: compound we've never seen before, maybe we've unlocked some tiny
Speaker 1: piece of the puzzle for how brains work and how
Speaker 1: you can modify behavior. And you know, you could imagine
Speaker 1: maybe if you've got some pest in a field, if
Speaker 1: you make them all like you know, climb up and
Speaker 1: stay up and then die, they'll like stop messing with
Speaker 1: your field. And so like, whenever we can understand even
Speaker 1: how insect behavior works, it gives you some extra tools
Speaker 1: to not just you know, understand how your world works,
Speaker 1: but also to maybe sort of control some of the
Speaker 1: negative aspects of like pest organisms.
Speaker 2: Wow, so the fungus has been doing neuroscience experiments on
Speaker 2: the ants for forty eight million years without ever writing
Speaker 2: a paper and getting their PhD. That's got to set
Speaker 2: some kind of record.
Speaker 1: They don't have to worry about tenure. They don't have
Speaker 1: to get brands, they don't have to write permits and protocols.
Speaker 1: It really seems unfair the head start that they've gotten.
Speaker 1: But if we study them, then we can sort of
Speaker 1: extract their secrets and maybe this will help us like
Speaker 1: jump ahead in our you know, study of neuroscience, which
Speaker 1: I think is a cool idea. And so they also
Speaker 1: found what they call a bioactive compound where they've they've
Speaker 1: never sort of seen this before, but it looks like
Speaker 1: another compound that, as we talked about earlier, causes insects
Speaker 1: to stagger, and so this might explain why they sort
Speaker 1: of like walk down the tree like they're drunk. But
Speaker 1: we think, and this is this is just hypothesizing at
Speaker 1: this point, we think it might be important in those
Speaker 1: systems where the ants are clinging to the bottom of stems.
Speaker 1: If the ants are feeling like all sort of wobbly
Speaker 1: and uneven, they might hug down on the stem to
Speaker 1: hold themselves so they don't fall off of it, and
Speaker 1: that could be sort of the moment that the fungus
Speaker 1: kills them, so that they will be really clinging hard
Speaker 1: to the stem. And at this point. This is just
Speaker 1: a story, and we know that we need to dig
Speaker 1: into it more. But that's where we are right now.
Speaker 1: So it's complicated.
Speaker 2: And do we know like where in the ant the
Speaker 2: fungus ends up, Like does the ant have a little
Speaker 2: ant brain and the fungus is sitting on top of it,
Speaker 2: like cackling maniacally and pulling levers.
Speaker 1: Yeah, so this is really neat. So you know, I've
Speaker 1: already mentioned that Terissa de Becker's lab has been doing
Speaker 1: some important work on timing, and they've been working on
Speaker 1: like chemicals that are produced by the fungus. David Hughes
Speaker 1: did some work with collaborators where they scanned ants with
Speaker 1: an electron microscope, so like very very detailed scans, and
Speaker 1: they put all of the scans together and what they
Speaker 1: found was that the fungus is forming a network and
Speaker 1: it's invading a bunch of different muscles. And so the
Speaker 1: way it was described in the popular press was that
Speaker 1: you could think of it as like the fungus essentially
Speaker 1: having strings on a puppet, where it could be like
Speaker 1: pulling up and down, and that might be over selling
Speaker 1: it a little bit, but one of the things that
Speaker 1: they thought was interesting was that it doesn't seem to
Speaker 1: be invading the brain tissue, so it's touching the brain
Speaker 1: but not going into the brain tissue. This was made
Speaker 1: a pretty big deal in the POPSI articles at the time.
Speaker 1: I wasn't as impressed with that. So, like the brain
Speaker 1: infecting parasite that I studied on fish for my PhD
Speaker 1: also sat on top of the brain and not inside
Speaker 1: of it. And there's some other evidence in the zombieant
Speaker 1: system that the fungus is kind of protecting the brain.
Speaker 1: So you can imagine that, like if you're inside of
Speaker 1: the brain, you might just like totally screw up your ride,
Speaker 1: like it's not gonna do what you want, because you've
Speaker 1: just totally debilitated it. And now it's obvious and the
Speaker 1: other ants can tell. And so it looks like it's
Speaker 1: sort of tinkering with the brain without actually like sticking
Speaker 1: its hands in there. But it does have its you know,
Speaker 1: hipha which are like fungal fingers inside the other muscles.
Speaker 2: Wow, amazing, and I see something amazing here in the outline.
Speaker 2: Tell me about hyper parasites. Are these like the superhero
Speaker 2: version of parasites? Kind of were they bitten by a
Speaker 2: radioactive spider.
Speaker 1: No no, no, no, no, you've watched too many movies, Daniel.
Speaker 2: This is true.
Speaker 1: Yeah, this is cool. So you know, you've got this
Speaker 1: fungus that manipulates ant behavior. But there are other fungal
Speaker 1: species that infect opio cordyceps. So the ant will be like,
Speaker 1: you know, clinging to a stem, and you'll find fungus
Speaker 1: that is living on top of Ofio cordyceps and is
Speaker 1: sapping the o fio cortaceps energy.
Speaker 2: It's like fungus inception. Wait, fungus antception.
Speaker 1: Whoa dead jokes galore. This might be our most dead
Speaker 1: jokey episode. Yet I didn't see it coming.
Speaker 2: Wow. So this fungus thought I was pulling the strings,
Speaker 2: but its strings were being pulled the whole time.
Speaker 1: There are so many levels in nature. I am so
Speaker 1: glad to be uh where I am so okay. So
Speaker 1: I promised at the beginning of the episode that I
Speaker 1: would answer if Ofio cordyceps could jump to humans and
Speaker 1: manipulate us, Daniel. So now I'm going to ask you
Speaker 1: what is your favorite representation of a fungus that jumps
Speaker 1: to humans and the ant. You could just say I
Speaker 1: don't watch the same shows as 'di Kelly.
Speaker 2: I'm not a fan of the zombie genre in general,
Speaker 2: the violence and the goo and like not a fan.
Speaker 1: So yeah, I'm gonna have to leave it to you,
Speaker 1: all right, Well, okay, I've been really liking The Last
Speaker 1: of Us lately, but not necessarily because it like hues
Speaker 1: so closely to what happens in nature, so that one
Speaker 1: starts by saying, like, yes, I know it seems unlikely
Speaker 1: that I think they call it cort aceps. The genus
Speaker 1: name has changed a little bit, but anyway, yes, it
Speaker 1: seems unlikely that it could jump to humans, but the
Speaker 1: way our environment is changing, we can't rule it out
Speaker 1: or something like that. And then fast forward decades and
Speaker 1: humans are infected by the fungus. I think it is
Speaker 1: highly unlikely.
Speaker 2: Why is that?
Speaker 1: Well, okay, so even in nature we talked about at
Speaker 1: the beginning of the show that each opio cort Aceps
Speaker 1: species tends to infect and manipulate specific ant species, so
Speaker 1: they are so specialized that they can't even like manipulate
Speaker 1: closely related ants. Like that's too much of a jump.
Speaker 2: So maybe like, if you you know how to fly
Speaker 2: a Sessana. That doesn't mean that if somebody drops you
Speaker 2: into like a seven forty seven, you're going to know
Speaker 2: how to land that thing.
Speaker 1: Yes, exactly right, And human brains are so incredibly different
Speaker 1: than ant brains. I suppose it's possible that a fungus
Speaker 1: might be able to eke out an existence in us,
Speaker 1: but I even think that would be quite a jump.
Speaker 1: But if it could, the probability that it would be
Speaker 1: able to control our behavior in a way that would
Speaker 1: benefit the fungus seems pretty close to zero. And I'm
Speaker 1: not being negative about the movies and TV shows and
Speaker 1: books that are great and Daniel's missing out. I think
Speaker 1: it's great that they created these worlds, and if they're
Speaker 1: consistent with their rules, I'm on board. But I'm a
Speaker 1: person with massive anxiety and it doesn't keep me up
Speaker 1: at night worrying that ofiocordyceps is going to jump to
Speaker 1: me or my kids.
Speaker 2: Well, I have a theory for how this fungus can
Speaker 2: jump to humans and benefit itself. Okay, if you think
Speaker 2: of this fungus as little neuroscientists, then what you to
Speaker 2: do It should get humans to help it out. So
Speaker 2: if it infects human brains and makes those humans interested
Speaker 2: in this and puzzle. So they come along basically acting
Speaker 2: like colleagues and figuring out like, hey, how does this
Speaker 2: actually work? And maybe you can help, like you know,
Speaker 2: super engineer this fungus to be even more efficient.
Speaker 1: I feel like you're in a roundabout way trying to
Speaker 1: get back to the like it's okay that I eat
Speaker 1: cookies at night thing, like you know, if the if
Speaker 1: the fungus benefits from me eating cookies. But you know
Speaker 1: what is interesting, So ofio cord accepts Senensis infects I
Speaker 1: think it's caterpillars, but it infects craters, but instead of
Speaker 1: having them climb up, it has them burrow into the
Speaker 1: ground and then the fungal stalk grows out of the
Speaker 1: ground and like pops up. Okay, and humans have decided
Speaker 1: that this is amazing in tea, and so people will
Speaker 1: actually go out in search of this and they can
Speaker 1: sell it for a lot of money. And I think
Speaker 1: you can even buy this in the United States, like
Speaker 1: tea with ofio cord accepts senensus in it, and so
Speaker 1: you know, I don't maybe ofio cordceps senensus jumps to
Speaker 1: us and makes us want the tea, and so then
Speaker 1: we'll start big farms where we sort of seed their
Speaker 1: hosts with the fungus so that they can start growing
Speaker 1: up and then we can replicate it. So maybe that'll
Speaker 1: be the route.
Speaker 2: Or maybe that'll just be the story in your Netflix show.
Speaker 2: Netflix call us We're ready.
Speaker 1: Yeah, you know, I wrote fiction once and I kind
Speaker 1: of think it was a disaster. So I don't see
Speaker 1: me starting a new fictional series. But if anybody would
Speaker 1: like scientific input on their own series, I am available.
Speaker 2: And she promises not to be completely a wet blanket.
Speaker 1: I you know, I don't like to make promises I
Speaker 1: can't keep. I'll try to play along, all right, So,
Speaker 1: just to sort of reiterate, I love this system because
Speaker 1: we've dug into more of the different pieces in this
Speaker 1: system than a bunch of other systems. But there's so
Speaker 1: much we have left to learn. And as we mentioned earlier,
Speaker 1: like we're discovering molecules that we've never seen before. This
Speaker 1: might be a way to help us understand how brains
Speaker 1: work and how we can sort of tinker with behavior.
Speaker 1: It might give us some inputs on how to control
Speaker 1: insect populations. There's so much cool stuff we might have
Speaker 1: left to learn as we continue digging into the system.
Speaker 2: Amazing and it's incredible what we can learn from like
Speaker 2: ants and fungus, and sometimes that tells us something deeper
Speaker 2: about the way brains work. And so you never know
Speaker 2: where the next great scientific discovery will come from and
Speaker 2: who's really pulling your strings?
Speaker 1: That's right, But the next great scientific discovery is probably
Speaker 1: coming from biology. That's what I think.
Speaker 2: As long as it gets into people's heads and makes
Speaker 2: them listen to the podcast, I'm all for it.
Speaker 1: Or it gives Daniel an excuse for eating cookies in
Speaker 1: the middle of the night.
Speaker 2: Chomp, chomp, chomp.
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