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Speaker 1: Imagine sitting out on a porch on a warm spring evening.

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Speaker 1: You hear the spring peepers calling out to each other

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Speaker 1: in a nearby pond. Birds are chirping in the trees,

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Speaker 1: preparing to turn into their nest for the night. Off

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Speaker 1: in the distance, you see a deer walking with her fawn.

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Speaker 1: It's a beautiful scene, reminding you how wonderful it is

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Speaker 1: to live in Virginia when I hear and see these

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Speaker 1: denizens of the forest, though I see something else as well,

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Speaker 1: walking ecosystems for parasites. You see on average a bird

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Speaker 1: species harbors more than three species of tapeworm nearly three

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Speaker 1: nematode species. Probably call that frog home. Those deer are

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Speaker 1: harboring treematodes, tapeworms, nematodes, and more. Though hidden from sight,

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Speaker 1: parasites are thought to make up over half of the

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Speaker 1: biodiversity of multicellular organisms on our planet. Today, we're going

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Speaker 1: to answer listener questions about the evolution of parasitism. Hope

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Speaker 1: you're not listening to the show while eating dinner. Welcome

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Speaker 1: to Daniel and Kelly's Extraordinarily Infected Universe.

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Speaker 2: Hi, I'm Daniel, I'm a particle physicist, and I'm looking

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Speaker 2: forward to meeting alien parasites.

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Speaker 1: Hello. I'm Kelly Wiener Smith. I study parasites and space,

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Speaker 1: but not parasites in space. But maybe one day I'll

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Speaker 1: study Yeah, maybe one day I'll be studying parasites in space.

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Speaker 2: So my question for you today, Kelly, is what is

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Speaker 2: your favorite depiction of parasites in science fiction?

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Speaker 1: Probably aliens don't need to think about it. Aliens, it's

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Speaker 1: a great parasitoid in there. I went through a phase

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Speaker 1: where I was just love all of the zombie movies

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Speaker 1: and I was actually taking notes on like what mechanism

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Speaker 1: was producing the zombies. So for a while, you know,

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Speaker 1: when there were big fears of nuclear bombs getting dropped

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Speaker 1: on the US for example, you know, nuclear material was

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Speaker 1: the cause of zombies. But then it became like infectious diseases,

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Speaker 1: and I've gotten off course. I was thinking about writing

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Speaker 1: a whole book on this actually.

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Speaker 2: And why didn't you?

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Speaker 1: It sounds fascinating, you know enough people told me that, like,

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Speaker 1: the zombie craze is behind us, and that this is

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Speaker 1: a book nobody would want to read because it would

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Speaker 1: be two of the time. Yeah, two of the moment, right,

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Speaker 1: like when people weren't watching the zombie movies like The

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Speaker 1: Last of Us Sword, which I guess that's running still now.

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Speaker 2: Yeah, but zombies aren't a moment, They're a movement.

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Speaker 1: You know, that's right. Well, and I gave a talk

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Speaker 1: at the Zombie Apocalypse Medicine Meeting, or I think I

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Speaker 1: for Sam. Yeah, and it's happening in October of this year.

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Speaker 1: I highly recommend folks go to it.

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Speaker 2: These are legit scientists.

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Speaker 1: These are legit scientists. Yes, wow. And I gave a

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Speaker 1: talk on that topic and it was like the most

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Speaker 1: fun research I've ever done in my life.

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Speaker 2: Well, I think I speak for the audience and saying

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Speaker 2: that we all want to read your book on the

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Speaker 2: science of zombies. That sounds fantastic.

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Speaker 1: You know. I've got a link to the talk that

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Speaker 1: I could share if anyone wants to see the talk,

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Speaker 1: But I don't think it's going to become a full

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Speaker 1: length book, not with what I've got on my agenda

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Speaker 1: right now.

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Speaker 2: All right, Well, today we're not talking about space or

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Speaker 2: science fiction or zombies. We're answering a really fascinating question

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Speaker 2: from a listener about the context, the evolution, and maybe

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Speaker 2: even the future of parasites in our world.

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Speaker 3: Take it away, Zach, Hey, they're extraordinaries. The recent episode

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Speaker 3: on the history of Trickinella, I should say, the recent

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Speaker 3: history of trick and Ella got me wondering about the

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Speaker 3: more ancient history of parasites. I assume that being a

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Speaker 3: parasite is a strategy that existed back in the time

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Speaker 3: of the dinosaurs, maybe even further back. I'm curious if

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Speaker 3: we have evidence of that, and if parasites tend to

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Speaker 3: become extinct when their host species does as well, or

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Speaker 3: if we're still living with the same kind of parasites

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Speaker 3: the dinosaurs dealt with. I'm also curious if we know

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Speaker 3: about how parasites evolve, how does an organism go from

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Speaker 3: being not a parasite to a parasite? Do we have

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Speaker 3: any idea of that evolutionary history. Looking forward to hearing

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Speaker 3: more squishy wormy biology from you guys.

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Speaker 2: Thank you Zach for sending in this question. If you

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Speaker 2: have questions about the nature of the universe, or the

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Speaker 2: history of parasites, or anything in this extraordinary universe, we

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Speaker 2: want to hear from you. We want to answer your questions.

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Speaker 2: We want to scratch your itch because everybody's curious about

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Speaker 2: the universe, so don't be shy. Write to us two

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Speaker 2: questions at Danielandkelly dot org. Everyone gets an answer.

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Speaker 1: And I am currently researching why we scratch itches, which

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Speaker 1: is a question sent by a listener. So you even

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Speaker 1: get those kinds of questions answered.

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Speaker 2: Amazing, yep, So dig into this for us, Kelly, tell

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Speaker 2: us about the history of parasites and why we call

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Speaker 2: something a parasite and what fraction of species we could

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Speaker 2: classify as parasites.

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Speaker 1: Well, Daniel, let's pretend that you didn't read the outline,

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Speaker 1: which maybe maybe you didn't, although you're usually very well prepared.

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Speaker 1: If you had to guess what percent of multicellular organisms

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Speaker 1: were parasites, what percent would you guess?

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Speaker 2: It doesn't seem to me like most things are parasites.

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Speaker 2: Bunnies are not parasites, flies are not parasites. Whales or

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Speaker 2: not parasites, So you know, it seems to me unusual.

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Speaker 2: So I guess one percent is my absolutely no information.

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Speaker 1: Guess are you playing along? Are you really guessing one percent?

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Speaker 2: I'm really guessing one percent?

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Speaker 1: Oh wow, that's fantastic. Okay. I love those moments where

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Speaker 1: you can be like, you're totally wrong. So Dan, you're

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Speaker 1: totally wrong. Yes, yay. So if you look at that rabbit, So,

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Speaker 1: rabbits are mammals, and on average, mammals harbor one to

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Speaker 1: two species of trematodes, one to two species of tapeworms,

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Speaker 1: and four nematode species.

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Speaker 2: Well, I didn't want to eat rabbits before, but I

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Speaker 2: certainly don't want to eat rabbits now.

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Speaker 1: Well, then let's not talk about more typical food animals

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Speaker 1: like cows and pigs. We'll stay away from those. But

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Speaker 1: it's estimated that this was from a two thousand and

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Speaker 1: eight paper that was estimating about forty four thousand host

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Speaker 1: species with vertebrates and about seventy seven thousand species of trematodes, tapeworms, nematodes,

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Speaker 1: and acanthoscephalins. So this is four kinds of parasites, almost

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Speaker 1: twice as many parasites as there are hosts. And that

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Speaker 1: doesn't even include things like lice and ticks and stuff

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Speaker 1: like that.

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Speaker 2: What hold on a second, you're telling me that like

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Speaker 2: every species of critter out there has like two unique

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Speaker 2: species of parasites, So there's like a two to one

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Speaker 2: parasite to creater ratio.

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Speaker 1: This is a great question. This is where it gets

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Speaker 1: a little bit complicated. So, for example, if you have

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Speaker 1: two different species of rabbit, they might share one of

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Speaker 1: their trematode species for example. So there are some parasites

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Speaker 1: that are generalists and you can find them in more

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Speaker 1: than one host species, but there are also a lot

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Speaker 1: of parasites that are found in one species. And so

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Speaker 1: in general, when we look at how many parasites are

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Speaker 1: generalists and how many are specially listener just found in

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Speaker 1: one host, we get this estimate where we feel comfortable

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Speaker 1: saying that probably more than fifty percent of the multicellular

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Speaker 1: biodiversity on Earth is using the parasitic strategy in some way.

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Speaker 2: Oh my gosh, we're in the minority. Yeah, for not

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Speaker 2: sucking on some other critter, we are like unusual.

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Speaker 1: We're total chumps, man.

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Speaker 2: So we got to rethink this.

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Speaker 1: Wow, I know there's a lot of interesting questions that

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Speaker 1: arise from there. So we know that a bunch of

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Speaker 1: species have this strategy of being a parasite, which essentially

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Speaker 1: means that you rely on another organism where you're extracting

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Speaker 1: their energy. It's not benefiting them, and you need them

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Speaker 1: to get the energy.

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Speaker 2: Well, then can I ask a technical question like, yeah,

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Speaker 2: is a cow a parasite because it relies on grass

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Speaker 2: and you know it's extracting the energy from the grass.

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Speaker 2: Why isn't a cow listed as a grass parasite?

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Speaker 1: So it is eating lots of different blades of grass,

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Speaker 1: and so this is usually an intimate, endurable interaction between

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Speaker 1: two INDs.

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Speaker 2: Intimate, wow, intimate.

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Speaker 1: Well, you know, if you're living inside, for example, of

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Speaker 1: something and sharing gets dinner with it every night, that's

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Speaker 1: pretty intimate. And so, yeah, cows are eating lots of

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Speaker 1: different grass. We call mosquitoes and lamb preys and ticks

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Speaker 1: and stuff micro predators. So they take little meals from

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Speaker 1: lots of animals. They don't kill them, which predators usually do,

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Speaker 1: but they just take little meals from lots of animals.

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Speaker 1: And so the idea is that to be a parasite

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Speaker 1: you have to be on one organism for a long time.

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Speaker 2: Okay, so mosquito's technically not parasites then, right.

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Speaker 1: You would be amazing how much fur flies at parasitology

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Speaker 1: conferences when the mosquito and the leech people are like,

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Speaker 1: these are parasites. And then some of the community is

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Speaker 1: like they're micro predators, and the leech people are like,

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Speaker 1: we belong here, and I'm like, they belong here, don't

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Speaker 1: kick them out.

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Speaker 2: Well, they're parasites in spirit, even if they don't qualify technically, right,

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Speaker 2: because otherwise, like a giraffe which nibbles on this tree

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Speaker 2: and then the other tree in the other trees basically

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Speaker 2: has the same relation with a tree as a mosquito

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Speaker 2: does with people, right, So.

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Speaker 1: That's because it's not killing all of them. Yeah, yeah,

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Speaker 1: And so sometimes you can get into debates with some

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Speaker 1: folks about to what extent herbivores can be thought of

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Speaker 1: as parasites solely. You know, if like an insect lives

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Speaker 1: on the same tree for a long time, is it

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Speaker 1: a parasite or is it a different category altogether because

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Speaker 1: it's a plant And anyway, I guess at the end

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Speaker 1: of the day, nature doesn't care that humans like to

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Speaker 1: have very nice clear boxes to put things in. She's

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Speaker 1: always giving us edge cases to make things complicated.

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Speaker 2: And life is an ecosystem, right, It's a web, and

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Speaker 2: there's nothing isolated. We're all munching on each other and

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Speaker 2: eating each other and being eaten by each other. It's

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Speaker 2: a big party, right.

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Speaker 1: I don't want to go to the parties you go to, Daniel.

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Speaker 1: Based on what you've just described, we have fun.

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Speaker 2: We have fun. But how useful are these categorizations? I mean,

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Speaker 2: does it matter what we call a parasite or not?

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Speaker 1: So I think it does. And the main reason I

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Speaker 1: think it does is because often folks will try to

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Speaker 1: model the impact of parasites on populations, or use some

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Speaker 1: modeling to try to understand how to control a parasite population,

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Speaker 1: and those models depend on the assumptions you make about

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Speaker 1: what that organism is doing, how many organisms it's feeding on,

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Speaker 1: how many babies it produces. Like, having these details helps

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Speaker 1: you create models that can describe different groups of strategies,

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Speaker 1: and those models can be important for a lot of things,

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Speaker 1: including epidemiology.

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Speaker 2: I see, all right. And also it's nice to get

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Speaker 2: like minded people together, right, And so yeah, you gotta

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Speaker 2: people want to know which conference do I go to?

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Speaker 2: Do I go to the zombie conference or the parasite

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Speaker 2: conference or the zombie parasite conference or whatever? And so

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Speaker 2: we got to put names on things so we can

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Speaker 2: get ourselves organized, even if we admit that the names

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Speaker 2: are fuzzy. You know, is Pluto a planet or not

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Speaker 2: doesn't really matter. We're interested in studying this stuff fluting

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Speaker 2: in outer space.

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Speaker 1: I wants organized a symposium called how to Make a

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Speaker 1: Zombie with my friend zen Folks, who has like the

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Speaker 1: coolest name ever, and then it was me, who has

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Speaker 1: the least cool name ever. And it was a very

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Speaker 1: interesting combo. But anyway, it was all about parasites that

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Speaker 1: manipulate host behavior and how they do that.

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Speaker 2: Right, right, Yeah, parasites and zombies are connected in the end.

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Speaker 1: Sure.

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Speaker 2: So the bottom line is that there are lots and

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Speaker 2: lots and lots of parasites out there. I was totally wrong,

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Speaker 2: and there's lots of different kinds of parasites out there.

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Speaker 2: But what about by body mass? Are parasites like a

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Speaker 2: tiny fraction of the mass or if you made a

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Speaker 2: big pile of all the parasites on the planet, would

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Speaker 2: be bigger than the pile of non parasites.

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Speaker 1: This is a great question. So I didn't necessarily prepare

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Speaker 1: for you to ask this question, so I don't have

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Speaker 1: all the numbers that I want at my fingertips. But

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Speaker 1: there was a system where this question was studied explicitly

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Speaker 1: and it was the estuaries in southern California. And essentially

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Speaker 1: they took the biomass of all of the free living organisms,

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Speaker 1: and they extracted the parasites from them, and they took

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Speaker 1: the biomass of them. And in these systems, the main

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Speaker 1: predators are predatory birds. They eat the crustaceans, they eat

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Speaker 1: the fish. They're like the main predator out there. And

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Speaker 1: the biomass of trematode parasites was equal to and maybe

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Speaker 1: I think in some cases greater than the biomass of

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Speaker 1: the top predators in the system, which is to say,

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Speaker 1: greater than the biomass of the birds.

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Speaker 2: Wow.

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Speaker 1: And that's because this system has a lot of trematode

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Speaker 1: parasites that infect the snails, and when the snails get infected,

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Speaker 1: they get castrated and all of the energy that would

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Speaker 1: have gone to making baby snails now becomes parasite biomass.

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Speaker 1: And so the ground it's like a carpet of snails

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Speaker 1: in these estuaries. There's just loads and loads of them.

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Speaker 2: I'm imagining stepping on them to the crunch, crunch, crunch.

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Speaker 1: It's not crunch crunch, crunch, crunch, because it's very muddy

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Speaker 1: out there, so you're like squishing them underground, like they're

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Speaker 1: getting covered in mud. So you do feel bad about that.

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Speaker 1: I did feel bad. It was great exercise working in

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Speaker 1: this system though. This is what I did for my PhD,

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Speaker 1: because every step you take you need to like steal

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Speaker 1: your foot back from the mud. And anyway, good exercise.

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Speaker 1: Point is some systems have really really high parasite biomass.

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Speaker 1: But for example, if you were to collect a deer,

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Speaker 1: the biomass of parasites in a deer is probably a

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Speaker 1: very small percent.

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Speaker 2: Like one percent.

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Speaker 1: Yeah, I guess you know, probably like one percent. That's

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Speaker 1: where you came from.

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Speaker 2: Day I tell what I meant. Yeah, yeah, let's see.

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Speaker 1: Totally right. You hit the nail on the head. It

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Speaker 1: was perfect.

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Speaker 2: If we keep asking questions, we'll eventually find one that

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Speaker 2: lines up in my answer.

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Speaker 1: That's right, And we got there pretty quick. We got

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Speaker 1: there pretty quick. And and this biomass question that you

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Speaker 1: asked depends a lot on what the strategy of the

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Speaker 1: parasite is. And in our next segment we're going to

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Speaker 1: talk about different strategies. But basically, when the strategy involves

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Speaker 1: killing your host, you can take up more of that

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Speaker 1: host biomass because the host is going to die anyway.

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Speaker 1: But now I want to talk about you know, so

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Speaker 1: we've determined that maybe as much as fifty percent or

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Speaker 1: more of the number of species on the planet that

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Speaker 1: are multicellular are parasites. But how many times did you

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Speaker 1: get a transition from free living to a parasitic strategy?

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Speaker 2: Right? Like? Did this evolve one time and now we

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Speaker 2: have a huge explosion to parasites or is it a

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Speaker 2: common thing that's been developed independently multiple times, like flight

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Speaker 2: for example.

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Speaker 1: I mean, do you want to give a like, guess

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Speaker 1: at how many times parasitism has evolved.

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Speaker 2: This time a good sport. I would guess that it's

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Speaker 2: evolved multiple times because it seems like kind of an

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Speaker 2: obvious strategy and it doesn't require like some huge technological

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Speaker 2: innovation like photosynthesis or the engineering a flight. Even so

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Speaker 2: I would guess it's pretty common. I don't know a

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Speaker 2: dozen times.

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Speaker 1: When we had Joe Wolf on the show, she pointed

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Speaker 1: out that the crab body plan has popped up I

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Speaker 1: think eight times. I think you undersold the difficulty of

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Speaker 1: parasitism a little bit. So if you are trying to

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Speaker 1: infect a host, you need to find that host you

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Speaker 1: need to survive its immune system. You're now in a

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Speaker 1: completely foreign environment that is actively trying to kill you

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Speaker 1: all the time. But despite those challenges, we think that

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Speaker 1: parasitism has shown up at least two hundred and twenty

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Speaker 1: three times in Kingdom Animalia.

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Speaker 2: Sorry, two hundred and twenty.

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Speaker 1: Three times, two hundred and twenty three times.

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Speaker 2: Like you can identify individual moments when something went from

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Speaker 2: non parasite to parasite in the evolutionary record hundreds of.

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Speaker 1: Times, hundreds of times.

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Speaker 2: Yes, wow, why aren't we all parasites?

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Speaker 1: Well, you know, there's got to be some.

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Speaker 2: Hosts, I see. For the grifters to keep drifting, we

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Speaker 2: need some suckers, that's what you're saying.

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Speaker 1: And you and I are the suckers, I guess. But

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Speaker 1: so sometimes you get this transition to parasitism that results

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Speaker 1: in a lot of additional species. So I think when

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Speaker 1: you ask people about parasites, they usually think about things

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Speaker 1: like tapeworms and trematodes and nematodes and stuff like that.

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Speaker 2: Unfortunately, that is my mental image, and that's why it

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Speaker 2: gives me the willies.

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Speaker 1: Yeah, I'm sorry.

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Speaker 2: It's intimate, though, it's.

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Speaker 1: Very intimate So in phylum plati helminthis, so that's where

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Speaker 1: you get the trematodes and the tapeworms and stuff. They

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Speaker 1: were about transitions to parasitism last time we counted. But

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Speaker 1: in arthropodas, so these are invertebrates with exoskeletons. So we're

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Speaker 1: thinking about like wasps and crustaceans and stuff like that.

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Speaker 1: It evolved one hundred and forty three times. Wow, So

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Speaker 1: lots of transitions and lots of times it happened in insects,

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Speaker 1: and it happened sixty times in flies. So flies you

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Speaker 1: often get a transition from free living two parasitic strategies.

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Speaker 2: How do we trace these transitions? Like I understand we

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Speaker 2: can look at the fossil record and see how whales

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Speaker 2: return to the ocean this kind of stuff. But insects,

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Speaker 2: we don't have fossils. How do we know this history.

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Speaker 1: We do have some insect fossils. Often they get trapped

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Speaker 1: in things like amber, and amber actually does a really

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Speaker 1: great job of preserving things and making it so you

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Speaker 1: can still see their features. Yeah, but we probably are

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Speaker 1: undercounting because there probably are a lot of like transitions

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Speaker 1: that happened and then we're lost those species went extinct,

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Speaker 1: or a lot of just instances where there was like

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Speaker 1: a free living host that we'd just never found. And

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Speaker 1: so these you should imagine that all of these estimates

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Speaker 1: are very likely to change over time. But we have

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Speaker 1: been lucky to get a fair number of fossils in

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Speaker 1: the record, and the fossils are usually not beautiful exactly

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Speaker 1: what you want fossils. But for example, there's a lot

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Speaker 1: of tapeworms and monogeneans. So these are monogeneans are parasites

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Speaker 1: that you often find on the outside of fish. They

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Speaker 1: have these hooks that they use to hold onto the

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Speaker 1: fish and then they suck like the mucus. Sometimes they

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Speaker 1: suck blood, but they live on the outside.

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Speaker 2: The less intimate side, we'll say.

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Speaker 1: Yeah, slightly less intimate, but no less durable, and so

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Speaker 1: they use these hooks. And then tapeworms also tend to

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Speaker 1: have these hooks and they use them to hold on inside.

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Speaker 1: So now we've got intimate and durable. But these hooks

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Speaker 1: have very distinctive shapes, and sometimes we can find in

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Speaker 1: fossilized animal poops called coprolites, which we've talked about before,

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Speaker 1: these hooks in like the pairings that you would expect

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Speaker 1: and in the shapes that you would expect and inside

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Speaker 1: of or of, like very adjacent to organisms that you

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Speaker 1: would expect to find them in. And we found evidence wow,

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Speaker 1: of these sorts of relationships from the Mesozoic area, which

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Speaker 1: was sixty six to about two hundred and fifty million

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Speaker 1: years ago. Wow. This includes like the Jurassic period where

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Speaker 1: you know Jurassic Park and the Paleozoic period, which is

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Speaker 1: even later. I think Paleozoic means something like old life.

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Speaker 1: And we found some evidence of these parasites from back

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Speaker 1: then too, so it's totally reasonable to assume that like

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Speaker 1: t Rex was probably carrying around some nematodes. These are

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Speaker 1: ancient interactions.

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Speaker 2: I love thinking about when things arose because it's a

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Speaker 2: way to figure out, like how hard is it to happen?

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Speaker 2: And also is it like that happen on alien planets?

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Speaker 2: Like we think about how quickly did we get life

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Speaker 2: after there were the conditions for life on Earth? Pretty quickly?

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Speaker 2: How quickly did we get intelligence after they were their

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Speaker 2: conditions for intelligence? Not that quickly? And it's only end

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Speaker 2: equals one, but it's like a hint as to like

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Speaker 2: is this likely to happen elsewhere, And so how far

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Speaker 2: back is the evidence of parasitism? How quickly did people

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Speaker 2: start to slurp and munch intimately on each other?

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Speaker 1: Well, so we are mostly focusing on multicellular organisms going

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Speaker 1: after other multicellular organisms. I think it would be really

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Speaker 1: hard to know if there was like a bacterial parasite

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Speaker 1: going after other organisms in the like primordial soup era

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Speaker 1: of life.

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Speaker 2: I guess bacteria phages could be considered parasites and viruses

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Speaker 2: that infect.

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Speaker 1: Bacteria, right, Yeah, I meant conferences. We like to joke

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Speaker 1: that the first organism was free living, in the second

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Speaker 1: one found some way to exploit it. But you know,

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Speaker 1: we don't know that for sure.

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Speaker 2: This economy that's just happening.

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Speaker 1: Yeh, that's right, that's right. And so you know, I

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Speaker 1: think pretty early on, when you start getting multicellular organisms,

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Speaker 1: you get parasites also.

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Speaker 2: And remind us how early did we get multicellular organisms

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Speaker 2: For those of us who are not evolutionary.

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Speaker 1: Biologists, So multicellular life is probably something like seven hundred

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Speaker 1: million years ago, and I think we have decent evidence

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Speaker 1: of parasites in multi cellular organisms from at least two

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Speaker 1: hundred and fifty million years ago, and I'm guessing that

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Speaker 1: before that it gets even harder to find evidence of parasites,

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Speaker 1: and you have to be super careful that you're not

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Speaker 1: tricking yourself. So, for example, there are these isopods that

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Speaker 1: attached to fish, and sometimes they'll like live on top

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Speaker 1: of their gill arches, so like underneath their gill flap,

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Speaker 1: and then other times they'll live on their tongue. And

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Speaker 1: so if you find an isopod next to a fish,

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Speaker 1: you might be like, oh, there's a parasitic isopod, But

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Speaker 1: how do you know that it wasn't just like fossilized

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Speaker 1: next to the fish. How do you know it was

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Speaker 1: actually a parasitic relationship. So this stuff can be really difficult.

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Speaker 2: These glimpses into deep time are super fascinating. One of

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Speaker 2: my favorite things in science. You know, to think that

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Speaker 2: like Earth had life on it for billions of years

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Speaker 2: before it had multicellular life. You know, like so many years,

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Speaker 2: so many seasons, so many days past with just like

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Speaker 2: frothing bacteria and stuff floating in the oceans. Now really interesting,

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Speaker 2: which is also kind of depressing because it means like

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Speaker 2: if you find a planet with life on it. There's

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Speaker 2: a good chance it's just a bunch of single cell

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Speaker 2: organisms nobody really to talk to. It's incredible how rapidly

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Speaker 2: things have changed. Like seven hundred million years ago, we

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Speaker 2: get multi cellular life and then you know, things explode.

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Speaker 2: And only recently have we had intelligence and technology and podcasts.

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Speaker 1: Why I promise to not rat you out because you

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Speaker 1: essentially said there's just bacteria and that's not interesting. I

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Speaker 1: promise I won't tell Katrina that you said that, but

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Speaker 1: I agree, Well, this is.

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Speaker 2: Our way to find out if she listens to the

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Speaker 2: podcast or not. If I get in trouble over.

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Speaker 1: That, that's all right, Well, keep me posted, all right.

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Speaker 1: So when we come back, let's talk about categories that

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Speaker 1: parasites fall into. So we were talking about how do

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Speaker 1: you define and categorize these things. We'll talk about the

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Speaker 1: categories that we think make the most sense.

437
00:22:11,400 --> 00:22:13,840
Speaker 2: All right, we are back, and we are talking about

438
00:22:13,840 --> 00:22:16,760
Speaker 2: a very intimate topic today. We're talking about the incredible

439
00:22:16,760 --> 00:22:20,080
Speaker 2: community of folks that live off of you, that you

440
00:22:20,200 --> 00:22:23,760
Speaker 2: are supporting your parasites and the parasites of everybody else

441
00:22:23,840 --> 00:22:27,200
Speaker 2: on earth. We're digging deep into the history to understand

442
00:22:27,280 --> 00:22:30,000
Speaker 2: how often this happens, how it happens, why it happens,

443
00:22:30,480 --> 00:22:34,280
Speaker 2: and what is the future of parasitism. So let's keep

444
00:22:34,280 --> 00:22:37,119
Speaker 2: digging into the past. Kelly tell us about like how

445
00:22:37,160 --> 00:22:40,520
Speaker 2: these things become parasites, How does the species decide from

446
00:22:40,520 --> 00:22:42,720
Speaker 2: being a maker to becoming a taker?

447
00:22:43,800 --> 00:22:47,280
Speaker 1: I love that phrasing. And the answer is really like,

448
00:22:47,560 --> 00:22:49,879
Speaker 1: we don't have a great handle on this. So you know,

449
00:22:49,920 --> 00:22:52,760
Speaker 1: we talked about how this transition has happened probably more

450
00:22:52,800 --> 00:22:55,400
Speaker 1: than two hundred and twenty three times, and there's this

451
00:22:55,560 --> 00:22:59,879
Speaker 1: long running belief in the community that the what usually

452
00:23:00,000 --> 00:23:03,600
Speaker 1: what happens is that an organism starts specializing on dead stuff.

453
00:23:03,640 --> 00:23:06,520
Speaker 1: So you go from a decomposer to a parasite. And

454
00:23:06,560 --> 00:23:08,439
Speaker 1: the idea is you get good at living off of

455
00:23:08,520 --> 00:23:12,639
Speaker 1: flesh when it's dead, and that sort of lowers the

456
00:23:12,680 --> 00:23:15,400
Speaker 1: threshold to becoming a parasite and living on that thing

457
00:23:15,800 --> 00:23:17,919
Speaker 1: and taking its energy while it's still alive.

458
00:23:18,320 --> 00:23:21,560
Speaker 2: So first you identify like, hey, these corpses are rich

459
00:23:21,600 --> 00:23:24,240
Speaker 2: in nutrients, I might as well eat them, and then

460
00:23:24,320 --> 00:23:26,160
Speaker 2: you start eating the living versions of them.

461
00:23:26,359 --> 00:23:28,679
Speaker 1: Yeah, And so my friend Dan Metz and I wrote

462
00:23:28,720 --> 00:23:30,639
Speaker 1: a paper. He was leading this paper I was just

463
00:23:30,840 --> 00:23:34,159
Speaker 1: on the support team, but we wanted to find like

464
00:23:34,200 --> 00:23:36,800
Speaker 1: the papers that showed this, because this is a thing

465
00:23:36,800 --> 00:23:39,600
Speaker 1: that you can see found in the literature for like

466
00:23:40,040 --> 00:23:42,600
Speaker 1: one hundred years or more, but when you look into

467
00:23:42,640 --> 00:23:45,840
Speaker 1: the literature, it actually hasn't been tested that often. So

468
00:23:45,840 --> 00:23:48,120
Speaker 1: I think a lot of us have this gut feeling

469
00:23:48,240 --> 00:23:50,639
Speaker 1: that you know, being a decomposer is the step before

470
00:23:50,720 --> 00:23:54,240
Speaker 1: becoming a parasite, But folks really haven't done the nice

471
00:23:54,280 --> 00:23:56,320
Speaker 1: kind of analyzes you need. Where you'd need a tree

472
00:23:56,359 --> 00:23:58,440
Speaker 1: of life. You'd need to know who the free living

473
00:23:58,520 --> 00:24:00,879
Speaker 1: organisms and the parasites are are, and you'd need to

474
00:24:00,880 --> 00:24:03,720
Speaker 1: know what that free living organism was doing before the

475
00:24:03,760 --> 00:24:07,520
Speaker 1: transition to parasitism, and then look to see if certain

476
00:24:07,600 --> 00:24:10,480
Speaker 1: kinds of free living organisms were more likely to transition

477
00:24:10,520 --> 00:24:13,040
Speaker 1: to parasites. And you need some control groups too, and

478
00:24:13,119 --> 00:24:16,159
Speaker 1: that requires a lot of natural history data. And so

479
00:24:16,400 --> 00:24:19,359
Speaker 1: you and I have talked in the past about, you know,

480
00:24:19,440 --> 00:24:21,760
Speaker 1: the value of taxonomy and the value of going out

481
00:24:21,760 --> 00:24:24,720
Speaker 1: and collecting information, and I think it's critical because a

482
00:24:24,760 --> 00:24:26,600
Speaker 1: lot of times we'll want to do these sorts of

483
00:24:26,640 --> 00:24:28,680
Speaker 1: analyzes and then you'll get your tree of life together

484
00:24:28,720 --> 00:24:30,480
Speaker 1: and you'll be like, oh, we have no idea what

485
00:24:30,520 --> 00:24:32,320
Speaker 1: any of these pieces are doing in the wild, and

486
00:24:32,359 --> 00:24:35,960
Speaker 1: so you can't ask these questions that really help us understand,

487
00:24:36,640 --> 00:24:39,000
Speaker 1: you know, the paths that life take. You need that

488
00:24:39,119 --> 00:24:40,080
Speaker 1: natural history data.

489
00:24:40,400 --> 00:24:44,440
Speaker 2: And you always need data, right, especially to check your intuitions. Yeah,

490
00:24:44,480 --> 00:24:46,920
Speaker 2: because you know, science is a story and we're putting

491
00:24:46,960 --> 00:24:50,239
Speaker 2: together a history of what happened, and when we don't know,

492
00:24:50,640 --> 00:24:53,040
Speaker 2: we're inclined to like fill in with our intuition, say well,

493
00:24:53,080 --> 00:24:55,600
Speaker 2: here's an idea. Maybe this is reasonable, and if it

494
00:24:55,640 --> 00:24:57,960
Speaker 2: sounds natural to us, we accept it. We're like, okay, yeah,

495
00:24:58,000 --> 00:25:00,480
Speaker 2: I believe that. Yeah, but sometimes the you verse is

496
00:25:00,520 --> 00:25:02,280
Speaker 2: not intuitive. So you always got to go out there

497
00:25:02,320 --> 00:25:05,720
Speaker 2: and check, especially when you're telling a reasonable sounding story

498
00:25:05,960 --> 00:25:09,040
Speaker 2: that doesn't have any actual data to support it. So

499
00:25:09,320 --> 00:25:10,560
Speaker 2: more science, people.

500
00:25:10,400 --> 00:25:14,119
Speaker 1: Right, So much more science, Yes, so much more science. Okay.

501
00:25:14,200 --> 00:25:16,840
Speaker 1: So we were talking a little bit earlier about why

502
00:25:16,920 --> 00:25:19,560
Speaker 1: you would want to try to create boxes to describe

503
00:25:19,600 --> 00:25:22,119
Speaker 1: what parasites are doing, what different animals are doing, and

504
00:25:22,160 --> 00:25:24,199
Speaker 1: I was arguing that you need those boxes so that

505
00:25:24,240 --> 00:25:27,239
Speaker 1: you can create models to help understand what's happening. And

506
00:25:27,280 --> 00:25:29,640
Speaker 1: there's a couple of different folks who have come up

507
00:25:29,680 --> 00:25:33,080
Speaker 1: with categories that they think keep popping up as strategies

508
00:25:33,080 --> 00:25:35,560
Speaker 1: that parasites take. And I saw a quote in one

509
00:25:35,560 --> 00:25:38,199
Speaker 1: of these papers that made me think, oh, man, this

510
00:25:38,359 --> 00:25:42,280
Speaker 1: is for Daniel uh oh, so here it is. This

511
00:25:42,320 --> 00:25:46,000
Speaker 1: is from Poola twenty eleven. It seems safe to speculate

512
00:25:46,040 --> 00:25:49,240
Speaker 1: that if life exists on other planets, as long as

513
00:25:49,280 --> 00:25:54,520
Speaker 1: alien ecosystems show some basic similarities to ours, then parasitism

514
00:25:54,640 --> 00:25:57,600
Speaker 1: will not only have evolved, but alien parasites would be

515
00:25:57,720 --> 00:26:01,560
Speaker 1: using exploitation strategies very close to the ones to find.

516
00:26:01,440 --> 00:26:04,600
Speaker 2: Here well parasites in the universe.

517
00:26:07,680 --> 00:26:09,880
Speaker 1: So he was really going out on a limb here,

518
00:26:10,400 --> 00:26:14,280
Speaker 1: very strongly worded. He believes these categories explained like truths

519
00:26:14,480 --> 00:26:16,160
Speaker 1: about paths taken by life.

520
00:26:16,280 --> 00:26:18,680
Speaker 2: I think it's fascinating when scientists do that. When they

521
00:26:19,040 --> 00:26:21,560
Speaker 2: find something here, they understand it, and then they say

522
00:26:21,840 --> 00:26:24,320
Speaker 2: this must be universal. We found it here, and therefore

523
00:26:24,359 --> 00:26:26,720
Speaker 2: it's everywhere. It seems like it could be the only way,

524
00:26:27,280 --> 00:26:30,639
Speaker 2: And that's so often just reveals like a lack of

525
00:26:30,680 --> 00:26:33,960
Speaker 2: the broader context, like you're within a certain set of

526
00:26:34,080 --> 00:26:36,760
Speaker 2: box of ways of thinking about the universe and it's

527
00:26:36,880 --> 00:26:39,639
Speaker 2: hard to imagine. Outside that box doesn't mean that outside

528
00:26:39,680 --> 00:26:42,359
Speaker 2: the box doesn't exist. And like, as I was just saying,

529
00:26:42,400 --> 00:26:44,240
Speaker 2: like this is why we got to go and find

530
00:26:44,240 --> 00:26:48,239
Speaker 2: alien parasites and blow earthling parasitologists minds about ways that

531
00:26:48,280 --> 00:26:50,600
Speaker 2: you can suck on other people. Right, there may be

532
00:26:50,680 --> 00:26:53,360
Speaker 2: even more intimate ways to be a parasite we never

533
00:26:53,440 --> 00:26:56,440
Speaker 2: even imagined, totally true, as you know. And that's why

534
00:26:56,560 --> 00:26:59,439
Speaker 2: I wrote this whole book about how aliens might do science,

535
00:26:59,560 --> 00:27:01,080
Speaker 2: trying to think outside the box.

536
00:27:01,200 --> 00:27:02,480
Speaker 1: Daniel, what is that book called.

537
00:27:03,840 --> 00:27:06,200
Speaker 2: It's called Do Aliens Speak Physics? And it's for sale

538
00:27:06,200 --> 00:27:07,920
Speaker 2: in November. Check it out at.

539
00:27:07,840 --> 00:27:10,920
Speaker 1: All fine bookstores. Yeah, no, it is a fantastic book.

540
00:27:11,080 --> 00:27:11,800
Speaker 1: I got to read it.

541
00:27:11,920 --> 00:27:14,760
Speaker 2: So I love that this parasitologist is thinking about aliens.

542
00:27:14,760 --> 00:27:18,320
Speaker 2: But I'm a little skeptical that our earthly categories of

543
00:27:18,359 --> 00:27:21,399
Speaker 2: parasites are the only ones in the universe. But anyway,

544
00:27:21,480 --> 00:27:24,640
Speaker 2: walk us through the kinds of parasites we have found

545
00:27:24,640 --> 00:27:27,200
Speaker 2: here on Earth, and everybody out there, if you're eating dinner,

546
00:27:27,320 --> 00:27:30,160
Speaker 2: maybe finish up before we dig into all of these

547
00:27:30,320 --> 00:27:31,480
Speaker 2: intimate details.

548
00:27:31,920 --> 00:27:36,200
Speaker 1: Okay, So, one of the exciting things about these strategies

549
00:27:36,359 --> 00:27:39,480
Speaker 1: is that organisms from very different locations on the tree

550
00:27:39,520 --> 00:27:43,240
Speaker 1: of life seem to have ended up with very similar strategies,

551
00:27:43,280 --> 00:27:46,320
Speaker 1: which suggests that there's something critical about these boxes that

552
00:27:46,359 --> 00:27:46,960
Speaker 1: we're creating.

553
00:27:47,080 --> 00:27:47,399
Speaker 2: Yeah.

554
00:27:47,440 --> 00:27:50,080
Speaker 1: So one of the strategies, which we've already talked about,

555
00:27:50,160 --> 00:27:53,119
Speaker 1: is parasitoids. So the idea here is that you infect

556
00:27:53,160 --> 00:27:56,399
Speaker 1: one host species, you use all of its energy. You

557
00:27:56,520 --> 00:27:58,439
Speaker 1: have to kill it as part of your life cycle,

558
00:27:58,880 --> 00:28:02,480
Speaker 1: and so we get parasit wasps that do this. We

559
00:28:02,600 --> 00:28:06,000
Speaker 1: get nomatomorphs. So these are sort of nematode looking things

560
00:28:06,560 --> 00:28:08,679
Speaker 1: that live in cricket So have you ever seen that

561
00:28:08,760 --> 00:28:11,560
Speaker 1: video of a cricket that jumps into a pool and

562
00:28:11,800 --> 00:28:14,720
Speaker 1: a worm that's like ten times the length of the cricket,

563
00:28:14,760 --> 00:28:16,920
Speaker 1: maybe even more, glides out of its back end.

564
00:28:17,119 --> 00:28:17,639
Speaker 2: Mm hmmm.

565
00:28:18,400 --> 00:28:20,879
Speaker 1: Nightmare fuel, Yes, absolute nightmare fuel.

566
00:28:20,960 --> 00:28:23,760
Speaker 2: There's one with the praying mantis also, I think yeah, yeah.

567
00:28:23,640 --> 00:28:27,359
Speaker 1: Yeah, yeah. So sometimes those animals survive actually after they

568
00:28:27,440 --> 00:28:29,240
Speaker 1: jump into the water, which blows my mind because you

569
00:28:29,280 --> 00:28:31,000
Speaker 1: would think something that big comes out of you, you're

570
00:28:31,000 --> 00:28:31,439
Speaker 1: a goner.

571
00:28:31,520 --> 00:28:39,560
Speaker 2: Yeah, I think that some mornings. Yes, oh god, I

572
00:28:39,600 --> 00:28:41,720
Speaker 2: think there's an intimate detail for everybody.

573
00:28:41,400 --> 00:28:43,880
Speaker 1: That's right intimate, I hope not durable. I hope we

574
00:28:43,920 --> 00:28:49,400
Speaker 1: can all forget that. Okay, So you get those like

575
00:28:49,440 --> 00:28:52,320
Speaker 1: wormy things that eat almost everything inside of the organism,

576
00:28:52,360 --> 00:28:55,240
Speaker 1: and it's kind of amazing because they've managed to take

577
00:28:55,720 --> 00:28:58,760
Speaker 1: everything from the organism without killing it, so they're able

578
00:28:58,800 --> 00:29:01,080
Speaker 1: to like avoid the critical organs, but all the like

579
00:29:01,160 --> 00:29:04,280
Speaker 1: fat has been slurped out. Anything that's not absolutely critical

580
00:29:04,600 --> 00:29:07,280
Speaker 1: has been slurped out and turned into parasite. And those

581
00:29:07,360 --> 00:29:10,200
Speaker 1: zombie ants that you see with the Cordyceps fungus, they

582
00:29:10,240 --> 00:29:13,320
Speaker 1: also are exhibiting a parasitoid strategy. They kill the ant

583
00:29:13,760 --> 00:29:15,640
Speaker 1: and then they use all of that energy to make

584
00:29:15,680 --> 00:29:16,400
Speaker 1: their own babies.

585
00:29:16,760 --> 00:29:20,120
Speaker 2: So explain to me the word here parasitoid, because as

586
00:29:20,120 --> 00:29:21,880
Speaker 2: a non expert, I hear that, and I think that's

587
00:29:21,880 --> 00:29:24,760
Speaker 2: sort of like a quasi parasite or a semi parasite

588
00:29:24,880 --> 00:29:29,000
Speaker 2: or something oid. Makes me think, like, not quite, what

589
00:29:29,120 --> 00:29:31,080
Speaker 2: does the word mean parasitoid?

590
00:29:31,480 --> 00:29:34,240
Speaker 1: This is a great question. I think the original phrase

591
00:29:34,360 --> 00:29:38,800
Speaker 1: came from a German scientist, and that doesn't necessarily mean that,

592
00:29:38,840 --> 00:29:42,560
Speaker 1: like their prefixes and suffixes meant something different. You're right,

593
00:29:42,640 --> 00:29:45,760
Speaker 1: I'm looking up Merriam Webster and the first definition of

594
00:29:45,800 --> 00:29:49,200
Speaker 1: parasitoid is resembling a parasite, which must be the oid

595
00:29:49,600 --> 00:29:50,560
Speaker 1: thing the.

596
00:29:50,480 --> 00:29:53,440
Speaker 2: Way that like our jokes resemble humor but aren't always

597
00:29:53,480 --> 00:29:55,360
Speaker 2: right on the money. You know, it's humoroid.

598
00:29:55,880 --> 00:29:59,680
Speaker 1: That's right, that's right, we're humoroid kind of podcasts, which

599
00:29:59,720 --> 00:30:01,320
Speaker 1: sounds maybe too close to hemorrhoid.

600
00:30:01,600 --> 00:30:05,400
Speaker 2: But uh so a lot of intimate jokes today, yes.

601
00:30:05,480 --> 00:30:09,640
Speaker 1: Right, so many, my guess would be and I this

602
00:30:09,760 --> 00:30:12,959
Speaker 1: is total spitball. Okay, So there are no parasitoids that

603
00:30:13,040 --> 00:30:15,680
Speaker 1: infect humans, and so I think that when we think

604
00:30:15,760 --> 00:30:19,760
Speaker 1: of parasites, we think of things that are like living

605
00:30:19,800 --> 00:30:21,800
Speaker 1: in your guts or you know, like we think of

606
00:30:21,840 --> 00:30:24,560
Speaker 1: the kind of parasites that we have. And so it's

607
00:30:24,640 --> 00:30:28,160
Speaker 1: possible that when parasitoid was first named, they were like, oh, like,

608
00:30:28,200 --> 00:30:31,400
Speaker 1: it's living in another thing. We're familiar with that. But

609
00:30:31,400 --> 00:30:33,200
Speaker 1: then it like kills them and bursts out of them,

610
00:30:33,240 --> 00:30:36,240
Speaker 1: and it's this is something different. So let's call it parasitoid.

611
00:30:36,520 --> 00:30:38,640
Speaker 1: And I'm totally spitball. Like you have asked me yet

612
00:30:38,680 --> 00:30:41,080
Speaker 1: another question. I don't know the answer too, but I'm

613
00:30:41,120 --> 00:30:42,800
Speaker 1: gonna double down on my answer.

614
00:30:43,360 --> 00:30:46,320
Speaker 2: All right, So these guys don't live in humans. They

615
00:30:46,440 --> 00:30:50,080
Speaker 2: infect their host, slurp up all the in crucial bits,

616
00:30:50,120 --> 00:30:51,480
Speaker 2: and then eventually kill them.

617
00:30:51,640 --> 00:30:53,520
Speaker 1: Yep, that's a strategy, all right.

618
00:30:53,560 --> 00:30:55,800
Speaker 2: And so if that wasn't gross enough for you, let's

619
00:30:55,840 --> 00:30:59,560
Speaker 2: hear about the next category, which I shiver to even say.

620
00:31:00,200 --> 00:31:01,960
Speaker 2: Parasitic castrators.

621
00:31:02,480 --> 00:31:08,600
Speaker 1: Yes, lovely. So they don't kill the hosts, but they

622
00:31:08,680 --> 00:31:12,440
Speaker 1: do reduce their evolutionary fitness to zero. So essentially they

623
00:31:12,480 --> 00:31:14,840
Speaker 1: make it so that that organism will never be able

624
00:31:14,880 --> 00:31:16,960
Speaker 1: to pass down its genes again. It won't be able

625
00:31:16,960 --> 00:31:18,280
Speaker 1: to have any more of its babies.

626
00:31:18,320 --> 00:31:18,560
Speaker 2: Wow.

627
00:31:19,240 --> 00:31:20,600
Speaker 1: But now the parasites get to.

628
00:31:20,600 --> 00:31:24,960
Speaker 2: Live cute little parasite babies. You know.

629
00:31:25,040 --> 00:31:27,360
Speaker 1: The parasite studied for my PhD has these two little

630
00:31:27,400 --> 00:31:31,080
Speaker 1: eye spots, and it has like a little suckery kind

631
00:31:31,080 --> 00:31:33,000
Speaker 1: of mouth that opens and closes. And by the end

632
00:31:33,080 --> 00:31:36,440
Speaker 1: of my very long PhD it took a really long

633
00:31:36,480 --> 00:31:38,880
Speaker 1: time to finish, I kind of thought that they were cute.

634
00:31:39,240 --> 00:31:42,080
Speaker 1: So I am capable of thinking some parasites are cute.

635
00:31:42,160 --> 00:31:45,280
Speaker 2: They've infected your brain. See, they're working their magic on you.

636
00:31:45,520 --> 00:31:46,520
Speaker 1: That's right, that's right.

637
00:31:46,600 --> 00:31:48,000
Speaker 2: So tell us about what these guys do.

638
00:31:48,200 --> 00:31:49,560
Speaker 1: All right, So at the top of the show, we

639
00:31:49,600 --> 00:31:52,480
Speaker 1: talked about those snails where a bunch of the biomass

640
00:31:52,480 --> 00:31:54,720
Speaker 1: of those snails is actually going towards the production of

641
00:31:54,720 --> 00:31:58,920
Speaker 1: parasite babies. That's an example of castration. All of the

642
00:31:59,040 --> 00:32:01,600
Speaker 1: energy that would have gone TODs making snail babies is

643
00:32:01,640 --> 00:32:04,120
Speaker 1: now making parasite babies. And those snails can live for

644
00:32:04,280 --> 00:32:06,680
Speaker 1: like I think it's like a decade after getting infected.

645
00:32:07,120 --> 00:32:09,520
Speaker 1: And sometimes when the tide comes in on a warm day,

646
00:32:09,520 --> 00:32:12,480
Speaker 1: they can release up to two thousand of those parasites

647
00:32:12,480 --> 00:32:15,320
Speaker 1: into the water column. And so we think of them

648
00:32:15,320 --> 00:32:18,640
Speaker 1: as essentially like extended versions of parasites. At that point,

649
00:32:18,680 --> 00:32:22,000
Speaker 1: they're not working towards their own evolutionary goals anymore. Also,

650
00:32:22,480 --> 00:32:25,640
Speaker 1: side note, the parasites that live in the snails have

651
00:32:25,760 --> 00:32:29,400
Speaker 1: social behaviors, Like do you know how ant communities have

652
00:32:30,000 --> 00:32:32,320
Speaker 1: different jobs for the different ants, and the ants have

653
00:32:32,320 --> 00:32:36,479
Speaker 1: different shapes. Yeah, you've got like a million mile stare

654
00:32:36,840 --> 00:32:38,320
Speaker 1: right now? Is this too much?

655
00:32:38,680 --> 00:32:39,880
Speaker 2: No, I'm thinking about ants?

656
00:32:39,920 --> 00:32:41,200
Speaker 1: Oh all right, okay, I was thinking.

657
00:32:41,000 --> 00:32:43,320
Speaker 2: About that time they poured aluminum into an ant farm.

658
00:32:43,360 --> 00:32:44,920
Speaker 2: I remember, like the shape of it.

659
00:32:45,120 --> 00:32:49,680
Speaker 1: That's a mean but informative way of getting that information. Okay,

660
00:32:49,920 --> 00:32:53,880
Speaker 1: So ants have individuals who have different jobs, and they

661
00:32:53,880 --> 00:32:57,040
Speaker 1: have different shapes, and they have some individuals who never

662
00:32:57,080 --> 00:32:59,440
Speaker 1: have their own offspring. Their job is just to support

663
00:32:59,440 --> 00:33:03,080
Speaker 1: the colony. The same thing is happening inside of these snails.

664
00:33:03,480 --> 00:33:07,920
Speaker 1: So there are attacker morphs that are essentially just like

665
00:33:08,440 --> 00:33:12,160
Speaker 1: giant mouths that go around and when a parasite tries

666
00:33:12,200 --> 00:33:15,080
Speaker 1: to invade the snail, because sometimes a new parasite species

667
00:33:15,120 --> 00:33:17,720
Speaker 1: will come in invade a snail that already has parasites

668
00:33:17,720 --> 00:33:20,240
Speaker 1: living in there, and it could kick out the parasites

669
00:33:20,280 --> 00:33:22,280
Speaker 1: that are living in there and then take over the gonad.

670
00:33:22,440 --> 00:33:25,520
Speaker 2: So it's like parasite versus parasite battle inside the snail.

671
00:33:25,880 --> 00:33:29,360
Speaker 1: Yes, wow, yes, And some kinds of trematode parasites have

672
00:33:29,480 --> 00:33:32,000
Speaker 1: essentially these mouths that never reproduce on their own. Their

673
00:33:32,040 --> 00:33:35,200
Speaker 1: whole job is to just patrol the snail, and if

674
00:33:35,240 --> 00:33:38,360
Speaker 1: a parasite comes in, they go and they suck a

675
00:33:38,400 --> 00:33:40,160
Speaker 1: hole into the side of the tree with toad and

676
00:33:40,200 --> 00:33:43,000
Speaker 1: like suck out the insides and kill it that way.

677
00:33:43,200 --> 00:33:46,080
Speaker 2: Wow, this is like gang violenceers. This is our territory.

678
00:33:46,440 --> 00:33:48,959
Speaker 1: Yes, yeah, they have like more interesting social lives than

679
00:33:49,000 --> 00:33:50,200
Speaker 1: I do. They're fascinating.

680
00:33:50,800 --> 00:33:52,440
Speaker 2: But how high bar is that?

681
00:33:52,520 --> 00:33:55,000
Speaker 1: Kelly tell me, Oh my god, it's like it's like

682
00:33:55,080 --> 00:33:56,680
Speaker 1: on the ground. You don't have to lift your foot

683
00:33:56,720 --> 00:34:00,160
Speaker 1: up much at all. I don't go out much. But anyway, okay,

684
00:34:00,520 --> 00:34:04,440
Speaker 1: parasitic castrators, trematodes. Let's do one other example. There are

685
00:34:04,880 --> 00:34:07,400
Speaker 1: barnacles and so like if you've been to the ocean,

686
00:34:07,400 --> 00:34:09,840
Speaker 1: you've probably seen barnacles. There are barnacles that stick to

687
00:34:09,880 --> 00:34:12,680
Speaker 1: the sides of like whales and turtles. There are also

688
00:34:12,800 --> 00:34:16,319
Speaker 1: barnacles and isopods. These are these little crustacean things that

689
00:34:16,360 --> 00:34:21,120
Speaker 1: are both able to castrate crustaceans like crabs. So the

690
00:34:21,160 --> 00:34:24,719
Speaker 1: barnacle in particular does this very interesting thing where it

691
00:34:25,160 --> 00:34:28,880
Speaker 1: has a sack where female crabs would usually have their babies,

692
00:34:29,800 --> 00:34:33,080
Speaker 1: and it sets up shop there, and females usually will

693
00:34:33,160 --> 00:34:35,279
Speaker 1: use their claws, so this is on the underside of

694
00:34:35,280 --> 00:34:37,279
Speaker 1: what you'd think of as like the crab's belly. They

695
00:34:37,360 --> 00:34:39,800
Speaker 1: use their claws to like pass water over it to

696
00:34:39,840 --> 00:34:42,560
Speaker 1: make sure that their eggs stay oxygenated. They will do

697
00:34:42,600 --> 00:34:45,800
Speaker 1: that when the barnacles down there to keep the barnacle oxygenated,

698
00:34:46,239 --> 00:34:48,480
Speaker 1: and males will start doing that too, So it looks

699
00:34:48,480 --> 00:34:51,720
Speaker 1: like not only do they castrate male and female crabs,

700
00:34:52,040 --> 00:34:55,200
Speaker 1: but they get the males to start acting like females

701
00:34:55,360 --> 00:34:58,440
Speaker 1: to take care of the barnacles. We call this feminization,

702
00:34:58,680 --> 00:35:02,120
Speaker 1: and it's kind of poorly understood, but anyway, So barnacles

703
00:35:02,200 --> 00:35:08,880
Speaker 1: are castrating crabs, trematodes are castrating snails, and there's insects

704
00:35:08,880 --> 00:35:12,280
Speaker 1: castrating other insects. This is another very common strategy.

705
00:35:12,400 --> 00:35:14,560
Speaker 2: You just said the word castrating way too many times

706
00:35:14,560 --> 00:35:17,479
Speaker 2: from that country. Let's move on.

707
00:35:18,760 --> 00:35:21,879
Speaker 1: There's a total of six categories, but rather than making

708
00:35:21,960 --> 00:35:24,560
Speaker 1: you all sit through all six, let's pick one more

709
00:35:25,160 --> 00:35:28,840
Speaker 1: to give you a flavor of the amazing strategies that

710
00:35:28,920 --> 00:35:30,040
Speaker 1: parasites have taken on.

711
00:35:30,840 --> 00:35:34,640
Speaker 2: Let's do vector transmitted parasites. Because that sounds physics, y vectors.

712
00:35:35,000 --> 00:35:37,279
Speaker 1: Ooh, all right, Well you can try to connect this

713
00:35:37,360 --> 00:35:39,440
Speaker 1: with physics at the end, we'll see. But so, what

714
00:35:39,480 --> 00:35:43,160
Speaker 1: we mean by vector transmitted is that you have one

715
00:35:43,280 --> 00:35:46,719
Speaker 1: animal that is bringing a parasite to another animal and

716
00:35:46,800 --> 00:35:50,440
Speaker 1: essentially injecting it into that other animal. Probably the most

717
00:35:50,640 --> 00:35:56,239
Speaker 1: famous vector transmitted parasite is malaria. So mosquitoes will take

718
00:35:56,280 --> 00:35:58,480
Speaker 1: a blood meal from a person who has malaria, they

719
00:35:58,560 --> 00:36:01,880
Speaker 1: suck the parasite up. A parasite does some developing inside

720
00:36:01,880 --> 00:36:03,799
Speaker 1: of the mosquito and eventually goes to live in the

721
00:36:03,840 --> 00:36:07,200
Speaker 1: mosquito's salivary glands. And then when a mosquito goes to

722
00:36:07,200 --> 00:36:10,160
Speaker 1: take a blood meal from another human who isn't infected yet,

723
00:36:10,560 --> 00:36:14,200
Speaker 1: the parasite ends up in that person's blood, and then

724
00:36:14,200 --> 00:36:16,320
Speaker 1: that person gets infected and the cycle starts again.

725
00:36:16,440 --> 00:36:18,800
Speaker 2: I think it's fascinating. You call this a blood meal.

726
00:36:19,160 --> 00:36:21,600
Speaker 2: Makes it sound so wholesome, you know, like it's just

727
00:36:21,640 --> 00:36:23,640
Speaker 2: going home to have dinner after a long day of work.

728
00:36:23,840 --> 00:36:26,160
Speaker 2: You know it deserves it, But like, this thing is

729
00:36:26,200 --> 00:36:27,880
Speaker 2: sucking my blood, you know.

730
00:36:28,000 --> 00:36:30,680
Speaker 1: I've read stories from the early nineteen hundreds in the

731
00:36:30,760 --> 00:36:32,960
Speaker 1: Journal of Parasitology where they sort of mentioned in an

732
00:36:33,000 --> 00:36:36,040
Speaker 1: offhanded way that like the mosquitoes and the lice in

733
00:36:36,080 --> 00:36:40,840
Speaker 1: the colonies were fed blood meals by volunteers, which means

734
00:36:40,880 --> 00:36:43,480
Speaker 1: somebody was like sticking their arms in the mosquito cage.

735
00:36:43,719 --> 00:36:45,840
Speaker 1: Anna Phillips was telling us in the Leech episode that

736
00:36:45,920 --> 00:36:49,760
Speaker 1: now you can like fill medical gloves up with blood

737
00:36:49,880 --> 00:36:52,600
Speaker 1: from you know, a hospital or something and feeds them

738
00:36:52,600 --> 00:36:55,239
Speaker 1: that way. But I love the faces you make when

739
00:36:55,239 --> 00:36:58,600
Speaker 1: we talk about parasites. It's so entertaining for me. But Mike,

740
00:36:58,640 --> 00:37:00,879
Speaker 1: you know I if I I tell you my big

741
00:37:00,920 --> 00:37:04,000
Speaker 1: goal here, I feel like when you start learning about parasites,

742
00:37:04,280 --> 00:37:07,000
Speaker 1: you can't get over the disgust hump Ye. It's just

743
00:37:07,120 --> 00:37:09,640
Speaker 1: like so upsetting. But the more you learn about it.

744
00:37:10,280 --> 00:37:13,160
Speaker 1: This doesn't happen for everybody, but maybe you'll get there.

745
00:37:13,640 --> 00:37:15,160
Speaker 1: I feel like the more you learn about it, the

746
00:37:15,160 --> 00:37:19,400
Speaker 1: more kind of amazing it is that evolution has resulted

747
00:37:19,480 --> 00:37:23,440
Speaker 1: in this super complicated strategy. Like I mean, imagine being

748
00:37:23,480 --> 00:37:26,560
Speaker 1: able to live in environments as different as a mosquito

749
00:37:26,760 --> 00:37:30,000
Speaker 1: and a human, like to conquer both of those hosts

750
00:37:30,040 --> 00:37:32,359
Speaker 1: in a way that like human ingenuity has just not

751
00:37:32,400 --> 00:37:35,279
Speaker 1: been able to outsmart. There's good evidence that malaria is

752
00:37:35,360 --> 00:37:38,839
Speaker 1: able to essentially like change the proteins on the outside

753
00:37:39,200 --> 00:37:42,080
Speaker 1: so that our immune system can't recognize it. Like we

754
00:37:42,120 --> 00:37:43,520
Speaker 1: start to get a handle on it, and then it

755
00:37:43,560 --> 00:37:45,640
Speaker 1: shows up again in like a whole different outfit, and

756
00:37:45,640 --> 00:37:48,239
Speaker 1: our body is like, where did the malaria go? But

757
00:37:48,280 --> 00:37:51,239
Speaker 1: it's still there and it's like racing us and you

758
00:37:51,239 --> 00:37:53,440
Speaker 1: know we have We've created all of these vaccines that

759
00:37:53,560 --> 00:37:56,239
Speaker 1: keep you know, not quite keeping up. These are kind

760
00:37:56,280 --> 00:37:58,719
Speaker 1: of incredible creatures. You can hate them, and I wish

761
00:37:58,719 --> 00:38:00,480
Speaker 1: there was no malaria because I don't want to see

762
00:38:00,480 --> 00:38:03,680
Speaker 1: any child with malaria ever again. But you kind of

763
00:38:03,680 --> 00:38:07,320
Speaker 1: have to respect sort of the amazing strategies that they've

764
00:38:07,360 --> 00:38:09,440
Speaker 1: been able to come up with with the help of

765
00:38:09,520 --> 00:38:10,240
Speaker 1: natural selection.

766
00:38:10,560 --> 00:38:13,799
Speaker 2: Yeah, I totally appreciate you leaning into the wonders of

767
00:38:13,840 --> 00:38:16,440
Speaker 2: the universe, and you know, that's our whole brand, and

768
00:38:16,480 --> 00:38:20,200
Speaker 2: the universe is extraordinary and these things are incredible. And

769
00:38:20,239 --> 00:38:21,879
Speaker 2: I guess I'll try to think about that next time

770
00:38:21,920 --> 00:38:24,440
Speaker 2: I see a mosquito biting Meia be like, wow, think

771
00:38:24,440 --> 00:38:27,480
Speaker 2: about all the amazing science going into this itch that

772
00:38:27,520 --> 00:38:29,520
Speaker 2: I'm going to be suffering for the next three days.

773
00:38:29,840 --> 00:38:37,000
Speaker 1: Well, that's a micro predator, Daniel, I'm not interested, just kidding.

774
00:38:36,840 --> 00:38:38,839
Speaker 2: All right, So let's take another break and we come back.

775
00:38:38,920 --> 00:39:03,480
Speaker 2: Let's hear some good news about how parasites can go extinct. Okay,

776
00:39:03,520 --> 00:39:06,560
Speaker 2: we're back, and Kelly is grossing me out with intimate

777
00:39:06,640 --> 00:39:10,000
Speaker 2: details of how parasites infect their hosts, castrate them, and

778
00:39:10,120 --> 00:39:14,760
Speaker 2: pass on diseases. Yay, we're all supposed to think. Yay.

779
00:39:15,719 --> 00:39:17,959
Speaker 2: So let's turn to some good news. We heard about

780
00:39:18,000 --> 00:39:21,560
Speaker 2: how parasites have evolved many many times in the record.

781
00:39:21,760 --> 00:39:25,440
Speaker 2: Do parasites also go extinct? We have evidence for parasites disappearing.

782
00:39:25,480 --> 00:39:26,320
Speaker 2: How does that happen?

783
00:39:26,800 --> 00:39:29,080
Speaker 1: They do go extinct, and so, you know, we talked

784
00:39:29,120 --> 00:39:32,000
Speaker 1: about how parasitism as a strategy popped up, you know,

785
00:39:32,040 --> 00:39:33,960
Speaker 1: over two hundred times in the tree of life. It

786
00:39:34,000 --> 00:39:36,240
Speaker 1: appears it's also been lost a few times.

787
00:39:36,400 --> 00:39:37,400
Speaker 2: Ah, I know.

788
00:39:38,280 --> 00:39:40,600
Speaker 1: So sometimes it's hard to get a handle on those

789
00:39:40,640 --> 00:39:43,479
Speaker 1: losses because if an animal loses it and then doesn't

790
00:39:43,560 --> 00:39:45,120
Speaker 1: end up in the fossil record, it can just be

791
00:39:45,200 --> 00:39:48,480
Speaker 1: kind of complicated. But yeah, parasites go extinct, and in fact,

792
00:39:48,920 --> 00:39:52,360
Speaker 1: some parasites are more susceptible to extinction than their hosts.

793
00:39:52,360 --> 00:39:55,399
Speaker 1: And I know that's not sad for you, but we're

794
00:39:55,440 --> 00:39:58,719
Speaker 1: losing diversity. So one parasite strategy that we didn't talk

795
00:39:58,719 --> 00:40:01,920
Speaker 1: about in the last section are trophically transmitted parasites.

796
00:40:02,560 --> 00:40:03,640
Speaker 2: What does trophic mean?

797
00:40:03,960 --> 00:40:06,280
Speaker 1: So, like, think about trophic levels in a food web,

798
00:40:06,800 --> 00:40:10,920
Speaker 1: and so trophic transmission is essentially a predator consumes an

799
00:40:10,960 --> 00:40:14,440
Speaker 1: animal that was infected, and the parasite gets into the predator.

800
00:40:14,520 --> 00:40:18,160
Speaker 1: So the trophically transmitted system I studied for my PhD

801
00:40:18,800 --> 00:40:21,640
Speaker 1: was California killifish. There are these small fish in southern

802
00:40:21,719 --> 00:40:25,759
Speaker 1: California estuaries and they get eaten by predatory birds like egrets,

803
00:40:26,080 --> 00:40:28,080
Speaker 1: and the parasite goes from living on top of the

804
00:40:28,080 --> 00:40:30,640
Speaker 1: fish's brain to living in the egrets gut.

805
00:40:30,920 --> 00:40:32,640
Speaker 2: I wouldn't want to live in either of those places.

806
00:40:32,640 --> 00:40:34,760
Speaker 2: I mean, you're in southern California. There's lots of beautiful

807
00:40:34,760 --> 00:40:37,560
Speaker 2: places to live. Why would you choose a fish brain?

808
00:40:37,680 --> 00:40:38,640
Speaker 2: But hey, you do you?

809
00:40:39,200 --> 00:40:41,960
Speaker 1: I mean, I'd rather live in Virginia. But that's all right.

810
00:40:42,400 --> 00:40:45,800
Speaker 1: So everyone knew that was coming. But this parasite actually

811
00:40:45,800 --> 00:40:48,759
Speaker 1: has an even more complicated life cycle. So parasites can

812
00:40:48,800 --> 00:40:51,040
Speaker 1: have different strategies depending on where they are in the

813
00:40:51,080 --> 00:40:54,400
Speaker 1: life cycle. So there you've got trophic transmission from fish

814
00:40:54,400 --> 00:40:59,040
Speaker 1: to bird. The parasites then find love in the bird's

815
00:40:59,080 --> 00:41:02,040
Speaker 1: gut and they may eggs that pass with the bird

816
00:41:02,080 --> 00:41:05,839
Speaker 1: species into the salt marsh, where they're accidentally consumed by

817
00:41:05,840 --> 00:41:09,120
Speaker 1: those snails that we talked about that get castrated and

818
00:41:09,160 --> 00:41:10,719
Speaker 1: then this is.

819
00:41:10,680 --> 00:41:13,000
Speaker 2: Such a horror movie. This whole thing is a horror movie.

820
00:41:13,480 --> 00:41:15,719
Speaker 1: I love it, I eat it up. My mom loved

821
00:41:15,719 --> 00:41:17,520
Speaker 1: horror movies. Maybe that's what's set me up for all

822
00:41:17,520 --> 00:41:17,759
Speaker 1: of this.

823
00:41:17,719 --> 00:41:18,560
Speaker 2: It's her fault.

824
00:41:18,680 --> 00:41:22,640
Speaker 1: Yes, yeah, yeah. So anyway, in order for this parasite,

825
00:41:22,760 --> 00:41:25,440
Speaker 1: this trematode parasite, to complete its life cycle, you need

826
00:41:25,480 --> 00:41:27,360
Speaker 1: to have the fish, you need to have the birds,

827
00:41:27,400 --> 00:41:29,480
Speaker 1: and you need to have the snail. If you lose

828
00:41:29,600 --> 00:41:32,000
Speaker 1: any of those hosts in the cycle, or any of

829
00:41:32,040 --> 00:41:34,239
Speaker 1: them falls to numbers that are small enough where it's

830
00:41:34,239 --> 00:41:37,160
Speaker 1: hard for the parasite to find them, then that animal

831
00:41:37,160 --> 00:41:40,080
Speaker 1: can go extinct. And so parasites have all of these

832
00:41:40,120 --> 00:41:43,200
Speaker 1: extra requirements that depend on what's happening with their hosts,

833
00:41:43,560 --> 00:41:45,759
Speaker 1: and so in some cases we think that parasites might

834
00:41:45,800 --> 00:41:48,560
Speaker 1: be more susceptible to extinction than a lot of free

835
00:41:48,560 --> 00:41:51,879
Speaker 1: living animals because there's so many different components that need

836
00:41:51,920 --> 00:41:54,360
Speaker 1: to work well for the parasite to complete the life cycle.

837
00:41:54,400 --> 00:41:56,319
Speaker 2: It's kind of a fragile system, a bit of.

838
00:41:56,239 --> 00:41:58,480
Speaker 1: A fragile system, and so parasites can be used as

839
00:41:58,480 --> 00:42:01,319
Speaker 1: what we call ecological indicator. So if you go to

840
00:42:01,360 --> 00:42:03,920
Speaker 1: an estuary and you find a lot of parasites, that

841
00:42:04,000 --> 00:42:06,000
Speaker 1: probably means a lot of host species are there, and

842
00:42:06,000 --> 00:42:08,200
Speaker 1: they're there in pretty high numbers, and so a lot

843
00:42:08,280 --> 00:42:12,479
Speaker 1: of parasites can be indicative of a healthy ecosystem, which

844
00:42:12,480 --> 00:42:15,360
Speaker 1: I think is counterintuitive to some people but makes perfect

845
00:42:15,400 --> 00:42:16,960
Speaker 1: sense to my parasitologists heart.

846
00:42:18,440 --> 00:42:19,880
Speaker 2: Like if you go to a new neighborhood and you

847
00:42:19,880 --> 00:42:22,120
Speaker 2: discover there's lots of gangs there, you're like, oh, wow,

848
00:42:22,160 --> 00:42:24,759
Speaker 2: this must have a thriving economy for the gangs to

849
00:42:24,840 --> 00:42:25,960
Speaker 2: be siphoning money off of.

850
00:42:30,480 --> 00:42:32,600
Speaker 1: Wow, where do I go with that? I mean, I

851
00:42:32,600 --> 00:42:35,000
Speaker 1: guess it means that the police aren't really doing their job,

852
00:42:35,000 --> 00:42:38,120
Speaker 1: which maybe means there's immune systems and hosts that are compromised,

853
00:42:38,120 --> 00:42:41,000
Speaker 1: perhaps by pollutants. But maybe we're pulling this analogy a

854
00:42:41,080 --> 00:42:45,040
Speaker 1: little bit too tight, so let's move on.

855
00:42:45,120 --> 00:42:47,520
Speaker 2: All right. So they do go extinct, and maybe even

856
00:42:47,520 --> 00:42:49,239
Speaker 2: more often than their hosts because they rely on like

857
00:42:49,280 --> 00:42:52,640
Speaker 2: a complex system and getting passed from one to the other.

858
00:42:53,160 --> 00:42:55,359
Speaker 2: But then they're everywhere and they're very common and they've

859
00:42:55,400 --> 00:42:58,160
Speaker 2: evolved many many times. How do we understand that altogether?

860
00:42:58,480 --> 00:43:00,400
Speaker 1: I mean, there's a lot of hosts all and you

861
00:43:00,400 --> 00:43:02,000
Speaker 1: can be losing a lot of hosts, but you still

862
00:43:02,000 --> 00:43:04,160
Speaker 1: look around and there's a lot of birds outside and stuff.

863
00:43:04,160 --> 00:43:05,680
Speaker 1: It's just, you know, hard to keep track of all

864
00:43:05,719 --> 00:43:08,000
Speaker 1: of this stuff. But if I can, just for one

865
00:43:08,040 --> 00:43:10,560
Speaker 1: second try to convince you that you should care about

866
00:43:10,640 --> 00:43:12,760
Speaker 1: parasites going extinct, and I won't.

867
00:43:12,600 --> 00:43:13,120
Speaker 2: You can try.

868
00:43:13,320 --> 00:43:17,520
Speaker 1: Yeah, So, parasites are important parts of ecosystem. So we

869
00:43:17,640 --> 00:43:21,160
Speaker 1: mentioned that those snails that are castrated can release up

870
00:43:21,160 --> 00:43:24,319
Speaker 1: to two thousand parasites into the water. Those parasites are

871
00:43:24,360 --> 00:43:27,319
Speaker 1: free swimming bags of energy that get eaten by a

872
00:43:27,320 --> 00:43:30,920
Speaker 1: lot of organisms, so they provide food to the system. Also,

873
00:43:31,520 --> 00:43:33,719
Speaker 1: you know, we talked about those crickets that have those

874
00:43:34,160 --> 00:43:36,480
Speaker 1: long worms in them, and the crickets are forced into

875
00:43:36,560 --> 00:43:40,040
Speaker 1: jumping into the river and then the worms, the nomatomorphs,

876
00:43:40,080 --> 00:43:43,120
Speaker 1: come out the back of them. Those crickets are terrestrial

877
00:43:43,200 --> 00:43:46,440
Speaker 1: organisms that jump into creeks, And in Japan there's this

878
00:43:46,719 --> 00:43:49,680
Speaker 1: endangered trout where a lot of the food that it

879
00:43:49,719 --> 00:43:52,640
Speaker 1: gets comes from crickets that are jumping into the creek

880
00:43:52,680 --> 00:43:55,239
Speaker 1: that they wouldn't have access to otherwise. And so these

881
00:43:55,280 --> 00:43:58,920
Speaker 1: parasites often make lots of food available to other animals

882
00:43:58,960 --> 00:44:01,720
Speaker 1: or make that food easy to catch. They play important

883
00:44:01,760 --> 00:44:04,919
Speaker 1: roles in ecosystems that we don't always understand very well,

884
00:44:04,920 --> 00:44:07,279
Speaker 1: and if you lose them that could be bad in

885
00:44:07,320 --> 00:44:07,880
Speaker 1: some cases.

886
00:44:08,120 --> 00:44:10,480
Speaker 2: Yeah, I totally appreciate that. And it's sort of curious

887
00:44:10,520 --> 00:44:13,240
Speaker 2: to me, like, why do parasites have this ick factor

888
00:44:13,680 --> 00:44:17,160
Speaker 2: that like predators don't, you know, like a jaguar, it's

889
00:44:17,160 --> 00:44:20,040
Speaker 2: still like finding another critter and taking it and eating

890
00:44:20,080 --> 00:44:23,560
Speaker 2: its resources. Why is this somehow grosser to be like

891
00:44:23,680 --> 00:44:26,880
Speaker 2: living inside as you consume somebody for some reason, it

892
00:44:26,960 --> 00:44:30,439
Speaker 2: is definitely grosser though like morally it's not any better

893
00:44:30,560 --> 00:44:32,759
Speaker 2: or worse. So I don't know, there's just some sort

894
00:44:32,800 --> 00:44:35,200
Speaker 2: of like human ick factor there. And maybe when we

895
00:44:35,239 --> 00:44:38,160
Speaker 2: meet the aliens they'll be like, yay parasites, and Kelly

896
00:44:38,200 --> 00:44:39,600
Speaker 2: will be like, I found my people.

897
00:44:40,840 --> 00:44:44,160
Speaker 1: That's right, that's right. I understand you guys, you no,

898
00:44:44,200 --> 00:44:46,200
Speaker 1: I agree. There's definitely a judgment called people think of

899
00:44:46,239 --> 00:44:49,360
Speaker 1: parasites as like these super degenerate organisms. They have fewer

900
00:44:49,400 --> 00:44:52,200
Speaker 1: sort of abilities to like sense the exterior environment, but

901
00:44:52,200 --> 00:44:55,000
Speaker 1: they do manage to thrive in really complicated systems where

902
00:44:55,000 --> 00:44:58,600
Speaker 1: they're being attacked. And yeah, anyway, people do tend to

903
00:44:58,640 --> 00:45:00,960
Speaker 1: find parasites to be much gross to the lions. I

904
00:45:01,160 --> 00:45:03,239
Speaker 1: get that some people could look at a lion and

905
00:45:03,280 --> 00:45:06,000
Speaker 1: be like, that looks much nicer than a tapeworm. But

906
00:45:06,080 --> 00:45:08,440
Speaker 1: if you know what to look for in a tapeworm,

907
00:45:08,480 --> 00:45:11,440
Speaker 1: some of them are quite beautiful. I've got my tapeworm

908
00:45:11,440 --> 00:45:12,240
Speaker 1: picture right here.

909
00:45:12,560 --> 00:45:14,920
Speaker 2: Oh wow. Do you know anybody who like has a

910
00:45:14,960 --> 00:45:17,960
Speaker 2: coat made out of tapeworms or something like that, You know, tapeworms.

911
00:45:18,000 --> 00:45:21,160
Speaker 2: Maybe we need a fashion industry, you know, to replace

912
00:45:21,239 --> 00:45:22,720
Speaker 2: fur with parasites somehow.

913
00:45:23,000 --> 00:45:27,759
Speaker 1: I think that any parasite themed fashion that is available

914
00:45:28,200 --> 00:45:31,680
Speaker 1: is found at the American Society of Parasitologists Student Travel Auction.

915
00:45:32,239 --> 00:45:34,239
Speaker 1: We bring it in and we all pay way too

916
00:45:34,320 --> 00:45:36,120
Speaker 1: much for it to try to pay for student travel

917
00:45:36,160 --> 00:45:37,920
Speaker 1: so that they can come to our conferences. But anyway,

918
00:45:37,920 --> 00:45:40,239
Speaker 1: we're getting off track. We've got one more question from

919
00:45:40,239 --> 00:45:43,080
Speaker 1: the listener, and the question is do parasites go extinct

920
00:45:43,120 --> 00:45:45,719
Speaker 1: with hosts? So there's a number of different things that

921
00:45:45,760 --> 00:45:48,560
Speaker 1: can happen when hosts go extinct or when hosts sort

922
00:45:48,560 --> 00:45:52,239
Speaker 1: of split into multiple species, and so yes, often when

923
00:45:52,400 --> 00:45:55,200
Speaker 1: a host goes extinct, the parasite can go extinct. Also,

924
00:45:55,680 --> 00:45:58,240
Speaker 1: if the parasite was infecting lots of other host species,

925
00:45:58,280 --> 00:46:00,520
Speaker 1: then maybe it will be fine. But we already talked

926
00:46:00,560 --> 00:46:03,600
Speaker 1: about complex life cycles where if you lose one host

927
00:46:03,840 --> 00:46:06,360
Speaker 1: in the system, you can lose the parasite too. But

928
00:46:06,440 --> 00:46:09,000
Speaker 1: there's also examples where you get these splits in the

929
00:46:09,040 --> 00:46:11,520
Speaker 1: tree of life, and as you get those splits in

930
00:46:11,560 --> 00:46:15,279
Speaker 1: the hosts, the parasites also split into new species over

931
00:46:15,320 --> 00:46:18,680
Speaker 1: time because you now get like separations of parasite populations,

932
00:46:18,680 --> 00:46:21,480
Speaker 1: and over enough time they become their own species. And

933
00:46:21,520 --> 00:46:25,080
Speaker 1: so there's a sort of famous example where pelicans, as

934
00:46:25,160 --> 00:46:29,799
Speaker 1: they sort of speciated over time, they're lice speciated with them.

935
00:46:30,200 --> 00:46:33,200
Speaker 1: So pelicans, if you like create the tree of life

936
00:46:33,239 --> 00:46:35,320
Speaker 1: for pelicans and then you create the tree of life

937
00:46:35,320 --> 00:46:37,879
Speaker 1: for their lice, you could almost lay them on top

938
00:46:37,920 --> 00:46:40,719
Speaker 1: of each other. They follow very similar paths. But you

939
00:46:40,760 --> 00:46:44,200
Speaker 1: can also get cases where the parasites don't seem to

940
00:46:44,239 --> 00:46:47,000
Speaker 1: be tracking what's happening with their hosts. So, for example, guppies,

941
00:46:47,040 --> 00:46:49,800
Speaker 1: they are these these tiny little fish they get infected

942
00:46:49,840 --> 00:46:52,959
Speaker 1: by monogenians. These are these external parasites we were talking

943
00:46:52,960 --> 00:46:54,640
Speaker 1: about that have the hooks and they hold onto the

944
00:46:54,640 --> 00:46:57,680
Speaker 1: outside of the fish. They don't seem to be following

945
00:46:58,000 --> 00:47:00,960
Speaker 1: the evolutionary trajectory of their hosts. And right now we

946
00:47:01,000 --> 00:47:03,960
Speaker 1: don't have a really good framework for when you should

947
00:47:03,960 --> 00:47:06,680
Speaker 1: expect the tree of life for parasites and species to

948
00:47:06,800 --> 00:47:10,480
Speaker 1: essentially mirror one another, and when you shouldn't. But we

949
00:47:10,560 --> 00:47:13,640
Speaker 1: get all of these different options because nature is amazing

950
00:47:13,760 --> 00:47:15,360
Speaker 1: and it depends, but we don't.

951
00:47:15,160 --> 00:47:17,719
Speaker 2: Always know on what, and the incredible variety of strategies

952
00:47:17,719 --> 00:47:20,640
Speaker 2: we see helps us explore like the space of possibilities

953
00:47:21,120 --> 00:47:23,640
Speaker 2: and maybe even helps us think outside the box to

954
00:47:23,719 --> 00:47:26,200
Speaker 2: like what might be happening elsewhere in the universe.

955
00:47:26,560 --> 00:47:30,520
Speaker 1: Absolutely, yes, I would love to find a planet that

956
00:47:30,680 --> 00:47:35,239
Speaker 1: was rich with free living hosts and dissect a bunch

957
00:47:35,239 --> 00:47:38,600
Speaker 1: of them to see if they have parasites, but only

958
00:47:38,640 --> 00:47:40,240
Speaker 1: if it was humane and ethical.

959
00:47:40,920 --> 00:47:43,759
Speaker 2: All right, aliensf you're listening, come on by. Kelly wants

960
00:47:43,800 --> 00:47:44,600
Speaker 2: to look inside you.

961
00:47:44,880 --> 00:47:46,040
Speaker 1: Kelly wants to say huh.

962
00:47:46,520 --> 00:47:48,000
Speaker 2: In an intimate sort of way.

963
00:47:48,360 --> 00:47:50,719
Speaker 1: All right, Well, thank you so much to Zach for

964
00:47:50,800 --> 00:47:53,239
Speaker 1: sending in his questions. Let's see if Zach feels like

965
00:47:53,280 --> 00:47:56,120
Speaker 1: we've answered the many questions he posed about the evolution

966
00:47:56,200 --> 00:47:56,920
Speaker 1: of parasitism.

967
00:47:57,320 --> 00:48:00,360
Speaker 3: Hey, they're extraordinaries. Thank you so much for this credible

968
00:48:00,400 --> 00:48:03,160
Speaker 3: primer on parasites and their history. I feel like I

969
00:48:03,160 --> 00:48:05,640
Speaker 3: got way more than I bargained for, which is awesome.

970
00:48:05,920 --> 00:48:10,120
Speaker 3: You definitely answered my essential question that, yes, t Rex

971
00:48:10,160 --> 00:48:12,759
Speaker 3: probably had tapeworms or something like it, that we can't

972
00:48:12,800 --> 00:48:16,040
Speaker 3: be totally sure. I also really enjoyed hearing about all

973
00:48:16,040 --> 00:48:20,960
Speaker 3: the different categories of parasite strategies, and really appreciated hearing

974
00:48:21,000 --> 00:48:25,400
Speaker 3: that there are no parasitoids or castrating parasites for humans,

975
00:48:25,440 --> 00:48:27,640
Speaker 3: so I can sleep a little better at night. I

976
00:48:27,719 --> 00:48:31,799
Speaker 3: was also definitely convinced that parasites have an important role

977
00:48:31,840 --> 00:48:34,120
Speaker 3: to play in our ecosystems, so I'll try to be

978
00:48:34,160 --> 00:48:36,640
Speaker 3: a little bit more appreciative and a little less grossed out.

979
00:48:37,320 --> 00:48:39,960
Speaker 3: I am still a little curious. Seems like it's still

980
00:48:40,000 --> 00:48:42,439
Speaker 3: an open question how something goes from being a free

981
00:48:42,440 --> 00:48:45,000
Speaker 3: living organism to being a parasite, even if we can

982
00:48:45,320 --> 00:48:48,160
Speaker 3: count when it happens. I'm also curious if anything has

983
00:48:48,200 --> 00:48:51,600
Speaker 3: ever gone from being a parasite back to being a

984
00:48:51,640 --> 00:48:55,879
Speaker 3: free living organism. In any case, you guys rock. Thank

985
00:48:55,920 --> 00:48:56,879
Speaker 3: you again so much.

986
00:48:57,320 --> 00:48:59,160
Speaker 1: All right, thank you so much to Zach for all

987
00:48:59,160 --> 00:49:01,120
Speaker 1: of his many questions. If you would like to send

988
00:49:01,160 --> 00:49:03,160
Speaker 1: us questions, we would love to hear from you. Send

989
00:49:03,200 --> 00:49:06,560
Speaker 1: them to questions at danieland Kelly dot org. And I

990
00:49:06,680 --> 00:49:09,239
Speaker 1: hope that you enjoy your meal or you ate it

991
00:49:09,280 --> 00:49:11,480
Speaker 1: before we began this conversation.

992
00:49:11,200 --> 00:49:14,279
Speaker 2: And before you heard Kelly say the word castraid uncountable

993
00:49:14,360 --> 00:49:15,120
Speaker 2: number of times.

994
00:49:15,400 --> 00:49:17,160
Speaker 1: I don't think there's a limit on how many times

995
00:49:17,200 --> 00:49:19,120
Speaker 1: you can say castrat. It's a great word.

996
00:49:20,200 --> 00:49:22,320
Speaker 2: All right, everyone, thanks for joining us on this tour

997
00:49:22,440 --> 00:49:25,240
Speaker 2: of one more aspect of our extraordinary universe.

998
00:49:32,640 --> 00:49:36,480
Speaker 1: Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We

999
00:49:36,520 --> 00:49:37,919
Speaker 1: would love to hear from you.

1000
00:49:38,040 --> 00:49:41,000
Speaker 2: We really would. We want to know what questions you

1001
00:49:41,200 --> 00:49:43,840
Speaker 2: have about this extraordinary universe.

1002
00:49:43,920 --> 00:49:46,880
Speaker 1: We want to know your thoughts on recent shows, suggestions

1003
00:49:46,880 --> 00:49:49,879
Speaker 1: for future shows. If you contact us, we will get

1004
00:49:49,920 --> 00:49:50,319
Speaker 1: back to you.

1005
00:49:50,600 --> 00:49:54,120
Speaker 2: We really mean it. We answer every message. Email us

1006
00:49:54,160 --> 00:49:57,360
Speaker 2: at Questions at Danielankelly.

1007
00:49:56,440 --> 00:49:58,520
Speaker 1: Dot org, or you can find us on social media.

1008
00:49:58,600 --> 00:50:02,640
Speaker 1: We have accounts on Instagram, Blue Sky and on all

1009
00:50:02,680 --> 00:50:04,960
Speaker 1: of those platforms. You can find us at D and

1010
00:50:05,360 --> 00:50:06,400
Speaker 1: K Universe.

1011
00:50:06,600 --> 00:50:08,160
Speaker 2: Don't be shy write to us