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How to become a parasite · Daniel and Kelly’s Extraordinary Universe

• 0:09
  Speaker 1: Imagine sitting out on a porch on a warm spring evening.
• 0:13
  Speaker 1: You hear the spring peepers calling out to each other
• 0:16
  Speaker 1: in a nearby pond. Birds are chirping in the trees,
• 0:20
  Speaker 1: preparing to turn into their nest for the night. Off
• 0:22
  Speaker 1: in the distance, you see a deer walking with her fawn.
• 0:26
  Speaker 1: It's a beautiful scene, reminding you how wonderful it is
• 0:30
  Speaker 1: to live in Virginia when I hear and see these
• 0:33
  Speaker 1: denizens of the forest, though I see something else as well,
• 0:37
  Speaker 1: walking ecosystems for parasites. You see on average a bird
• 0:42
  Speaker 1: species harbors more than three species of tapeworm nearly three
• 0:46
  Speaker 1: nematode species. Probably call that frog home. Those deer are
• 0:51
  Speaker 1: harboring treematodes, tapeworms, nematodes, and more. Though hidden from sight,
• 0:57
  Speaker 1: parasites are thought to make up over half of the
• 1:00
  Speaker 1: biodiversity of multicellular organisms on our planet. Today, we're going
• 1:05
  Speaker 1: to answer listener questions about the evolution of parasitism. Hope
• 1:09
  Speaker 1: you're not listening to the show while eating dinner. Welcome
• 1:13
  Speaker 1: to Daniel and Kelly's Extraordinarily Infected Universe.
• 1:30
  Speaker 2: Hi, I'm Daniel, I'm a particle physicist, and I'm looking
• 1:32
  Speaker 2: forward to meeting alien parasites.
• 1:35
  Speaker 1: Hello. I'm Kelly Wiener Smith. I study parasites and space,
• 1:38
  Speaker 1: but not parasites in space. But maybe one day I'll
• 1:41
  Speaker 1: study Yeah, maybe one day I'll be studying parasites in space.
• 1:45
  Speaker 2: So my question for you today, Kelly, is what is
• 1:47
  Speaker 2: your favorite depiction of parasites in science fiction?
• 1:51
  Speaker 1: Probably aliens don't need to think about it. Aliens, it's
• 1:55
  Speaker 1: a great parasitoid in there. I went through a phase
• 1:58
  Speaker 1: where I was just love all of the zombie movies
• 2:01
  Speaker 1: and I was actually taking notes on like what mechanism
• 2:05
  Speaker 1: was producing the zombies. So for a while, you know,
• 2:07
  Speaker 1: when there were big fears of nuclear bombs getting dropped
• 2:09
  Speaker 1: on the US for example, you know, nuclear material was
• 2:13
  Speaker 1: the cause of zombies. But then it became like infectious diseases,
• 2:16
  Speaker 1: and I've gotten off course. I was thinking about writing
• 2:19
  Speaker 1: a whole book on this actually.
• 2:22
  Speaker 2: And why didn't you?
• 2:23
  Speaker 1: It sounds fascinating, you know enough people told me that, like,
• 2:26
  Speaker 1: the zombie craze is behind us, and that this is
• 2:29
  Speaker 1: a book nobody would want to read because it would
• 2:31
  Speaker 1: be two of the time. Yeah, two of the moment, right,
• 2:34
  Speaker 1: like when people weren't watching the zombie movies like The
• 2:36
  Speaker 1: Last of Us Sword, which I guess that's running still now.
• 2:39
  Speaker 2: Yeah, but zombies aren't a moment, They're a movement.
• 2:42
  Speaker 1: You know, that's right. Well, and I gave a talk
• 2:44
  Speaker 1: at the Zombie Apocalypse Medicine Meeting, or I think I
• 2:49
  Speaker 1: for Sam. Yeah, and it's happening in October of this year.
• 2:53
  Speaker 1: I highly recommend folks go to it.
• 2:55
  Speaker 2: These are legit scientists.
• 2:56
  Speaker 1: These are legit scientists. Yes, wow. And I gave a
• 2:59
  Speaker 1: talk on that topic and it was like the most
• 3:02
  Speaker 1: fun research I've ever done in my life.
• 3:07
  Speaker 2: Well, I think I speak for the audience and saying
• 3:08
  Speaker 2: that we all want to read your book on the
• 3:10
  Speaker 2: science of zombies. That sounds fantastic.
• 3:12
  Speaker 1: You know. I've got a link to the talk that
• 3:14
  Speaker 1: I could share if anyone wants to see the talk,
• 3:16
  Speaker 1: But I don't think it's going to become a full
• 3:17
  Speaker 1: length book, not with what I've got on my agenda
• 3:20
  Speaker 1: right now.
• 3:21
  Speaker 2: All right, Well, today we're not talking about space or
• 3:23
  Speaker 2: science fiction or zombies. We're answering a really fascinating question
• 3:27
  Speaker 2: from a listener about the context, the evolution, and maybe
• 3:30
  Speaker 2: even the future of parasites in our world.
• 3:33
  Speaker 3: Take it away, Zach, Hey, they're extraordinaries. The recent episode
• 3:37
  Speaker 3: on the history of Trickinella, I should say, the recent
• 3:41
  Speaker 3: history of trick and Ella got me wondering about the
• 3:44
  Speaker 3: more ancient history of parasites. I assume that being a
• 3:47
  Speaker 3: parasite is a strategy that existed back in the time
• 3:51
  Speaker 3: of the dinosaurs, maybe even further back. I'm curious if
• 3:55
  Speaker 3: we have evidence of that, and if parasites tend to
• 3:58
  Speaker 3: become extinct when their host species does as well, or
• 4:02
  Speaker 3: if we're still living with the same kind of parasites
• 4:04
  Speaker 3: the dinosaurs dealt with. I'm also curious if we know
• 4:09
  Speaker 3: about how parasites evolve, how does an organism go from
• 4:13
  Speaker 3: being not a parasite to a parasite? Do we have
• 4:16
  Speaker 3: any idea of that evolutionary history. Looking forward to hearing
• 4:20
  Speaker 3: more squishy wormy biology from you guys.
• 4:23
  Speaker 2: Thank you Zach for sending in this question. If you
• 4:25
  Speaker 2: have questions about the nature of the universe, or the
• 4:28
  Speaker 2: history of parasites, or anything in this extraordinary universe, we
• 4:32
  Speaker 2: want to hear from you. We want to answer your questions.
• 4:34
  Speaker 2: We want to scratch your itch because everybody's curious about
• 4:37
  Speaker 2: the universe, so don't be shy. Write to us two
• 4:40
  Speaker 2: questions at Danielandkelly dot org. Everyone gets an answer.
• 4:44
  Speaker 1: And I am currently researching why we scratch itches, which
• 4:47
  Speaker 1: is a question sent by a listener. So you even
• 4:50
  Speaker 1: get those kinds of questions answered.
• 4:52
  Speaker 2: Amazing, yep, So dig into this for us, Kelly, tell
• 4:55
  Speaker 2: us about the history of parasites and why we call
• 4:58
  Speaker 2: something a parasite and what fraction of species we could
• 5:01
  Speaker 2: classify as parasites.
• 5:02
  Speaker 1: Well, Daniel, let's pretend that you didn't read the outline,
• 5:05
  Speaker 1: which maybe maybe you didn't, although you're usually very well prepared.
• 5:08
  Speaker 1: If you had to guess what percent of multicellular organisms
• 5:12
  Speaker 1: were parasites, what percent would you guess?
• 5:15
  Speaker 2: It doesn't seem to me like most things are parasites.
• 5:18
  Speaker 2: Bunnies are not parasites, flies are not parasites. Whales or
• 5:21
  Speaker 2: not parasites, So you know, it seems to me unusual.
• 5:24
  Speaker 2: So I guess one percent is my absolutely no information.
• 5:28
  Speaker 1: Guess are you playing along? Are you really guessing one percent?
• 5:31
  Speaker 2: I'm really guessing one percent?
• 5:32
  Speaker 1: Oh wow, that's fantastic. Okay. I love those moments where
• 5:34
  Speaker 1: you can be like, you're totally wrong. So Dan, you're
• 5:36
  Speaker 1: totally wrong. Yes, yay. So if you look at that rabbit, So,
• 5:41
  Speaker 1: rabbits are mammals, and on average, mammals harbor one to
• 5:45
  Speaker 1: two species of trematodes, one to two species of tapeworms,
• 5:49
  Speaker 1: and four nematode species.
• 5:51
  Speaker 2: Well, I didn't want to eat rabbits before, but I
• 5:53
  Speaker 2: certainly don't want to eat rabbits now.
• 5:55
  Speaker 1: Well, then let's not talk about more typical food animals
• 5:58
  Speaker 1: like cows and pigs. We'll stay away from those. But
• 6:01
  Speaker 1: it's estimated that this was from a two thousand and
• 6:03
  Speaker 1: eight paper that was estimating about forty four thousand host
• 6:07
  Speaker 1: species with vertebrates and about seventy seven thousand species of trematodes, tapeworms, nematodes,
• 6:14
  Speaker 1: and acanthoscephalins. So this is four kinds of parasites, almost
• 6:17
  Speaker 1: twice as many parasites as there are hosts. And that
• 6:20
  Speaker 1: doesn't even include things like lice and ticks and stuff
• 6:24
  Speaker 1: like that.
• 6:25
  Speaker 2: What hold on a second, you're telling me that like
• 6:27
  Speaker 2: every species of critter out there has like two unique
• 6:31
  Speaker 2: species of parasites, So there's like a two to one
• 6:35
  Speaker 2: parasite to creater ratio.
• 6:36
  Speaker 1: This is a great question. This is where it gets
• 6:38
  Speaker 1: a little bit complicated. So, for example, if you have
• 6:41
  Speaker 1: two different species of rabbit, they might share one of
• 6:44
  Speaker 1: their trematode species for example. So there are some parasites
• 6:47
  Speaker 1: that are generalists and you can find them in more
• 6:49
  Speaker 1: than one host species, but there are also a lot
• 6:52
  Speaker 1: of parasites that are found in one species. And so
• 6:56
  Speaker 1: in general, when we look at how many parasites are
• 6:58
  Speaker 1: generalists and how many are specially listener just found in
• 7:01
  Speaker 1: one host, we get this estimate where we feel comfortable
• 7:03
  Speaker 1: saying that probably more than fifty percent of the multicellular
• 7:07
  Speaker 1: biodiversity on Earth is using the parasitic strategy in some way.
• 7:10
  Speaker 2: Oh my gosh, we're in the minority. Yeah, for not
• 7:13
  Speaker 2: sucking on some other critter, we are like unusual.
• 7:17
  Speaker 1: We're total chumps, man.
• 7:19
  Speaker 2: So we got to rethink this.
• 7:22
  Speaker 1: Wow, I know there's a lot of interesting questions that
• 7:25
  Speaker 1: arise from there. So we know that a bunch of
• 7:28
  Speaker 1: species have this strategy of being a parasite, which essentially
• 7:31
  Speaker 1: means that you rely on another organism where you're extracting
• 7:35
  Speaker 1: their energy. It's not benefiting them, and you need them
• 7:39
  Speaker 1: to get the energy.
• 7:39
  Speaker 2: Well, then can I ask a technical question like, yeah,
• 7:42
  Speaker 2: is a cow a parasite because it relies on grass
• 7:44
  Speaker 2: and you know it's extracting the energy from the grass.
• 7:48
  Speaker 2: Why isn't a cow listed as a grass parasite?
• 7:50
  Speaker 1: So it is eating lots of different blades of grass,
• 7:55
  Speaker 1: and so this is usually an intimate, endurable interaction between
• 7:59
  Speaker 1: two INDs.
• 8:00
  Speaker 2: Intimate, wow, intimate.
• 8:02
  Speaker 1: Well, you know, if you're living inside, for example, of
• 8:04
  Speaker 1: something and sharing gets dinner with it every night, that's
• 8:08
  Speaker 1: pretty intimate. And so, yeah, cows are eating lots of
• 8:11
  Speaker 1: different grass. We call mosquitoes and lamb preys and ticks
• 8:17
  Speaker 1: and stuff micro predators. So they take little meals from
• 8:22
  Speaker 1: lots of animals. They don't kill them, which predators usually do,
• 8:25
  Speaker 1: but they just take little meals from lots of animals.
• 8:28
  Speaker 1: And so the idea is that to be a parasite
• 8:30
  Speaker 1: you have to be on one organism for a long time.
• 8:33
  Speaker 2: Okay, so mosquito's technically not parasites then, right.
• 8:36
  Speaker 1: You would be amazing how much fur flies at parasitology
• 8:39
  Speaker 1: conferences when the mosquito and the leech people are like,
• 8:43
  Speaker 1: these are parasites. And then some of the community is
• 8:45
  Speaker 1: like they're micro predators, and the leech people are like,
• 8:47
  Speaker 1: we belong here, and I'm like, they belong here, don't
• 8:50
  Speaker 1: kick them out.
• 8:51
  Speaker 2: Well, they're parasites in spirit, even if they don't qualify technically, right,
• 8:54
  Speaker 2: because otherwise, like a giraffe which nibbles on this tree
• 8:57
  Speaker 2: and then the other tree in the other trees basically
• 8:59
  Speaker 2: has the same relation with a tree as a mosquito
• 9:01
  Speaker 2: does with people, right, So.
• 9:03
  Speaker 1: That's because it's not killing all of them. Yeah, yeah,
• 9:05
  Speaker 1: And so sometimes you can get into debates with some
• 9:08
  Speaker 1: folks about to what extent herbivores can be thought of
• 9:11
  Speaker 1: as parasites solely. You know, if like an insect lives
• 9:15
  Speaker 1: on the same tree for a long time, is it
• 9:17
  Speaker 1: a parasite or is it a different category altogether because
• 9:19
  Speaker 1: it's a plant And anyway, I guess at the end
• 9:22
  Speaker 1: of the day, nature doesn't care that humans like to
• 9:25
  Speaker 1: have very nice clear boxes to put things in. She's
• 9:28
  Speaker 1: always giving us edge cases to make things complicated.
• 9:31
  Speaker 2: And life is an ecosystem, right, It's a web, and
• 9:34
  Speaker 2: there's nothing isolated. We're all munching on each other and
• 9:38
  Speaker 2: eating each other and being eaten by each other. It's
• 9:40
  Speaker 2: a big party, right.
• 9:42
  Speaker 1: I don't want to go to the parties you go to, Daniel.
• 9:43
  Speaker 1: Based on what you've just described, we have fun.
• 9:47
  Speaker 2: We have fun. But how useful are these categorizations? I mean,
• 9:52
  Speaker 2: does it matter what we call a parasite or not?
• 9:55
  Speaker 1: So I think it does. And the main reason I
• 9:57
  Speaker 1: think it does is because often folks will try to
• 10:00
  Speaker 1: model the impact of parasites on populations, or use some
• 10:04
  Speaker 1: modeling to try to understand how to control a parasite population,
• 10:08
  Speaker 1: and those models depend on the assumptions you make about
• 10:12
  Speaker 1: what that organism is doing, how many organisms it's feeding on,
• 10:15
  Speaker 1: how many babies it produces. Like, having these details helps
• 10:19
  Speaker 1: you create models that can describe different groups of strategies,
• 10:24
  Speaker 1: and those models can be important for a lot of things,
• 10:26
  Speaker 1: including epidemiology.
• 10:27
  Speaker 2: I see, all right. And also it's nice to get
• 10:30
  Speaker 2: like minded people together, right, And so yeah, you gotta
• 10:33
  Speaker 2: people want to know which conference do I go to?
• 10:35
  Speaker 2: Do I go to the zombie conference or the parasite
• 10:37
  Speaker 2: conference or the zombie parasite conference or whatever? And so
• 10:40
  Speaker 2: we got to put names on things so we can
• 10:42
  Speaker 2: get ourselves organized, even if we admit that the names
• 10:45
  Speaker 2: are fuzzy. You know, is Pluto a planet or not
• 10:47
  Speaker 2: doesn't really matter. We're interested in studying this stuff fluting
• 10:50
  Speaker 2: in outer space.
• 10:51
  Speaker 1: I wants organized a symposium called how to Make a
• 10:53
  Speaker 1: Zombie with my friend zen Folks, who has like the
• 10:56
  Speaker 1: coolest name ever, and then it was me, who has
• 10:59
  Speaker 1: the least cool name ever. And it was a very
• 11:00
  Speaker 1: interesting combo. But anyway, it was all about parasites that
• 11:03
  Speaker 1: manipulate host behavior and how they do that.
• 11:06
  Speaker 2: Right, right, Yeah, parasites and zombies are connected in the end.
• 11:09
  Speaker 1: Sure.
• 11:10
  Speaker 2: So the bottom line is that there are lots and
• 11:12
  Speaker 2: lots and lots of parasites out there. I was totally wrong,
• 11:15
  Speaker 2: and there's lots of different kinds of parasites out there.
• 11:18
  Speaker 2: But what about by body mass? Are parasites like a
• 11:20
  Speaker 2: tiny fraction of the mass or if you made a
• 11:24
  Speaker 2: big pile of all the parasites on the planet, would
• 11:26
  Speaker 2: be bigger than the pile of non parasites.
• 11:28
  Speaker 1: This is a great question. So I didn't necessarily prepare
• 11:32
  Speaker 1: for you to ask this question, so I don't have
• 11:33
  Speaker 1: all the numbers that I want at my fingertips. But
• 11:36
  Speaker 1: there was a system where this question was studied explicitly
• 11:39
  Speaker 1: and it was the estuaries in southern California. And essentially
• 11:43
  Speaker 1: they took the biomass of all of the free living organisms,
• 11:46
  Speaker 1: and they extracted the parasites from them, and they took
• 11:48
  Speaker 1: the biomass of them. And in these systems, the main
• 11:51
  Speaker 1: predators are predatory birds. They eat the crustaceans, they eat
• 11:55
  Speaker 1: the fish. They're like the main predator out there. And
• 11:58
  Speaker 1: the biomass of trematode parasites was equal to and maybe
• 12:03
  Speaker 1: I think in some cases greater than the biomass of
• 12:06
  Speaker 1: the top predators in the system, which is to say,
• 12:08
  Speaker 1: greater than the biomass of the birds.
• 12:09
  Speaker 2: Wow.
• 12:10
  Speaker 1: And that's because this system has a lot of trematode
• 12:12
  Speaker 1: parasites that infect the snails, and when the snails get infected,
• 12:15
  Speaker 1: they get castrated and all of the energy that would
• 12:18
  Speaker 1: have gone to making baby snails now becomes parasite biomass.
• 12:22
  Speaker 1: And so the ground it's like a carpet of snails
• 12:25
  Speaker 1: in these estuaries. There's just loads and loads of them.
• 12:27
  Speaker 2: I'm imagining stepping on them to the crunch, crunch, crunch.
• 12:30
  Speaker 1: It's not crunch crunch, crunch, crunch, because it's very muddy
• 12:33
  Speaker 1: out there, so you're like squishing them underground, like they're
• 12:36
  Speaker 1: getting covered in mud. So you do feel bad about that.
• 12:39
  Speaker 1: I did feel bad. It was great exercise working in
• 12:42
  Speaker 1: this system though. This is what I did for my PhD,
• 12:45
  Speaker 1: because every step you take you need to like steal
• 12:48
  Speaker 1: your foot back from the mud. And anyway, good exercise.
• 12:51
  Speaker 1: Point is some systems have really really high parasite biomass.
• 12:56
  Speaker 1: But for example, if you were to collect a deer,
• 12:59
  Speaker 1: the biomass of parasites in a deer is probably a
• 13:03
  Speaker 1: very small percent.
• 13:04
  Speaker 2: Like one percent.
• 13:05
  Speaker 1: Yeah, I guess you know, probably like one percent. That's
• 13:07
  Speaker 1: where you came from.
• 13:08
  Speaker 2: Day I tell what I meant. Yeah, yeah, let's see.
• 13:13
  Speaker 1: Totally right. You hit the nail on the head. It
• 13:15
  Speaker 1: was perfect.
• 13:18
  Speaker 2: If we keep asking questions, we'll eventually find one that
• 13:20
  Speaker 2: lines up in my answer.
• 13:21
  Speaker 1: That's right, And we got there pretty quick. We got
• 13:23
  Speaker 1: there pretty quick. And and this biomass question that you
• 13:25
  Speaker 1: asked depends a lot on what the strategy of the
• 13:28
  Speaker 1: parasite is. And in our next segment we're going to
• 13:30
  Speaker 1: talk about different strategies. But basically, when the strategy involves
• 13:33
  Speaker 1: killing your host, you can take up more of that
• 13:36
  Speaker 1: host biomass because the host is going to die anyway.
• 13:39
  Speaker 1: But now I want to talk about you know, so
• 13:40
  Speaker 1: we've determined that maybe as much as fifty percent or
• 13:43
  Speaker 1: more of the number of species on the planet that
• 13:46
  Speaker 1: are multicellular are parasites. But how many times did you
• 13:50
  Speaker 1: get a transition from free living to a parasitic strategy?
• 13:54
  Speaker 2: Right? Like? Did this evolve one time and now we
• 13:57
  Speaker 2: have a huge explosion to parasites or is it a
• 14:00
  Speaker 2: common thing that's been developed independently multiple times, like flight
• 14:03
  Speaker 2: for example.
• 14:04
  Speaker 1: I mean, do you want to give a like, guess
• 14:07
  Speaker 1: at how many times parasitism has evolved.
• 14:09
  Speaker 2: This time a good sport. I would guess that it's
• 14:13
  Speaker 2: evolved multiple times because it seems like kind of an
• 14:15
  Speaker 2: obvious strategy and it doesn't require like some huge technological
• 14:20
  Speaker 2: innovation like photosynthesis or the engineering a flight. Even so
• 14:25
  Speaker 2: I would guess it's pretty common. I don't know a
• 14:27
  Speaker 2: dozen times.
• 14:28
  Speaker 1: When we had Joe Wolf on the show, she pointed
• 14:31
  Speaker 1: out that the crab body plan has popped up I
• 14:34
  Speaker 1: think eight times. I think you undersold the difficulty of
• 14:38
  Speaker 1: parasitism a little bit. So if you are trying to
• 14:42
  Speaker 1: infect a host, you need to find that host you
• 14:44
  Speaker 1: need to survive its immune system. You're now in a
• 14:46
  Speaker 1: completely foreign environment that is actively trying to kill you
• 14:50
  Speaker 1: all the time. But despite those challenges, we think that
• 14:53
  Speaker 1: parasitism has shown up at least two hundred and twenty
• 14:57
  Speaker 1: three times in Kingdom Animalia.
• 15:00
  Speaker 2: Sorry, two hundred and twenty.
• 15:02
  Speaker 1: Three times, two hundred and twenty three times.
• 15:05
  Speaker 2: Like you can identify individual moments when something went from
• 15:09
  Speaker 2: non parasite to parasite in the evolutionary record hundreds of.
• 15:13
  Speaker 1: Times, hundreds of times.
• 15:16
  Speaker 2: Yes, wow, why aren't we all parasites?
• 15:19
  Speaker 1: Well, you know, there's got to be some.
• 15:20
  Speaker 2: Hosts, I see. For the grifters to keep drifting, we
• 15:24
  Speaker 2: need some suckers, that's what you're saying.
• 15:26
  Speaker 1: And you and I are the suckers, I guess. But
• 15:30
  Speaker 1: so sometimes you get this transition to parasitism that results
• 15:33
  Speaker 1: in a lot of additional species. So I think when
• 15:36
  Speaker 1: you ask people about parasites, they usually think about things
• 15:39
  Speaker 1: like tapeworms and trematodes and nematodes and stuff like that.
• 15:43
  Speaker 2: Unfortunately, that is my mental image, and that's why it
• 15:45
  Speaker 2: gives me the willies.
• 15:47
  Speaker 1: Yeah, I'm sorry.
• 15:48
  Speaker 2: It's intimate, though, it's.
• 15:50
  Speaker 1: Very intimate So in phylum plati helminthis, so that's where
• 15:55
  Speaker 1: you get the trematodes and the tapeworms and stuff. They
• 15:59
  Speaker 1: were about transitions to parasitism last time we counted. But
• 16:04
  Speaker 1: in arthropodas, so these are invertebrates with exoskeletons. So we're
• 16:08
  Speaker 1: thinking about like wasps and crustaceans and stuff like that.
• 16:12
  Speaker 1: It evolved one hundred and forty three times. Wow, So
• 16:15
  Speaker 1: lots of transitions and lots of times it happened in insects,
• 16:19
  Speaker 1: and it happened sixty times in flies. So flies you
• 16:23
  Speaker 1: often get a transition from free living two parasitic strategies.
• 16:28
  Speaker 2: How do we trace these transitions? Like I understand we
• 16:31
  Speaker 2: can look at the fossil record and see how whales
• 16:33
  Speaker 2: return to the ocean this kind of stuff. But insects,
• 16:36
  Speaker 2: we don't have fossils. How do we know this history.
• 16:39
  Speaker 1: We do have some insect fossils. Often they get trapped
• 16:43
  Speaker 1: in things like amber, and amber actually does a really
• 16:45
  Speaker 1: great job of preserving things and making it so you
• 16:47
  Speaker 1: can still see their features. Yeah, but we probably are
• 16:50
  Speaker 1: undercounting because there probably are a lot of like transitions
• 16:53
  Speaker 1: that happened and then we're lost those species went extinct,
• 16:56
  Speaker 1: or a lot of just instances where there was like
• 16:58
  Speaker 1: a free living host that we'd just never found. And
• 17:01
  Speaker 1: so these you should imagine that all of these estimates
• 17:03
  Speaker 1: are very likely to change over time. But we have
• 17:07
  Speaker 1: been lucky to get a fair number of fossils in
• 17:10
  Speaker 1: the record, and the fossils are usually not beautiful exactly
• 17:14
  Speaker 1: what you want fossils. But for example, there's a lot
• 17:17
  Speaker 1: of tapeworms and monogeneans. So these are monogeneans are parasites
• 17:21
  Speaker 1: that you often find on the outside of fish. They
• 17:24
  Speaker 1: have these hooks that they use to hold onto the
• 17:27
  Speaker 1: fish and then they suck like the mucus. Sometimes they
• 17:30
  Speaker 1: suck blood, but they live on the outside.
• 17:32
  Speaker 2: The less intimate side, we'll say.
• 17:34
  Speaker 1: Yeah, slightly less intimate, but no less durable, and so
• 17:40
  Speaker 1: they use these hooks. And then tapeworms also tend to
• 17:42
  Speaker 1: have these hooks and they use them to hold on inside.
• 17:45
  Speaker 1: So now we've got intimate and durable. But these hooks
• 17:48
  Speaker 1: have very distinctive shapes, and sometimes we can find in
• 17:53
  Speaker 1: fossilized animal poops called coprolites, which we've talked about before,
• 17:57
  Speaker 1: these hooks in like the pairings that you would expect
• 18:00
  Speaker 1: and in the shapes that you would expect and inside
• 18:03
  Speaker 1: of or of, like very adjacent to organisms that you
• 18:07
  Speaker 1: would expect to find them in. And we found evidence wow,
• 18:10
  Speaker 1: of these sorts of relationships from the Mesozoic area, which
• 18:13
  Speaker 1: was sixty six to about two hundred and fifty million
• 18:15
  Speaker 1: years ago. Wow. This includes like the Jurassic period where
• 18:18
  Speaker 1: you know Jurassic Park and the Paleozoic period, which is
• 18:22
  Speaker 1: even later. I think Paleozoic means something like old life.
• 18:26
  Speaker 1: And we found some evidence of these parasites from back
• 18:28
  Speaker 1: then too, so it's totally reasonable to assume that like
• 18:31
  Speaker 1: t Rex was probably carrying around some nematodes. These are
• 18:34
  Speaker 1: ancient interactions.
• 18:36
  Speaker 2: I love thinking about when things arose because it's a
• 18:39
  Speaker 2: way to figure out, like how hard is it to happen?
• 18:41
  Speaker 2: And also is it like that happen on alien planets?
• 18:44
  Speaker 2: Like we think about how quickly did we get life
• 18:47
  Speaker 2: after there were the conditions for life on Earth? Pretty quickly?
• 18:50
  Speaker 2: How quickly did we get intelligence after they were their
• 18:53
  Speaker 2: conditions for intelligence? Not that quickly? And it's only end
• 18:56
  Speaker 2: equals one, but it's like a hint as to like
• 18:58
  Speaker 2: is this likely to happen elsewhere, And so how far
• 19:01
  Speaker 2: back is the evidence of parasitism? How quickly did people
• 19:05
  Speaker 2: start to slurp and munch intimately on each other?
• 19:08
  Speaker 1: Well, so we are mostly focusing on multicellular organisms going
• 19:13
  Speaker 1: after other multicellular organisms. I think it would be really
• 19:16
  Speaker 1: hard to know if there was like a bacterial parasite
• 19:20
  Speaker 1: going after other organisms in the like primordial soup era
• 19:25
  Speaker 1: of life.
• 19:26
  Speaker 2: I guess bacteria phages could be considered parasites and viruses
• 19:29
  Speaker 2: that infect.
• 19:29
  Speaker 1: Bacteria, right, Yeah, I meant conferences. We like to joke
• 19:32
  Speaker 1: that the first organism was free living, in the second
• 19:34
  Speaker 1: one found some way to exploit it. But you know,
• 19:37
  Speaker 1: we don't know that for sure.
• 19:39
  Speaker 2: This economy that's just happening.
• 19:40
  Speaker 1: Yeh, that's right, that's right. And so you know, I
• 19:43
  Speaker 1: think pretty early on, when you start getting multicellular organisms,
• 19:47
  Speaker 1: you get parasites also.
• 19:48
  Speaker 2: And remind us how early did we get multicellular organisms
• 19:51
  Speaker 2: For those of us who are not evolutionary.
• 19:53
  Speaker 1: Biologists, So multicellular life is probably something like seven hundred
• 19:58
  Speaker 1: million years ago, and I think we have decent evidence
• 20:02
  Speaker 1: of parasites in multi cellular organisms from at least two
• 20:06
  Speaker 1: hundred and fifty million years ago, and I'm guessing that
• 20:09
  Speaker 1: before that it gets even harder to find evidence of parasites,
• 20:13
  Speaker 1: and you have to be super careful that you're not
• 20:15
  Speaker 1: tricking yourself. So, for example, there are these isopods that
• 20:18
  Speaker 1: attached to fish, and sometimes they'll like live on top
• 20:21
  Speaker 1: of their gill arches, so like underneath their gill flap,
• 20:24
  Speaker 1: and then other times they'll live on their tongue. And
• 20:27
  Speaker 1: so if you find an isopod next to a fish,
• 20:30
  Speaker 1: you might be like, oh, there's a parasitic isopod, But
• 20:32
  Speaker 1: how do you know that it wasn't just like fossilized
• 20:35
  Speaker 1: next to the fish. How do you know it was
• 20:36
  Speaker 1: actually a parasitic relationship. So this stuff can be really difficult.
• 20:40
  Speaker 2: These glimpses into deep time are super fascinating. One of
• 20:43
  Speaker 2: my favorite things in science. You know, to think that
• 20:46
  Speaker 2: like Earth had life on it for billions of years
• 20:49
  Speaker 2: before it had multicellular life. You know, like so many years,
• 20:53
  Speaker 2: so many seasons, so many days past with just like
• 20:56
  Speaker 2: frothing bacteria and stuff floating in the oceans. Now really interesting,
• 21:00
  Speaker 2: which is also kind of depressing because it means like
• 21:03
  Speaker 2: if you find a planet with life on it. There's
• 21:05
  Speaker 2: a good chance it's just a bunch of single cell
• 21:07
  Speaker 2: organisms nobody really to talk to. It's incredible how rapidly
• 21:12
  Speaker 2: things have changed. Like seven hundred million years ago, we
• 21:14
  Speaker 2: get multi cellular life and then you know, things explode.
• 21:17
  Speaker 2: And only recently have we had intelligence and technology and podcasts.
• 21:22
  Speaker 1: Why I promise to not rat you out because you
• 21:24
  Speaker 1: essentially said there's just bacteria and that's not interesting. I
• 21:28
  Speaker 1: promise I won't tell Katrina that you said that, but
• 21:32
  Speaker 1: I agree, Well, this is.
• 21:33
  Speaker 2: Our way to find out if she listens to the
• 21:35
  Speaker 2: podcast or not. If I get in trouble over.
• 21:36
  Speaker 1: That, that's all right, Well, keep me posted, all right.
• 21:41
  Speaker 1: So when we come back, let's talk about categories that
• 21:45
  Speaker 1: parasites fall into. So we were talking about how do
• 21:47
  Speaker 1: you define and categorize these things. We'll talk about the
• 21:49
  Speaker 1: categories that we think make the most sense.
• 22:11
  Speaker 2: All right, we are back, and we are talking about
• 22:13
  Speaker 2: a very intimate topic today. We're talking about the incredible
• 22:16
  Speaker 2: community of folks that live off of you, that you
• 22:20
  Speaker 2: are supporting your parasites and the parasites of everybody else
• 22:23
  Speaker 2: on earth. We're digging deep into the history to understand
• 22:27
  Speaker 2: how often this happens, how it happens, why it happens,
• 22:30
  Speaker 2: and what is the future of parasitism. So let's keep
• 22:34
  Speaker 2: digging into the past. Kelly tell us about like how
• 22:37
  Speaker 2: these things become parasites, How does the species decide from
• 22:40
  Speaker 2: being a maker to becoming a taker?
• 22:43
  Speaker 1: I love that phrasing. And the answer is really like,
• 22:47
  Speaker 1: we don't have a great handle on this. So you know,
• 22:49
  Speaker 1: we talked about how this transition has happened probably more
• 22:52
  Speaker 1: than two hundred and twenty three times, and there's this
• 22:55
  Speaker 1: long running belief in the community that the what usually
• 23:00
  Speaker 1: what happens is that an organism starts specializing on dead stuff.
• 23:03
  Speaker 1: So you go from a decomposer to a parasite. And
• 23:06
  Speaker 1: the idea is you get good at living off of
• 23:08
  Speaker 1: flesh when it's dead, and that sort of lowers the
• 23:12
  Speaker 1: threshold to becoming a parasite and living on that thing
• 23:15
  Speaker 1: and taking its energy while it's still alive.
• 23:18
  Speaker 2: So first you identify like, hey, these corpses are rich
• 23:21
  Speaker 2: in nutrients, I might as well eat them, and then
• 23:24
  Speaker 2: you start eating the living versions of them.
• 23:26
  Speaker 1: Yeah, And so my friend Dan Metz and I wrote
• 23:28
  Speaker 1: a paper. He was leading this paper I was just
• 23:30
  Speaker 1: on the support team, but we wanted to find like
• 23:34
  Speaker 1: the papers that showed this, because this is a thing
• 23:36
  Speaker 1: that you can see found in the literature for like
• 23:40
  Speaker 1: one hundred years or more, but when you look into
• 23:42
  Speaker 1: the literature, it actually hasn't been tested that often. So
• 23:45
  Speaker 1: I think a lot of us have this gut feeling
• 23:48
  Speaker 1: that you know, being a decomposer is the step before
• 23:50
  Speaker 1: becoming a parasite, But folks really haven't done the nice
• 23:54
  Speaker 1: kind of analyzes you need. Where you'd need a tree
• 23:56
  Speaker 1: of life. You'd need to know who the free living
• 23:58
  Speaker 1: organisms and the parasites are are, and you'd need to
• 24:00
  Speaker 1: know what that free living organism was doing before the
• 24:03
  Speaker 1: transition to parasitism, and then look to see if certain
• 24:07
  Speaker 1: kinds of free living organisms were more likely to transition
• 24:10
  Speaker 1: to parasites. And you need some control groups too, and
• 24:13
  Speaker 1: that requires a lot of natural history data. And so
• 24:16
  Speaker 1: you and I have talked in the past about, you know,
• 24:19
  Speaker 1: the value of taxonomy and the value of going out
• 24:21
  Speaker 1: and collecting information, and I think it's critical because a
• 24:24
  Speaker 1: lot of times we'll want to do these sorts of
• 24:26
  Speaker 1: analyzes and then you'll get your tree of life together
• 24:28
  Speaker 1: and you'll be like, oh, we have no idea what
• 24:30
  Speaker 1: any of these pieces are doing in the wild, and
• 24:32
  Speaker 1: so you can't ask these questions that really help us understand,
• 24:36
  Speaker 1: you know, the paths that life take. You need that
• 24:39
  Speaker 1: natural history data.
• 24:40
  Speaker 2: And you always need data, right, especially to check your intuitions. Yeah,
• 24:44
  Speaker 2: because you know, science is a story and we're putting
• 24:46
  Speaker 2: together a history of what happened, and when we don't know,
• 24:50
  Speaker 2: we're inclined to like fill in with our intuition, say well,
• 24:53
  Speaker 2: here's an idea. Maybe this is reasonable, and if it
• 24:55
  Speaker 2: sounds natural to us, we accept it. We're like, okay, yeah,
• 24:58
  Speaker 2: I believe that. Yeah, but sometimes the you verse is
• 25:00
  Speaker 2: not intuitive. So you always got to go out there
• 25:02
  Speaker 2: and check, especially when you're telling a reasonable sounding story
• 25:05
  Speaker 2: that doesn't have any actual data to support it. So
• 25:09
  Speaker 2: more science, people.
• 25:10
  Speaker 1: Right, So much more science, Yes, so much more science. Okay.
• 25:14
  Speaker 1: So we were talking a little bit earlier about why
• 25:16
  Speaker 1: you would want to try to create boxes to describe
• 25:19
  Speaker 1: what parasites are doing, what different animals are doing, and
• 25:22
  Speaker 1: I was arguing that you need those boxes so that
• 25:24
  Speaker 1: you can create models to help understand what's happening. And
• 25:27
  Speaker 1: there's a couple of different folks who have come up
• 25:29
  Speaker 1: with categories that they think keep popping up as strategies
• 25:33
  Speaker 1: that parasites take. And I saw a quote in one
• 25:35
  Speaker 1: of these papers that made me think, oh, man, this
• 25:38
  Speaker 1: is for Daniel uh oh, so here it is. This
• 25:42
  Speaker 1: is from Poola twenty eleven. It seems safe to speculate
• 25:46
  Speaker 1: that if life exists on other planets, as long as
• 25:49
  Speaker 1: alien ecosystems show some basic similarities to ours, then parasitism
• 25:54
  Speaker 1: will not only have evolved, but alien parasites would be
• 25:57
  Speaker 1: using exploitation strategies very close to the ones to find.
• 26:01
  Speaker 2: Here well parasites in the universe.
• 26:07
  Speaker 1: So he was really going out on a limb here,
• 26:10
  Speaker 1: very strongly worded. He believes these categories explained like truths
• 26:14
  Speaker 1: about paths taken by life.
• 26:16
  Speaker 2: I think it's fascinating when scientists do that. When they
• 26:19
  Speaker 2: find something here, they understand it, and then they say
• 26:21
  Speaker 2: this must be universal. We found it here, and therefore
• 26:24
  Speaker 2: it's everywhere. It seems like it could be the only way,
• 26:27
  Speaker 2: And that's so often just reveals like a lack of
• 26:30
  Speaker 2: the broader context, like you're within a certain set of
• 26:34
  Speaker 2: box of ways of thinking about the universe and it's
• 26:36
  Speaker 2: hard to imagine. Outside that box doesn't mean that outside
• 26:39
  Speaker 2: the box doesn't exist. And like, as I was just saying,
• 26:42
  Speaker 2: like this is why we got to go and find
• 26:44
  Speaker 2: alien parasites and blow earthling parasitologists minds about ways that
• 26:48
  Speaker 2: you can suck on other people. Right, there may be
• 26:50
  Speaker 2: even more intimate ways to be a parasite we never
• 26:53
  Speaker 2: even imagined, totally true, as you know. And that's why
• 26:56
  Speaker 2: I wrote this whole book about how aliens might do science,
• 26:59
  Speaker 2: trying to think outside the box.
• 27:01
  Speaker 1: Daniel, what is that book called.
• 27:03
  Speaker 2: It's called Do Aliens Speak Physics? And it's for sale
• 27:06
  Speaker 2: in November. Check it out at.
• 27:07
  Speaker 1: All fine bookstores. Yeah, no, it is a fantastic book.
• 27:11
  Speaker 1: I got to read it.
• 27:11
  Speaker 2: So I love that this parasitologist is thinking about aliens.
• 27:14
  Speaker 2: But I'm a little skeptical that our earthly categories of
• 27:18
  Speaker 2: parasites are the only ones in the universe. But anyway,
• 27:21
  Speaker 2: walk us through the kinds of parasites we have found
• 27:24
  Speaker 2: here on Earth, and everybody out there, if you're eating dinner,
• 27:27
  Speaker 2: maybe finish up before we dig into all of these
• 27:30
  Speaker 2: intimate details.
• 27:31
  Speaker 1: Okay, So, one of the exciting things about these strategies
• 27:36
  Speaker 1: is that organisms from very different locations on the tree
• 27:39
  Speaker 1: of life seem to have ended up with very similar strategies,
• 27:43
  Speaker 1: which suggests that there's something critical about these boxes that
• 27:46
  Speaker 1: we're creating.
• 27:47
  Speaker 2: Yeah.
• 27:47
  Speaker 1: So one of the strategies, which we've already talked about,
• 27:50
  Speaker 1: is parasitoids. So the idea here is that you infect
• 27:53
  Speaker 1: one host species, you use all of its energy. You
• 27:56
  Speaker 1: have to kill it as part of your life cycle,
• 27:58
  Speaker 1: and so we get parasit wasps that do this. We
• 28:02
  Speaker 1: get nomatomorphs. So these are sort of nematode looking things
• 28:06
  Speaker 1: that live in cricket So have you ever seen that
• 28:08
  Speaker 1: video of a cricket that jumps into a pool and
• 28:11
  Speaker 1: a worm that's like ten times the length of the cricket,
• 28:14
  Speaker 1: maybe even more, glides out of its back end.
• 28:17
  Speaker 2: Mm hmmm.
• 28:18
  Speaker 1: Nightmare fuel, Yes, absolute nightmare fuel.
• 28:20
  Speaker 2: There's one with the praying mantis also, I think yeah, yeah.
• 28:23
  Speaker 1: Yeah, yeah. So sometimes those animals survive actually after they
• 28:27
  Speaker 1: jump into the water, which blows my mind because you
• 28:29
  Speaker 1: would think something that big comes out of you, you're
• 28:31
  Speaker 1: a goner.
• 28:31
  Speaker 2: Yeah, I think that some mornings. Yes, oh god, I
• 28:39
  Speaker 2: think there's an intimate detail for everybody.
• 28:41
  Speaker 1: That's right intimate, I hope not durable. I hope we
• 28:43
  Speaker 1: can all forget that. Okay, So you get those like
• 28:49
  Speaker 1: wormy things that eat almost everything inside of the organism,
• 28:52
  Speaker 1: and it's kind of amazing because they've managed to take
• 28:55
  Speaker 1: everything from the organism without killing it, so they're able
• 28:58
  Speaker 1: to like avoid the critical organs, but all the like
• 29:01
  Speaker 1: fat has been slurped out. Anything that's not absolutely critical
• 29:04
  Speaker 1: has been slurped out and turned into parasite. And those
• 29:07
  Speaker 1: zombie ants that you see with the Cordyceps fungus, they
• 29:10
  Speaker 1: also are exhibiting a parasitoid strategy. They kill the ant
• 29:13
  Speaker 1: and then they use all of that energy to make
• 29:15
  Speaker 1: their own babies.
• 29:16
  Speaker 2: So explain to me the word here parasitoid, because as
• 29:20
  Speaker 2: a non expert, I hear that, and I think that's
• 29:21
  Speaker 2: sort of like a quasi parasite or a semi parasite
• 29:24
  Speaker 2: or something oid. Makes me think, like, not quite, what
• 29:29
  Speaker 2: does the word mean parasitoid?
• 29:31
  Speaker 1: This is a great question. I think the original phrase
• 29:34
  Speaker 1: came from a German scientist, and that doesn't necessarily mean that,
• 29:38
  Speaker 1: like their prefixes and suffixes meant something different. You're right,
• 29:42
  Speaker 1: I'm looking up Merriam Webster and the first definition of
• 29:45
  Speaker 1: parasitoid is resembling a parasite, which must be the oid
• 29:49
  Speaker 1: thing the.
• 29:50
  Speaker 2: Way that like our jokes resemble humor but aren't always
• 29:53
  Speaker 2: right on the money. You know, it's humoroid.
• 29:55
  Speaker 1: That's right, that's right, we're humoroid kind of podcasts, which
• 29:59
  Speaker 1: sounds maybe too close to hemorrhoid.
• 30:01
  Speaker 2: But uh so a lot of intimate jokes today, yes.
• 30:05
  Speaker 1: Right, so many, my guess would be and I this
• 30:09
  Speaker 1: is total spitball. Okay, So there are no parasitoids that
• 30:13
  Speaker 1: infect humans, and so I think that when we think
• 30:15
  Speaker 1: of parasites, we think of things that are like living
• 30:19
  Speaker 1: in your guts or you know, like we think of
• 30:21
  Speaker 1: the kind of parasites that we have. And so it's
• 30:24
  Speaker 1: possible that when parasitoid was first named, they were like, oh, like,
• 30:28
  Speaker 1: it's living in another thing. We're familiar with that. But
• 30:31
  Speaker 1: then it like kills them and bursts out of them,
• 30:33
  Speaker 1: and it's this is something different. So let's call it parasitoid.
• 30:36
  Speaker 1: And I'm totally spitball. Like you have asked me yet
• 30:38
  Speaker 1: another question. I don't know the answer too, but I'm
• 30:41
  Speaker 1: gonna double down on my answer.
• 30:43
  Speaker 2: All right, So these guys don't live in humans. They
• 30:46
  Speaker 2: infect their host, slurp up all the in crucial bits,
• 30:50
  Speaker 2: and then eventually kill them.
• 30:51
  Speaker 1: Yep, that's a strategy, all right.
• 30:53
  Speaker 2: And so if that wasn't gross enough for you, let's
• 30:55
  Speaker 2: hear about the next category, which I shiver to even say.
• 31:00
  Speaker 2: Parasitic castrators.
• 31:02
  Speaker 1: Yes, lovely. So they don't kill the hosts, but they
• 31:08
  Speaker 1: do reduce their evolutionary fitness to zero. So essentially they
• 31:12
  Speaker 1: make it so that that organism will never be able
• 31:14
  Speaker 1: to pass down its genes again. It won't be able
• 31:16
  Speaker 1: to have any more of its babies.
• 31:18
  Speaker 2: Wow.
• 31:19
  Speaker 1: But now the parasites get to.
• 31:20
  Speaker 2: Live cute little parasite babies. You know.
• 31:25
  Speaker 1: The parasite studied for my PhD has these two little
• 31:27
  Speaker 1: eye spots, and it has like a little suckery kind
• 31:31
  Speaker 1: of mouth that opens and closes. And by the end
• 31:33
  Speaker 1: of my very long PhD it took a really long
• 31:36
  Speaker 1: time to finish, I kind of thought that they were cute.
• 31:39
  Speaker 1: So I am capable of thinking some parasites are cute.
• 31:42
  Speaker 2: They've infected your brain. See, they're working their magic on you.
• 31:45
  Speaker 1: That's right, that's right.
• 31:46
  Speaker 2: So tell us about what these guys do.
• 31:48
  Speaker 1: All right, So at the top of the show, we
• 31:49
  Speaker 1: talked about those snails where a bunch of the biomass
• 31:52
  Speaker 1: of those snails is actually going towards the production of
• 31:54
  Speaker 1: parasite babies. That's an example of castration. All of the
• 31:59
  Speaker 1: energy that would have gone TODs making snail babies is
• 32:01
  Speaker 1: now making parasite babies. And those snails can live for
• 32:04
  Speaker 1: like I think it's like a decade after getting infected.
• 32:07
  Speaker 1: And sometimes when the tide comes in on a warm day,
• 32:09
  Speaker 1: they can release up to two thousand of those parasites
• 32:12
  Speaker 1: into the water column. And so we think of them
• 32:15
  Speaker 1: as essentially like extended versions of parasites. At that point,
• 32:18
  Speaker 1: they're not working towards their own evolutionary goals anymore. Also,
• 32:22
  Speaker 1: side note, the parasites that live in the snails have
• 32:25
  Speaker 1: social behaviors, Like do you know how ant communities have
• 32:30
  Speaker 1: different jobs for the different ants, and the ants have
• 32:32
  Speaker 1: different shapes. Yeah, you've got like a million mile stare
• 32:36
  Speaker 1: right now? Is this too much?
• 32:38
  Speaker 2: No, I'm thinking about ants?
• 32:39
  Speaker 1: Oh all right, okay, I was thinking.
• 32:41
  Speaker 2: About that time they poured aluminum into an ant farm.
• 32:43
  Speaker 2: I remember, like the shape of it.
• 32:45
  Speaker 1: That's a mean but informative way of getting that information. Okay,
• 32:49
  Speaker 1: So ants have individuals who have different jobs, and they
• 32:53
  Speaker 1: have different shapes, and they have some individuals who never
• 32:57
  Speaker 1: have their own offspring. Their job is just to support
• 32:59
  Speaker 1: the colony. The same thing is happening inside of these snails.
• 33:03
  Speaker 1: So there are attacker morphs that are essentially just like
• 33:08
  Speaker 1: giant mouths that go around and when a parasite tries
• 33:12
  Speaker 1: to invade the snail, because sometimes a new parasite species
• 33:15
  Speaker 1: will come in invade a snail that already has parasites
• 33:17
  Speaker 1: living in there, and it could kick out the parasites
• 33:20
  Speaker 1: that are living in there and then take over the gonad.
• 33:22
  Speaker 2: So it's like parasite versus parasite battle inside the snail.
• 33:25
  Speaker 1: Yes, wow, yes, And some kinds of trematode parasites have
• 33:29
  Speaker 1: essentially these mouths that never reproduce on their own. Their
• 33:32
  Speaker 1: whole job is to just patrol the snail, and if
• 33:35
  Speaker 1: a parasite comes in, they go and they suck a
• 33:38
  Speaker 1: hole into the side of the tree with toad and
• 33:40
  Speaker 1: like suck out the insides and kill it that way.
• 33:43
  Speaker 2: Wow, this is like gang violenceers. This is our territory.
• 33:46
  Speaker 1: Yes, yeah, they have like more interesting social lives than
• 33:49
  Speaker 1: I do. They're fascinating.
• 33:50
  Speaker 2: But how high bar is that?
• 33:52
  Speaker 1: Kelly tell me, Oh my god, it's like it's like
• 33:55
  Speaker 1: on the ground. You don't have to lift your foot
• 33:56
  Speaker 1: up much at all. I don't go out much. But anyway, okay,
• 34:00
  Speaker 1: parasitic castrators, trematodes. Let's do one other example. There are
• 34:04
  Speaker 1: barnacles and so like if you've been to the ocean,
• 34:07
  Speaker 1: you've probably seen barnacles. There are barnacles that stick to
• 34:09
  Speaker 1: the sides of like whales and turtles. There are also
• 34:12
  Speaker 1: barnacles and isopods. These are these little crustacean things that
• 34:16
  Speaker 1: are both able to castrate crustaceans like crabs. So the
• 34:21
  Speaker 1: barnacle in particular does this very interesting thing where it
• 34:25
  Speaker 1: has a sack where female crabs would usually have their babies,
• 34:29
  Speaker 1: and it sets up shop there, and females usually will
• 34:33
  Speaker 1: use their claws, so this is on the underside of
• 34:35
  Speaker 1: what you'd think of as like the crab's belly. They
• 34:37
  Speaker 1: use their claws to like pass water over it to
• 34:39
  Speaker 1: make sure that their eggs stay oxygenated. They will do
• 34:42
  Speaker 1: that when the barnacles down there to keep the barnacle oxygenated,
• 34:46
  Speaker 1: and males will start doing that too, So it looks
• 34:48
  Speaker 1: like not only do they castrate male and female crabs,
• 34:52
  Speaker 1: but they get the males to start acting like females
• 34:55
  Speaker 1: to take care of the barnacles. We call this feminization,
• 34:58
  Speaker 1: and it's kind of poorly understood, but anyway, So barnacles
• 35:02
  Speaker 1: are castrating crabs, trematodes are castrating snails, and there's insects
• 35:08
  Speaker 1: castrating other insects. This is another very common strategy.
• 35:12
  Speaker 2: You just said the word castrating way too many times
• 35:14
  Speaker 2: from that country. Let's move on.
• 35:18
  Speaker 1: There's a total of six categories, but rather than making
• 35:21
  Speaker 1: you all sit through all six, let's pick one more
• 35:25
  Speaker 1: to give you a flavor of the amazing strategies that
• 35:28
  Speaker 1: parasites have taken on.
• 35:30
  Speaker 2: Let's do vector transmitted parasites. Because that sounds physics, y vectors.
• 35:35
  Speaker 1: Ooh, all right, Well you can try to connect this
• 35:37
  Speaker 1: with physics at the end, we'll see. But so, what
• 35:39
  Speaker 1: we mean by vector transmitted is that you have one
• 35:43
  Speaker 1: animal that is bringing a parasite to another animal and
• 35:46
  Speaker 1: essentially injecting it into that other animal. Probably the most
• 35:50
  Speaker 1: famous vector transmitted parasite is malaria. So mosquitoes will take
• 35:56
  Speaker 1: a blood meal from a person who has malaria, they
• 35:58
  Speaker 1: suck the parasite up. A parasite does some developing inside
• 36:01
  Speaker 1: of the mosquito and eventually goes to live in the
• 36:03
  Speaker 1: mosquito's salivary glands. And then when a mosquito goes to
• 36:07
  Speaker 1: take a blood meal from another human who isn't infected yet,
• 36:10
  Speaker 1: the parasite ends up in that person's blood, and then
• 36:14
  Speaker 1: that person gets infected and the cycle starts again.
• 36:16
  Speaker 2: I think it's fascinating. You call this a blood meal.
• 36:19
  Speaker 2: Makes it sound so wholesome, you know, like it's just
• 36:21
  Speaker 2: going home to have dinner after a long day of work.
• 36:23
  Speaker 2: You know it deserves it, But like, this thing is
• 36:26
  Speaker 2: sucking my blood, you know.
• 36:28
  Speaker 1: I've read stories from the early nineteen hundreds in the
• 36:30
  Speaker 1: Journal of Parasitology where they sort of mentioned in an
• 36:33
  Speaker 1: offhanded way that like the mosquitoes and the lice in
• 36:36
  Speaker 1: the colonies were fed blood meals by volunteers, which means
• 36:40
  Speaker 1: somebody was like sticking their arms in the mosquito cage.
• 36:43
  Speaker 1: Anna Phillips was telling us in the Leech episode that
• 36:45
  Speaker 1: now you can like fill medical gloves up with blood
• 36:49
  Speaker 1: from you know, a hospital or something and feeds them
• 36:52
  Speaker 1: that way. But I love the faces you make when
• 36:55
  Speaker 1: we talk about parasites. It's so entertaining for me. But Mike,
• 36:58
  Speaker 1: you know I if I I tell you my big
• 37:00
  Speaker 1: goal here, I feel like when you start learning about parasites,
• 37:04
  Speaker 1: you can't get over the disgust hump Ye. It's just
• 37:07
  Speaker 1: like so upsetting. But the more you learn about it.
• 37:10
  Speaker 1: This doesn't happen for everybody, but maybe you'll get there.
• 37:13
  Speaker 1: I feel like the more you learn about it, the
• 37:15
  Speaker 1: more kind of amazing it is that evolution has resulted
• 37:19
  Speaker 1: in this super complicated strategy. Like I mean, imagine being
• 37:23
  Speaker 1: able to live in environments as different as a mosquito
• 37:26
  Speaker 1: and a human, like to conquer both of those hosts
• 37:30
  Speaker 1: in a way that like human ingenuity has just not
• 37:32
  Speaker 1: been able to outsmart. There's good evidence that malaria is
• 37:35
  Speaker 1: able to essentially like change the proteins on the outside
• 37:39
  Speaker 1: so that our immune system can't recognize it. Like we
• 37:42
  Speaker 1: start to get a handle on it, and then it
• 37:43
  Speaker 1: shows up again in like a whole different outfit, and
• 37:45
  Speaker 1: our body is like, where did the malaria go? But
• 37:48
  Speaker 1: it's still there and it's like racing us and you
• 37:51
  Speaker 1: know we have We've created all of these vaccines that
• 37:53
  Speaker 1: keep you know, not quite keeping up. These are kind
• 37:56
  Speaker 1: of incredible creatures. You can hate them, and I wish
• 37:58
  Speaker 1: there was no malaria because I don't want to see
• 38:00
  Speaker 1: any child with malaria ever again. But you kind of
• 38:03
  Speaker 1: have to respect sort of the amazing strategies that they've
• 38:07
  Speaker 1: been able to come up with with the help of
• 38:09
  Speaker 1: natural selection.
• 38:10
  Speaker 2: Yeah, I totally appreciate you leaning into the wonders of
• 38:13
  Speaker 2: the universe, and you know, that's our whole brand, and
• 38:16
  Speaker 2: the universe is extraordinary and these things are incredible. And
• 38:20
  Speaker 2: I guess I'll try to think about that next time
• 38:21
  Speaker 2: I see a mosquito biting Meia be like, wow, think
• 38:24
  Speaker 2: about all the amazing science going into this itch that
• 38:27
  Speaker 2: I'm going to be suffering for the next three days.
• 38:29
  Speaker 1: Well, that's a micro predator, Daniel, I'm not interested, just kidding.
• 38:36
  Speaker 2: All right, So let's take another break and we come back.
• 38:38
  Speaker 2: Let's hear some good news about how parasites can go extinct. Okay,
• 39:03
  Speaker 2: we're back, and Kelly is grossing me out with intimate
• 39:06
  Speaker 2: details of how parasites infect their hosts, castrate them, and
• 39:10
  Speaker 2: pass on diseases. Yay, we're all supposed to think. Yay.
• 39:15
  Speaker 2: So let's turn to some good news. We heard about
• 39:18
  Speaker 2: how parasites have evolved many many times in the record.
• 39:21
  Speaker 2: Do parasites also go extinct? We have evidence for parasites disappearing.
• 39:25
  Speaker 2: How does that happen?
• 39:26
  Speaker 1: They do go extinct, and so, you know, we talked
• 39:29
  Speaker 1: about how parasitism as a strategy popped up, you know,
• 39:32
  Speaker 1: over two hundred times in the tree of life. It
• 39:34
  Speaker 1: appears it's also been lost a few times.
• 39:36
  Speaker 2: Ah, I know.
• 39:38
  Speaker 1: So sometimes it's hard to get a handle on those
• 39:40
  Speaker 1: losses because if an animal loses it and then doesn't
• 39:43
  Speaker 1: end up in the fossil record, it can just be
• 39:45
  Speaker 1: kind of complicated. But yeah, parasites go extinct, and in fact,
• 39:48
  Speaker 1: some parasites are more susceptible to extinction than their hosts.
• 39:52
  Speaker 1: And I know that's not sad for you, but we're
• 39:55
  Speaker 1: losing diversity. So one parasite strategy that we didn't talk
• 39:58
  Speaker 1: about in the last section are trophically transmitted parasites.
• 40:02
  Speaker 2: What does trophic mean?
• 40:03
  Speaker 1: So, like, think about trophic levels in a food web,
• 40:06
  Speaker 1: and so trophic transmission is essentially a predator consumes an
• 40:10
  Speaker 1: animal that was infected, and the parasite gets into the predator.
• 40:14
  Speaker 1: So the trophically transmitted system I studied for my PhD
• 40:18
  Speaker 1: was California killifish. There are these small fish in southern
• 40:21
  Speaker 1: California estuaries and they get eaten by predatory birds like egrets,
• 40:26
  Speaker 1: and the parasite goes from living on top of the
• 40:28
  Speaker 1: fish's brain to living in the egrets gut.
• 40:30
  Speaker 2: I wouldn't want to live in either of those places.
• 40:32
  Speaker 2: I mean, you're in southern California. There's lots of beautiful
• 40:34
  Speaker 2: places to live. Why would you choose a fish brain?
• 40:37
  Speaker 2: But hey, you do you?
• 40:39
  Speaker 1: I mean, I'd rather live in Virginia. But that's all right.
• 40:42
  Speaker 1: So everyone knew that was coming. But this parasite actually
• 40:45
  Speaker 1: has an even more complicated life cycle. So parasites can
• 40:48
  Speaker 1: have different strategies depending on where they are in the
• 40:51
  Speaker 1: life cycle. So there you've got trophic transmission from fish
• 40:54
  Speaker 1: to bird. The parasites then find love in the bird's
• 40:59
  Speaker 1: gut and they may eggs that pass with the bird
• 41:02
  Speaker 1: species into the salt marsh, where they're accidentally consumed by
• 41:05
  Speaker 1: those snails that we talked about that get castrated and
• 41:09
  Speaker 1: then this is.
• 41:10
  Speaker 2: Such a horror movie. This whole thing is a horror movie.
• 41:13
  Speaker 1: I love it, I eat it up. My mom loved
• 41:15
  Speaker 1: horror movies. Maybe that's what's set me up for all
• 41:17
  Speaker 1: of this.
• 41:17
  Speaker 2: It's her fault.
• 41:18
  Speaker 1: Yes, yeah, yeah. So anyway, in order for this parasite,
• 41:22
  Speaker 1: this trematode parasite, to complete its life cycle, you need
• 41:25
  Speaker 1: to have the fish, you need to have the birds,
• 41:27
  Speaker 1: and you need to have the snail. If you lose
• 41:29
  Speaker 1: any of those hosts in the cycle, or any of
• 41:32
  Speaker 1: them falls to numbers that are small enough where it's
• 41:34
  Speaker 1: hard for the parasite to find them, then that animal
• 41:37
  Speaker 1: can go extinct. And so parasites have all of these
• 41:40
  Speaker 1: extra requirements that depend on what's happening with their hosts,
• 41:43
  Speaker 1: and so in some cases we think that parasites might
• 41:45
  Speaker 1: be more susceptible to extinction than a lot of free
• 41:48
  Speaker 1: living animals because there's so many different components that need
• 41:51
  Speaker 1: to work well for the parasite to complete the life cycle.
• 41:54
  Speaker 2: It's kind of a fragile system, a bit of.
• 41:56
  Speaker 1: A fragile system, and so parasites can be used as
• 41:58
  Speaker 1: what we call ecological indicator. So if you go to
• 42:01
  Speaker 1: an estuary and you find a lot of parasites, that
• 42:04
  Speaker 1: probably means a lot of host species are there, and
• 42:06
  Speaker 1: they're there in pretty high numbers, and so a lot
• 42:08
  Speaker 1: of parasites can be indicative of a healthy ecosystem, which
• 42:12
  Speaker 1: I think is counterintuitive to some people but makes perfect
• 42:15
  Speaker 1: sense to my parasitologists heart.
• 42:18
  Speaker 2: Like if you go to a new neighborhood and you
• 42:19
  Speaker 2: discover there's lots of gangs there, you're like, oh, wow,
• 42:22
  Speaker 2: this must have a thriving economy for the gangs to
• 42:24
  Speaker 2: be siphoning money off of.
• 42:30
  Speaker 1: Wow, where do I go with that? I mean, I
• 42:32
  Speaker 1: guess it means that the police aren't really doing their job,
• 42:35
  Speaker 1: which maybe means there's immune systems and hosts that are compromised,
• 42:38
  Speaker 1: perhaps by pollutants. But maybe we're pulling this analogy a
• 42:41
  Speaker 1: little bit too tight, so let's move on.
• 42:45
  Speaker 2: All right. So they do go extinct, and maybe even
• 42:47
  Speaker 2: more often than their hosts because they rely on like
• 42:49
  Speaker 2: a complex system and getting passed from one to the other.
• 42:53
  Speaker 2: But then they're everywhere and they're very common and they've
• 42:55
  Speaker 2: evolved many many times. How do we understand that altogether?
• 42:58
  Speaker 1: I mean, there's a lot of hosts all and you
• 43:00
  Speaker 1: can be losing a lot of hosts, but you still
• 43:02
  Speaker 1: look around and there's a lot of birds outside and stuff.
• 43:04
  Speaker 1: It's just, you know, hard to keep track of all
• 43:05
  Speaker 1: of this stuff. But if I can, just for one
• 43:08
  Speaker 1: second try to convince you that you should care about
• 43:10
  Speaker 1: parasites going extinct, and I won't.
• 43:12
  Speaker 2: You can try.
• 43:13
  Speaker 1: Yeah, So, parasites are important parts of ecosystem. So we
• 43:17
  Speaker 1: mentioned that those snails that are castrated can release up
• 43:21
  Speaker 1: to two thousand parasites into the water. Those parasites are
• 43:24
  Speaker 1: free swimming bags of energy that get eaten by a
• 43:27
  Speaker 1: lot of organisms, so they provide food to the system. Also,
• 43:31
  Speaker 1: you know, we talked about those crickets that have those
• 43:34
  Speaker 1: long worms in them, and the crickets are forced into
• 43:36
  Speaker 1: jumping into the river and then the worms, the nomatomorphs,
• 43:40
  Speaker 1: come out the back of them. Those crickets are terrestrial
• 43:43
  Speaker 1: organisms that jump into creeks, And in Japan there's this
• 43:46
  Speaker 1: endangered trout where a lot of the food that it
• 43:49
  Speaker 1: gets comes from crickets that are jumping into the creek
• 43:52
  Speaker 1: that they wouldn't have access to otherwise. And so these
• 43:55
  Speaker 1: parasites often make lots of food available to other animals
• 43:58
  Speaker 1: or make that food easy to catch. They play important
• 44:01
  Speaker 1: roles in ecosystems that we don't always understand very well,
• 44:04
  Speaker 1: and if you lose them that could be bad in
• 44:07
  Speaker 1: some cases.
• 44:08
  Speaker 2: Yeah, I totally appreciate that. And it's sort of curious
• 44:10
  Speaker 2: to me, like, why do parasites have this ick factor
• 44:13
  Speaker 2: that like predators don't, you know, like a jaguar, it's
• 44:17
  Speaker 2: still like finding another critter and taking it and eating
• 44:20
  Speaker 2: its resources. Why is this somehow grosser to be like
• 44:23
  Speaker 2: living inside as you consume somebody for some reason, it
• 44:26
  Speaker 2: is definitely grosser though like morally it's not any better
• 44:30
  Speaker 2: or worse. So I don't know, there's just some sort
• 44:32
  Speaker 2: of like human ick factor there. And maybe when we
• 44:35
  Speaker 2: meet the aliens they'll be like, yay parasites, and Kelly
• 44:38
  Speaker 2: will be like, I found my people.
• 44:40
  Speaker 1: That's right, that's right. I understand you guys, you no,
• 44:44
  Speaker 1: I agree. There's definitely a judgment called people think of
• 44:46
  Speaker 1: parasites as like these super degenerate organisms. They have fewer
• 44:49
  Speaker 1: sort of abilities to like sense the exterior environment, but
• 44:52
  Speaker 1: they do manage to thrive in really complicated systems where
• 44:55
  Speaker 1: they're being attacked. And yeah, anyway, people do tend to
• 44:58
  Speaker 1: find parasites to be much gross to the lions. I
• 45:01
  Speaker 1: get that some people could look at a lion and
• 45:03
  Speaker 1: be like, that looks much nicer than a tapeworm. But
• 45:06
  Speaker 1: if you know what to look for in a tapeworm,
• 45:08
  Speaker 1: some of them are quite beautiful. I've got my tapeworm
• 45:11
  Speaker 1: picture right here.
• 45:12
  Speaker 2: Oh wow. Do you know anybody who like has a
• 45:14
  Speaker 2: coat made out of tapeworms or something like that, You know, tapeworms.
• 45:18
  Speaker 2: Maybe we need a fashion industry, you know, to replace
• 45:21
  Speaker 2: fur with parasites somehow.
• 45:23
  Speaker 1: I think that any parasite themed fashion that is available
• 45:28
  Speaker 1: is found at the American Society of Parasitologists Student Travel Auction.
• 45:32
  Speaker 1: We bring it in and we all pay way too
• 45:34
  Speaker 1: much for it to try to pay for student travel
• 45:36
  Speaker 1: so that they can come to our conferences. But anyway,
• 45:37
  Speaker 1: we're getting off track. We've got one more question from
• 45:40
  Speaker 1: the listener, and the question is do parasites go extinct
• 45:43
  Speaker 1: with hosts? So there's a number of different things that
• 45:45
  Speaker 1: can happen when hosts go extinct or when hosts sort
• 45:48
  Speaker 1: of split into multiple species, and so yes, often when
• 45:52
  Speaker 1: a host goes extinct, the parasite can go extinct. Also,
• 45:55
  Speaker 1: if the parasite was infecting lots of other host species,
• 45:58
  Speaker 1: then maybe it will be fine. But we already talked
• 46:00
  Speaker 1: about complex life cycles where if you lose one host
• 46:03
  Speaker 1: in the system, you can lose the parasite too. But
• 46:06
  Speaker 1: there's also examples where you get these splits in the
• 46:09
  Speaker 1: tree of life, and as you get those splits in
• 46:11
  Speaker 1: the hosts, the parasites also split into new species over
• 46:15
  Speaker 1: time because you now get like separations of parasite populations,
• 46:18
  Speaker 1: and over enough time they become their own species. And
• 46:21
  Speaker 1: so there's a sort of famous example where pelicans, as
• 46:25
  Speaker 1: they sort of speciated over time, they're lice speciated with them.
• 46:30
  Speaker 1: So pelicans, if you like create the tree of life
• 46:33
  Speaker 1: for pelicans and then you create the tree of life
• 46:35
  Speaker 1: for their lice, you could almost lay them on top
• 46:37
  Speaker 1: of each other. They follow very similar paths. But you
• 46:40
  Speaker 1: can also get cases where the parasites don't seem to
• 46:44
  Speaker 1: be tracking what's happening with their hosts. So, for example, guppies,
• 46:47
  Speaker 1: they are these these tiny little fish they get infected
• 46:49
  Speaker 1: by monogenians. These are these external parasites we were talking
• 46:52
  Speaker 1: about that have the hooks and they hold onto the
• 46:54
  Speaker 1: outside of the fish. They don't seem to be following
• 46:58
  Speaker 1: the evolutionary trajectory of their hosts. And right now we
• 47:01
  Speaker 1: don't have a really good framework for when you should
• 47:03
  Speaker 1: expect the tree of life for parasites and species to
• 47:06
  Speaker 1: essentially mirror one another, and when you shouldn't. But we
• 47:10
  Speaker 1: get all of these different options because nature is amazing
• 47:13
  Speaker 1: and it depends, but we don't.
• 47:15
  Speaker 2: Always know on what, and the incredible variety of strategies
• 47:17
  Speaker 2: we see helps us explore like the space of possibilities
• 47:21
  Speaker 2: and maybe even helps us think outside the box to
• 47:23
  Speaker 2: like what might be happening elsewhere in the universe.
• 47:26
  Speaker 1: Absolutely, yes, I would love to find a planet that
• 47:30
  Speaker 1: was rich with free living hosts and dissect a bunch
• 47:35
  Speaker 1: of them to see if they have parasites, but only
• 47:38
  Speaker 1: if it was humane and ethical.
• 47:40
  Speaker 2: All right, aliensf you're listening, come on by. Kelly wants
• 47:43
  Speaker 2: to look inside you.
• 47:44
  Speaker 1: Kelly wants to say huh.
• 47:46
  Speaker 2: In an intimate sort of way.
• 47:48
  Speaker 1: All right, Well, thank you so much to Zach for
• 47:50
  Speaker 1: sending in his questions. Let's see if Zach feels like
• 47:53
  Speaker 1: we've answered the many questions he posed about the evolution
• 47:56
  Speaker 1: of parasitism.
• 47:57
  Speaker 3: Hey, they're extraordinaries. Thank you so much for this credible
• 48:00
  Speaker 3: primer on parasites and their history. I feel like I
• 48:03
  Speaker 3: got way more than I bargained for, which is awesome.
• 48:05
  Speaker 3: You definitely answered my essential question that, yes, t Rex
• 48:10
  Speaker 3: probably had tapeworms or something like it, that we can't
• 48:12
  Speaker 3: be totally sure. I also really enjoyed hearing about all
• 48:16
  Speaker 3: the different categories of parasite strategies, and really appreciated hearing
• 48:21
  Speaker 3: that there are no parasitoids or castrating parasites for humans,
• 48:25
  Speaker 3: so I can sleep a little better at night. I
• 48:27
  Speaker 3: was also definitely convinced that parasites have an important role
• 48:31
  Speaker 3: to play in our ecosystems, so I'll try to be
• 48:34
  Speaker 3: a little bit more appreciative and a little less grossed out.
• 48:37
  Speaker 3: I am still a little curious. Seems like it's still
• 48:40
  Speaker 3: an open question how something goes from being a free
• 48:42
  Speaker 3: living organism to being a parasite, even if we can
• 48:45
  Speaker 3: count when it happens. I'm also curious if anything has
• 48:48
  Speaker 3: ever gone from being a parasite back to being a
• 48:51
  Speaker 3: free living organism. In any case, you guys rock. Thank
• 48:55
  Speaker 3: you again so much.
• 48:57
  Speaker 1: All right, thank you so much to Zach for all
• 48:59
  Speaker 1: of his many questions. If you would like to send
• 49:01
  Speaker 1: us questions, we would love to hear from you. Send
• 49:03
  Speaker 1: them to questions at danieland Kelly dot org. And I
• 49:06
  Speaker 1: hope that you enjoy your meal or you ate it
• 49:09
  Speaker 1: before we began this conversation.
• 49:11
  Speaker 2: And before you heard Kelly say the word castraid uncountable
• 49:14
  Speaker 2: number of times.
• 49:15
  Speaker 1: I don't think there's a limit on how many times
• 49:17
  Speaker 1: you can say castrat. It's a great word.
• 49:20
  Speaker 2: All right, everyone, thanks for joining us on this tour
• 49:22
  Speaker 2: of one more aspect of our extraordinary universe.
• 49:32
  Speaker 1: Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We
• 49:36
  Speaker 1: would love to hear from you.
• 49:38
  Speaker 2: We really would. We want to know what questions you
• 49:41
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