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Speaker 1: If you sit on the banks of the estuaries in

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Speaker 1: southern California and Baja California, the seat of your pants

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Speaker 1: will get super money. But also you'll likely see schools

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Speaker 1: of silvery fish swimming through the water. If you watch closely,

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Speaker 1: some of those silvery fish will begin behaving rather strangely.

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Speaker 1: They'll shoot upwards quickly, breaking the water surface and creating

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Speaker 1: these super conspicuous ripples on the surface. Or they'll turn

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Speaker 1: on their sides as they scratch their bodies against a rock.

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Speaker 1: As they do this, their silvery bellies reflect the sun

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Speaker 1: and create this quick and vibrant flash of light.

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Speaker 2: Why are they doing this?

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Speaker 1: These fish are bite size to the sharks and the

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Speaker 1: predatory birds that sometimes roam these estuaries in search of food.

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Speaker 1: Shouldn't they be trying to look a little less conspicuous.

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Speaker 1: Why are they drawing so much attention to themselves. Well,

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Speaker 1: it's me speaking, so you've probably guessed that the answer

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Speaker 1: is parasites.

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Speaker 2: Today we're going to talk about you.

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Speaker 1: Heplurcus california aansis a brain infecting parasite of California chillefish,

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Speaker 1: which are the silvery fish dancing through the waters in

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Speaker 1: California that we were just talking about. Welcome to Daniel

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Speaker 1: and Kelly's extraordinarily infected universe.

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Speaker 3: Hi. I'm Daniel, I'm a particle physicist, and I hope

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Speaker 3: I'm parasite free.

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Speaker 2: Hello. I'm Kelly Wiersmith.

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Speaker 1: I study exactly what we're talking about today, and I'm

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Speaker 1: okay if I'm harboring a parasite or two, depending on

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Speaker 1: what they are.

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Speaker 3: All right, Well, that was actually my question for you, Kelly,

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Speaker 3: if you had to harbor a parasite, what would be

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Speaker 3: your parasite of choice?

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Speaker 1: All right, Well, so I probably have some demodex mites

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Speaker 1: on my face.

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Speaker 2: I'm okay with that.

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Speaker 1: You know, they might not count as a parasite depending

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Speaker 1: on you know, what they're doing on the given day.

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Speaker 3: Are those the ones that live in your pores and

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Speaker 3: climb out? And there was uncertainty at whether or not

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Speaker 3: they had anuses or if they just exploded when they

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Speaker 3: got filled up.

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Speaker 1: That's right, but they do have anuses. Science figured that

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Speaker 1: out recently. Way to go science.

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Speaker 3: What's better that they're taking a dump on your face?

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Speaker 3: They're exploding on your face? I don't know. I don't

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Speaker 3: feel great about either option.

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Speaker 1: Yeah, I think in the end, you know, the waste

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Speaker 1: ends up on your face either way. So Daniel almost

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Speaker 1: spit his coffee out there.

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Speaker 2: It's just great.

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Speaker 3: How do you know we're talking about biology because it's

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Speaker 3: poop on your face in the first five minutes.

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Speaker 2: That's right, this is a chilly lead episode.

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Speaker 1: I don't know that we'll get to cannibalism today though,

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Speaker 1: so that's too bad.

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Speaker 3: See. Yeah, I'll do my best to bring us there.

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Speaker 2: Yeah, okay, all right.

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Speaker 1: You know, I guess I wouldn't be too upset if

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Speaker 1: I had one or two pinworms. I wouldn't mind having

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Speaker 1: a small load of pinworms because they probably wouldn't hurt

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Speaker 1: me that much.

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Speaker 3: Pinworms aren't those the ones that at night crawl out

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Speaker 3: and like make you itch in uncomfortable places?

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Speaker 1: Yeah, I mean, no, parasite is good, right, Like that

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Speaker 1: would defy the definition of parasite. I'm trying to pick

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Speaker 1: something that would be least bad, and pinworms are probably it.

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Speaker 1: Although not a lot of adults get pinworms.

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Speaker 2: What about you? Oh man, you're making a lot of

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Speaker 2: curse faces today. I wish we did video.

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Speaker 3: There is no parasite I would be happy with. Yes, absolutely, no,

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Speaker 3: that was an answer. Yes, that's my answer. It just

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Speaker 3: creeps me out. It just bothers me to imagine like

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Speaker 3: something living inside of me, treating me like a cave

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Speaker 3: or like a habitat or something like. No, I would

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Speaker 3: just like I would get a rusty spoon and dig

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Speaker 3: it out.

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Speaker 1: Okay, hold on, is this a question of magnitude? Because

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Speaker 1: you have billions of bacteria living in your gut doing

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Speaker 1: exactly what you just described.

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Speaker 3: Katrina is convinced to me that they are part of me.

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Speaker 3: I contain multitudes, I am multitudes.

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Speaker 1: Why can't the demodex and the pinworms be part of

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Speaker 1: your multitudes?

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Speaker 3: Not invited to the party. No, okay, No, there's a

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Speaker 3: fuzzy but bright line between the microbial invaders and then

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Speaker 3: non microbial invaders. Maybe it's just because I'm married to

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Speaker 3: a microbiologist and not a parasologist. Do you think Zach

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Speaker 3: would be happy having parasites within him?

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Speaker 2: Absolutely not.

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Speaker 1: But but so one of the things that made me

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Speaker 1: interested in microbiome science initially was this idea that there's

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Speaker 1: a connection between the brain and the gut, and that

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Speaker 1: microbes sometimes release neurotransmitters that.

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Speaker 2: Can speak to you, know, speak, I'm being.

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Speaker 1: Super anthromorphic here, but influence influence, Like you know, there

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Speaker 1: are nerves that go from your brain to your gut,

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Speaker 1: and the neurotransmitters released by those microbes, you know, might

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Speaker 1: be influencing how we feel about certain things. And so

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Speaker 1: I became super interested in this idea that the way

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Speaker 1: that we respond to the world might be influenced by

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Speaker 1: the things that are living inside of us. And my

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Speaker 1: advisor at the University of California, Davis Andy C who

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Speaker 1: is amazing I adore him. One day was like, Kelly,

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Speaker 1: have you heard about toaso plasma gandhi. It's a parasite

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Speaker 1: that you can get from your cat that changes your behavior.

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Speaker 1: And in a very early Listener Questions episode, we talked

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Speaker 1: about like how good the science is, what we know

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Speaker 1: about that, so you can look for that. But that

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Speaker 1: started me on my journey being like interested in how

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Speaker 1: parasites impact behavior.

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Speaker 2: And so today we're going to talk about you know,

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Speaker 2: what I spent a decade.

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Speaker 1: It wasn't supposed to be that long, what I spent

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Speaker 1: a decade working on, And this is.

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Speaker 3: All the research we're going to talk about today already published.

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Speaker 1: Yes, because I think my collaborators would appreciate if the

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Speaker 1: two papers that we haven't quite finished yet, we're.

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Speaker 2: Not highlighted on the episode.

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Speaker 1: I don't care, but they are, you know, still hoping

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Speaker 1: to get tenures. So I will I will not mention

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Speaker 1: those in press or in prep results.

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Speaker 3: But yeah, I do agree, that's super fascinating, and it

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Speaker 3: makes a lot of sense that the things living inside

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Speaker 3: of us don't just live inside of us. They influence us.

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Speaker 3: They change the way our bodies work, and that includes

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Speaker 3: potentially changing our behavior because we are these biological machines

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Speaker 3: and the decisions we make are not divorced from that, right,

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Speaker 3: they're completely influenced by that. But still, I find it

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Speaker 3: okay to imagine that my microbiome is influencing the decisions

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Speaker 3: I make in the way I perceive the world. But

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Speaker 3: I do feel hijacked if there's like some critter living

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Speaker 3: inside me that's forcing me to like eat that second donut.

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Speaker 1: Yeah, well, so I think there's a difference in goal

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Speaker 1: in some cases, you know. So like I would like

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Speaker 1: to think that a lot of you are my grow

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Speaker 1: biome is in sync with you. You know, the microbiome

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Speaker 1: wants you to thrive, so that they can thrive. But

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Speaker 1: for a lot of the systems that I've ended up

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Speaker 1: working in, the host needs.

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Speaker 2: To die for the parasite to thrive.

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Speaker 1: And so when we're looking at manipulation, which is what

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Speaker 1: I sort of specialized in grad school, which is an

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Speaker 1: instance where the host's behavior is changing in a way

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Speaker 1: that's driven by the parasite in a way that's usually

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Speaker 1: bad for the host but good for the parasite. You know,

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Speaker 1: that's that's very different than what you're imagining. But folks

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Speaker 1: might remember that we did a zombie ant episode a

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Speaker 1: little while back, And what I love about these systems

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Speaker 1: is that often parasites are changing behaviors of their hosts

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Speaker 1: in ways that we couldn't replicate in a lab like

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Speaker 1: and by way I mean neuroscientists, you know, So like ants,

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Speaker 1: they've got these simple little brains relative to humans, you know,

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Speaker 1: but we still couldn't get the ants to do these

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Speaker 1: like series of behaviors that this fungus, like operating the

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Speaker 1: ant by remote control, can get the ant to do.

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Speaker 1: And so you know, through the process of natural selection,

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Speaker 1: this fungus has essentially acquired the ability to control ant behavior,

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Speaker 1: and it you know, in a very anthropomorphic sense. It

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Speaker 1: knows neuroscience better than we do, and so I love

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Speaker 1: these systems as a way to you know, maybe jumpstart

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Speaker 1: our understanding of how brains work by like studying what

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Speaker 1: these parasites have essentially learned about how brains work over

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Speaker 1: evolutionary history. And so I get super excited about, you know,

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Speaker 1: using parasites as tools to understand how brains work. Although,

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Speaker 1: as we'll discover over the course of this episode, neuroscience

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Speaker 1: baffles me, and so I mostly focus on the behavior

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Speaker 1: stuff and then collaborate with neuroscientists.

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Speaker 3: All right, So today we're not talking about the things

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Speaker 3: living in Daniel's gut or toxoplasmi or zombie ants or

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Speaker 3: any of that kind of stuff. What is the system

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Speaker 3: that you and ten years of your life.

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Speaker 1: Exploring, oh Man, Okay, So in Baja California, in southern California,

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Speaker 1: in estuarys so. Estuaries are areas where the ocean is

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Speaker 1: coming in and there's a freshwater system meeting the ocean.

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Speaker 1: So it's where freshwater and saltwater are mixing. They tend

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Speaker 1: to be super productive areas where like baby fish are

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Speaker 1: growing and sharks will come in to eat.

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Speaker 2: Some food, and there's a lot of crabs and stuff

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Speaker 2: like that. They're super productive systems. They are these tiny

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Speaker 2: little fish. They are silvery.

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Speaker 1: They're you know, like maybe the adults are a bit

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Speaker 1: bigger than the length of your maybe middle finger, but

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Speaker 1: they're not as big as like your whole hand, so

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Speaker 1: they're you know, somewhere in between.

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Speaker 2: They're pretty small. They're pretty drab.

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Speaker 1: The males will sometimes have some yellow coloration during the

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Speaker 1: breeding season, but in general they're just like these silvery,

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Speaker 1: kind of drabfish.

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Speaker 3: And they're called killyfish, killyfish, not kellyfish, not killfish, killy fish, killyfish.

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Speaker 3: What does that mean? A?

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Speaker 2: I don't know. I don't know. Why are they called

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Speaker 2: killy fish?

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Speaker 3: You only spent ten years studying it and never thought,

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Speaker 3: why are they have this silly name?

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Speaker 1: Well, stuff doesn't always mean stuff. You know, that was

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Speaker 1: really articulate of me. I don't I don't think it's

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Speaker 1: I don't know that it means anything.

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Speaker 3: See, it's of uncertain origin, but it's likely to have

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Speaker 3: come from the Dutch kill for a small stream.

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Speaker 1: Nah, if you say so.

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Speaker 3: So these sillily named fish.

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Speaker 1: Yeah, So, Actually, when I met Zach the person who

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Speaker 1: would eventually become my husband. He asked me what I

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Speaker 1: studied and I said killy fish. And he said, you

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Speaker 1: study kelly fish and I said no, no, killyfish, and

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Speaker 1: for a while left that he called me kelly fish,

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Speaker 1: which is kind of cute. But anyway, so these are

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Speaker 1: super abundant fish. They're social, so they they're you know,

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Speaker 1: you off and find them in big schools. And Kevin

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Speaker 1: Lafferty and Kimo Morris in the nineties they notice that

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Speaker 1: if you walk around in the estuaries and you look

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Speaker 1: into all of these like channels, you see schools of

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Speaker 1: these fish swimming by, but they're really obvious, Like there

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Speaker 1: are other schools of fish that will swim by and

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Speaker 1: you sort of like don't really notice them. But when

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Speaker 1: the chilly fish swim by, they start doing all of

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Speaker 1: these weird behaviors. It's like they're dancing through the water.

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Speaker 1: They'll like break the surface of the water and you'll

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Speaker 1: see these obvious ripples and then they'll be all these

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Speaker 1: flashes of silver because they're they're shooting forward, they're turning

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Speaker 1: on their sides, they're rubbing against things, they're contorting in

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Speaker 1: the shape of s they're just doing all of these

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Speaker 1: like really conspicuous behaviors that the other fish species didn't

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Speaker 1: seem to be doing. And then you bring a bunch

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Speaker 1: of fish back into the lab and you survey what's

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Speaker 1: happening in the estuaries, and you discover that the California

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Speaker 1: chillifish have a bunch of parasites on their brain, which

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Speaker 1: makes you wonder, is that what's going on?

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Speaker 3: So is that the reason they began studying this fish?

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Speaker 3: Were they the first people to study this fish, or

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Speaker 3: is this like a well known model fish in the community.

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Speaker 1: A bunch of people have studied this fish, but not

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Speaker 1: in relation to the fact that it had a brain

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Speaker 1: infecting parasite. Because it's a superabundant fish in these super

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Speaker 1: productive ecosystems, people have studied other things about them, like

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Speaker 1: how the heck do these fish survive the fact that

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Speaker 1: when the ocean goes out and the river is still

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Speaker 1: coming in, the salinity goes from like, you know, almost

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Speaker 1: completely fresh water, and then when the ocean comes in

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Speaker 1: it's almost completely saltwater? How do they survive that? But

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Speaker 1: a lot of people hadn't been studying the parasite stuff.

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Speaker 3: Because I don't know if it's widely appreciated. But in biology,

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Speaker 3: we have like these model systems where we don't study

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Speaker 3: things in the wild. We have like a few things

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Speaker 3: that we grow in the lab and study in detail.

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Speaker 3: You know, mice and fruitflies and all sorts of stuff.

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Speaker 3: And I wonder, like what makes an animal suitable to

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Speaker 3: be selected? But these are being studied in the wild, right,

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Speaker 3: So it's because of their interesting behaviors and these fascinating questions, right,

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Speaker 3: not because they're quick to grow or they eat something

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Speaker 3: easy or anything.

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Speaker 2: Yeah, right, So I hate these guys.

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Speaker 1: So so uh, it turns out so mummy chugs, which

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Speaker 1: is Fungilus heteroclitis. I study Fungilius parva pinnis, but a

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Speaker 1: closely related species on the opposite coast is very easy

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Speaker 1: to study in the lab.

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Speaker 2: This is a model species.

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Speaker 1: We've got the genome, we've got a bunch of genetic tools.

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Speaker 1: You can grow them up super easy. But fungilis part

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Speaker 1: of a pinnis You bring into the lab and it

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Speaker 1: is really hard to keep them from dying, which is

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Speaker 1: crazy because they live in these environments where the salinity

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Speaker 1: is changing. You'd like they survive all of these extremes.

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Speaker 1: You'd think you bring them in the lab where life

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Speaker 1: is easy, they would.

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Speaker 2: Thrive, and they do not. And I don't know why.

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Speaker 1: And I like, literally years of my PhD was figuring

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Speaker 1: out how to keep them happy in the lab. And

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Speaker 1: that's probably why they're not a model organism, because they're

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Speaker 1: little jerks. You think about them at home at night,

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Speaker 1: and they start dying in the lab.

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Speaker 3: All right. So these guys Lafferdy and Morris notice these

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Speaker 3: fascinating behaviors and they studied these fish and what did

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Speaker 3: they learn about them?

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Speaker 1: Okay, well, so they brought the fish into the lab

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Speaker 1: and they were like, oh my gosh, the brains of

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Speaker 1: these fish are like carpeted by this parasite on their brain.

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Speaker 1: Like a thousand parasites on the brain of an adult

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Speaker 1: is pretty typical.

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Speaker 2: Eight thousand can happen sometimes too.

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Speaker 1: So there are these tiny little like cysts, these tiny

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Speaker 1: little balls. They almost could look like their little glass balls.

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Speaker 1: And this is a trematod parasite. So a trematoad parasite

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Speaker 1: that you might have heard of is schistosoma. Mansonite causes shistosomiasis.

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Speaker 1: This is a problem in places like Africa. This parasite

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Speaker 1: is also a trematoid parasite, not necessarily particularly closely related

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Speaker 1: to that one, but this is the only other trematode

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Speaker 1: you're likely to have heard of, and it has a

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Speaker 1: complex life cycle. And let's go through the life cycle

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Speaker 1: because it helps you understand why this parasite might want

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Speaker 1: to make the fish behave conspicuously.

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Speaker 3: And this is the life cycle of the fish, or

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Speaker 3: of the parasite, or the harmonious combination.

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Speaker 2: Of the parasite.

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Speaker 1: All right, and I'm gonna start calling the parasite Youha,

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Speaker 1: because you have blurcis California asis is way too much

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Speaker 1: to say every time.

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Speaker 3: All right, so tell us about Uha's lifestyle.

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Speaker 1: Okay, So youh accidentally gets consumed by California horn snails

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Speaker 1: that live in the salt marshes. Bad news for the snails.

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Speaker 1: The snails get castrated.

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Speaker 2: By the parasite. What I know, it's crazy.

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Speaker 3: Chemically or like surgically, I mean, are we losing bits

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Speaker 3: of the body here or are they just becoming deactivated?

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Speaker 1: Well, okay, so all of the gonads, I'm not quite

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Speaker 1: sure how you're imagining this, but the gonads are.

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Speaker 3: All you don't want to know how I'm imagining.

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Speaker 1: Yeah, no, I didn't ask you to explain it. And

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Speaker 1: so the gonads are inside of the snail. All of

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Speaker 1: the gonad tissue ends up being taken up by parasite tissues.

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Speaker 1: The parasite start replicating, replicating, replicating, replicating, replicating, and they

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Speaker 1: produce a stage that will swim out from the snail

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Speaker 1: to go off in search of fish.

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Speaker 3: This is nightmare fuel already, Kelly.

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Speaker 1: It is, and these snails can still live for like

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Speaker 1: a decade or more with this parasite. And when the

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Speaker 1: tide comes in in the summer, up to two thousand

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Speaker 1: of the free swimming stages of this parasite can emerge

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Speaker 1: from the snail to go off in search of fish.

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Speaker 1: It's crazy, and okay, parasites have social lives, all right.

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Speaker 2: So look, I'm gonna be honest everybody.

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Speaker 1: This is gonna be a little bit of a ranty

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Speaker 1: episode because I love this parasite and I've just spent

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Speaker 1: a decade like falling in love with its weirdness.

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Speaker 3: Okayyi, this warning is fifteen minutes too late, Kelly.

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Speaker 1: Guys and Daniel tried to get me on track before

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Speaker 1: the start of this episode. He's like, Kelly, I can

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Speaker 1: tell you're gonna get ranty. Let's focus, and I'm here.

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Speaker 1: I am being like, sorry, Daniel.

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Speaker 3: All right, ran away really quick.

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Speaker 2: Okay.

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Speaker 1: So, once you're inside of a snail and you've taken

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Speaker 1: control of a gonad, there are other trematodes that would

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Speaker 1: like to come in and usurp the gonad that you're

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Speaker 1: living in. And so you have Lurcis Californian sas and

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Speaker 1: other trematode species out in the estuary make a stage

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Speaker 1: called a soldier, and the soldier is essentially just like

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Speaker 1: a giant mouth that patrols the snail, and if another

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Speaker 1: stage comes in, it will go. At this stage in

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Speaker 1: their life, they're essentially just giant bags of fluid, and

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Speaker 1: so it will like try to pop the other bags

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Speaker 1: of fluid so that they can't come in and take

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Speaker 1: control of the snail gonad. And so anyway, they've got

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Speaker 1: reproductive stages that are like making this free swimming stage

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Speaker 1: of the parasite reproducing, reproducing, reproducing, and then they're making

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Speaker 1: a bunch of soldiers that are patrolling the snail to

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Speaker 1: keep everything safe.

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Speaker 2: It's just absolutely amazing to me.

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Speaker 3: That there's this like grand battle for the snail gonad exactly, yes, incredible.

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Speaker 3: And so these parasites are working together, they're like cooperating

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Speaker 3: with each other against the snail and against competing parasites.

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Speaker 1: Yes, but they're also they're reproducing asexually, so they're like

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Speaker 1: all clones. So it's like the exact same individual clone clone, clone,

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Speaker 1: clone clone, but some of them look like soldiers, some

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Speaker 1: of them look like reproductives. But like if you were

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Speaker 1: to sequence them genetically, they're all like the same.

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Speaker 3: All right, So it's like the snail gonad hive. Mind. Ye,

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Speaker 3: that sounds like the title of.

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Speaker 2: A book I'd like to read, sure, yeah, or the

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Speaker 2: book I'd like to write.

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Speaker 1: And so all right, when the tide comes in in

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Speaker 1: the summers, when the water is nice and warm, thousands

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Speaker 1: of these parasites leave the snail and each one of

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Speaker 1: them has a very low probability of finding the fish,

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Speaker 1: and they only live for like twenty four hours. They're

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Speaker 1: like little sacks of energy and they're gonna run out

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Speaker 1: real fast. But if they do encounter the fish, we

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Speaker 1: think what happens is they burrow through the fish's skin,

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Speaker 1: they find a nerve and they follow that nerve up

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Speaker 1: to the fish's brain and then they go on top

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Speaker 1: of the brain and they form a cyst on the brain,

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Speaker 1: so they're not in the brain tissue. They're like resting

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Speaker 1: on top of the brain.

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Speaker 3: And why do they want to be on top of

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Speaker 3: the brain.

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Speaker 2: Ah, there's a couple of different ideas there.

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Speaker 1: So one of the ideas, and this was like a

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Speaker 1: very early idea, is that if you're on top of

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Speaker 1: the brain, you're kind of protected from the immune response,

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Speaker 1: because if the brain's immune system overreacts, then that could

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Speaker 1: be really.

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Speaker 2: Bad for the fish. That could kill the fish.

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Speaker 1: The fish could start like swimming on its side, then

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Speaker 1: it could get eaten by another fish. And so by

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Speaker 1: being in an area where the host can't allow the

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Speaker 1: immune system to attack too strongly, you sort of increase

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Speaker 1: your odds of survival.

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Speaker 2: But it could also be because it's.

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Speaker 1: A pretty good place if you're going to be trying

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Speaker 1: to manipulate behavior, that's a good location from which to

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Speaker 1: do that.

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00:19:33,600 --> 00:19:36,560
Speaker 3: Yeah, that makes sense. And so there are multiple of

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Speaker 3: these parasites crawling up the fish nerve to the brain.

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Speaker 3: Are they all working in tandem like they did in

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Speaker 3: the snail gonet. Are they now fighting each other for

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Speaker 3: who gets to like ratitude drive this fish?

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Speaker 1: That's a great question, so hard to say. We think

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Speaker 1: that they are working together because usually you see signs

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Speaker 1: of competition between parasites. But when we studied this, we

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Speaker 1: saw some evident that they were cooperating. And so the

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00:20:02,240 --> 00:20:04,680
Speaker 1: way that we measured this was we looked at the

401
00:20:04,880 --> 00:20:09,160
Speaker 1: volume of the parasites. As the density of parasites increased.

402
00:20:09,400 --> 00:20:11,720
Speaker 1: So usually what you see is that as you get

403
00:20:11,800 --> 00:20:15,119
Speaker 1: more and more parasites crammed into the same size of

404
00:20:15,160 --> 00:20:18,480
Speaker 1: a space, they start getting smaller, and that's probably because

405
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Speaker 1: they're competing for food resources. But what we saw was

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Speaker 1: that the more parasites you got crammed onto the brain

407
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Speaker 1: of a fish, the bigger the parasites.

408
00:20:28,320 --> 00:20:29,919
Speaker 3: Seemed to get because they're cooperating.

409
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Speaker 1: Yeah, which suggested to us maybe they're secreting some compound

410
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Speaker 1: that suppresses the immune system, or they're creating some compound

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Speaker 1: that manipulates behavior, and the more of them that are present,

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Speaker 1: the less each one needs to create in order to

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Speaker 1: accomplish the same goal.

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Speaker 3: So even though they're not identical, they can still cooperate.

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Speaker 2: Maybe so these were fish that were caught in the wild.

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Speaker 1: This was just an observational study, So this is indirect

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Speaker 1: evidence that maybe they are cooperating, and we didn't see

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Speaker 1: the same thing happening when we look at trematodes that

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00:21:01,520 --> 00:21:04,639
Speaker 1: we're living in their liver. So it looks like, you know,

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Speaker 1: maybe there's some cooperation happening. We don't know for sure.

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Speaker 3: All Right, these ideas have parasited my brain and they

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Speaker 3: are now gratituding me to suggest that we should take

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Speaker 3: a break, so everybody can go off and cleanse their

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Speaker 3: mind from snail gonads, and when we'll come back, we'll

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Speaker 3: discover what these parasites do to these poor little killyfish. Okay,

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Speaker 3: we're back. Welcome to the Kelly Rants about Parasites episode.

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Speaker 3: So you've been telling us about how these parasites grow

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Speaker 3: in the snail gonads and then crawl up the nerve

429
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Speaker 3: into the brains of these killyfish and work together to

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Speaker 3: influence them. But you're also talking about this nineteen ninety

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Speaker 3: six paper by Lafferty and Morris, the sort of the

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Speaker 3: seminole work on this. What did they find initially about

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Speaker 3: how these parasites affected the behavior of these fish.

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Speaker 1: Yeah, but in order to understand the results of the

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Speaker 1: Laffarty and Morris study, you need to understand where the

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Speaker 1: parasites have to get after they're in the fish.

437
00:22:20,960 --> 00:22:23,040
Speaker 3: Oh wait, the fish is not the end of the cycle.

438
00:22:23,160 --> 00:22:23,680
Speaker 3: There's more.

439
00:22:24,080 --> 00:22:25,560
Speaker 2: There's more, there's more.

440
00:22:25,720 --> 00:22:28,400
Speaker 3: The nightmare continues, people, it does, it does.

441
00:22:28,600 --> 00:22:30,440
Speaker 1: Okay, So all right, so you've got like a bunch

442
00:22:30,440 --> 00:22:33,680
Speaker 1: of parasites on the brains of the fish. But actually

443
00:22:33,920 --> 00:22:35,879
Speaker 1: the last host that the parasite needs to get to

444
00:22:36,400 --> 00:22:37,720
Speaker 1: are predatory birds.

445
00:22:38,320 --> 00:22:40,960
Speaker 2: And so once a California killyfish gets eaten by a.

446
00:22:40,960 --> 00:22:45,040
Speaker 1: Predatory bird, the digestive juices in the predatory birds start

447
00:22:45,119 --> 00:22:47,520
Speaker 1: breaking down the fish. That breaks down the cysts that

448
00:22:47,600 --> 00:22:50,720
Speaker 1: the parasites are in. The parasites break out of the cysts,

449
00:22:51,080 --> 00:22:54,800
Speaker 1: they find love, they find a mate, they produce eggs.

450
00:22:55,160 --> 00:22:57,840
Speaker 3: So being eaten by the bird is bad for the fish,

451
00:22:57,960 --> 00:22:59,920
Speaker 3: but good for the parasite exactly.

452
00:23:00,440 --> 00:23:03,639
Speaker 1: Yes, the parasite cannot complete its life cycle unless the

453
00:23:03,800 --> 00:23:05,160
Speaker 1: fish gets eaten by a bird.

454
00:23:05,240 --> 00:23:08,400
Speaker 2: And if the fish gets eaten by a shark, that's bad.

455
00:23:08,320 --> 00:23:10,119
Speaker 1: For the parasites. They have to get eaten in a

456
00:23:10,280 --> 00:23:12,760
Speaker 1: certain way. There are wrong ways to get eaten and

457
00:23:12,880 --> 00:23:13,760
Speaker 1: right ways to get eaten.

458
00:23:13,920 --> 00:23:16,760
Speaker 3: I gotta say, these parasites are bad engineers. This whole

459
00:23:16,840 --> 00:23:19,080
Speaker 3: thing is every time I hear about a parasite life cycle,

460
00:23:19,119 --> 00:23:23,399
Speaker 3: it's some ridiculously complicated Rube Goldberg machine where everything has

461
00:23:23,440 --> 00:23:24,240
Speaker 3: to go just right.

462
00:23:24,680 --> 00:23:27,159
Speaker 1: Yeah, well, in another episode, we should talk about the

463
00:23:27,160 --> 00:23:29,600
Speaker 1: evolution of these life cycles, because we think that they

464
00:23:29,680 --> 00:23:32,960
Speaker 1: came about because like, you know, so say it started

465
00:23:33,000 --> 00:23:35,280
Speaker 1: at the snail, and you got the parasites that leave

466
00:23:35,359 --> 00:23:37,240
Speaker 1: the snail, and maybe they were going off in search

467
00:23:37,280 --> 00:23:39,879
Speaker 1: of another snail. The idea is that so many of

468
00:23:39,960 --> 00:23:42,920
Speaker 1: them were getting eaten by fish it made more sense

469
00:23:42,960 --> 00:23:45,119
Speaker 1: to capture fish as a host in your life cycle

470
00:23:45,680 --> 00:23:48,240
Speaker 1: than to you know, just keep getting eaten by fish.

471
00:23:48,280 --> 00:23:51,639
Speaker 1: And in this way complexity arose, so you know, this

472
00:23:52,200 --> 00:23:54,800
Speaker 1: complexity might be better than what was happening before.

473
00:23:54,920 --> 00:23:57,280
Speaker 3: It's also the kind of example that makes me just

474
00:23:57,359 --> 00:23:59,920
Speaker 3: like sort of squish up my eyebrows when somebody says

475
00:24:00,200 --> 00:24:03,280
Speaker 3: nature is so obviously designed, because I'm like, nobody would

476
00:24:03,359 --> 00:24:05,280
Speaker 3: design this. This is a mess.

477
00:24:05,720 --> 00:24:09,320
Speaker 2: This is a mess, it really is. It's wild, all right.

478
00:24:09,400 --> 00:24:11,359
Speaker 3: So now they're happy that they're in these birds and

479
00:24:11,359 --> 00:24:13,560
Speaker 3: they've killed these poor chilly fish by feeding them to

480
00:24:13,640 --> 00:24:14,240
Speaker 3: these birds.

481
00:24:14,840 --> 00:24:17,679
Speaker 1: Then what happens, okay, and then when the bird poops,

482
00:24:17,920 --> 00:24:20,320
Speaker 1: they poop the parasite eggs out into the salt marsh,

483
00:24:20,359 --> 00:24:23,280
Speaker 1: where the snails accidentally eat the eggs and the cycle

484
00:24:23,320 --> 00:24:23,760
Speaker 1: starts again.

485
00:24:24,280 --> 00:24:25,760
Speaker 2: So that is the life sign.

486
00:24:25,800 --> 00:24:28,520
Speaker 3: Oh my gosh. Wow. All right, so it really is

487
00:24:28,560 --> 00:24:28,880
Speaker 3: a loop.

488
00:24:29,040 --> 00:24:30,000
Speaker 2: It really is a loop.

489
00:24:30,359 --> 00:24:33,119
Speaker 3: Snails eat them, they grow in the gonads, then they

490
00:24:33,240 --> 00:24:35,639
Speaker 3: crawl up the fish into the brain influence. The fish

491
00:24:35,840 --> 00:24:38,479
Speaker 3: get eaten by birds, and then the birds poop them

492
00:24:38,520 --> 00:24:40,920
Speaker 3: out and they're eaten by snails and the cycle continues.

493
00:24:41,200 --> 00:24:42,359
Speaker 2: Yes, right, okay.

494
00:24:42,600 --> 00:24:45,920
Speaker 1: So Kevin Lafferty and Chemo Morris were out in the

495
00:24:46,160 --> 00:24:49,560
Speaker 1: estuaris in southern California and they were looking at these

496
00:24:49,640 --> 00:24:52,960
Speaker 1: California killyfish populations, which they knew they had a bunch

497
00:24:52,960 --> 00:24:54,200
Speaker 1: of parasites on their brains.

498
00:24:54,600 --> 00:24:56,800
Speaker 2: And they saw these fish just like.

499
00:24:57,119 --> 00:24:59,760
Speaker 1: Doing all of these weird, conspicuous behaviors, and they knew

500
00:25:00,200 --> 00:25:03,119
Speaker 1: that this parasite had to get to birds next. So

501
00:25:03,240 --> 00:25:06,520
Speaker 1: they thought to themselves, are all of those weird behaviors

502
00:25:06,600 --> 00:25:09,320
Speaker 1: that the fish are doing things that they're doing to

503
00:25:09,400 --> 00:25:11,800
Speaker 1: try to draw the attention of the predatory birds, so

504
00:25:11,880 --> 00:25:14,280
Speaker 1: that the predatory birds will eat the fish that are

505
00:25:14,320 --> 00:25:19,040
Speaker 1: behaving conspicuously. So they went to a population that doesn't

506
00:25:19,080 --> 00:25:23,080
Speaker 1: have the parasite so that they could get naturally uninfected fish.

507
00:25:23,440 --> 00:25:25,440
Speaker 3: Are there populations that don't have the parasite?

508
00:25:25,960 --> 00:25:26,160
Speaker 2: Yes?

509
00:25:26,680 --> 00:25:27,119
Speaker 3: Why is that?

510
00:25:27,480 --> 00:25:30,680
Speaker 1: So there's populations that have the parasite and populations that don't,

511
00:25:30,840 --> 00:25:33,679
Speaker 1: and they differ in actually kind of a lot of ways.

512
00:25:34,160 --> 00:25:36,920
Speaker 1: So the way you get a population that doesn't have

513
00:25:37,080 --> 00:25:40,600
Speaker 1: the parasite usually is that the population becomes landlocked in

514
00:25:40,720 --> 00:25:43,560
Speaker 1: some way. So for example, on the campus of the

515
00:25:43,680 --> 00:25:47,159
Speaker 1: University of California, Santa Barbara, there is a lagoon that

516
00:25:47,359 --> 00:25:52,840
Speaker 1: has California killeyfish in it and because it isn't tidally influenced.

517
00:25:52,359 --> 00:25:53,360
Speaker 2: Or maybe for some other reason.

518
00:25:53,400 --> 00:25:55,520
Speaker 1: I don't know a lot about snails, but for whatever reason,

519
00:25:55,760 --> 00:25:59,560
Speaker 1: there's not snails in there, and so this environment doesn't

520
00:25:59,560 --> 00:26:03,119
Speaker 1: have the snaw. Without the snails, you don't get the parasite,

521
00:26:03,160 --> 00:26:05,520
Speaker 1: you don't get the life cycle. But you also don't

522
00:26:05,600 --> 00:26:08,560
Speaker 1: have tides, which means the fish aren't like you know,

523
00:26:08,680 --> 00:26:10,720
Speaker 1: going out into the ocean. Sometimes they're not comming. Like

524
00:26:10,800 --> 00:26:13,560
Speaker 1: the whole system is different in a bunch of ways.

525
00:26:13,680 --> 00:26:16,359
Speaker 1: And so these fish differ not only in that they

526
00:26:16,440 --> 00:26:19,080
Speaker 1: don't have the parasite, they also differ in a lot

527
00:26:19,160 --> 00:26:21,879
Speaker 1: of like their daily activities, the predators that they encounter,

528
00:26:22,400 --> 00:26:23,400
Speaker 1: blah blah, blah, blah blah.

529
00:26:23,440 --> 00:26:25,800
Speaker 3: And immediately this makes me wonder if they're a good

530
00:26:25,840 --> 00:26:28,879
Speaker 3: control sample, right, because they're different, not just in the

531
00:26:28,920 --> 00:26:30,639
Speaker 3: fact that they don't have the parasite, but in all

532
00:26:30,760 --> 00:26:34,000
Speaker 3: these other ways. And somebody out there might be thinking

533
00:26:34,480 --> 00:26:37,280
Speaker 3: that's bad science. But my reaction is like, well, this

534
00:26:37,440 --> 00:26:40,320
Speaker 3: is where the experimental science comes in, right, and understanding

535
00:26:40,359 --> 00:26:43,239
Speaker 3: those differences and can you draw conclusions and what can

536
00:26:43,320 --> 00:26:47,119
Speaker 3: you do to quantify your uncertainties about them? So what

537
00:26:47,280 --> 00:26:50,159
Speaker 3: kind of conclusions could they draw from this other sample,

538
00:26:50,240 --> 00:26:51,399
Speaker 3: a slightly different fish.

539
00:26:51,960 --> 00:26:55,080
Speaker 1: Well, so they were very clear about the limitations in

540
00:26:55,119 --> 00:26:57,000
Speaker 1: the study. They you know, they pointed out, it's a

541
00:26:57,040 --> 00:27:00,240
Speaker 1: different population, it differs for a variety of reasons. This

542
00:27:00,320 --> 00:27:03,399
Speaker 1: should be the start of our studies in this system,

543
00:27:03,600 --> 00:27:06,119
Speaker 1: not the end of our studies in this system. But

544
00:27:06,600 --> 00:27:07,920
Speaker 1: I'm going to tell you about the rest of the

545
00:27:07,960 --> 00:27:09,760
Speaker 1: study that they did, and then I'm going to tell

546
00:27:09,760 --> 00:27:13,680
Speaker 1: you that like two decades later, I did the follow

547
00:27:13,760 --> 00:27:17,719
Speaker 1: up work to address this problem.

548
00:27:18,600 --> 00:27:20,960
Speaker 3: As is often the case, the nuance is lost and

549
00:27:21,040 --> 00:27:23,120
Speaker 3: the bigger story sort of dominates the lore.

550
00:27:23,720 --> 00:27:25,920
Speaker 1: Yeah, I'm gonna jump ahead a little bit and tell

551
00:27:25,920 --> 00:27:28,960
Speaker 1: you that this paper has been cited over seven hundred

552
00:27:29,040 --> 00:27:32,440
Speaker 1: times and continues to clock a bunch of citations. And

553
00:27:32,600 --> 00:27:36,080
Speaker 1: my paper that was the boring study that was like

554
00:27:36,200 --> 00:27:39,760
Speaker 1: super painstaking, is not getting anywhere near that many citations.

555
00:27:39,800 --> 00:27:41,840
Speaker 1: But anyway, it's still interesting and you're gonna have to

556
00:27:41,880 --> 00:27:46,639
Speaker 1: listen to it, everybody, thank you, so, all right, So

557
00:27:46,880 --> 00:27:49,480
Speaker 1: they got fish from a population without the parasites. Yea,

558
00:27:49,760 --> 00:27:52,199
Speaker 1: they got fish from a population that had the parasites,

559
00:27:52,480 --> 00:27:55,520
Speaker 1: but they also had a bunch of other parasites, because

560
00:27:55,720 --> 00:27:59,199
Speaker 1: the fish in these systems, they're not just infected by

561
00:27:59,240 --> 00:28:02,200
Speaker 1: the parasite on their they're infected by something like seven

562
00:28:02,480 --> 00:28:03,359
Speaker 1: other truma toad.

563
00:28:03,320 --> 00:28:03,959
Speaker 2: Parasites as well.

564
00:28:04,040 --> 00:28:04,600
Speaker 3: Oh my god.

565
00:28:05,040 --> 00:28:07,520
Speaker 2: Yeah, they're just like riddled with paras lousy with parasites,

566
00:28:07,800 --> 00:28:09,320
Speaker 2: lousy with parasites. All right.

567
00:28:09,359 --> 00:28:11,280
Speaker 1: So they brought them into the lab and what they

568
00:28:11,400 --> 00:28:14,080
Speaker 1: noticed was that the fish that had parasites on their

569
00:28:14,119 --> 00:28:18,400
Speaker 1: brain were doing about three to four fold more conspicuous

570
00:28:18,440 --> 00:28:21,720
Speaker 1: behaviors than the fish from the population without the parasites,

571
00:28:22,320 --> 00:28:25,000
Speaker 1: So they were doing these conspicuous behaviors a lot more often.

572
00:28:25,640 --> 00:28:30,200
Speaker 1: And then they set up enclosures in a lagoon where

573
00:28:30,640 --> 00:28:34,000
Speaker 1: the fish would be out in these enclosures, and predatory

574
00:28:34,080 --> 00:28:36,879
Speaker 1: birds could wade in and eat whatever fish they wanted

575
00:28:37,040 --> 00:28:40,280
Speaker 1: and then come back out again. And then after about

576
00:28:40,320 --> 00:28:42,040
Speaker 1: fifty percent of the fish had been eaten or something,

577
00:28:42,080 --> 00:28:44,200
Speaker 1: they went out and they looked to see which fish

578
00:28:44,240 --> 00:28:46,040
Speaker 1: had been eaten and which fish were left behind.

579
00:28:46,280 --> 00:28:48,680
Speaker 3: So these enclosures paint me a picture of them. I

580
00:28:48,840 --> 00:28:52,160
Speaker 3: was imagining first that like sectioned off various parts of

581
00:28:52,320 --> 00:28:54,960
Speaker 3: the lagoon. But are these things open from the top?

582
00:28:55,120 --> 00:28:56,320
Speaker 3: Why did the birds have to wade in?

583
00:28:56,920 --> 00:28:59,320
Speaker 1: So these were along the shoreline, and it was a

584
00:28:59,480 --> 00:29:02,840
Speaker 1: net that sort of went out from the shoreline, traveled

585
00:29:02,840 --> 00:29:05,040
Speaker 1: along the shoreline, and then came back to the shoreline.

586
00:29:05,080 --> 00:29:07,600
Speaker 1: So it had like three netted sides, and they did

587
00:29:07,680 --> 00:29:10,400
Speaker 1: that twice, and one side they covered so that they

588
00:29:10,440 --> 00:29:14,120
Speaker 1: could just measure how often the fish were just sort

589
00:29:14,120 --> 00:29:17,200
Speaker 1: of like escaping from the net. And then the fish

590
00:29:17,280 --> 00:29:20,600
Speaker 1: could either just sort of drop from the top in

591
00:29:20,920 --> 00:29:23,920
Speaker 1: if they wanted, or they could walk along the beach

592
00:29:24,040 --> 00:29:24,720
Speaker 1: and wade in.

593
00:29:25,240 --> 00:29:26,640
Speaker 2: Oh, I see along that way.

594
00:29:27,080 --> 00:29:29,600
Speaker 3: So the death from swooping down to gobble your lunch

595
00:29:29,680 --> 00:29:30,880
Speaker 3: is still an option, yep.

596
00:29:30,840 --> 00:29:33,280
Speaker 1: Still an option, okay. And so what they found was

597
00:29:33,400 --> 00:29:36,680
Speaker 1: that the fish that had more parasites were more likely

598
00:29:36,760 --> 00:29:38,720
Speaker 1: to be eaten. And the way they inferred that was

599
00:29:38,760 --> 00:29:42,280
Speaker 1: when they did the dissections afterwards. They would have expected

600
00:29:42,360 --> 00:29:44,800
Speaker 1: to see, you know, something like ten fish with a

601
00:29:44,880 --> 00:29:47,400
Speaker 1: thousand parasites on their brain, but they didn't see any

602
00:29:47,440 --> 00:29:49,360
Speaker 1: fish with a thousand parasites on their brain. Most of

603
00:29:49,400 --> 00:29:52,000
Speaker 1: the fish that were left had very few parasites on

604
00:29:52,000 --> 00:29:54,600
Speaker 1: their brain. And so they end up concluding that the

605
00:29:54,760 --> 00:29:57,600
Speaker 1: more parasites you have on the brain, the more conspicuous

606
00:29:57,640 --> 00:29:59,680
Speaker 1: behaviors you do, and the more likely you are to

607
00:29:59,720 --> 00:30:01,120
Speaker 1: be e and by predatory birds.

608
00:30:01,400 --> 00:30:03,360
Speaker 3: And I feel like that's a story I've heard before,

609
00:30:03,480 --> 00:30:06,560
Speaker 3: that parasites manipulate host behavior makes it more likely for

610
00:30:06,640 --> 00:30:08,960
Speaker 3: them to be eaten. Was this like the first time

611
00:30:09,000 --> 00:30:11,480
Speaker 3: that had been observed in detail? Was this a new

612
00:30:11,600 --> 00:30:13,560
Speaker 3: story just in this animal or more.

613
00:30:13,480 --> 00:30:17,000
Speaker 1: Broadly, this was not the first time, like, you know,

614
00:30:17,080 --> 00:30:20,080
Speaker 1: since the seventies, I think people had been talking about this,

615
00:30:20,280 --> 00:30:22,719
Speaker 1: but this was one of the first times it had

616
00:30:22,800 --> 00:30:26,360
Speaker 1: been well studied in a vertebrate and one of the

617
00:30:26,400 --> 00:30:29,480
Speaker 1: first times there was a really elegant experiment that showed

618
00:30:29,760 --> 00:30:33,720
Speaker 1: that not only was the parasite associated with the behavior

619
00:30:33,800 --> 00:30:38,160
Speaker 1: that seemed intuitively like it really should be increasing risk

620
00:30:38,640 --> 00:30:41,480
Speaker 1: for the host, but also then they showed that, like, yeah,

621
00:30:41,520 --> 00:30:45,040
Speaker 1: the predatory birds are actually eating the infected fish. The

622
00:30:45,120 --> 00:30:48,280
Speaker 1: authors were like really good about explaining all of the caveats,

623
00:30:48,480 --> 00:30:50,720
Speaker 1: like all of the limitations of the study, and like

624
00:30:50,880 --> 00:30:54,040
Speaker 1: this paper got me. You know, I spent the next

625
00:30:54,120 --> 00:30:56,680
Speaker 1: decade following up on this paper. I found this study

626
00:30:56,760 --> 00:30:59,960
Speaker 1: super exciting, and I moved to Santa Barbara for two

627
00:31:00,240 --> 00:31:03,160
Speaker 1: years to study underneath the lab that did this work.

628
00:31:03,400 --> 00:31:03,600
Speaker 3: Wow.

629
00:31:03,960 --> 00:31:06,960
Speaker 2: Yeah, this is like a now classic example of manipulation.

630
00:31:07,360 --> 00:31:09,800
Speaker 3: And in their first paper, do they come up with

631
00:31:09,960 --> 00:31:13,160
Speaker 3: a causal mechanism to explain this or is it more

632
00:31:13,280 --> 00:31:17,000
Speaker 3: just correlational? More parasites means more behavior, and therefore we're

633
00:31:17,080 --> 00:31:19,200
Speaker 3: inferring that the parasites are causing the behavior.

634
00:31:19,400 --> 00:31:20,200
Speaker 2: It's correlational.

635
00:31:20,880 --> 00:31:23,560
Speaker 1: Yeah, and so there's another parasite that they quantify that

636
00:31:23,880 --> 00:31:27,480
Speaker 1: is living in the liver, and they look for correlations

637
00:31:27,560 --> 00:31:31,520
Speaker 1: between this liver trematode and conspicuous behaviors as well, and

638
00:31:31,600 --> 00:31:34,360
Speaker 1: they find some correlations, but the correlations are stronger with

639
00:31:34,440 --> 00:31:38,160
Speaker 1: the brain parasite, and so they hypothesize that from its

640
00:31:38,240 --> 00:31:43,280
Speaker 1: location in the brain, this parasite is probably hijacking behavior,

641
00:31:43,360 --> 00:31:45,560
Speaker 1: and so there's probably something about being in the brain

642
00:31:45,640 --> 00:31:48,480
Speaker 1: that helps the parasite do that. But you know, since

643
00:31:48,520 --> 00:31:52,040
Speaker 1: they hadn't actually done experiments on mechanisms, they leave that

644
00:31:52,200 --> 00:31:55,720
Speaker 1: to future work, and their post doc Jenny Shaw, actually

645
00:31:55,760 --> 00:31:58,040
Speaker 1: would go ahead and follow up on that, which way

646
00:31:58,160 --> 00:31:59,760
Speaker 1: will talk about a little bit later in.

647
00:31:59,800 --> 00:32:03,280
Speaker 3: The r tradition of leaving the hard questions to future work,

648
00:32:04,360 --> 00:32:07,560
Speaker 3: as we all do in our papers. Ooh, that's important

649
00:32:07,720 --> 00:32:10,640
Speaker 3: weakness in my study. I'm going to say, that's future work.

650
00:32:11,080 --> 00:32:13,200
Speaker 2: Yeah, well, you know, you can't do everything all at once.

651
00:32:13,600 --> 00:32:15,920
Speaker 3: No, you certainly can't. I do that all the time.

652
00:32:16,240 --> 00:32:18,320
Speaker 3: But I guess that leaves us open to the possibility

653
00:32:18,640 --> 00:32:21,040
Speaker 3: that the parasites are not causing this behavior, but there's

654
00:32:21,080 --> 00:32:25,440
Speaker 3: some third unknown thing which is causing both the parasites

655
00:32:25,520 --> 00:32:28,080
Speaker 3: and the behavior, for example, which would induce a correlation

656
00:32:28,200 --> 00:32:28,520
Speaker 3: as well.

657
00:32:29,040 --> 00:32:29,640
Speaker 2: Yes, right.

658
00:32:29,720 --> 00:32:32,440
Speaker 1: Okay, So first of all, there's the problem of them

659
00:32:32,480 --> 00:32:35,200
Speaker 1: coming from different populations and the populations differing in a

660
00:32:35,240 --> 00:32:38,080
Speaker 1: lot of ways. Second, there's the problem that not all

661
00:32:38,240 --> 00:32:41,600
Speaker 1: of the parasites in the wild fish were quantified. It

662
00:32:41,680 --> 00:32:44,920
Speaker 1: could be some other parasite or some combination of parasites

663
00:32:44,960 --> 00:32:47,960
Speaker 1: that we're causing the problem. And so this is not

664
00:32:48,120 --> 00:32:54,000
Speaker 1: an ideal study design, as noted by the authors. Right, Ideally,

665
00:32:54,080 --> 00:32:56,840
Speaker 1: what you'd want to do is, you know, get fish

666
00:32:57,040 --> 00:32:59,720
Speaker 1: from a population that has like an evolutionary history with

667
00:32:59,760 --> 00:33:02,520
Speaker 1: the pairs site, bring them into the lab, like maybe

668
00:33:02,600 --> 00:33:05,200
Speaker 1: hatch them in the lab, grow them up in the lab,

669
00:33:05,400 --> 00:33:08,440
Speaker 1: infect some of them with the parasite, and a lot

670
00:33:08,480 --> 00:33:11,480
Speaker 1: of folks when they infect fish with parasites, they'll infect

671
00:33:11,560 --> 00:33:16,360
Speaker 1: them like once with like five thousand parasites, whereas actually,

672
00:33:16,440 --> 00:33:19,440
Speaker 1: when they're in nature, they start acquiring parasites like almost

673
00:33:19,480 --> 00:33:21,880
Speaker 1: as soon as they hatch, and they acquire like two

674
00:33:22,080 --> 00:33:24,280
Speaker 1: or three every day. And you can imagine a brain

675
00:33:24,320 --> 00:33:27,880
Speaker 1: would respond very differently to like getting yeah, like slammed

676
00:33:27,920 --> 00:33:30,440
Speaker 1: with five thousand parasites and one day, you know, relative

677
00:33:30,480 --> 00:33:33,320
Speaker 1: to picking up a few every day. So yeah, ideally

678
00:33:33,400 --> 00:33:35,840
Speaker 1: you'd hatch fish in a lab, infect them a little

679
00:33:35,840 --> 00:33:38,640
Speaker 1: bit every day, leave some fish as controls where they

680
00:33:38,640 --> 00:33:41,840
Speaker 1: don't get infected, and then observe how their behaviors change

681
00:33:41,840 --> 00:33:42,280
Speaker 1: over time.

682
00:33:42,440 --> 00:33:45,080
Speaker 3: And that gives us some more direct answer to this question,

683
00:33:45,320 --> 00:33:47,680
Speaker 3: because we're inducing the effect, so we're not open to

684
00:33:47,720 --> 00:33:50,680
Speaker 3: the possibility that something else is causing both the parasite

685
00:33:50,720 --> 00:33:53,480
Speaker 3: and the behavior. That's right, all right, So let's take

686
00:33:53,480 --> 00:33:55,120
Speaker 3: a break and when we come back, we'll hear all

687
00:33:55,160 --> 00:34:01,840
Speaker 3: about Kelly's painstaking slog through through the questions of the killyfish.

688
00:34:21,640 --> 00:34:23,279
Speaker 3: All right, we're back, and we've sort of set up

689
00:34:23,320 --> 00:34:26,000
Speaker 3: the question. Now we understand what the killyfish is and

690
00:34:26,120 --> 00:34:29,160
Speaker 3: the life cycle of this parasite, what people had studied,

691
00:34:29,200 --> 00:34:31,880
Speaker 3: the sort of clickbaity result that's gotten a lot of attention,

692
00:34:32,239 --> 00:34:34,719
Speaker 3: and now Kelly, as is her wont is going to

693
00:34:34,760 --> 00:34:37,880
Speaker 3: pour cold water all over all that understanding.

694
00:34:38,719 --> 00:34:41,239
Speaker 1: Since you said clickbaity, you know, Kevin Lafferty, one of

695
00:34:41,239 --> 00:34:43,400
Speaker 1: the authors, is a good friend of mine, so I

696
00:34:43,400 --> 00:34:46,160
Speaker 1: don't feel like he clickbaited it. He was very clear

697
00:34:46,200 --> 00:34:48,520
Speaker 1: about the limitations, but it took off and had a

698
00:34:48,600 --> 00:34:49,239
Speaker 1: life of its own.

699
00:34:49,560 --> 00:34:52,000
Speaker 3: Right now, it sounds like they were responsible and clear

700
00:34:52,080 --> 00:34:54,920
Speaker 3: about the limitations and didn't overstate their conclusions.

701
00:34:55,160 --> 00:34:57,640
Speaker 2: Yes, perfect, thank you. Okay, But as is.

702
00:34:57,680 --> 00:34:59,640
Speaker 3: Often the case, if you have nuance in your paper,

703
00:34:59,680 --> 00:35:02,520
Speaker 3: that's some times overlooked in the coverage. Yes, even if

704
00:35:02,520 --> 00:35:03,479
Speaker 3: it's not the author's fault.

705
00:35:03,640 --> 00:35:05,640
Speaker 2: Yeah, yes, right, that absolutely happened. Okay.

706
00:35:06,040 --> 00:35:09,640
Speaker 1: So, working with Ryan Heckinger and oven Overly, we decided

707
00:35:09,680 --> 00:35:12,480
Speaker 1: that we were going to try to do a bit

708
00:35:12,520 --> 00:35:14,600
Speaker 1: of a better design to try to nail down exactly

709
00:35:14,719 --> 00:35:17,080
Speaker 1: what this brain infecting parasite was doing. And so what

710
00:35:17,200 --> 00:35:20,160
Speaker 1: we did was we went out to an estuary and

711
00:35:20,840 --> 00:35:23,319
Speaker 1: during the full moon when the killy fish breed over

712
00:35:23,400 --> 00:35:26,000
Speaker 1: the summer, we went out there and we said.

713
00:35:26,360 --> 00:35:29,279
Speaker 2: Excuse me, mister and missus killy fish, may we please

714
00:35:29,360 --> 00:35:30,120
Speaker 2: have some gammeats?

715
00:35:30,640 --> 00:35:33,359
Speaker 3: Why did the killy fish only breed during the full moon?

716
00:35:33,400 --> 00:35:36,040
Speaker 3: I mean, I yet, it's romantic, but like the system

717
00:35:36,160 --> 00:35:40,720
Speaker 3: was complicated enough without introduced like astronomical coincidences.

718
00:35:41,080 --> 00:35:41,520
Speaker 2: I don't know.

719
00:35:42,000 --> 00:35:43,719
Speaker 1: It would have been great if we could have gone

720
00:35:43,719 --> 00:35:45,840
Speaker 1: out there more often. But it's synced up to.

721
00:35:45,880 --> 00:35:49,160
Speaker 3: The moon, all right, So there's some were wolf connection

722
00:35:49,280 --> 00:35:50,120
Speaker 3: here we don't know about.

723
00:35:50,360 --> 00:35:51,239
Speaker 2: That's right, that's right.

724
00:35:51,520 --> 00:35:54,439
Speaker 1: But I was like six months pregnant at the time,

725
00:35:54,520 --> 00:35:56,520
Speaker 1: and so we were like, you know, very gently getting

726
00:35:56,520 --> 00:35:58,960
Speaker 1: the fish to release their gam meats into a bucket

727
00:35:59,040 --> 00:36:02,080
Speaker 1: for us so that we could fertilize eggs. And I

728
00:36:02,280 --> 00:36:04,319
Speaker 1: was trying really hard to not puke into the gam

729
00:36:04,360 --> 00:36:07,279
Speaker 1: meat bucket, as like so many science moms before me

730
00:36:07,480 --> 00:36:09,239
Speaker 1: have had to try to avoid doing.

731
00:36:09,680 --> 00:36:11,920
Speaker 3: So you're pleasuring these fish by hand to get them

732
00:36:11,960 --> 00:36:13,080
Speaker 3: to produce these gam meats.

733
00:36:13,280 --> 00:36:16,279
Speaker 2: Nice, That's not how I'd put it, But all right, this.

734
00:36:16,440 --> 00:36:17,840
Speaker 3: Is the glamorous work of science.

735
00:36:17,880 --> 00:36:19,640
Speaker 2: It's the glamorous work of ecology.

736
00:36:19,760 --> 00:36:23,640
Speaker 1: But so we were able to actually hatch a bunch

737
00:36:23,680 --> 00:36:26,480
Speaker 1: of fish in the lab, and then we went out

738
00:36:26,680 --> 00:36:30,280
Speaker 1: and we collected snails and we figured out which snails

739
00:36:30,320 --> 00:36:34,200
Speaker 1: were infected by HU and you can get them to

740
00:36:34,560 --> 00:36:37,440
Speaker 1: repeatedly give you the same, you know, genotypes of the

741
00:36:37,480 --> 00:36:39,760
Speaker 1: parasites over and over and over again. But we collected

742
00:36:39,760 --> 00:36:40,960
Speaker 1: a bunch of the snails so we could get a

743
00:36:40,960 --> 00:36:43,799
Speaker 1: bunch of different genotypes of the parasites. We kept those

744
00:36:43,840 --> 00:36:47,040
Speaker 1: snails in the lab. Unfortunately, we had to get snails

745
00:36:47,120 --> 00:36:50,200
Speaker 1: from like one estuary down. We had hoped to get

746
00:36:50,239 --> 00:36:53,760
Speaker 1: everything from the same estuary. That's a long story, but anyway,

747
00:36:53,840 --> 00:36:55,640
Speaker 1: so we were able to get our parasites, able to

748
00:36:55,680 --> 00:36:58,520
Speaker 1: get our fish. They were hatched, and then twice a

749
00:36:58,600 --> 00:37:03,919
Speaker 1: week every week we did controlled infections in their tanks. Wow.

750
00:37:04,239 --> 00:37:07,479
Speaker 1: And so we would like extract some parasites, we would

751
00:37:07,520 --> 00:37:09,520
Speaker 1: put it in a vial, we would slowly lower the

752
00:37:09,600 --> 00:37:11,760
Speaker 1: viol into the tank, and we'd leave it in there overnight,

753
00:37:11,960 --> 00:37:15,279
Speaker 1: so they slowly built up infections. And at one point

754
00:37:15,320 --> 00:37:17,640
Speaker 1: we went out into the wild and we collected wildfish

755
00:37:17,800 --> 00:37:20,440
Speaker 1: and we were able to confirm that we had about

756
00:37:20,600 --> 00:37:23,880
Speaker 1: the same number of parasites in our fish as you

757
00:37:24,040 --> 00:37:27,200
Speaker 1: found in the wildfish at the same time. So we

758
00:37:27,400 --> 00:37:29,920
Speaker 1: had sort of mimicked what was happening in the wild,

759
00:37:30,520 --> 00:37:32,440
Speaker 1: which was a ton of work good for us.

760
00:37:33,200 --> 00:37:35,560
Speaker 3: And again, the goal of mimicking what's happening in the

761
00:37:35,640 --> 00:37:38,040
Speaker 3: wild is to have a little bit more control over it.

762
00:37:38,080 --> 00:37:40,040
Speaker 3: And you have some fish with the parasites and some

763
00:37:40,160 --> 00:37:42,920
Speaker 3: fish without the parasites to get a better understanding of

764
00:37:43,040 --> 00:37:44,680
Speaker 3: like the actual mechanism here.

765
00:37:45,000 --> 00:37:47,400
Speaker 1: Well, yeah, and because if we eventually want them to

766
00:37:47,520 --> 00:37:49,440
Speaker 1: have like two thousand parasites on their brain, like they

767
00:37:49,440 --> 00:37:51,560
Speaker 1: would have in the wild. We didn't want to slam

768
00:37:51,640 --> 00:37:53,759
Speaker 1: them with two thousand parasites all at once because that

769
00:37:53,760 --> 00:37:55,640
Speaker 1: could kill them, and so we were trying to sort

770
00:37:55,640 --> 00:37:57,920
Speaker 1: of slowly build it up so that what was happening

771
00:37:57,960 --> 00:38:00,759
Speaker 1: in the wild was also happening in the last and

772
00:38:00,920 --> 00:38:03,560
Speaker 1: so we did that. We did have a slightly higher

773
00:38:03,680 --> 00:38:06,279
Speaker 1: density because our fish didn't grow quite as fast as

774
00:38:06,320 --> 00:38:07,080
Speaker 1: the wildfish.

775
00:38:07,719 --> 00:38:09,680
Speaker 2: We don't know why that's annoying.

776
00:38:12,320 --> 00:38:15,600
Speaker 3: Why won't biol as you'd just obey my commands, right,

777
00:38:16,000 --> 00:38:17,160
Speaker 3: I know, I know.

778
00:38:17,280 --> 00:38:20,040
Speaker 1: And so anyway, then we measured the behavior of the

779
00:38:20,080 --> 00:38:23,200
Speaker 1: fish at three, seven and eight months of age, and

780
00:38:23,320 --> 00:38:25,240
Speaker 1: we found out that there were a bunch of different

781
00:38:25,280 --> 00:38:28,640
Speaker 1: conspicuous behaviors that were measuring. The effect that was the

782
00:38:28,680 --> 00:38:31,640
Speaker 1: most pronounced was that the fish that had parasites on

783
00:38:31,760 --> 00:38:33,480
Speaker 1: their brain darted.

784
00:38:33,200 --> 00:38:36,400
Speaker 2: About twice as much as the control fish. So that

785
00:38:36,640 --> 00:38:37,440
Speaker 2: was the main effect.

786
00:38:37,760 --> 00:38:39,800
Speaker 1: I thought the main effect was going to be scratching,

787
00:38:39,800 --> 00:38:42,759
Speaker 1: because to me, the most obvious conspicuous behavior when you're

788
00:38:42,800 --> 00:38:45,480
Speaker 1: standing on the shoreline is when they flip on their

789
00:38:45,520 --> 00:38:47,840
Speaker 1: sides and the sun reflects off of their belly. That

790
00:38:48,040 --> 00:38:51,400
Speaker 1: really draws my attention. But the behavior that seems to

791
00:38:51,480 --> 00:38:53,520
Speaker 1: be impacted is what we call darting. So this is

792
00:38:53,560 --> 00:38:56,880
Speaker 1: when a fish sort of like out of nowhere, it

793
00:38:56,960 --> 00:38:59,880
Speaker 1: will shoot forward really quick, like something really scared it,

794
00:39:00,280 --> 00:39:02,560
Speaker 1: and then it's like it forgot that it was afraid

795
00:39:02,920 --> 00:39:05,240
Speaker 1: and it just goes back to its normal behavior.

796
00:39:05,760 --> 00:39:06,680
Speaker 2: And it's really weird.

797
00:39:06,760 --> 00:39:09,719
Speaker 1: So darting is a behavior that fish often use when

798
00:39:09,719 --> 00:39:12,760
Speaker 1: a predator is around. But when they dart, they're darting

799
00:39:12,920 --> 00:39:16,080
Speaker 1: like behind a piece of vegetation, or they're like darting

800
00:39:16,200 --> 00:39:18,960
Speaker 1: into like a turbid zone, like you know, there's like

801
00:39:19,080 --> 00:39:21,399
Speaker 1: a plume of sand and they're darting into the middle

802
00:39:21,400 --> 00:39:23,879
Speaker 1: so that they can hide. It's very strange to see

803
00:39:23,920 --> 00:39:27,840
Speaker 1: a fish dart forward and then immediately resume normal movement.

804
00:39:28,520 --> 00:39:31,280
Speaker 1: And so the idea here is that if they dart forward,

805
00:39:31,520 --> 00:39:33,440
Speaker 1: they draw the attention of the predatory bird, and then

806
00:39:33,440 --> 00:39:35,960
Speaker 1: if they're not hiding afterwards, they're very easy to like

807
00:39:36,400 --> 00:39:40,200
Speaker 1: hone in on. Maybe we haven't actually like done videos

808
00:39:40,560 --> 00:39:41,960
Speaker 1: just show that that's exactly what's happening.

809
00:39:42,120 --> 00:39:44,520
Speaker 3: And so there were some categories of behavior you were

810
00:39:44,560 --> 00:39:49,120
Speaker 3: looking for, scratching, darting, et cetera. How did you come

811
00:39:49,200 --> 00:39:51,200
Speaker 3: up with these categories, is there a possibility that there's

812
00:39:51,520 --> 00:39:53,640
Speaker 3: some kind of category of behavior that the fish are

813
00:39:53,680 --> 00:39:57,200
Speaker 3: doing different between the two populations that you didn't think

814
00:39:57,280 --> 00:39:57,800
Speaker 3: to observe.

815
00:39:58,040 --> 00:39:58,759
Speaker 2: Yeah, that's so.

816
00:39:58,920 --> 00:40:02,440
Speaker 1: First of all, in in Lafferty and Morris's paper, they

817
00:40:02,640 --> 00:40:04,600
Speaker 1: watched the fish for a long time. They came up

818
00:40:04,640 --> 00:40:06,839
Speaker 1: with like any category of weird behavior that they could

819
00:40:06,880 --> 00:40:09,640
Speaker 1: think of. That's called like an ethogram, where you watch

820
00:40:09,719 --> 00:40:12,359
Speaker 1: for a long time and you you know, take notes

821
00:40:12,400 --> 00:40:13,920
Speaker 1: on any behaviors that you think are relevant.

822
00:40:14,200 --> 00:40:16,120
Speaker 3: But it feels a little subjective.

823
00:40:15,640 --> 00:40:22,920
Speaker 2: Right, yes, behavior exactly, Yes, it is sort of subjective.

824
00:40:23,239 --> 00:40:27,120
Speaker 1: I'll actually be very interested in what AI does to

825
00:40:27,239 --> 00:40:31,600
Speaker 1: this field, because if you can have computers analyzing everything

826
00:40:31,640 --> 00:40:34,360
Speaker 1: about behavior, it's some you know, is a computer able

827
00:40:34,440 --> 00:40:36,960
Speaker 1: to analyze behavior in a way that's different and maybe

828
00:40:37,040 --> 00:40:40,080
Speaker 1: less subjective than how human eyes do. And there's some

829
00:40:40,200 --> 00:40:42,840
Speaker 1: programs now that analyze behaviors that weren't available when I

830
00:40:42,920 --> 00:40:43,320
Speaker 1: was doing it.

831
00:40:43,600 --> 00:40:45,279
Speaker 3: No, it's still going to be biased, just in a

832
00:40:45,320 --> 00:40:46,560
Speaker 3: way you don't understand as well.

833
00:40:46,920 --> 00:40:47,960
Speaker 2: Yeah, no, you might be right.

834
00:40:48,560 --> 00:40:51,040
Speaker 1: So anyway, so I looked at their ethogram, what what

835
00:40:51,200 --> 00:40:54,200
Speaker 1: behaviors they thought were important and then I watched also

836
00:40:54,320 --> 00:40:56,120
Speaker 1: and looked to see if I was seeing something different.

837
00:40:56,560 --> 00:40:59,960
Speaker 1: And I've also watched fish from a couple of different estuaries,

838
00:41:00,440 --> 00:41:02,080
Speaker 1: so this is not the only study I've done with

839
00:41:02,160 --> 00:41:05,319
Speaker 1: these fish. And so I've spent a lot of time staring.

840
00:41:05,000 --> 00:41:09,440
Speaker 3: At fish, the glamorous work of science.

841
00:41:09,960 --> 00:41:12,040
Speaker 2: That's right, that's right. Maybe I haven't captured all the

842
00:41:12,080 --> 00:41:14,080
Speaker 2: important behaviors, but I feel like I.

843
00:41:14,160 --> 00:41:16,880
Speaker 3: Have all right. And so you saw this darting effect,

844
00:41:17,400 --> 00:41:21,080
Speaker 3: so compare contrast that with the original effect in the earlier.

845
00:41:20,840 --> 00:41:22,080
Speaker 2: Paper less strong.

846
00:41:22,560 --> 00:41:26,000
Speaker 1: So before they didn't see that darting was the behavior

847
00:41:26,080 --> 00:41:29,719
Speaker 1: most strongly associated with this brain infecting parasite, and they

848
00:41:29,800 --> 00:41:32,960
Speaker 1: saw that behaviors were like four times more pronounced in

849
00:41:33,000 --> 00:41:36,480
Speaker 1: their infected fish. So we're seeing a different behavior most

850
00:41:36,480 --> 00:41:40,759
Speaker 1: strongly impacted by the parasite and a lower magnitude. And

851
00:41:40,880 --> 00:41:42,480
Speaker 1: we don't know if that's because it was a different

852
00:41:42,719 --> 00:41:43,600
Speaker 1: population that we.

853
00:41:43,640 --> 00:41:44,239
Speaker 2: Were looking at.

854
00:41:44,440 --> 00:41:47,280
Speaker 1: It could be because the wildfish in the other study

855
00:41:47,760 --> 00:41:51,400
Speaker 1: had a whole community of parasites, and a lot of

856
00:41:51,520 --> 00:41:55,640
Speaker 1: those community of parasites also go to predatory birds. Maybe

857
00:41:55,800 --> 00:41:58,600
Speaker 1: each of those parasites are like manipulating a different part

858
00:41:58,680 --> 00:42:01,959
Speaker 1: of the behavior, or like they're all sharing the cost

859
00:42:02,040 --> 00:42:05,560
Speaker 1: of manipulating. There's a lot of different reasons, but at

860
00:42:05,600 --> 00:42:07,040
Speaker 1: the end of the day, what I found was that

861
00:42:07,120 --> 00:42:10,239
Speaker 1: the effect is a little bit more complicated and a

862
00:42:10,280 --> 00:42:13,080
Speaker 1: little bit smaller than what had been found before.

863
00:42:13,480 --> 00:42:16,880
Speaker 2: So no one cites my work exactly.

864
00:42:19,719 --> 00:42:21,719
Speaker 3: But this was the exact goal of this studies to

865
00:42:21,800 --> 00:42:24,560
Speaker 3: tease this part and try to understand more specifically what

866
00:42:24,719 --> 00:42:27,200
Speaker 3: is the effect of this parasite. Yes, and so the

867
00:42:27,280 --> 00:42:29,560
Speaker 3: answer is that on its own, this parasite is not

868
00:42:29,719 --> 00:42:31,839
Speaker 3: doing everything that the original guy saw.

869
00:42:32,040 --> 00:42:32,920
Speaker 2: That's right, that's right.

870
00:42:33,160 --> 00:42:34,640
Speaker 1: But so let's dive in a little bit to what

871
00:42:34,760 --> 00:42:37,600
Speaker 1: we know about how the parasite might be doing this. Yeah,

872
00:42:37,840 --> 00:42:40,480
Speaker 1: the first thing you usually wonder when you discover that

873
00:42:40,760 --> 00:42:45,040
Speaker 1: a infected organism is getting eaten by another organism more

874
00:42:45,080 --> 00:42:47,880
Speaker 1: often is like, well, is the parasite just debilitating it

875
00:42:48,040 --> 00:42:50,719
Speaker 1: in some way? Like is it just making it slower,

876
00:42:50,960 --> 00:42:53,840
Speaker 1: easier to catch or something? And that doesn't seem to

877
00:42:53,880 --> 00:42:55,320
Speaker 1: be the case. So, first of all, you know, just

878
00:42:55,400 --> 00:42:58,640
Speaker 1: like observations, if you watch these fish, they've got eight

879
00:42:58,800 --> 00:43:01,680
Speaker 1: thousand parasites on the brain. Man, it's like a carpet.

880
00:43:02,120 --> 00:43:05,239
Speaker 1: It's so crazy to see all these parasites. But they're

881
00:43:05,280 --> 00:43:08,000
Speaker 1: not like swimming on their sides, they're not having trouble

882
00:43:08,080 --> 00:43:12,040
Speaker 1: catching their food. They school normally, like they look normal.

883
00:43:12,760 --> 00:43:15,800
Speaker 1: And my friend Laura Nadler, who worked on this system

884
00:43:15,840 --> 00:43:18,759
Speaker 1: as a postdoc, she stuck them in these little metabolic

885
00:43:18,880 --> 00:43:22,640
Speaker 1: chambers and she measured their acute metabolism, so she like,

886
00:43:22,880 --> 00:43:24,399
Speaker 1: you know, got them to swim real fast.

887
00:43:24,480 --> 00:43:26,319
Speaker 2: And I don't really know how you do this kind

888
00:43:26,320 --> 00:43:26,919
Speaker 2: of stuff and fish.

889
00:43:27,040 --> 00:43:29,040
Speaker 3: This is like what they do to Olympic athletes.

890
00:43:28,719 --> 00:43:31,920
Speaker 2: Right, treadmills And yeah, I don't know how you treadmill.

891
00:43:31,560 --> 00:43:33,719
Speaker 3: Is I'm imagining a fish on a treadmill right now?

892
00:43:33,800 --> 00:43:34,680
Speaker 2: Yeah, yeah, yeah.

893
00:43:34,920 --> 00:43:36,600
Speaker 1: She did a bunch of different things to like get

894
00:43:36,680 --> 00:43:39,880
Speaker 1: their like maximum metabolic rate and they're resting metabolic rate

895
00:43:39,920 --> 00:43:40,640
Speaker 1: and blah blah blah.

896
00:43:40,640 --> 00:43:43,040
Speaker 3: Okay, she fed them red bull and stuff like this.

897
00:43:43,480 --> 00:43:45,440
Speaker 2: I'm sure she did. Yeah, I'm sure she got a

898
00:43:45,480 --> 00:43:46,719
Speaker 2: protocol and a permit and all.

899
00:43:46,640 --> 00:43:49,839
Speaker 1: That for that. And what she found, like using our

900
00:43:49,960 --> 00:43:52,479
Speaker 1: fish from our lab experiments where we had like hatched

901
00:43:52,520 --> 00:43:55,000
Speaker 1: them in the lab, infected, some didn't infect others that

902
00:43:55,200 --> 00:43:58,719
Speaker 1: the infected fish, and the uninfected fish had like no

903
00:43:58,880 --> 00:44:01,600
Speaker 1: difference in metabolism, So it doesn't look like having a

904
00:44:01,680 --> 00:44:05,360
Speaker 1: bunch of fish on your brain is that energetically expensive. Like,

905
00:44:05,760 --> 00:44:09,880
Speaker 1: they're pretty efficient at resource extraction when they're on the brain.

906
00:44:09,960 --> 00:44:13,960
Speaker 1: They're like, you know, semi dormant after they finish growing,

907
00:44:14,520 --> 00:44:17,080
Speaker 1: So it doesn't seem like it's that. And their body

908
00:44:17,120 --> 00:44:19,520
Speaker 1: condition is good if you compare them to uninfected fish.

909
00:44:19,600 --> 00:44:22,560
Speaker 1: They have, like their gonads are about the same size

910
00:44:22,600 --> 00:44:25,600
Speaker 1: because ecologists do grow stuff like way gonads, and like

911
00:44:26,000 --> 00:44:28,640
Speaker 1: they seem just as good at having babies. They have

912
00:44:28,920 --> 00:44:31,399
Speaker 1: the same amount of fat reserves. Like, so it doesn't

913
00:44:31,440 --> 00:44:33,880
Speaker 1: seem like they're making them debilitated in any way that

914
00:44:33,960 --> 00:44:34,640
Speaker 1: we can measure.

915
00:44:35,000 --> 00:44:36,720
Speaker 3: Well, what about coming at it from the other direction

916
00:44:36,960 --> 00:44:40,520
Speaker 3: and asking, like, how is the parasite benefiting, because that

917
00:44:40,719 --> 00:44:42,160
Speaker 3: might be the other side of the equation. If the

918
00:44:42,200 --> 00:44:45,880
Speaker 3: parasite is like extracting something specific from the brain or

919
00:44:45,920 --> 00:44:48,560
Speaker 3: from the fish, then maybe you could understand the impact

920
00:44:48,719 --> 00:44:50,160
Speaker 3: of losing that on the fish.

921
00:44:50,760 --> 00:44:53,719
Speaker 1: Uh so, Okay, So the idea would be that, like

922
00:44:54,360 --> 00:44:58,919
Speaker 1: the parasite is extracting like a neurotransmitter or something.

923
00:44:58,960 --> 00:45:01,000
Speaker 3: I don't know what is the benefit to the parasite.

924
00:45:01,080 --> 00:45:03,360
Speaker 2: What do you mean, what is the benefit of the parasite.

925
00:45:02,920 --> 00:45:05,600
Speaker 3: To being on the brain? Like, what is this doing

926
00:45:05,719 --> 00:45:06,719
Speaker 3: there that's helping it?

927
00:45:07,080 --> 00:45:09,440
Speaker 1: Yeah, So usually what the parasites do at this stage

928
00:45:09,520 --> 00:45:12,279
Speaker 1: is they grow a little and then they kind of

929
00:45:12,440 --> 00:45:15,040
Speaker 1: like they reach you know, asymptotic growth. They grow, and

930
00:45:15,080 --> 00:45:17,160
Speaker 1: then they stop growing. And I think they mostly stop

931
00:45:17,239 --> 00:45:20,359
Speaker 1: growing because while they're growing, they're forming a cyst around them,

932
00:45:20,760 --> 00:45:23,040
Speaker 1: and this cyst protects them from the immune system. And

933
00:45:23,120 --> 00:45:26,160
Speaker 1: when that cyst finishes growing, they've sort of run out

934
00:45:26,200 --> 00:45:28,239
Speaker 1: of room to grow, and so that's as big as

935
00:45:28,280 --> 00:45:31,640
Speaker 1: they're going to get. But presumably they can extract some

936
00:45:31,840 --> 00:45:36,600
Speaker 1: resources across the cyst wall and maybe even secrete some

937
00:45:36,719 --> 00:45:40,840
Speaker 1: stuff across the cyst wall. Presumably somebody has looked to

938
00:45:40,880 --> 00:45:45,520
Speaker 1: see what they are sucking up on the brain, but

939
00:45:45,640 --> 00:45:48,000
Speaker 1: I don't think we've looked to see if they're like specifically,

940
00:45:48,800 --> 00:45:50,680
Speaker 1: like I think they're sucking up like nutrients and stuff,

941
00:45:50,680 --> 00:45:52,400
Speaker 1: but I don't know if they're specifically sucking up like

942
00:45:52,760 --> 00:45:55,920
Speaker 1: serotonin to try to mess with brain stuff.

943
00:45:56,080 --> 00:45:58,120
Speaker 3: Because for example, like a tapeworm lives in my gut,

944
00:45:58,360 --> 00:46:00,520
Speaker 3: eat some of my food, I get less food. So

945
00:46:00,640 --> 00:46:03,200
Speaker 3: it's easy to understand from the tapeworms benefit what the

946
00:46:03,239 --> 00:46:06,760
Speaker 3: impact is on me. I don't know. I'm not a parasitologist,

947
00:46:06,840 --> 00:46:10,120
Speaker 3: but it seems like maybe an avenue. So what do

948
00:46:10,239 --> 00:46:14,240
Speaker 3: we know about how these parasites are influencing these fish

949
00:46:14,920 --> 00:46:15,800
Speaker 3: spoiler alert.

950
00:46:16,400 --> 00:46:18,480
Speaker 1: We don't know at the end of the day, but

951
00:46:18,600 --> 00:46:20,279
Speaker 1: we think that what might be happening is that the

952
00:46:20,400 --> 00:46:26,040
Speaker 1: parasite is making it so that the fish doesn't respond

953
00:46:26,760 --> 00:46:29,280
Speaker 1: with as much of a stress response as it should.

954
00:46:29,680 --> 00:46:33,280
Speaker 1: So essentially the parasite is like dampening the stress response.

955
00:46:34,040 --> 00:46:35,680
Speaker 1: And so here's what we think is happening. So there's

956
00:46:35,680 --> 00:46:38,600
Speaker 1: a part of the brain in fish that is usually

957
00:46:38,600 --> 00:46:41,480
Speaker 1: associated with the stress response, and when you look at

958
00:46:41,520 --> 00:46:44,719
Speaker 1: that part of the brain, we see that the typical

959
00:46:45,040 --> 00:46:48,520
Speaker 1: response to the chemicals in the brain in fish when

960
00:46:48,520 --> 00:46:51,759
Speaker 1: they're stressed is much lower when the fish has a

961
00:46:51,800 --> 00:46:55,120
Speaker 1: bunch of parasites in that part of the brain. And

962
00:46:55,280 --> 00:46:58,920
Speaker 1: so that's got us wondering, like if a predatory bird

963
00:46:59,000 --> 00:47:02,560
Speaker 1: is in the area, for example, is maybe what's happening

964
00:47:02,800 --> 00:47:05,120
Speaker 1: is that like uninfected fish would be like.

965
00:47:05,200 --> 00:47:07,080
Speaker 2: Ah predatory bird, I gotta run away.

966
00:47:07,560 --> 00:47:10,320
Speaker 1: But in a fish that has these parasites, are the

967
00:47:10,400 --> 00:47:13,440
Speaker 1: parasites making the fish be like, eh, no, big deal,

968
00:47:13,560 --> 00:47:15,520
Speaker 1: probably not gonna choose me. In fact, actually I'm gonna

969
00:47:15,520 --> 00:47:16,480
Speaker 1: shoot forward really quick.

970
00:47:16,560 --> 00:47:18,000
Speaker 2: Oh look at how cool I am.

971
00:47:18,480 --> 00:47:21,360
Speaker 1: And I should say that we have measured these differences

972
00:47:21,600 --> 00:47:24,880
Speaker 1: in infected and uninfected fish brains, but we have not

973
00:47:25,200 --> 00:47:29,360
Speaker 1: tied these differences to behavior or tied these differences to like,

974
00:47:29,680 --> 00:47:32,120
Speaker 1: you know, fish getting eaten by birds more often. So

975
00:47:32,239 --> 00:47:35,400
Speaker 1: this is just like preliminary observations and how these brains

976
00:47:35,440 --> 00:47:35,960
Speaker 1: look different.

977
00:47:36,520 --> 00:47:38,560
Speaker 3: So all that makes sense, except for the part where

978
00:47:39,040 --> 00:47:42,080
Speaker 3: being less stressed makes them dart more. Because I thought

979
00:47:42,200 --> 00:47:44,640
Speaker 3: darting was a response to like, oh no, I think

980
00:47:44,680 --> 00:47:45,520
Speaker 3: I'm gonna get eaten.

981
00:47:46,120 --> 00:47:48,239
Speaker 1: Yeah, but so so it is a response to oh no,

982
00:47:48,320 --> 00:47:51,480
Speaker 1: I think I'm gonna get eaten, but usually it ends

983
00:47:51,600 --> 00:47:55,040
Speaker 1: in and so I'm going to hide, right, and so,

984
00:47:55,719 --> 00:47:57,799
Speaker 1: but here it's like, oh no, I'm gonna get oh wait,

985
00:47:57,880 --> 00:48:00,920
Speaker 1: oh wait, what was I running from? And there's another

986
00:48:01,000 --> 00:48:03,680
Speaker 1: part of the brain that's associated with locomotion, and you

987
00:48:03,840 --> 00:48:07,239
Speaker 1: tend to find a high density of the parasites there.

988
00:48:07,680 --> 00:48:09,480
Speaker 1: And so I mentioned that you know, the parasites are

989
00:48:09,520 --> 00:48:11,439
Speaker 1: sort of like a carpet on the brain, but they're

990
00:48:11,560 --> 00:48:14,680
Speaker 1: like a carpet, but they also tend to like be

991
00:48:14,840 --> 00:48:16,919
Speaker 1: a little bit more dense in two parts of the brain,

992
00:48:17,320 --> 00:48:20,279
Speaker 1: and one of those parts deals with stress, and one

993
00:48:20,320 --> 00:48:23,840
Speaker 1: of those parts deals with locomotion. And so you know,

994
00:48:24,120 --> 00:48:26,520
Speaker 1: again these are just observations. We haven't linked it to

995
00:48:26,640 --> 00:48:29,040
Speaker 1: behavior yet, but it could be that, like, you know,

996
00:48:29,400 --> 00:48:32,120
Speaker 1: there's some stimulation of the locomotion part of the brain

997
00:48:32,200 --> 00:48:34,239
Speaker 1: to get those fish moving, to get the darts going.

998
00:48:34,680 --> 00:48:36,719
Speaker 1: And then the part where usually they're like and now

999
00:48:36,800 --> 00:48:39,560
Speaker 1: go run and hide is being turned off. So they're

1000
00:48:39,640 --> 00:48:41,480
Speaker 1: moving around, but they're not hiding.

1001
00:48:42,520 --> 00:48:45,719
Speaker 3: Maybe so these fish are just like more chill, they

1002
00:48:45,800 --> 00:48:48,080
Speaker 3: sound like of anything. They might be happier they could be.

1003
00:48:48,400 --> 00:48:52,120
Speaker 1: And so actually part of how we get funding for

1004
00:48:52,280 --> 00:48:55,279
Speaker 1: this system is we say, you know, look, maybe what

1005
00:48:55,360 --> 00:48:58,640
Speaker 1: the parasite is doing is it's secreting some chemical that

1006
00:48:59,000 --> 00:49:03,200
Speaker 1: is suppressed saying stress. Maybe there's like a treatment for

1007
00:49:03,320 --> 00:49:06,480
Speaker 1: anxiety or something that we could find by something that's

1008
00:49:06,480 --> 00:49:08,640
Speaker 1: being secreted by this parasite. There could be a novel

1009
00:49:08,840 --> 00:49:11,880
Speaker 1: compound that we could discover with this parasite.

1010
00:49:11,600 --> 00:49:14,760
Speaker 3: Wasn't ozembic discovered when they were studying like lizard venom

1011
00:49:14,880 --> 00:49:15,600
Speaker 3: or something crazy.

1012
00:49:15,880 --> 00:49:17,280
Speaker 2: You never know, I think.

1013
00:49:17,200 --> 00:49:20,719
Speaker 1: HeLa HeLa monster or venom or something like that. Yeah,

1014
00:49:20,760 --> 00:49:23,560
Speaker 1: you never know where the next treatment's going to be found.

1015
00:49:23,800 --> 00:49:25,680
Speaker 3: Your science could change, Hollywood.

1016
00:49:26,000 --> 00:49:28,479
Speaker 1: That's right, that's right. One of the cool things about

1017
00:49:28,480 --> 00:49:31,239
Speaker 1: studying fish is that if you stick them in a

1018
00:49:31,280 --> 00:49:35,400
Speaker 1: beaker of water, the steroid hormones, which are things like cortisol,

1019
00:49:35,440 --> 00:49:37,719
Speaker 1: which is associated with your stress response, and things like

1020
00:49:37,800 --> 00:49:42,320
Speaker 1: testosterone and estrogen and stuff like that, they leak across

1021
00:49:42,400 --> 00:49:45,439
Speaker 1: the fish's gills and into the water and they'll reach

1022
00:49:45,480 --> 00:49:48,440
Speaker 1: an equilibrium, so the concentration in the water is equal

1023
00:49:48,520 --> 00:49:50,840
Speaker 1: to the concentration in the blood. And you have to

1024
00:49:50,880 --> 00:49:54,440
Speaker 1: do some validating work, but you can repeatedly make measurements

1025
00:49:54,480 --> 00:49:58,160
Speaker 1: of hormones in fish without needing to draw any blood

1026
00:49:58,280 --> 00:50:01,440
Speaker 1: by just putting them in beakers of water. And so

1027
00:50:01,800 --> 00:50:06,080
Speaker 1: I collected cortisol levels from fish repeatedly, and these fish

1028
00:50:06,120 --> 00:50:09,200
Speaker 1: had different levels of parasites on their brain, and we

1029
00:50:09,280 --> 00:50:11,480
Speaker 1: found that the density of parasites on their brain does

1030
00:50:11,640 --> 00:50:15,239
Speaker 1: impact how much cordisol they release, But it wasn't in

1031
00:50:15,360 --> 00:50:17,920
Speaker 1: a like nice, predictable way. And this is when I

1032
00:50:18,040 --> 00:50:23,680
Speaker 1: decided I didn't want to work on hormones and neurotransmitters.

1033
00:50:22,880 --> 00:50:24,800
Speaker 2: Anymore because I had a prediction.

1034
00:50:25,000 --> 00:50:26,680
Speaker 1: And I talked to the experts and I was like,

1035
00:50:26,920 --> 00:50:28,560
Speaker 1: there was supposed to be a straight line up, but

1036
00:50:28,640 --> 00:50:30,759
Speaker 1: instead it made au and they were like, yeah, this

1037
00:50:30,840 --> 00:50:32,879
Speaker 1: stuff never works out the way we think it's gonna

1038
00:50:32,960 --> 00:50:34,440
Speaker 1: and I was like, I'm done.

1039
00:50:35,200 --> 00:50:37,640
Speaker 2: I'm done. I'm not doing this anymore.

1040
00:50:38,120 --> 00:50:41,200
Speaker 3: I've had enough snail gonads. I'm moving on right.

1041
00:50:41,239 --> 00:50:44,680
Speaker 2: I don't even like pipettes, and so I was that

1042
00:50:45,239 --> 00:50:45,680
Speaker 2: was it for me.

1043
00:50:45,840 --> 00:50:49,800
Speaker 3: But that is one of my fears about biology is

1044
00:50:49,920 --> 00:50:53,680
Speaker 3: that you're doomed to working in complex systems. You can

1045
00:50:53,840 --> 00:50:58,279
Speaker 3: never really use reductionism and simplify things because everything you're

1046
00:50:58,320 --> 00:51:01,960
Speaker 3: doing is most interesting in a complex system, which means

1047
00:51:02,120 --> 00:51:05,759
Speaker 3: it might be forever before you actually untangle stuff. It's

1048
00:51:05,800 --> 00:51:08,360
Speaker 3: incredible to me that we've made any progress in biology

1049
00:51:08,480 --> 00:51:08,839
Speaker 3: at all.

1050
00:51:09,400 --> 00:51:11,239
Speaker 1: I have to admit a lot of my friends are

1051
00:51:11,280 --> 00:51:13,920
Speaker 1: working on these kinds of problems, and I am so

1052
00:51:14,080 --> 00:51:16,239
Speaker 1: glad they are, because this is how we get to

1053
00:51:16,320 --> 00:51:20,040
Speaker 1: the bottom of things, like, you know, why are parasites

1054
00:51:20,120 --> 00:51:23,800
Speaker 1: becoming resistant to our drugs, and so like super important questions.

1055
00:51:24,560 --> 00:51:28,000
Speaker 1: I found it really frustrating, and I was like, I can't.

1056
00:51:28,160 --> 00:51:29,400
Speaker 1: I don't think I can keep doing this.

1057
00:51:30,560 --> 00:51:33,200
Speaker 3: I think something that's not widely enough appreciated about how

1058
00:51:33,280 --> 00:51:35,400
Speaker 3: people end up in the science field. To end up

1059
00:51:35,440 --> 00:51:37,600
Speaker 3: in is that you have to be excited about the

1060
00:51:37,640 --> 00:51:40,480
Speaker 3: big questions of the field, but also you have to

1061
00:51:40,560 --> 00:51:43,920
Speaker 3: find the day to day work fun. Yeah, and so

1062
00:51:44,160 --> 00:51:47,520
Speaker 3: many fields are fascinating the questions they ask, but then

1063
00:51:47,560 --> 00:51:49,600
Speaker 3: the day to day work is very different. You know,

1064
00:51:49,680 --> 00:51:52,600
Speaker 3: it's like working in a lab pipetting or you know,

1065
00:51:52,719 --> 00:51:55,080
Speaker 3: making a laser operate well or whatever. And you have

1066
00:51:55,160 --> 00:51:57,680
Speaker 3: to be interested in both sides of it if you're

1067
00:51:57,680 --> 00:51:59,920
Speaker 3: going to spend your life doing it, because it's not

1068
00:52:00,320 --> 00:52:02,719
Speaker 3: every day that you're answering the big questions. Mostly it's

1069
00:52:02,760 --> 00:52:05,279
Speaker 3: the day to day work, and so you've got to

1070
00:52:05,320 --> 00:52:07,759
Speaker 3: find that niche where the craft is also fun.

1071
00:52:08,360 --> 00:52:09,960
Speaker 1: I can't tell you how many days I wanted to

1072
00:52:10,160 --> 00:52:12,600
Speaker 1: hurl that pipette across the lab.

1073
00:52:13,040 --> 00:52:16,120
Speaker 2: I do not enjoy pipetting. I have friends who get

1074
00:52:16,160 --> 00:52:18,839
Speaker 2: in the flow, and I do not. I have no flow.

1075
00:52:19,080 --> 00:52:21,080
Speaker 3: Well, the wonderful thing about humanity is that we're all

1076
00:52:21,160 --> 00:52:24,080
Speaker 3: into different stuff. And so yeah, some of us trapes

1077
00:52:24,120 --> 00:52:27,160
Speaker 3: through rainforests and get their socks wet while studying spiders,

1078
00:52:27,160 --> 00:52:29,080
Speaker 3: and other people look up at the sky and wonder

1079
00:52:29,120 --> 00:52:32,160
Speaker 3: about all of that, and some people like to pipet.

1080
00:52:32,880 --> 00:52:35,360
Speaker 3: So because of that, we have a glorious diversity in

1081
00:52:35,520 --> 00:52:38,000
Speaker 3: all of the science stories that we extract from the universe.

1082
00:52:38,440 --> 00:52:38,719
Speaker 3: We do.

1083
00:52:38,960 --> 00:52:40,759
Speaker 1: And if I may so, you know, I hope that

1084
00:52:40,840 --> 00:52:43,239
Speaker 1: work continues in the system, because this could be the

1085
00:52:43,400 --> 00:52:45,360
Speaker 1: routes to another treatment for anxiety.

1086
00:52:45,680 --> 00:52:48,439
Speaker 2: Maybe this will be helping me a decade down the road,

1087
00:52:48,760 --> 00:52:49,439
Speaker 2: we can hope.

1088
00:52:49,800 --> 00:52:53,080
Speaker 1: But also there are other killy fish species and a

1089
00:52:53,160 --> 00:52:55,560
Speaker 1: bunch of estuaries in North America, And there are other

1090
00:52:55,680 --> 00:52:58,760
Speaker 1: Uplorcus species and a bunch of estuaries in North America.

1091
00:52:59,120 --> 00:53:01,799
Speaker 1: So it might be that similar interactions like this are

1092
00:53:01,920 --> 00:53:05,640
Speaker 1: playing out and a bunch of our super productive ecosystems,

1093
00:53:05,920 --> 00:53:08,640
Speaker 1: so this parasite might be impacting, you know, the flow

1094
00:53:08,719 --> 00:53:13,040
Speaker 1: of energy from aquatic systems to terrestrial systems all throughout

1095
00:53:13,120 --> 00:53:15,680
Speaker 1: North America. And we don't understand this very well. And

1096
00:53:16,200 --> 00:53:18,320
Speaker 1: a lot of people are interested in migratory birds. I

1097
00:53:18,400 --> 00:53:20,279
Speaker 1: think fish are cooler than birds. I'm going to die

1098
00:53:20,360 --> 00:53:23,680
Speaker 1: on that hill. But you know, bird people, you guys

1099
00:53:23,719 --> 00:53:25,960
Speaker 1: are cool too, and so this kind of stuff matters.

1100
00:53:26,200 --> 00:53:28,040
Speaker 3: And that's some of the excitement of science that you

1101
00:53:28,200 --> 00:53:31,520
Speaker 3: never know around which corner or under which snail gonad

1102
00:53:31,760 --> 00:53:34,640
Speaker 3: is going to be some amazing discovery that really changes

1103
00:53:34,760 --> 00:53:37,520
Speaker 3: the world. And it takes somebody like pushing on a

1104
00:53:37,640 --> 00:53:41,120
Speaker 3: question that seems maybe minor and in a corner, but

1105
00:53:41,280 --> 00:53:43,600
Speaker 3: that reveals a thread that you can use to unravel

1106
00:53:43,640 --> 00:53:47,160
Speaker 3: our understanding of something much broader. And when you're doing science,

1107
00:53:47,200 --> 00:53:49,279
Speaker 3: you never know, like, is today the day I'm going

1108
00:53:49,360 --> 00:53:52,440
Speaker 3: to learn something mind blowing? Because there have been days

1109
00:53:52,520 --> 00:53:54,960
Speaker 3: like that in the history of science. We just all

1110
00:53:55,040 --> 00:53:56,600
Speaker 3: hope that one of them is going to happen to us.

1111
00:53:57,440 --> 00:54:00,520
Speaker 2: That's right, Well, thanks for listening to me ramble. Hell everybody,

1112
00:54:00,680 --> 00:54:02,759
Speaker 2: I love this parasite and I.

1113
00:54:02,800 --> 00:54:05,600
Speaker 3: Thought that was interesting, even without any parasites controlling my

1114
00:54:05,719 --> 00:54:07,920
Speaker 3: brain and telling me what defined interesting.

1115
00:54:08,320 --> 00:54:19,480
Speaker 1: Yay. Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio.

1116
00:54:19,719 --> 00:54:20,880
Speaker 2: We would love to hear.

1117
00:54:20,760 --> 00:54:23,239
Speaker 3: From you, We really would. We want to know what

1118
00:54:23,440 --> 00:54:27,120
Speaker 3: questions you have about this extraordinary universe.

1119
00:54:27,239 --> 00:54:30,120
Speaker 1: We want to know your thoughts on recent shows, suggestions

1120
00:54:30,200 --> 00:54:31,120
Speaker 1: for future shows.

1121
00:54:31,280 --> 00:54:33,560
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1122
00:54:33,880 --> 00:54:37,360
Speaker 3: We really mean it. We answer every message. Email us

1123
00:54:37,480 --> 00:54:40,560
Speaker 3: at Questions at Danielankelly dot org, or.

1124
00:54:40,560 --> 00:54:42,640
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1125
00:54:42,760 --> 00:54:46,719
Speaker 1: on x, Instagram, Blue Sky and on all of those platforms.

1126
00:54:46,760 --> 00:54:49,719
Speaker 1: You can find us at d and kuniverse.

1127
00:54:49,920 --> 00:54:51,440
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