Zombie fish

25:00So you can stay vital, stay you. Visit VitalProteins.com to learn more and where to buy. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. Apple Vacations, where your story starts. The Splash into Savings event from Apple Vacations is here. Now through June 25th, save up to$150 on vacation packages, plus instant savings at select resorts in Mexico, the Caribbean, Central America, and top U.S. destinations. Use promo code JUNE26 for these limited-time offers. Start planning today at applevacations.com or contact your travel advisor.

25:34Apple Vacations, where your story starts. Ready to finally clean out your closet? With Trashy, you can donate your clothes, reduce waste, and earn cash rewards. All in one simple step. Just fill a take-back bag, send it in, and get rewards cash back for every bag. And now, with Trashy Unlimited, you get unlimited bags for just$48 your first year. Clean out, donate, earn rewards. Visit Trashy.io to get started.

26:20Okay, we're back. Welcome to the Kelly Rants About Parasites episode. Yay! So you've been telling us about how these parasites grow in the snail gonads and then crawl up the nerve into the brains of these killifish and work together to influence them. But you were also talking about this 1996 paper by Lafferty and Morris, sort of the seminal work on this. What did they find initially about how these parasites affected the behavior of these fish? Yeah, but in order to understand the results of the Lafferty and Morris study, you need to understand where the parasites have to get after they're in the fish.

26:57Oh, wait. The fish is not the end of the cycle? There's more? There's more. There's more. The nightmare continues, people. It does. It does. Okay, so, all right. So you've got like a bunch of parasites on the brains of the fish. But actually, the last host that the parasite needs to get to are predatory birds. Oh. And so once a California killifish gets eaten by a predatory bird, The digestive juices in the predatory bird start breaking down the fish. It breaks down the cysts that the parasites are in. The parasites break out of the cysts. They find love. They find a mate. They produce eggs. So being eaten by the bird is bad for the fish but good for the parasite.

27:36Exactly. Yes, the parasite cannot complete its life cycle unless the fish gets eaten by a bird. And if the fish gets eaten by a shark, that's bad for the parasites. They have to get eaten in a certain way. There are wrong ways to get eaten and right ways to get eaten. I got to say, these parasites are bad engineers. This whole thing is every time I hear about a parasite lifecycle, it's some ridiculously complicated Rube Goldberg machine where everything has to go just right. Yeah. Well, in another episode, we should talk about the evolution of these life cycles because we think that they came about because like, you know, so say it started at the snail and you got the parasites that leave the snail and maybe they were going off in search of another snail.

28:14The idea is that so many of them were getting eaten by fish. It made more sense to capture fish as a host in your life cycle than to just keep getting eaten by fish. And in this way, complexity arose. So this complexity might be better than what was happening before. It's also the kind of example that makes me just sort of squish up my eyebrows when somebody says, nature is so obviously designed. Because I'm like, nobody would design this. This is a mess. This is a mess. It really is. It's wild. All right. So now they're happy that they're in these birds and they've killed these poor killifish by feeding them to these birds.

28:51Then what happens? Okay. And then when the bird poops, they poop the parasite eggs out into the salt marsh where the snails accidentally eat the eggs and the cycle starts again. So that is the life cycle. Oh, my gosh. Wow. All right. So it really is a loop. It really is a loop. Snails eat them. They grow in the gonads. Then they crawl up the fish into the brain, influence the fish, get eaten by birds. And then the birds poop them out and they're eaten by snails. And the cycle continues. Yes. Right. Okay. So Kevin Lafferty and Kimo Morris were out in the estuaries in Southern California. And they were looking at these California killifish populations, which they knew they had a bunch of parasites on their brains.

29:30And they saw these fish just like doing all of these weird conspicuous behaviors. And they knew that this parasite had to get to birds next. So they thought to themselves, are all of those weird behaviors that the fish are doing, things that they're doing to try to draw the attention of the predatory birds so that the predatory birds will eat the fish that are behaving conspicuously? So they went to a population that doesn't have the parasite so that they could get naturally uninfected fish. Are there populations that don't have the parasite? Yes. Why is that? So there's populations that have the parasite and populations that don't.

30:07And they differ in actually kind of a lot of ways. So the way you get a population that doesn't have the parasite usually is that the population becomes landlocked in some way. So for example, on the campus of the University of California, Santa Barbara, there is a lagoon that has California killifish in it. And because it isn't tidally influenced, or maybe for some other reason, I don't know a lot about snails, but for whatever reason, there's not snails in there. And so this environment doesn't have the snails. Without the snails, you don't get the parasite. You don't get the life cycle. But you also don't have tides, which means the fish aren't like, you know, going out into the ocean sometimes.

30:46They're not coming. Like the whole system is different in a bunch of ways. And so these fish differ not only in that they don't have the parasite. They also differ in a lot of like their daily activities, the predators that they encounter, blah, blah, blah, blah, blah. And immediately this makes me wonder if they're a good control sample, right? because they're different not just in the fact that they don't have the parasite, but in all these other ways. And somebody out there might be thinking, that's bad science. But my reaction is like, well, this is where the experimental science comes in, right?

31:16In understanding those differences and can you draw conclusions and what can you do to quantify your uncertainties about them? So what kind of conclusions could they draw from this other sample of slightly different fish? Well, so they were very clear about the limitations in the study. They pointed it out. It's a different population. It differs for a variety of reasons. This should be the start of our studies in this system, not the end of our studies in this system. But I'm going to tell you about the rest of the study that they did. And then I'm going to tell you that like two decades later, I did the follow up work to address this problem.

31:54As is often the case, the nuance is lost and the bigger story sort of dominates the lore. Yeah. I'm going to jump ahead a little bit and tell you that this paper has been cited over 700 times and continues to clock a bunch of citations. And my paper that was the boring study that was like super painstaking is not getting anywhere near that many citations. But anyway, it's still interesting and you're going to have to listen to it, everybody. Thank you. So, all right. So they got fish from a population without the parasites. They got fish from a population that had the parasites, but they also had a bunch of other parasites because the fish in these systems, they're not just infected by the parasite on their brain.

32:36They're infected by, you know, something like seven other trematode parasites as well. Oh my God. Yeah. They're just like riddled with parasites. Lousy with parasites. Lousy with parasites. All right. So they brought them into the lab and what they noticed was that the fish that had parasites on their brain were doing about three to four fold more conspicuous behaviors than the fish from the population without the parasites. So they were doing these conspicuous behaviors a lot more often. And then they set up enclosures in a lagoon where the fish would be out in these enclosures and predatory birds could wade in and eat whatever fish they wanted and then come back out again.

33:15And then after about 50 % of the fish had been eaten or something, they went out and they looked to see which fish had been eaten and which fish were left behind. So these enclosures paint me a picture of them. I was imagining first that they like sectioned off various parts of the lagoon. But are these things open from the top? Why did the birds have to wade in? So these were along the shoreline, and it was a net that sort of went out from the shoreline, traveled along the shoreline, and then came back to the shoreline. So it had like three netted sides, and they did that twice. And one side they covered so that they could just measure how often the fish were just sort of like escaping from the net.

33:52And then the fish could either just sort of drop from the top in if they wanted, or they could walk along the beach and wade in along that way. So the death from above swooping down to gobble your lunch is still an option. Yep, still an option. Okay. And so what they found was that the fish that had more parasites were more likely to be eaten. And the way they inferred that was when they did the dissections afterwards, they would have expected to see, you know, something like 10 fish with a thousand parasites on their brain. But they didn't see any fish with a thousand parasites on their brain.

34:25Most of the fish that were left had very few parasites on their brain. And so they end up concluding that the more parasites you have on the brain, the more conspicuous behaviors you do and the more likely you are to be eaten by predatory birds. And I feel like that's a story I've heard before, that parasites manipulate host behavior, makes it more likely for them to be eaten. Was this like the first time that had been observed in detail? Was this a new story just in this animal or more broadly? This was not the first time. Like, you know, since the 70s, I think people had been talking about this.

34:56But this was one of the first times it had been well studied in a vertebrate. And one of the first times there was a really elegant experiment that showed that not only was the parasite associated with the behavior that seemed intuitively like it really should be increasing risk for the host. But also then they showed that like, yeah, the predatory birds are actually eating the infected fish. The authors were like really good about explaining all of the caveats, like all of the limitations of the study. And like this paper got me, you know, I spent the next decade following up on this paper. I found this study super exciting.

35:34And I moved to Santa Barbara for two years to like study underneath the lab that did this work. Yeah, this is like a now classic example of manipulation. And in their first paper, do they come up with a causal mechanism to explain this? Or is it more just correlational? More parasites means more behavior and therefore we're inferring that the parasites are causing the behavior. It's correlational. Yeah. And so there's another parasite that they quantify that is living in the liver. And they look for correlations between this liver trematode and conspicuous behaviors as well. And they find some correlations, but the correlations are stronger with the brain parasite.

36:12And so they hypothesize that from its location in the brain, this parasite is probably hijacking behavior. And so there's probably something about being in the brain that helps the parasite do that. But, you know, since they hadn't actually done experiments on mechanisms, they leave that to future work. and their postdoc Jenny Shaw actually would go ahead and follow up on that, which we will talk about a little bit later. In the grand tradition of leaving the hard questions to future work, as we all do in our papers. Ooh, that's an important weakness in my study. I'm going to say that's future work.

36:47Yeah, well, you know, you can't do everything all at once. No, you certainly can't. I do that all the time. But I guess that leaves us open to the possibility that the parasites are not causing this behavior, But there's some third unknown thing, which is causing both the parasites and the behavior, for example, which would induce a correlation as well. Yes. Right. OK. So first of all, there's the problem of them coming from different populations and the populations differing in a lot of ways. Second, there's the problem that not all of the parasites in the wild fish were quantified. It could be some other parasite or some combination of parasites that were causing the problem.

37:22And so this is not an ideal study design as noted by the authors. Ideally, what you'd want to do is, you know, get fish from a population that has like an evolutionary history with the parasite, bring them into the lab, like maybe hatch them in the lab, grow them up in the lab, infect some of them with the parasite. And a lot of folks, when they infect fish with parasites, they'll infect them like once with like 5 ,000 parasites. whereas actually when they're in nature, they start acquiring parasites like almost as soon as they hatch and they acquire like two or three every day. And you can imagine a brain would respond very differently to like getting like slammed with 5 ,000 parasites in one day, you know, relative to picking up a few every day.

38:08So yeah, ideally you'd hatch fish in a lab, infect them a little bit every day, leave some fish as controls where they don't get infected and then observe how their behaviors change over time. And that gives us a more direct answer to this question because we're inducing the effect. So we're not open to the possibility that something else is causing both the parasite and the behavior. That's right. All right. So let's take a break. And when we come back, we'll hear all about Kelly's painstaking slog through the questions of the killifish.

38:47Eczema is unpredictable, but you can flare less with EpGliss, a once-monthly treatment for moderate to severe eczema. After an initial four-month or longer dosing phase, about 4 in 10 people taking EpGliss achieved itch relief and clear or almost-clear skin at 16 weeks. And most of those people maintain skin that's still more clear at one year with monthly dosing. EBCLIS, Librikizumab, LBKZ, a 250 milligram per two milliliter injection is a prescription medicine used to treat adults and children 12 years of age and older who weigh at least 88 pounds or 40 kilograms with moderate to severe eczema.

39:18Also called atopic dermatitis that is not well controlled with prescription therapies used on the skin or topicals or who cannot use topical therapies. EBCLIS can be used with or without topical corticosteroids. Don't use if you're allergic to EBCLIS. Allergic reactions can occur that can be severe. Eye problems can occur. Tell your doctor if you have new or worsening eye problems. You should not receive a live vaccine when treated with EpGliss. Before starting EpGliss, tell your doctor if you have a parasitic infection. Ask your doctor about EpGliss and visit epgliss.lily.com or call 1-800-LILY-RX or 1-800-545-5979.

39:47Aging is real. And so are the benefits of adding Vital Proteins Collagen Peptides to your daily routine. Because around the age of 30, your body needs backup to keep your collagen up to help support healthy hair, skin, nails, bones, and joints. Available in the classic collagen peptides, collagen and protein shakes, and new Vital Proteins Collagen Sparkling Waters so you can stay vital, stay you. Visit vitalproteins.com to learn more and where to buy. These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

40:18Apple Vacations, where your story starts. The Splash into Savings event from Apple Vacations is here. Now through June 25th, save up to$150 on vacation packages plus instant savings at select resorts in Mexico, the Caribbean, Central America, and top U.S. destinations. Use promo code JUNE26 for these limited-time offers. Start planning today at AppleVacations.com or contact your travel advisor. Apple Vacations, where your story starts. Ready to finally clean out your closet? With Trashy, you can donate your clothes, reduce waste, and earn cash rewards. All in one simple step. Just fill a take-back bag, send it in, and get rewards cash back for every bag.

41:04And now with Trashy Unlimited, you get unlimited bags for just$48 your first year. Clean out, donate, earn rewards. Visit Trashy.io to get started.

41:28all right we're back and we've sort of set up the question now we understand what the killifish is and the life cycle of this parasite what people had studied the sort of click bitty result that's gotten a lot of attention and now kelly as is her want is going to pour cold water all over all that understanding. Since you said clickbaity, you know, Kevin Lafferty, one of the authors, is a good friend of mine. So, you know, I don't feel like he clickbaited it. He was very clear about the limitations, but it took off and had a life of its own. Right. No, it sounds like they were responsible and clear about the limitations and didn't overstate their conclusions.

42:02Yes. Perfect. Thank you. OK. But as is often the case, if you have nuance in your paper, that's sometimes overlooked in the coverage. Yes. Even if it's not the author's fault. Yeah. Yes. Right. That That absolutely happened. Okay. So working with Ryan Hechinger and Oven Overly, we decided that we were going to try to do a bit of a better design to try to nail down exactly what this brain infecting parasite was doing. And so what we did was we went out to an estuary and during the full moon when the killifish breed over the summer, we went out there and we said, excuse me, Mr. and Mrs. Killifish, may we please have some gametes?

42:37Why did the killifish only breed during the full moon? I mean, I get it's romantic, but like this system was complicated enough without you having to introduce like astronomical coincidences. I don't know. It would have been great if we could have got out there more often, but it's synced up to the moon. All right. So there's some werewolf connection here we don't know about. That's right. That's right. But I was like six months pregnant at the time. And so we were like, you know, very gently getting the fish to release their gametes into a bucket for us so that we could fertilize eggs. And I was trying really hard to not puke into the gamete bucket as like so many science moms before me have had to try to avoid doing.

43:16So you're pleasuring these fish by hand to get them to produce these gametes. Nice. That's not how I'd put it, but all right. This is the glamorous work of science. This is the glamorous work of ecology. But so we were able to actually hatch a bunch of fish in the lab. And then we went out and we collected snails. And we figured out which snails were infected by Yuhaw. And you can get them to repeatedly give you the same, you know, genotypes of the parasites over and over and over again. But we collected a bunch of the snails so we could get a bunch of different genotypes of the parasites. We kept those snails in the lab.

43:52Unfortunately, we had to get snails from like one estuary down. We had hoped to get everything from the same estuary. That's a long story. But anyway, so we were able to get our parasites, able to get our fish. They were hatched. And then twice a week, every week, we did controlled infections in their tanks. And so we would like extract some parasites. We would put it in a vial. We would slowly lower the vial into the tank and we'd leave it in there overnight. So they slowly built up infections. And at one point we went out into the wild and we collected wild fish and we were able to confirm that we had about the same number of parasites in our fish as you found in the wild fish at the same time.

44:33So we had sort of mimicked what was happening in the wild, which was a ton of work. Good for us. And again, the goal of mimicking what's happening in the wild is to have a little bit more control over it. And you have some fish with the parasites and some fish without the parasites to get a better understanding of like the actual mechanism here. Well, yeah. And because if we eventually want them to have like 2 ,000 parasites on their brain like they would have in the wild, we didn't want to slam them with 2 ,000 parasites all at once because that could kill them. And so we were trying to sort of slowly build it up so that what was happening in the wild was also happening in the lab.

45:07And so we did that. We did have a slightly higher density because our fish didn't grow quite as fast as the wild fish. We don't know why. That's annoying. Why won't biology just obey my commands? Right? I know. I know. And so anyway, then we measured the behavior of the fish at three, seven, and eight months of age. And we found out that there were a bunch of different conspicuous behaviors that we were measuring. the effect that was the most pronounced was that the fish that had parasites on their brain darted about twice as much as the control fish so that was the main effect i thought the main effect was going to be scratching because to me the most obvious conspicuous behavior when you're standing on the shoreline is when they flip on their sides and the sun reflects off of their belly that really draws my attention but the behavior that seems to be impacted is what we called darting.

46:00So this is when a fish sort of like out of nowhere, it will shoot forward really quick, like something really scared it. And then it's like, it forgot that it was afraid and it just goes back to its normal behavior. And it's really weird. So darting is a behavior that fish often use when a predator is around. But when they dart, they're darting like behind a piece of vegetation or they're like darting into like a turbid zone. Like, you know, there's like a plume of sand and they're darting into the middle so that they can hide. It's very strange to see a fish dart forward and then immediately resume normal movement.

46:35And so the idea here is that if they dart forward, they draw the attention of the predatory bird. And then if they're not hiding afterwards, they're very easy to like hone in on. Maybe. We haven't actually like done videos to show that that's exactly what's happening. And so there were some categories of behavior you were looking for, scratching, darting, et cetera. How did you come up with these categories? Is there a possibility that there's some kind of category of behavior that the fish are doing that's different between the two populations that you didn't think to observe? Yeah, so first of all, in Lafferty and Morris' paper, they watched the fish for a long time.

47:11They came up with like any category of weird behavior that they could think of. That's called like an ethogram where you watch for a long time and you, you know, take notes on any behaviors that you think are relevant. But it feels a little subjective, right? Yes. Behavior. Exactly. Yes, it is sort of subjective. I'll actually be very interested in what AI does to this field. Because if you can have computers analyzing everything about behavior at some, you know, is a computer able to analyze behavior in a way that's different and maybe less subjective than how human eyes do? And there's some programs now that analyze behaviors that weren't available when I was doing it.

47:50No, it's still going to be biased just in a way you don't understand as well. Yeah, no, you might be right. So anyway, so I looked at their ethogram, what behaviors they thought were important. And then I watched also and looked to see if I was seeing something different. And I've also watched fish from a couple of different estuaries. So this is not the only study I've done with these fish. And so I've spent a lot of time staring at fish. The glamorous work of science. That's right. That's right. Maybe I haven't captured all the important behaviors, but I feel like I have. All right. And so you saw this darting effect.

48:24So compare or contrast that with the original effect in the earlier paper. Less strong. So before, they didn't see that darting was the behavior most strongly associated with this brain-infecting parasite. And they saw that behaviors were like four times more pronounced in their infected fish. So we're seeing a different behavior most strongly impacted by the parasite and a lower magnitude. And we don't know if that's because it was a different population that we were looking at. It could be because the wild fish in the other study had a whole community of parasites and a lot of those community of parasites also go to predatory birds.

49:02Maybe each of those parasites are like manipulating a different part of the behavior or like they're all sharing the cost of manipulating. There's a lot of different reasons. But at the end of the day, what I found was that the effect is a little bit more complicated and a little bit smaller than what had been found before. So no one cites my work. Exactly.

49:26But this was the exact goal of this study is to tease this apart and try to understand more specifically, what is the effect of this parasite? Yes. And so the answer is that on its own, this parasite is not doing everything that the original guy saw. That's right. That's right. So but so let's dive in a little bit to what we know about how the parasite might be doing this. Yeah. The first thing you usually wonder when you discover that a infected organism is getting eaten by another organism more often is like, well, is the parasite just debilitating it in some way? Like, is it just making it slower, easier to catch or something?

50:00And that doesn't seem to be the case. So first of all, you know, just like observations, if you watch these fish, they've got 8 ,000 parasites on their brain, man. It's like a carpet. It's so crazy to see all these parasites, but they're not like swimming on their sides. They're not having trouble catching their food. They school normally. Like they look normal. And my friend, Lauren Nadler, who worked on this system as a postdoc, she stuck them in these little metabolic chambers and she measured their acute metabolism. So she like, you know, got them to swim real fast. I don't really know how you do this kind of stuff in fish.

50:34This is like what they do to Olympic athletes, right? Treadmills. And yeah, I don't know how you treadmill a fish. I'm imagining a fish on a treadmill right now. Yeah, yeah. She did a bunch of different things to like get their like maximum metabolic rate and their resting metabolic rate and blah, blah, blah. Okay. She fed them Red Bull and stuff like this. I'm sure she did, yeah. I'm sure she got a protocol and a permit and all that for that. And what she found like using our fish from our lab experiments where we had like hatched them in the lab, infected some, didn't infect others, that the infected fish and the uninfected fish had like no difference in metabolism.

51:07So it doesn't look like having a bunch of fish on your brain. is that energetically expensive. Like they're pretty efficient at resource extraction when they're on the brain. They're like, you know, semi-dormant after they finish growing. So it doesn't seem like it's that. And their body condition is good. If you compare them to uninfected fish, they have like their gonads are about the same size because ecologists do grow stuff like whey gonads and like they seem just as good at having babies. They have the same amount of fat reserves. So it doesn't seem like they're making them debilitated in any way that we can measure.

51:42Well, what about coming at it from the other direction and asking, like, how is the parasite benefiting? Because that might be the other side of the equation. If the parasite is, like, extracting something specific from the brain or from the fish, then maybe you could understand the impact of losing that on the fish. So, okay, so the idea would be that, like, the parasite is extracting, like, a neurotransmitter or something? I don't know. What is the benefit to the parasite? What do you mean? What is the benefit of the parasite to? Being on the brain. Like what is it doing there that's helping it?

52:14Yeah. So usually what the parasites do at this stage is they grow a little and then they kind of like they reach asymptotic growth. They grow and then they stop growing. And I think they mostly stop growing because while they're growing, they're forming a cyst around them. And this cyst protects them from the immune system. And when that cyst finishes growing, they've sort of run out of room to grow. And so that's as big as they're going to get. But presumably they can extract some resources across the cyst wall and maybe even secrete some stuff across the cyst wall. Presumably somebody has looked to see what they are sucking up on the brain.

52:52But I don't think we've looked to see if they're like specifically – like I think they're sucking up like nutrients and stuff. But I don't know if they're specifically sucking up like serotonin to try to mess with brain stuff. Because, for example, like a tapeworm lives in my gut, eats some of my food, I get less food. So it's easy to understand from the tapeworm's benefit what the impact is on me. I don't know. I'm not a parasitologist, but it seems like maybe an avenue. So what do we know about how these parasites are influencing these fish? Spoiler alert, we don't know at the end of the day.

53:25But we think that what might be happening is that the parasite is making it so that the fish doesn't respond with as much of a stress response as it should. So essentially, the parasite is like dampening the stress response. And so here's what we think is happening. So there's a part of the brain in fish that is usually associated with the stress response. And when you look at that part of the brain, we see that the typical response to the chemicals in the brain in fish when they're stressed is much lower when the fish has a bunch of parasites in that part of the brain. And so that's got us wondering, like, if a predatory bird is in the area, for example, is maybe what's happening is that, like, uninfected fish would be like, ah, predatory bird, I got to run away.

54:14But in a fish that has these parasites, are the parasites making the fish be like, no big deal, probably not going to choose me. In fact, actually, I'm going to shoot forward really quick. Oh, look at how cool I am. And I should say that we have measured these differences in infected and uninfected fish brains, but we have not tied these differences to behavior or tied these differences to like, you know, fish getting eaten by birds more often. So this is just like preliminary observations and how these brains look different. So all that makes sense except for the part where being less stressed makes them dart more because I thought darting was a response to like, oh, no, I think I'm going to get eaten.

54:53Yeah, but so it is a response to, oh, no, I think I'm going to get eaten. But usually it ends in, and so I'm going to hide. Right. But here it's like, oh, no, I'm going to get – oh, wait, oh, wait, what was I running from? And there's another part of the brain that's associated with locomotion, and you tend to find a high density of the parasites there. And so I mentioned that, you know, the parasites are sort of like a carpet on the brain. But they're like a carpet, but they also tend to, like, be a little bit more dense in two parts of the brain. And one of those parts deals with stress, and one of those parts deals with locomotion.

55:29And so, you know, again, these are just observations. We haven't linked it to behavior yet. But it could be that like, you know, there's some stimulation of the locomotion part of the brain to get those fish moving, to get the darts going. And then the part where usually they're like, and now go run and hide is being turned off. So they're moving around, but they're not hiding. Maybe. So these fish are just like more chill. They sound like, if anything, they might be happier. They could be. And so actually part of how we get funding for this system is we say, you know, look, maybe what the parasite is doing is it's secreting some chemical that is suppressing stress.

56:08Maybe there's like a treatment for anxiety or something that we could find by something that's being secreted by this parasite. There could be a novel compound that we could discover with this parasite. Wasn't Ozempic discovered when they were studying like lizard venom or something crazy? You never know. I think Gila monster venom or something like that. Yeah, you never know where the next treatment's going to be found. Your science could change Hollywood. That's right. That's right. One of the cool things about studying fish is that if you stick them in a beaker of water, the steroid hormones, which are things like cortisol, which is associated with your stress response, and things like testosterone and estrogen and stuff like that, they leak across the fish's gills and into the water, and they'll reach an equilibrium.

56:53So the concentration in the water is equal to the concentration in the blood. And you have to do some validating work, but you can repeatedly make measurements of hormones in fish without needing to draw any blood by just putting them in beakers of water. And so I collected cortisol levels from fish repeatedly and these fish had different levels of parasites on their brain. And we found that the density of parasites on their brain does impact how much cortisol they release. but it wasn't in a like nice predictable way. And this is when I decided I didn't want to work on hormones and neurotransmitters anymore because I had a prediction and I talked to the experts and I was like, it was supposed to be a straight line up, but instead it made a U.

57:37And they were like, yeah, this stuff never works out the way we think it's gonna. And I was like, I'm done. I'm done. I'm not doing this anymore. I've had enough snail gonads. I'm moving on. Right. I don't even like pipettes. And so that was it for me. That is one of my fears about biology is that you're doomed to working in complex systems. You can never really use reductionism and simplify things because everything you're doing is most interesting in a complex system, which means it might be forever before you actually untangle stuff. It's incredible to me that we've made any progress in biology at all.

58:16I have to admit, a lot of my friends are working on these kinds of problems. And I am so glad they are because this is how we like get to the bottom of things like, you know, why are parasites becoming resistant to our drugs and stuff like super important questions. I found it really frustrating and I was like, I can't, I don't think I can keep doing this. I think something that's not widely enough appreciated about how people end up in the science field to end up in is that you have to be excited about the big questions of the field, but also you have to find the day to day work fun. Yeah. And so many fields are fascinating, the questions they ask.

58:54But then the day-to-day work is very different. You know, it's like working in a lab, pipetting or, you know, making a laser operate well or whatever. And you have to be interested in both sides of it if you're going to spend your life doing it. Because it's not every day that you're answering the big questions. Mostly it's the day-to-day work. And so you've got to find that niche where the craft is also fun. I can't tell you how many days I wanted to hurl that pipette across the lab. I do not enjoy pipetting. I have friends who get in the flow and I do not. I have no flow. Well, the wonderful thing about humanity is that we're all into different stuff.

59:29And so some of us traipse through rainforests and get their socks wet while studying spiders and other people look up at the sky and wonder about all of that. And some people like to pipette. So because of that, we have a glorious diversity in all of the science stories that we extract from the universe. We do. And if I may, so I hope that work continues in this system because this could be the route to another treatment for anxiety. Maybe this will be helping me a decade down the road. We can hope. But also, there are other killifish species in a bunch of estuaries in North America, and there are other Uaplorcus species in a bunch of estuaries in North America.

1:00:06So it might be that similar interactions like this are playing out in a bunch of our super productive ecosystems. So this parasite might be impacting, you know, the flow of energy from aquatic systems to terrestrial systems all throughout North America. And we don't understand this very well. And a lot of people are interested in migratory birds. I think fish are cooler than birds. I'm going to die on that hill. But, you know, bird people, you guys are cool, too. And so this kind of stuff matters. And that's some of the excitement of science that you never know around which corner or under which snail gonad is going to be some amazing discovery that really changes the world.

1:00:42And it takes somebody like pushing on a question that seems maybe minor and in a corner, but that reveals a thread that you can use to unravel our understanding of something much broader. And when you're doing science, you never know, like, is today the day I'm going to learn something mind blowing? Because there have been days like that in the history of science. we just all hope that one of them is going to happen to us. That's right. Well, thanks for listening to me ramble, everybody. I love this parasite. And I thought that was interesting, even without any parasites controlling my brain and telling me what to find interesting.

1:01:15Yay!

1:01:23Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We would love to hear from you. We really would. We want to know what questions you have about this extraordinary universe. We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you. We really mean it. We answer every message. Email us at questions at danielandkelly.org. Or you can find us on social media. We have accounts on X, Instagram, Blue Sky, and on all of those platforms, you can find us at D &K Universe. Don't be shy. Write to us. The all-new Mazda CX-5. Featuring more connection.

1:02:05Hey Google, where's the nearest Pilates class? Safety that has your back. More discovery on the scenic routes. More passion in the details. And more control in changing weather. The all-new Mazda CX-5. More to move every side of you. See it in five films at mazdausa.com slash five sides. Google is a trademark of Google LLC. Seek. Sequence is shortened and simulated. Apple Vacations, where your story starts. The Splash into Savings event from Apple Vacations is here. Now through June 25th, save up to$150 on vacation packages, plus instant savings at select resorts in Mexico, the Caribbean, Central America, and top U.S.

1:02:47destinations. Use promo code JUNE26 for these limited-time offers. Start planning today at AppleVacations.com or contact your travel advisor. Apple Vacations, where your story starts. Ready to finally clean out your closet? With Trashy, you can donate your clothes, reduce waste, and earn cash rewards. All in one simple step. Just fill a take-back bag, send it in, and get rewards cash back for every bag. And now, with Trashy Unlimited, you get unlimited bags for just$48 your first year. Clean out, donate, earn rewards. Visit Trashy.io to get started. Running a business shouldn't feel like surviving a software group project.

1:03:35One app for accounting, another for inventory, another for sales. And somehow, none of them talk to each other. That's where Odoo comes in. An all-in-one business management software that brings every part of your business together. From sales and accounting to inventory and marketing, all in one powerful platform. No messy integrations, no bouncing between tabs. And best of all, no spreadsheets. Stop managing software and start managing your business with one unified system. Try for free today at odoo.com slash iHeartRadio. That's O-D-O-O-O dot com slash iHeartRadio. This is an iHeart Podcast.

1:04:16Guaranteed human.