WEBVTT - Zombie fish 0:00:07.800 --> 0:00:09.880 If you sit on the banks of the estuaries in 0:00:09.920 --> 0:00:13.640 southern California and Baja California, the seat of your pants 0:00:13.680 --> 0:00:17.560 will get super money. But also you'll likely see schools 0:00:17.640 --> 0:00:21.720 of silvery fish swimming through the water. If you watch closely, 0:00:22.239 --> 0:00:26.160 some of those silvery fish will begin behaving rather strangely. 0:00:26.720 --> 0:00:30.840 They'll shoot upwards quickly, breaking the water surface and creating 0:00:30.880 --> 0:00:35.160 these super conspicuous ripples on the surface. Or they'll turn 0:00:35.200 --> 0:00:37.960 on their sides as they scratch their bodies against a rock. 0:00:38.400 --> 0:00:41.600 As they do this, their silvery bellies reflect the sun 0:00:41.680 --> 0:00:44.440 and create this quick and vibrant flash of light. 0:00:45.440 --> 0:00:46.639 Why are they doing this? 0:00:47.040 --> 0:00:49.800 These fish are bite size to the sharks and the 0:00:49.800 --> 0:00:53.520 predatory birds that sometimes roam these estuaries in search of food. 0:00:53.960 --> 0:00:57.640 Shouldn't they be trying to look a little less conspicuous. 0:00:58.280 --> 0:01:01.560 Why are they drawing so much attention to themselves. Well, 0:01:01.800 --> 0:01:05.480 it's me speaking, so you've probably guessed that the answer 0:01:05.600 --> 0:01:07.280 is parasites. 0:01:07.800 --> 0:01:09.160 Today we're going to talk about you. 0:01:09.240 --> 0:01:14.319 Heplurcus california aansis a brain infecting parasite of California chillefish, 0:01:14.520 --> 0:01:17.560 which are the silvery fish dancing through the waters in 0:01:17.560 --> 0:01:21.880 California that we were just talking about. Welcome to Daniel 0:01:21.920 --> 0:01:25.080 and Kelly's extraordinarily infected universe. 0:01:38.360 --> 0:01:41.399 Hi. I'm Daniel, I'm a particle physicist, and I hope 0:01:41.440 --> 0:01:42.800 I'm parasite free. 0:01:43.040 --> 0:01:44.480 Hello. I'm Kelly Wiersmith. 0:01:44.560 --> 0:01:49.160 I study exactly what we're talking about today, and I'm 0:01:49.200 --> 0:01:51.480 okay if I'm harboring a parasite or two, depending on 0:01:51.520 --> 0:01:51.960 what they are. 0:01:52.280 --> 0:01:54.600 All right, Well, that was actually my question for you, Kelly, 0:01:55.000 --> 0:01:57.600 if you had to harbor a parasite, what would be 0:01:57.720 --> 0:01:59.240 your parasite of choice? 0:01:59.520 --> 0:02:02.920 All right, Well, so I probably have some demodex mites 0:02:02.920 --> 0:02:03.680 on my face. 0:02:03.760 --> 0:02:04.560 I'm okay with that. 0:02:05.720 --> 0:02:07.560 You know, they might not count as a parasite depending 0:02:07.560 --> 0:02:09.200 on you know, what they're doing on the given day. 0:02:09.360 --> 0:02:11.280 Are those the ones that live in your pores and 0:02:11.320 --> 0:02:13.280 climb out? And there was uncertainty at whether or not 0:02:13.280 --> 0:02:16.080 they had anuses or if they just exploded when they 0:02:16.120 --> 0:02:16.799 got filled up. 0:02:16.960 --> 0:02:19.680 That's right, but they do have anuses. Science figured that 0:02:19.760 --> 0:02:21.639 out recently. Way to go science. 0:02:22.639 --> 0:02:24.840 What's better that they're taking a dump on your face? 0:02:25.160 --> 0:02:27.560 They're exploding on your face? I don't know. I don't 0:02:27.560 --> 0:02:28.720 feel great about either option. 0:02:28.960 --> 0:02:30.560 Yeah, I think in the end, you know, the waste 0:02:30.639 --> 0:02:34.200 ends up on your face either way. So Daniel almost 0:02:34.200 --> 0:02:35.440 spit his coffee out there. 0:02:35.760 --> 0:02:36.519 It's just great. 0:02:38.320 --> 0:02:40.240 How do you know we're talking about biology because it's 0:02:40.280 --> 0:02:42.200 poop on your face in the first five minutes. 0:02:42.360 --> 0:02:44.960 That's right, this is a chilly lead episode. 0:02:45.720 --> 0:02:47.840 I don't know that we'll get to cannibalism today though, 0:02:47.880 --> 0:02:48.680 so that's too bad. 0:02:48.840 --> 0:02:50.839 See. Yeah, I'll do my best to bring us there. 0:02:50.960 --> 0:02:51.680 Yeah, okay, all right. 0:02:51.840 --> 0:02:54.200 You know, I guess I wouldn't be too upset if 0:02:54.240 --> 0:02:57.920 I had one or two pinworms. I wouldn't mind having 0:02:57.960 --> 0:03:01.560 a small load of pinworms because they probably wouldn't hurt 0:03:01.560 --> 0:03:02.160 me that much. 0:03:02.360 --> 0:03:05.480 Pinworms aren't those the ones that at night crawl out 0:03:05.639 --> 0:03:08.280 and like make you itch in uncomfortable places? 0:03:08.560 --> 0:03:11.519 Yeah, I mean, no, parasite is good, right, Like that 0:03:11.960 --> 0:03:15.160 would defy the definition of parasite. I'm trying to pick 0:03:15.320 --> 0:03:19.160 something that would be least bad, and pinworms are probably it. 0:03:19.600 --> 0:03:21.320 Although not a lot of adults get pinworms. 0:03:21.840 --> 0:03:25.480 What about you? Oh man, you're making a lot of 0:03:25.520 --> 0:03:28.320 curse faces today. I wish we did video. 0:03:31.320 --> 0:03:34.640 There is no parasite I would be happy with. Yes, absolutely, no, 0:03:34.680 --> 0:03:37.360 that was an answer. Yes, that's my answer. It just 0:03:37.440 --> 0:03:41.360 creeps me out. It just bothers me to imagine like 0:03:41.440 --> 0:03:45.520 something living inside of me, treating me like a cave 0:03:45.880 --> 0:03:48.880 or like a habitat or something like. No, I would 0:03:48.960 --> 0:03:50.960 just like I would get a rusty spoon and dig 0:03:51.000 --> 0:03:51.280 it out. 0:03:51.560 --> 0:03:53.880 Okay, hold on, is this a question of magnitude? Because 0:03:53.920 --> 0:03:56.560 you have billions of bacteria living in your gut doing 0:03:56.600 --> 0:03:58.680 exactly what you just described. 0:03:59.080 --> 0:04:01.120 Katrina is convinced to me that they are part of me. 0:04:01.480 --> 0:04:04.280 I contain multitudes, I am multitudes. 0:04:04.400 --> 0:04:08.600 Why can't the demodex and the pinworms be part of 0:04:08.600 --> 0:04:09.440 your multitudes? 0:04:09.800 --> 0:04:14.400 Not invited to the party. No, okay, No, there's a 0:04:14.440 --> 0:04:18.720 fuzzy but bright line between the microbial invaders and then 0:04:18.760 --> 0:04:22.120 non microbial invaders. Maybe it's just because I'm married to 0:04:22.160 --> 0:04:25.320 a microbiologist and not a parasologist. Do you think Zach 0:04:25.360 --> 0:04:27.400 would be happy having parasites within him? 0:04:27.480 --> 0:04:28.279 Absolutely not. 0:04:28.560 --> 0:04:31.919 But but so one of the things that made me 0:04:32.000 --> 0:04:38.320 interested in microbiome science initially was this idea that there's 0:04:38.320 --> 0:04:41.120 a connection between the brain and the gut, and that 0:04:41.440 --> 0:04:45.120 microbes sometimes release neurotransmitters that. 0:04:45.120 --> 0:04:48.599 Can speak to you, know, speak, I'm being. 0:04:48.440 --> 0:04:51.760 Super anthromorphic here, but influence influence, Like you know, there 0:04:51.760 --> 0:04:53.800 are nerves that go from your brain to your gut, 0:04:53.800 --> 0:04:57.440 and the neurotransmitters released by those microbes, you know, might 0:04:57.520 --> 0:05:00.359 be influencing how we feel about certain things. And so 0:05:00.440 --> 0:05:03.960 I became super interested in this idea that the way 0:05:04.040 --> 0:05:07.920 that we respond to the world might be influenced by 0:05:08.640 --> 0:05:11.479 the things that are living inside of us. And my 0:05:11.640 --> 0:05:14.960 advisor at the University of California, Davis Andy C who 0:05:15.080 --> 0:05:18.920 is amazing I adore him. One day was like, Kelly, 0:05:18.920 --> 0:05:22.080 have you heard about toaso plasma gandhi. It's a parasite 0:05:22.360 --> 0:05:25.640 that you can get from your cat that changes your behavior. 0:05:25.680 --> 0:05:28.720 And in a very early Listener Questions episode, we talked 0:05:28.720 --> 0:05:30.599 about like how good the science is, what we know 0:05:30.720 --> 0:05:33.359 about that, so you can look for that. But that 0:05:33.480 --> 0:05:36.680 started me on my journey being like interested in how 0:05:36.839 --> 0:05:38.360 parasites impact behavior. 0:05:38.400 --> 0:05:40.520 And so today we're going to talk about you know, 0:05:40.560 --> 0:05:42.840 what I spent a decade. 0:05:43.040 --> 0:05:46.360 It wasn't supposed to be that long, what I spent 0:05:46.440 --> 0:05:48.599 a decade working on, And this is. 0:05:48.600 --> 0:05:51.400 All the research we're going to talk about today already published. 0:05:52.279 --> 0:05:57.960 Yes, because I think my collaborators would appreciate if the 0:05:58.040 --> 0:06:00.919 two papers that we haven't quite finished yet, we're. 0:06:00.839 --> 0:06:04.040 Not highlighted on the episode. 0:06:04.320 --> 0:06:07.480 I don't care, but they are, you know, still hoping 0:06:07.480 --> 0:06:10.320 to get tenures. So I will I will not mention 0:06:10.680 --> 0:06:13.799 those in press or in prep results. 0:06:14.279 --> 0:06:18.320 But yeah, I do agree, that's super fascinating, and it 0:06:18.400 --> 0:06:21.080 makes a lot of sense that the things living inside 0:06:21.080 --> 0:06:24.240 of us don't just live inside of us. They influence us. 0:06:24.279 --> 0:06:27.000 They change the way our bodies work, and that includes 0:06:27.400 --> 0:06:31.880 potentially changing our behavior because we are these biological machines 0:06:31.920 --> 0:06:35.080 and the decisions we make are not divorced from that, right, 0:06:35.080 --> 0:06:38.520 they're completely influenced by that. But still, I find it 0:06:38.720 --> 0:06:43.040 okay to imagine that my microbiome is influencing the decisions 0:06:43.080 --> 0:06:45.200 I make in the way I perceive the world. But 0:06:45.320 --> 0:06:48.080 I do feel hijacked if there's like some critter living 0:06:48.120 --> 0:06:51.960 inside me that's forcing me to like eat that second donut. 0:06:52.279 --> 0:06:56.000 Yeah, well, so I think there's a difference in goal 0:06:56.440 --> 0:06:58.320 in some cases, you know. So like I would like 0:06:58.400 --> 0:07:00.279 to think that a lot of you are my grow 0:07:00.320 --> 0:07:04.160 biome is in sync with you. You know, the microbiome 0:07:04.240 --> 0:07:07.599 wants you to thrive, so that they can thrive. But 0:07:08.080 --> 0:07:10.520 for a lot of the systems that I've ended up 0:07:10.560 --> 0:07:13.160 working in, the host needs. 0:07:12.960 --> 0:07:15.640 To die for the parasite to thrive. 0:07:15.920 --> 0:07:19.400 And so when we're looking at manipulation, which is what 0:07:19.520 --> 0:07:21.560 I sort of specialized in grad school, which is an 0:07:21.600 --> 0:07:25.200 instance where the host's behavior is changing in a way 0:07:25.200 --> 0:07:28.280 that's driven by the parasite in a way that's usually 0:07:28.320 --> 0:07:31.760 bad for the host but good for the parasite. You know, 0:07:32.160 --> 0:07:35.720 that's that's very different than what you're imagining. But folks 0:07:35.800 --> 0:07:38.280 might remember that we did a zombie ant episode a 0:07:38.320 --> 0:07:42.120 little while back, And what I love about these systems 0:07:42.640 --> 0:07:46.440 is that often parasites are changing behaviors of their hosts 0:07:46.840 --> 0:07:50.040 in ways that we couldn't replicate in a lab like 0:07:50.080 --> 0:07:52.520 and by way I mean neuroscientists, you know, So like ants, 0:07:52.520 --> 0:07:55.800 they've got these simple little brains relative to humans, you know, 0:07:55.880 --> 0:07:59.360 but we still couldn't get the ants to do these 0:07:59.400 --> 0:08:02.960 like series of behaviors that this fungus, like operating the 0:08:02.960 --> 0:08:05.640 ant by remote control, can get the ant to do. 0:08:05.880 --> 0:08:08.040 And so you know, through the process of natural selection, 0:08:08.840 --> 0:08:13.760 this fungus has essentially acquired the ability to control ant behavior, 0:08:13.840 --> 0:08:16.600 and it you know, in a very anthropomorphic sense. It 0:08:17.200 --> 0:08:21.240 knows neuroscience better than we do, and so I love 0:08:21.320 --> 0:08:24.760 these systems as a way to you know, maybe jumpstart 0:08:24.800 --> 0:08:29.000 our understanding of how brains work by like studying what 0:08:29.080 --> 0:08:32.120 these parasites have essentially learned about how brains work over 0:08:32.200 --> 0:08:35.520 evolutionary history. And so I get super excited about, you know, 0:08:35.640 --> 0:08:38.840 using parasites as tools to understand how brains work. Although, 0:08:38.960 --> 0:08:43.800 as we'll discover over the course of this episode, neuroscience 0:08:43.840 --> 0:08:47.559 baffles me, and so I mostly focus on the behavior 0:08:47.600 --> 0:08:49.800 stuff and then collaborate with neuroscientists. 0:08:50.040 --> 0:08:52.320 All right, So today we're not talking about the things 0:08:52.360 --> 0:08:57.400 living in Daniel's gut or toxoplasmi or zombie ants or 0:08:57.440 --> 0:08:59.360 any of that kind of stuff. What is the system 0:08:59.480 --> 0:09:02.120 that you and ten years of your life. 0:09:01.800 --> 0:09:06.840 Exploring, oh Man, Okay, So in Baja California, in southern California, 0:09:06.960 --> 0:09:10.360 in estuarys so. Estuaries are areas where the ocean is 0:09:10.400 --> 0:09:13.560 coming in and there's a freshwater system meeting the ocean. 0:09:13.640 --> 0:09:17.600 So it's where freshwater and saltwater are mixing. They tend 0:09:17.600 --> 0:09:20.920 to be super productive areas where like baby fish are 0:09:21.120 --> 0:09:23.280 growing and sharks will come in to eat. 0:09:23.080 --> 0:09:25.160 Some food, and there's a lot of crabs and stuff 0:09:25.200 --> 0:09:28.160 like that. They're super productive systems. They are these tiny 0:09:28.200 --> 0:09:30.439 little fish. They are silvery. 0:09:30.679 --> 0:09:34.040 They're you know, like maybe the adults are a bit 0:09:34.080 --> 0:09:37.280 bigger than the length of your maybe middle finger, but 0:09:37.320 --> 0:09:41.439 they're not as big as like your whole hand, so 0:09:41.480 --> 0:09:42.600 they're you know, somewhere in between. 0:09:42.640 --> 0:09:44.400 They're pretty small. They're pretty drab. 0:09:44.480 --> 0:09:47.400 The males will sometimes have some yellow coloration during the 0:09:47.440 --> 0:09:50.439 breeding season, but in general they're just like these silvery, 0:09:50.559 --> 0:09:51.480 kind of drabfish. 0:09:51.840 --> 0:09:58.480 And they're called killyfish, killyfish, not kellyfish, not killfish, killy fish, killyfish. 0:09:58.600 --> 0:09:59.760 What does that mean? A? 0:10:00.880 --> 0:10:04.080 I don't know. I don't know. Why are they called 0:10:04.160 --> 0:10:04.680 killy fish? 0:10:04.840 --> 0:10:07.240 You only spent ten years studying it and never thought, 0:10:07.280 --> 0:10:08.640 why are they have this silly name? 0:10:09.040 --> 0:10:12.559 Well, stuff doesn't always mean stuff. You know, that was 0:10:12.600 --> 0:10:14.760 really articulate of me. I don't I don't think it's 0:10:14.760 --> 0:10:16.120 I don't know that it means anything. 0:10:21.600 --> 0:10:25.080 See, it's of uncertain origin, but it's likely to have 0:10:25.200 --> 0:10:29.720 come from the Dutch kill for a small stream. 0:10:30.160 --> 0:10:38.040 Nah, if you say so. 0:10:37.520 --> 0:10:39.680 So these sillily named fish. 0:10:39.840 --> 0:10:42.199 Yeah, So, Actually, when I met Zach the person who 0:10:42.200 --> 0:10:44.160 would eventually become my husband. He asked me what I 0:10:44.160 --> 0:10:46.680 studied and I said killy fish. And he said, you 0:10:46.720 --> 0:10:50.640 study kelly fish and I said no, no, killyfish, and 0:10:50.960 --> 0:10:52.760 for a while left that he called me kelly fish, 0:10:52.800 --> 0:10:55.880 which is kind of cute. But anyway, so these are 0:10:56.160 --> 0:10:59.640 super abundant fish. They're social, so they they're you know, 0:10:59.640 --> 0:11:02.680 you off and find them in big schools. And Kevin 0:11:02.760 --> 0:11:05.560 Lafferty and Kimo Morris in the nineties they notice that 0:11:05.600 --> 0:11:08.040 if you walk around in the estuaries and you look 0:11:08.080 --> 0:11:11.880 into all of these like channels, you see schools of 0:11:11.920 --> 0:11:15.280 these fish swimming by, but they're really obvious, Like there 0:11:15.280 --> 0:11:17.440 are other schools of fish that will swim by and 0:11:17.480 --> 0:11:19.760 you sort of like don't really notice them. But when 0:11:19.760 --> 0:11:22.400 the chilly fish swim by, they start doing all of 0:11:22.440 --> 0:11:24.880 these weird behaviors. It's like they're dancing through the water. 0:11:24.960 --> 0:11:27.199 They'll like break the surface of the water and you'll 0:11:27.200 --> 0:11:29.520 see these obvious ripples and then they'll be all these 0:11:29.559 --> 0:11:33.080 flashes of silver because they're they're shooting forward, they're turning 0:11:33.080 --> 0:11:35.880 on their sides, they're rubbing against things, they're contorting in 0:11:35.920 --> 0:11:38.280 the shape of s they're just doing all of these 0:11:38.400 --> 0:11:42.400 like really conspicuous behaviors that the other fish species didn't 0:11:42.440 --> 0:11:44.559 seem to be doing. And then you bring a bunch 0:11:44.559 --> 0:11:46.640 of fish back into the lab and you survey what's 0:11:46.640 --> 0:11:49.120 happening in the estuaries, and you discover that the California 0:11:49.200 --> 0:11:52.880 chillifish have a bunch of parasites on their brain, which 0:11:52.920 --> 0:11:55.000 makes you wonder, is that what's going on? 0:11:55.400 --> 0:11:57.480 So is that the reason they began studying this fish? 0:11:57.520 --> 0:11:59.600 Were they the first people to study this fish, or 0:11:59.679 --> 0:12:02.800 is this like a well known model fish in the community. 0:12:03.720 --> 0:12:05.920 A bunch of people have studied this fish, but not 0:12:06.080 --> 0:12:08.120 in relation to the fact that it had a brain 0:12:08.160 --> 0:12:12.840 infecting parasite. Because it's a superabundant fish in these super 0:12:12.840 --> 0:12:16.160 productive ecosystems, people have studied other things about them, like 0:12:16.600 --> 0:12:18.960 how the heck do these fish survive the fact that 0:12:19.000 --> 0:12:21.400 when the ocean goes out and the river is still 0:12:21.400 --> 0:12:24.679 coming in, the salinity goes from like, you know, almost 0:12:24.679 --> 0:12:27.000 completely fresh water, and then when the ocean comes in 0:12:27.040 --> 0:12:30.640 it's almost completely saltwater? How do they survive that? But 0:12:30.720 --> 0:12:33.120 a lot of people hadn't been studying the parasite stuff. 0:12:32.880 --> 0:12:35.160 Because I don't know if it's widely appreciated. But in biology, 0:12:35.200 --> 0:12:38.160 we have like these model systems where we don't study 0:12:38.160 --> 0:12:39.800 things in the wild. We have like a few things 0:12:39.800 --> 0:12:41.720 that we grow in the lab and study in detail. 0:12:41.760 --> 0:12:44.720 You know, mice and fruitflies and all sorts of stuff. 0:12:45.120 --> 0:12:48.240 And I wonder, like what makes an animal suitable to 0:12:48.240 --> 0:12:51.079 be selected? But these are being studied in the wild, right, 0:12:51.120 --> 0:12:55.280 So it's because of their interesting behaviors and these fascinating questions, right, 0:12:55.320 --> 0:12:59.120 not because they're quick to grow or they eat something 0:12:59.160 --> 0:12:59.960 easy or anything. 0:13:00.480 --> 0:13:01.960 Yeah, right, So I hate these guys. 0:13:02.000 --> 0:13:06.760 So so uh, it turns out so mummy chugs, which 0:13:06.800 --> 0:13:10.200 is Fungilus heteroclitis. I study Fungilius parva pinnis, but a 0:13:10.240 --> 0:13:15.520 closely related species on the opposite coast is very easy 0:13:15.559 --> 0:13:16.559 to study in the lab. 0:13:16.880 --> 0:13:18.400 This is a model species. 0:13:18.440 --> 0:13:21.200 We've got the genome, we've got a bunch of genetic tools. 0:13:21.600 --> 0:13:24.760 You can grow them up super easy. But fungilis part 0:13:24.760 --> 0:13:27.120 of a pinnis You bring into the lab and it 0:13:27.160 --> 0:13:29.600 is really hard to keep them from dying, which is 0:13:29.720 --> 0:13:32.160 crazy because they live in these environments where the salinity 0:13:32.240 --> 0:13:34.760 is changing. You'd like they survive all of these extremes. 0:13:34.800 --> 0:13:37.000 You'd think you bring them in the lab where life 0:13:37.040 --> 0:13:38.439 is easy, they would. 0:13:38.200 --> 0:13:41.400 Thrive, and they do not. And I don't know why. 0:13:41.520 --> 0:13:44.480 And I like, literally years of my PhD was figuring 0:13:44.480 --> 0:13:46.800 out how to keep them happy in the lab. And 0:13:46.840 --> 0:13:49.120 that's probably why they're not a model organism, because they're 0:13:49.160 --> 0:13:52.120 little jerks. You think about them at home at night, 0:13:52.120 --> 0:13:53.480 and they start dying in the lab. 0:13:54.520 --> 0:13:58.040 All right. So these guys Lafferdy and Morris notice these 0:13:58.040 --> 0:14:02.160 fascinating behaviors and they studied these fish and what did 0:14:02.160 --> 0:14:03.000 they learn about them? 0:14:03.120 --> 0:14:05.920 Okay, well, so they brought the fish into the lab 0:14:05.960 --> 0:14:08.440 and they were like, oh my gosh, the brains of 0:14:08.480 --> 0:14:14.199 these fish are like carpeted by this parasite on their brain. 0:14:14.640 --> 0:14:17.640 Like a thousand parasites on the brain of an adult 0:14:18.160 --> 0:14:19.040 is pretty typical. 0:14:19.400 --> 0:14:21.520 Eight thousand can happen sometimes too. 0:14:21.840 --> 0:14:25.560 So there are these tiny little like cysts, these tiny 0:14:25.600 --> 0:14:28.040 little balls. They almost could look like their little glass balls. 0:14:28.560 --> 0:14:32.960 And this is a trematod parasite. So a trematoad parasite 0:14:32.960 --> 0:14:37.160 that you might have heard of is schistosoma. Mansonite causes shistosomiasis. 0:14:37.240 --> 0:14:40.920 This is a problem in places like Africa. This parasite 0:14:41.040 --> 0:14:44.760 is also a trematoid parasite, not necessarily particularly closely related 0:14:44.760 --> 0:14:46.640 to that one, but this is the only other trematode 0:14:46.640 --> 0:14:49.120 you're likely to have heard of, and it has a 0:14:49.280 --> 0:14:51.840 complex life cycle. And let's go through the life cycle 0:14:51.960 --> 0:14:55.880 because it helps you understand why this parasite might want 0:14:56.000 --> 0:14:58.000 to make the fish behave conspicuously. 0:14:58.240 --> 0:15:00.360 And this is the life cycle of the fish, or 0:15:00.400 --> 0:15:03.760 of the parasite, or the harmonious combination. 0:15:03.480 --> 0:15:04.160 Of the parasite. 0:15:04.160 --> 0:15:07.080 All right, and I'm gonna start calling the parasite Youha, 0:15:07.400 --> 0:15:11.400 because you have blurcis California asis is way too much 0:15:11.440 --> 0:15:12.440 to say every time. 0:15:13.080 --> 0:15:15.640 All right, so tell us about Uha's lifestyle. 0:15:15.800 --> 0:15:21.600 Okay, So youh accidentally gets consumed by California horn snails 0:15:21.640 --> 0:15:25.120 that live in the salt marshes. Bad news for the snails. 0:15:25.720 --> 0:15:28.200 The snails get castrated. 0:15:27.600 --> 0:15:31.400 By the parasite. What I know, it's crazy. 0:15:31.120 --> 0:15:34.360 Chemically or like surgically, I mean, are we losing bits 0:15:34.360 --> 0:15:36.480 of the body here or are they just becoming deactivated? 0:15:36.560 --> 0:15:39.200 Well, okay, so all of the gonads, I'm not quite 0:15:39.200 --> 0:15:41.480 sure how you're imagining this, but the gonads are. 0:15:41.360 --> 0:15:43.600 All you don't want to know how I'm imagining. 0:15:44.000 --> 0:15:46.200 Yeah, no, I didn't ask you to explain it. And 0:15:46.240 --> 0:15:49.320 so the gonads are inside of the snail. All of 0:15:49.360 --> 0:15:53.480 the gonad tissue ends up being taken up by parasite tissues. 0:15:53.680 --> 0:15:59.080 The parasite start replicating, replicating, replicating, replicating, replicating, and they 0:15:59.120 --> 0:16:03.080 produce a stage that will swim out from the snail 0:16:03.120 --> 0:16:05.760 to go off in search of fish. 0:16:05.800 --> 0:16:08.360 This is nightmare fuel already, Kelly. 0:16:08.320 --> 0:16:10.680 It is, and these snails can still live for like 0:16:10.800 --> 0:16:13.440 a decade or more with this parasite. And when the 0:16:13.520 --> 0:16:16.640 tide comes in in the summer, up to two thousand 0:16:16.640 --> 0:16:19.120 of the free swimming stages of this parasite can emerge 0:16:19.120 --> 0:16:21.480 from the snail to go off in search of fish. 0:16:21.520 --> 0:16:26.840 It's crazy, and okay, parasites have social lives, all right. 0:16:26.880 --> 0:16:28.720 So look, I'm gonna be honest everybody. 0:16:28.880 --> 0:16:30.400 This is gonna be a little bit of a ranty 0:16:30.440 --> 0:16:34.240 episode because I love this parasite and I've just spent 0:16:34.280 --> 0:16:36.440 a decade like falling in love with its weirdness. 0:16:36.440 --> 0:16:39.400 Okayyi, this warning is fifteen minutes too late, Kelly. 0:16:42.320 --> 0:16:44.600 Guys and Daniel tried to get me on track before 0:16:44.600 --> 0:16:46.440 the start of this episode. He's like, Kelly, I can 0:16:46.440 --> 0:16:49.200 tell you're gonna get ranty. Let's focus, and I'm here. 0:16:49.240 --> 0:16:51.000 I am being like, sorry, Daniel. 0:16:51.000 --> 0:16:52.960 All right, ran away really quick. 0:16:53.000 --> 0:16:53.320 Okay. 0:16:53.400 --> 0:16:55.640 So, once you're inside of a snail and you've taken 0:16:55.720 --> 0:16:59.920 control of a gonad, there are other trematodes that would 0:17:00.120 --> 0:17:02.960 like to come in and usurp the gonad that you're 0:17:03.000 --> 0:17:06.320 living in. And so you have Lurcis Californian sas and 0:17:06.480 --> 0:17:10.200 other trematode species out in the estuary make a stage 0:17:10.320 --> 0:17:13.320 called a soldier, and the soldier is essentially just like 0:17:13.440 --> 0:17:17.560 a giant mouth that patrols the snail, and if another 0:17:17.640 --> 0:17:20.960 stage comes in, it will go. At this stage in 0:17:21.000 --> 0:17:23.399 their life, they're essentially just giant bags of fluid, and 0:17:23.440 --> 0:17:25.760 so it will like try to pop the other bags 0:17:25.800 --> 0:17:28.120 of fluid so that they can't come in and take 0:17:28.160 --> 0:17:30.879 control of the snail gonad. And so anyway, they've got 0:17:30.920 --> 0:17:34.160 reproductive stages that are like making this free swimming stage 0:17:34.160 --> 0:17:36.920 of the parasite reproducing, reproducing, reproducing, and then they're making 0:17:36.960 --> 0:17:39.080 a bunch of soldiers that are patrolling the snail to 0:17:39.200 --> 0:17:40.119 keep everything safe. 0:17:40.520 --> 0:17:42.000 It's just absolutely amazing to me. 0:17:42.080 --> 0:17:46.760 That there's this like grand battle for the snail gonad exactly, yes, incredible. 0:17:47.200 --> 0:17:50.320 And so these parasites are working together, they're like cooperating 0:17:50.359 --> 0:17:53.520 with each other against the snail and against competing parasites. 0:17:53.760 --> 0:17:56.639 Yes, but they're also they're reproducing asexually, so they're like 0:17:56.960 --> 0:18:01.600 all clones. So it's like the exact same individual clone clone, clone, 0:18:01.640 --> 0:18:05.480 clone clone, but some of them look like soldiers, some 0:18:05.640 --> 0:18:07.800 of them look like reproductives. But like if you were 0:18:07.880 --> 0:18:10.720 to sequence them genetically, they're all like the same. 0:18:11.000 --> 0:18:13.800 All right, So it's like the snail gonad hive. Mind. Ye, 0:18:13.920 --> 0:18:14.960 that sounds like the title of. 0:18:15.000 --> 0:18:17.080 A book I'd like to read, sure, yeah, or the 0:18:17.119 --> 0:18:18.040 book I'd like to write. 0:18:18.440 --> 0:18:21.359 And so all right, when the tide comes in in 0:18:21.440 --> 0:18:24.640 the summers, when the water is nice and warm, thousands 0:18:24.680 --> 0:18:27.960 of these parasites leave the snail and each one of 0:18:28.000 --> 0:18:30.639 them has a very low probability of finding the fish, 0:18:30.760 --> 0:18:32.600 and they only live for like twenty four hours. They're 0:18:32.640 --> 0:18:34.520 like little sacks of energy and they're gonna run out 0:18:34.520 --> 0:18:37.359 real fast. But if they do encounter the fish, we 0:18:37.520 --> 0:18:40.040 think what happens is they burrow through the fish's skin, 0:18:40.560 --> 0:18:43.439 they find a nerve and they follow that nerve up 0:18:43.480 --> 0:18:46.480 to the fish's brain and then they go on top 0:18:46.560 --> 0:18:49.280 of the brain and they form a cyst on the brain, 0:18:49.359 --> 0:18:52.119 so they're not in the brain tissue. They're like resting 0:18:52.200 --> 0:18:52.960 on top of the brain. 0:18:53.240 --> 0:18:54.800 And why do they want to be on top of 0:18:54.840 --> 0:18:55.160 the brain. 0:18:55.520 --> 0:18:57.080 Ah, there's a couple of different ideas there. 0:18:57.119 --> 0:18:59.200 So one of the ideas, and this was like a 0:18:59.320 --> 0:19:01.840 very early idea, is that if you're on top of 0:19:01.920 --> 0:19:05.000 the brain, you're kind of protected from the immune response, 0:19:05.520 --> 0:19:10.240 because if the brain's immune system overreacts, then that could 0:19:10.280 --> 0:19:10.920 be really. 0:19:10.760 --> 0:19:12.280 Bad for the fish. That could kill the fish. 0:19:12.320 --> 0:19:14.199 The fish could start like swimming on its side, then 0:19:14.240 --> 0:19:16.560 it could get eaten by another fish. And so by 0:19:16.760 --> 0:19:19.280 being in an area where the host can't allow the 0:19:19.320 --> 0:19:23.320 immune system to attack too strongly, you sort of increase 0:19:23.359 --> 0:19:24.280 your odds of survival. 0:19:24.600 --> 0:19:26.600 But it could also be because it's. 0:19:26.480 --> 0:19:28.600 A pretty good place if you're going to be trying 0:19:28.640 --> 0:19:32.119 to manipulate behavior, that's a good location from which to 0:19:32.240 --> 0:19:32.520 do that. 0:19:33.600 --> 0:19:36.560 Yeah, that makes sense. And so there are multiple of 0:19:36.640 --> 0:19:39.160 these parasites crawling up the fish nerve to the brain. 0:19:39.680 --> 0:19:41.960 Are they all working in tandem like they did in 0:19:42.040 --> 0:19:44.399 the snail gonet. Are they now fighting each other for 0:19:44.480 --> 0:19:46.920 who gets to like ratitude drive this fish? 0:19:48.359 --> 0:19:51.600 That's a great question, so hard to say. We think 0:19:51.680 --> 0:19:55.200 that they are working together because usually you see signs 0:19:55.200 --> 0:19:59.240 of competition between parasites. But when we studied this, we 0:19:59.320 --> 0:20:02.159 saw some evident that they were cooperating. And so the 0:20:02.240 --> 0:20:04.680 way that we measured this was we looked at the 0:20:04.880 --> 0:20:09.160