1 00:00:00,000 --> 00:00:00,330 Unknown: Theme music. 2 00:00:20,400 --> 00:00:24,120 Jane: This is But Why: A Podcast for Curious Kids from Vermont 3 00:00:24,120 --> 00:00:28,140 Public. I'm Jane Lindholm. On this show, we take questions 4 00:00:28,140 --> 00:00:32,970 from curious kids just like you, and we find answers. In making 5 00:00:32,970 --> 00:00:37,830 today's episode, I learned a lot and I had my mind kind of 6 00:00:37,860 --> 00:00:42,150 changed. So I want to know: at the end of the episode, if you 7 00:00:42,150 --> 00:00:44,640 experience the same thing, let me know. 8 00:00:45,960 --> 00:00:50,610 Have you ever heard the word parasite? A parasite is, by 9 00:00:50,610 --> 00:00:57,300 definition, bad. At least, it's bad for its host. A parasite is 10 00:00:57,300 --> 00:01:01,440 a living organism that uses a different organism--it either 11 00:01:01,440 --> 00:01:06,270 lives in or on this other organism--called the host. And 12 00:01:06,270 --> 00:01:10,230 the parasite uses its host to gain food or be able to 13 00:01:10,230 --> 00:01:15,240 reproduce in a way that's bad for the host. Basically, the 14 00:01:15,240 --> 00:01:20,310 parasite thrives at the expense of the host. Sounds bad, right? 15 00:01:20,730 --> 00:01:24,270 And it can be really bad. Sometimes parasites make their 16 00:01:24,270 --> 00:01:29,220 hosts too weak to eat. Sometimes they even kill their hosts. And 17 00:01:29,220 --> 00:01:34,020 sometimes humans can be the hosts to parasites. There's a 18 00:01:34,020 --> 00:01:36,750 lot of medicine designed to help us fight off and get rid of 19 00:01:36,750 --> 00:01:37,560 parasites. 20 00:01:38,610 --> 00:01:41,280 Of course, parasites aren't always super dangerous. 21 00:01:41,310 --> 00:01:44,940 Sometimes they're just really annoying and itchy, like head 22 00:01:44,940 --> 00:01:49,200 lice. But still, I would say that those head lice are still 23 00:01:49,200 --> 00:01:54,060 thriving at our expense, right? But our special guest today 24 00:01:54,120 --> 00:01:58,950 loves parasites. She says they're fascinating and often 25 00:01:58,950 --> 00:02:04,830 very beautiful, and she says they're really important, even 26 00:02:04,830 --> 00:02:09,840 good for our planet. She says, without parasites, our 27 00:02:09,870 --> 00:02:15,900 ecosystems would fall apart. So without further ado, let's meet 28 00:02:15,900 --> 00:02:19,800 this scientist and see if she can convince you to at least 29 00:02:19,800 --> 00:02:23,310 appreciate, if not love, the world of parasites. 30 00:02:23,790 --> 00:02:26,850 Chelsea Wood: I'm Chelsea Wood. I'm an associate professor in 31 00:02:26,850 --> 00:02:29,220 the School of Aquatic and Fishery Sciences at the 32 00:02:29,220 --> 00:02:33,510 University of Washington, but I prefer to be known as a parasite 33 00:02:33,510 --> 00:02:36,090 ecologist, because parasites are my favorite things. 34 00:02:36,000 --> 00:02:37,770 Jane: What does that mean, exactly? 35 00:02:37,920 --> 00:02:41,280 Chelsea Wood: Well, an ecologist is a person who studies living 36 00:02:41,280 --> 00:02:45,540 things, organisms, where they occur in the world, and why. And 37 00:02:45,540 --> 00:02:49,260 a parasite ecologist is someone who studies that question, but 38 00:02:49,260 --> 00:02:50,160 for parasites. 39 00:02:50,490 --> 00:02:54,000 Jane: Chelsea is also the author of a book for kids called Power 40 00:02:54,000 --> 00:02:58,170 to the Parasites. I read it and I learned a lot. We already went 41 00:02:58,170 --> 00:03:01,530 over what a parasite is, but let's hear it again, just so 42 00:03:01,530 --> 00:03:02,160 we're clear, 43 00:03:02,220 --> 00:03:05,580 Unknown: Parasites are organisms that live in or on other 44 00:03:05,580 --> 00:03:09,510 organisms and cause harm to those hosts that they're living 45 00:03:09,540 --> 00:03:16,230 in or on. And so my research extends from worms and other 46 00:03:16,230 --> 00:03:20,040 creepy crawlies that you'd find in your gut to ticks and lice 47 00:03:20,040 --> 00:03:24,720 crawling through your hair, but mostly I study the parasites of 48 00:03:24,720 --> 00:03:26,250 wildlife, not of people. 49 00:03:26,550 --> 00:03:29,670 Jane: Parasites are alive, but they aren't all animals. They 50 00:03:29,670 --> 00:03:33,750 can also be plants or other living organisms, and lots of 51 00:03:33,750 --> 00:03:36,810 things behave in parasitic ways. 52 00:03:37,410 --> 00:03:40,110 Unknown: Our definition of parasite encompasses parasites 53 00:03:40,110 --> 00:03:43,860 that are animals, like worms, ticks, lice, but also things 54 00:03:43,860 --> 00:03:48,600 that aren't animals, like bacteria, fungi, protozoa, 55 00:03:48,630 --> 00:03:53,760 viruses. So the term parasite applies to a whole broad swath 56 00:03:53,790 --> 00:03:54,840 of the tree of life. 57 00:03:55,080 --> 00:03:57,840 Jane: Why do they need a host? What do we mean when we say a 58 00:03:57,840 --> 00:03:59,370 parasite needs a host? 59 00:04:00,330 --> 00:04:02,520 Unknown: It's just another way of making a living in the world. 60 00:04:02,550 --> 00:04:05,580 You know, a lot of us are are familiar with the term predator. 61 00:04:05,730 --> 00:04:10,050 A predator is an organism that eats other organisms, and a 62 00:04:10,050 --> 00:04:15,750 parasite is a similar kind of category. Parasitism is a way of 63 00:04:15,750 --> 00:04:20,160 living in the world and a way of finding nutrition in the world. 64 00:04:20,520 --> 00:04:24,870 For parasites, they are living in or on their host and eating 65 00:04:24,870 --> 00:04:27,960 little bits of that host. For a predator, they don't live in or 66 00:04:27,960 --> 00:04:31,080 on their host, but they eat the whole thing when they come 67 00:04:31,080 --> 00:04:34,320 across it. So it's just a different way of eating and 68 00:04:34,320 --> 00:04:35,190 living in the world. 69 00:04:35,520 --> 00:04:37,200 Jane: How long do parasites live? 70 00:04:37,380 --> 00:04:40,440 Unknown: Oh, man, it really depends. Anywhere from you know, 71 00:04:40,440 --> 00:04:42,930 a couple of minutes to decades. 72 00:04:42,960 --> 00:04:43,410 Jane: Wow. 73 00:04:43,440 --> 00:04:47,700 Unknown: There are many human parasites where we know that 74 00:04:47,730 --> 00:04:51,630 they can live inside of their host for 30 years, sometimes 75 00:04:51,630 --> 00:04:56,850 more. Sometimes we are not sure how long their lifetime could 76 00:04:56,850 --> 00:04:59,070 extend, because, of course, they depend on the host. So if the 77 00:04:59,070 --> 00:05:03,000 host dies, the parasite dies with it. It's it really depends 78 00:05:03,000 --> 00:05:06,330 on the parasite. They are so different from one another, and 79 00:05:06,330 --> 00:05:09,480 they encompass the full range of lifetimes, from very short to 80 00:05:09,480 --> 00:05:10,080 very long. 81 00:05:10,380 --> 00:05:12,870 Jane: But there are some that only live for minutes, and 82 00:05:12,870 --> 00:05:14,280 that's their whole life cycle? 83 00:05:15,090 --> 00:05:18,780 Unknown: Yeah, that's their whole life stage. There are lots 84 00:05:18,780 --> 00:05:24,150 of parasite species that use transmissive stages, basically 85 00:05:24,150 --> 00:05:27,480 like little larval stages that are out in the environment for 86 00:05:27,540 --> 00:05:30,960 for a period of time in search of a host. And those larval 87 00:05:30,960 --> 00:05:35,040 stages can be very short lived. They can have only a matter of 88 00:05:35,040 --> 00:05:37,560 minutes to hours to find the right host. And if they don't, 89 00:05:37,560 --> 00:05:38,010 they die. 90 00:05:38,570 --> 00:05:41,240 Jane: Now, you might think we're just doing this episode to tell 91 00:05:41,240 --> 00:05:44,210 you all about parasites, and that none of you has ever sent 92 00:05:44,210 --> 00:05:49,280 us a question about parasites. Oh, no, no, no! We've gotten 93 00:05:49,280 --> 00:05:53,330 lots of questions about parasites. One type that a lot 94 00:05:53,330 --> 00:05:56,900 of you have asked us about is called a tapeworm. There are 95 00:05:56,900 --> 00:06:00,260 several thousand species of tapeworm, and they generally 96 00:06:00,260 --> 00:06:04,850 spend their adult stage inside the intestines of another 97 00:06:04,850 --> 00:06:09,080 animal. There are a few that sometimes live inside us humans, 98 00:06:09,080 --> 00:06:12,590 but it's really rare for a human to get a tapeworm. For humans 99 00:06:12,590 --> 00:06:16,340 that do get infected, it's often because they've eaten raw or 100 00:06:16,340 --> 00:06:18,170 undercooked beef or pork. 101 00:06:18,470 --> 00:06:21,410 Serenity: My name is Serenity, and I'm nine years old, and I 102 00:06:21,410 --> 00:06:24,590 live in Canada, and my question is, are tapeworms sticky? 103 00:06:25,670 --> 00:06:29,480 Unknown: Oh, great. Question. No, no. You'd think from looking 104 00:06:29,480 --> 00:06:31,130 at a picture of them that they might be sticky, because they 105 00:06:31,130 --> 00:06:34,850 look like a spool of tape, right? They look like what tape 106 00:06:34,850 --> 00:06:38,990 looks like after you've unspooled it from its roll, and 107 00:06:38,990 --> 00:06:41,480 they kind of glisten a little bit. So I can imagine, you might 108 00:06:41,480 --> 00:06:43,910 think that they are sticky, but they're actually slippery and 109 00:06:43,910 --> 00:06:44,540 slimy. 110 00:06:45,200 --> 00:06:50,450 Oliver: I'm Oliver, and I'm five years old. I live in Bloomfield, 111 00:06:50,450 --> 00:06:55,640 New Jersey, and my question is, how do tapeworms need be so 112 00:06:55,640 --> 00:06:56,450 long? 113 00:06:56,630 --> 00:07:00,470 Jane: Why do tapeworms need to be so long, wonders Oliver. 114 00:07:00,560 --> 00:07:05,030 Chelsea Wood: Tapeworms are really interesting because while 115 00:07:05,030 --> 00:07:09,860 they look like an unspooled strip of tape, they're actually 116 00:07:09,860 --> 00:07:15,410 made up of tens, sometimes hundreds of individual segments 117 00:07:15,680 --> 00:07:20,810 all strung together along that length of tape, and each one of 118 00:07:20,810 --> 00:07:24,800 those segments is a separate reproductive unit with its own 119 00:07:24,830 --> 00:07:29,660 male and female parts. And each one of those little units, which 120 00:07:29,750 --> 00:07:33,140 the technical term for them is proglottid. Each one of those 121 00:07:33,140 --> 00:07:38,570 proglottids can break off from the larger tapeworm tape and go 122 00:07:39,230 --> 00:07:43,400 out of the the gut that it's living in, in the poop of the 123 00:07:43,400 --> 00:07:47,180 host and out into the world. So the reason that tapeworms are 124 00:07:47,180 --> 00:07:51,590 long is that the longer they are, the more capacity they have 125 00:07:51,590 --> 00:07:54,890 to reproduce, the more babies they can make. And so there's a 126 00:07:54,890 --> 00:07:57,080 lot of incentive for a tapeworm to be long, because every 127 00:07:57,080 --> 00:07:58,730 tapeworm wants to make lots of babies. 128 00:07:58,970 --> 00:08:03,350 Jane: What kind of hosts do tapeworms live in? Humans can be 129 00:08:03,350 --> 00:08:05,150 hosts for some tapeworms, right? 130 00:08:05,600 --> 00:08:08,390 Chelsea Wood: Absolutely, we can be hosts for a couple different 131 00:08:08,390 --> 00:08:13,370 species of tapeworms. Tapeworms usually mature in the gut of a 132 00:08:13,370 --> 00:08:18,140 vertebrate, so an animal with a backbone, those tend to be the 133 00:08:18,140 --> 00:08:21,080 hosts for the adult form of the tapeworm, which is the form that 134 00:08:21,080 --> 00:08:23,960 we're talking about, the one that takes that long shape of an 135 00:08:23,960 --> 00:08:29,630 unspooled strand of tape. But tapeworms actually evolved 136 00:08:29,660 --> 00:08:35,300 alongside sharks. When they first evolved, sharks were their 137 00:08:35,330 --> 00:08:39,740 only hosts, and since then, they've evolved to use many 138 00:08:39,740 --> 00:08:42,860 different species of vertebrates, but because they 139 00:08:42,860 --> 00:08:47,390 originally evolved alongside sharks, still, the vast majority 140 00:08:47,390 --> 00:08:51,410 of tapeworm species use sharks as their final hosts. 141 00:08:51,560 --> 00:08:55,700 Bobby: Hello. My name is Bobby. I am 11 years old, and I live in 142 00:08:55,700 --> 00:08:59,660 Nigeria. I want to know why worms are in our stomach. 143 00:09:00,080 --> 00:09:04,340 Chelsea Wood: That's an example of species just trying to make 144 00:09:04,340 --> 00:09:09,680 their way in the world. Wherever there is a resource that can be 145 00:09:09,680 --> 00:09:14,570 used, you will find a species trying to use that resource. A 146 00:09:15,050 --> 00:09:20,030 term that we use in biology a lot is "nature abhors a vacuum," 147 00:09:20,420 --> 00:09:24,080 which means as soon as there is a resource that's not being 148 00:09:24,080 --> 00:09:26,990 used, some species is going to figure out a way to use that 149 00:09:27,020 --> 00:09:27,770 resource. 150 00:09:27,830 --> 00:09:31,940 Jane: Can I stop you to just say I love the word abhors, and it's 151 00:09:31,940 --> 00:09:37,250 a really great vocabulary word. It's spelled A, B, H, O, R, S, 152 00:09:37,520 --> 00:09:42,260 and it means hates, like really hates. So if you say "I abhor 153 00:09:42,260 --> 00:09:45,980 broccoli," you're saying I really hate broccoli. So when 154 00:09:45,980 --> 00:09:48,830 nature abhors a vacuum, it doesn't like when there's a 155 00:09:48,830 --> 00:09:49,370 vacuum. 156 00:09:50,060 --> 00:09:52,250 Chelsea Wood: Exactly. It hates it deeply. 157 00:09:52,340 --> 00:09:56,390 Jane: So in this sense, vacuum means an empty space. Nature 158 00:09:56,390 --> 00:09:59,570 will figure out a way to use that empty space. And your 159 00:09:59,570 --> 00:10:02,870 stomach could be considered an empty space, even if it's full 160 00:10:02,870 --> 00:10:06,050 of food, at least as far as parasites are concerned. 161 00:10:06,470 --> 00:10:09,440 Chelsea Wood: Your stomach is full of food, food for the 162 00:10:09,440 --> 00:10:14,390 taking, and of course, a parasite is going to evolve to 163 00:10:14,390 --> 00:10:17,480 use that food, because nature abhors a vacuum. 164 00:10:17,960 --> 00:10:21,710 Jane: But we just did an episode about how food turns into poop, 165 00:10:21,710 --> 00:10:24,530 and one of the things that we talked about was that you have a 166 00:10:24,530 --> 00:10:28,970 lot of bacteria in your gut that's really good. So those 167 00:10:28,970 --> 00:10:30,770 bacteria aren't parasites. 168 00:10:30,980 --> 00:10:33,080 Chelsea Wood: That's right, yeah, that's why our definition 169 00:10:33,080 --> 00:10:37,850 of parasitism has to involve the effect it has on a host. A 170 00:10:37,850 --> 00:10:42,230 parasite has a negative effect on host 100% of the time. If it 171 00:10:42,230 --> 00:10:44,570 doesn't have a negative effect on host, it's not a parasite. 172 00:10:44,930 --> 00:10:47,600 And so those bacteria that have a beneficial effect, we would 173 00:10:47,600 --> 00:10:50,930 actually call them mutualists, because they're living in or on 174 00:10:50,930 --> 00:10:54,200 the host, but they're having a beneficial effect for that host. 175 00:10:54,530 --> 00:10:56,990 There can also be bacteria living in your gut that really 176 00:10:56,990 --> 00:11:01,670 don't benefit or hurt you, and we call those commensals. So 177 00:11:01,670 --> 00:11:05,360 from parasites to commensals to mutualists, we go from organisms 178 00:11:05,360 --> 00:11:08,960 that have a negative effect to no effect to a positive effect. 179 00:11:09,350 --> 00:11:12,020 Jane: Grossed out yet? Coming up, we're going to talk about 180 00:11:12,050 --> 00:11:16,010 other parasites that might creep you out even more: lice and 181 00:11:16,010 --> 00:11:19,580 ticks. But we're also going to see if Chelsea can convince you 182 00:11:19,580 --> 00:11:20,990 that parasites are cool. 183 00:11:20,990 --> 00:11:21,110 BREAK: BREAK 184 00:11:22,790 --> 00:11:26,240 Jane: This is But Why: A Podcast for Curious Kids. I'm Jane 185 00:11:26,240 --> 00:11:29,540 Lindholm. We're learning about parasites with parasite 186 00:11:29,570 --> 00:11:33,410 ecologist Chelsea Wood today. Before we get back to your 187 00:11:33,410 --> 00:11:36,800 questions, are you curious how someone like Chelsea even 188 00:11:36,800 --> 00:11:41,240 becomes a parasite scientist? When she was your age she wanted 189 00:11:41,240 --> 00:11:42,830 to study whales and dolphins! 190 00:11:43,200 --> 00:11:46,230 Chelsea Wood: I got involved in a project early on in my career 191 00:11:46,260 --> 00:11:48,720 because I wanted to do marine biology, and it happened to be a 192 00:11:48,720 --> 00:11:52,410 parasite project. And I went into this project thinking 193 00:11:52,410 --> 00:11:55,770 parasites were gross, and I was honestly pretty disappointed 194 00:11:55,800 --> 00:11:59,760 that the marine project that I had drawn was one that involved 195 00:11:59,760 --> 00:12:03,570 parasites, because I thought that it was going to be boring 196 00:12:03,570 --> 00:12:06,120 and I was going to have to look at a bunch of disgusting worms, 197 00:12:06,120 --> 00:12:09,540 and I just was not into it. And as I got deeper and deeper into 198 00:12:09,540 --> 00:12:14,100 this project, I realized how amazing these things were. And 199 00:12:14,130 --> 00:12:16,530 one of the things that really drove that home for me was that 200 00:12:16,620 --> 00:12:19,770 when I was a kid, I used to collect snails into buckets, and 201 00:12:19,770 --> 00:12:23,190 I lived on the east coast of the United States, where the most 202 00:12:23,190 --> 00:12:27,360 common snail was the common periwinkle, and I probably put 203 00:12:27,510 --> 00:12:31,080 hundreds of these into my bucket over the course of my childhood. 204 00:12:31,440 --> 00:12:34,530 And then as I was working on this project, my job was to 205 00:12:34,530 --> 00:12:37,980 crack these snails open, same species, and to look at the 206 00:12:37,980 --> 00:12:40,590 parasites that were inside of them. It was the first time that 207 00:12:40,590 --> 00:12:44,250 I'd ever done that, and I realized that they were full of 208 00:12:44,250 --> 00:12:48,750 worms. I'd been looking at these snails for decades, and missing 209 00:12:48,750 --> 00:12:50,070 the most interesting part. 210 00:12:50,250 --> 00:12:53,310 And it made me realize that, you know, when you look across a 211 00:12:53,310 --> 00:12:58,770 beautiful landscape, you see trees and deer and rabbits and 212 00:12:59,070 --> 00:13:02,160 all that stuff is obvious to the naked eye, but what you don't 213 00:13:02,160 --> 00:13:04,620 see is that each one of those things is basically a package of 214 00:13:04,620 --> 00:13:08,010 parasites walking around in the world, and you just have to look 215 00:13:08,190 --> 00:13:11,970 only a tiny bit below the surface to see this whole other 216 00:13:11,970 --> 00:13:16,620 world of parasites that exists just beneath what's familiar to 217 00:13:16,620 --> 00:13:17,340 all of us. 218 00:13:17,580 --> 00:13:21,060 Jane: Okay, so that's how Chelsea got hooked. Here's her 219 00:13:21,060 --> 00:13:22,770 pitch to maybe hook you. 220 00:13:23,140 --> 00:13:25,720 Chelsea Wood: One of the things that I think people don't 221 00:13:25,750 --> 00:13:29,140 appreciate about parasites is that they are really, really 222 00:13:29,170 --> 00:13:33,250 beautiful. I know it sounds strange when I say that, because 223 00:13:33,280 --> 00:13:37,480 you know, when you look at a worm in your hand, it's slimy 224 00:13:37,510 --> 00:13:41,980 and it writhes. It's just it doesn't, it doesn't look like 225 00:13:42,070 --> 00:13:45,130 anything beautiful. Doesn't enter into the equation at all, 226 00:13:45,160 --> 00:13:47,950 right, but, but when you look at those worms under the 227 00:13:47,950 --> 00:13:51,370 microscope, when you look at them at their own scale, at the 228 00:13:51,370 --> 00:13:57,370 scale where they exist, you see these spectacular adaptations to 229 00:13:57,370 --> 00:14:01,630 the parasitic life that have evolved over millennia, and it's 230 00:14:01,630 --> 00:14:05,500 just mind boggling to see how perfect they are for the things 231 00:14:05,500 --> 00:14:08,950 that they need to do. And a great example is one of the 232 00:14:08,950 --> 00:14:13,900 shark tapeworms. This is a group of tapeworms in the order 233 00:14:13,930 --> 00:14:17,530 Trypanorhyncha. Informally, we call them the Trypanorhynch 234 00:14:17,560 --> 00:14:21,160 tapeworms, and they're one of those very, very old orders of 235 00:14:21,160 --> 00:14:24,250 tapeworms that stuck around with the sharks instead of evolving 236 00:14:24,250 --> 00:14:29,620 to use other groups of organisms, and they are 237 00:14:29,650 --> 00:14:32,800 perfectly adapted to living in the shark gut, which, as you can 238 00:14:32,800 --> 00:14:35,440 imagine, just like picture yourself inside a shark gut, 239 00:14:35,470 --> 00:14:39,190 it's dark, it's slippery, and there's this constant tide of 240 00:14:39,190 --> 00:14:43,060 poop running in one direction that if you didn't resist, it 241 00:14:43,060 --> 00:14:45,850 would take you straight out and into the ocean, and that would 242 00:14:45,850 --> 00:14:48,700 be death for a tapeworm. It can only survive in the gut of a 243 00:14:48,700 --> 00:14:49,150 shark. 244 00:14:50,110 --> 00:14:53,740 Jane: I'm starting to regret imagining myself inside of a 245 00:14:53,740 --> 00:14:54,250 shark. 246 00:14:55,480 --> 00:14:58,840 Chelsea Wood: It's a hard place to live for a lot of reasons, 247 00:14:59,140 --> 00:15:02,110 but the Trypanorhynchs have evolved these beautiful 248 00:15:02,110 --> 00:15:05,950 structures that allow them to resist the tide of poop that's 249 00:15:05,950 --> 00:15:10,570 constantly threatening to blast them out into this hostile 250 00:15:10,570 --> 00:15:16,120 ocean. What they have are these four tentacles on their head end 251 00:15:16,360 --> 00:15:19,390 that they are able to kind of like pull inside of their head, 252 00:15:19,390 --> 00:15:22,300 but they can also, like, shoot them out really fast if they 253 00:15:22,300 --> 00:15:26,830 need to. They're coiled up, and each tentacle is armed with 254 00:15:26,860 --> 00:15:30,820 thousands and thousands of backward facing spikes. So what 255 00:15:30,820 --> 00:15:34,270 this tapeworm can do is, you know, as it wants to move around 256 00:15:34,270 --> 00:15:39,070 in the shark intestine, it can burst those tentacles right out 257 00:15:39,070 --> 00:15:43,690 of its head end and lay them down on the gut wall of the 258 00:15:43,690 --> 00:15:48,760 shark. And then it can use its hooks to form a really close 259 00:15:48,760 --> 00:15:52,840 attachment to that gut wall, and then pull the tentacles back 260 00:15:52,840 --> 00:15:56,860 into its head, securely anchoring itself to the gut wall 261 00:15:56,890 --> 00:16:00,400 of the shark. And in that way, it can kind of crawl up, if it 262 00:16:00,400 --> 00:16:04,060 wants to, against the tide of poop, it can move around, and it 263 00:16:04,060 --> 00:16:06,700 can always make sure that it maintains a close connection 264 00:16:06,700 --> 00:16:11,440 with that gut wall, ensuring that it doesn't get burst out of 265 00:16:11,440 --> 00:16:15,370 that shark into the hostile ocean. So not only is it really 266 00:16:15,370 --> 00:16:17,950 good at doing this, but if you look at these tentacles under 267 00:16:17,950 --> 00:16:21,610 the microscope, they are just so beautiful. People are always 268 00:16:21,610 --> 00:16:25,900 really surprised. These animals are just spectacularly 269 00:16:25,900 --> 00:16:27,910 beautiful, and I think it's a real shame that more people 270 00:16:27,910 --> 00:16:29,110 don't appreciate them. 271 00:16:29,320 --> 00:16:33,070 Jane: That is disgustingly amazing to think about a river 272 00:16:33,100 --> 00:16:37,240 of fast flowing poop that these parasites are able to resist. 273 00:16:38,680 --> 00:16:41,230 All right, what do you think? Disregard the part about the 274 00:16:41,230 --> 00:16:44,950 river of poop and just concentrate on how impressive it 275 00:16:44,950 --> 00:16:49,600 is that these parasites are able to survive and thrive in such a 276 00:16:49,600 --> 00:16:52,900 harsh environment. Let's get back to some of your other 277 00:16:52,900 --> 00:16:53,560 questions. 278 00:16:54,050 --> 00:16:57,232 Levi: Hi, But Why. My name is Levi. I'm nine years old. I live 279 00:16:57,289 --> 00:17:00,756 in Canberra, Australia, and my question is, what is head lice 280 00:17:00,812 --> 00:17:02,120 and how does it spread? 281 00:17:02,160 --> 00:17:06,390 Ramona: My name is Ramona. I'm six years old. I'm from 282 00:17:06,390 --> 00:17:10,800 Providence, Rhode Island. My question is, where did the first 283 00:17:10,800 --> 00:17:11,970 lice come from? 284 00:17:13,200 --> 00:17:16,440 Hazel: Hi, I'm Hazel, from Austin, Texas, and I'm 10 years 285 00:17:16,440 --> 00:17:20,480 old. My question is, how did the first person get head lice, and 286 00:17:20,480 --> 00:17:23,780 how have they survived all these years? Thank you. 287 00:17:23,840 --> 00:17:28,100 Ludo: My name is Ludo. I'm from Audubon, Minnesota, and I'm five 288 00:17:28,100 --> 00:17:32,060 years old. My question is, why do lice itch? 289 00:17:33,080 --> 00:17:36,410 Chelsea Wood: That's a great question. Head lice are one 290 00:17:36,410 --> 00:17:42,530 species of many, many species of lice in the world, and this one 291 00:17:42,530 --> 00:17:46,250 has evolved to exploit humans only. Head lice can survive 292 00:17:46,490 --> 00:17:50,930 nowhere except on a human head. But they're certainly not the 293 00:17:50,930 --> 00:17:55,520 only species of louse in the world. Lots of birds have their 294 00:17:55,520 --> 00:18:00,560 own host specific species of lice, meaning their lice can 295 00:18:00,590 --> 00:18:05,870 only survive on that one species of bird and nowhere else, and 296 00:18:05,900 --> 00:18:11,180 there are many, many more examples among mammals and other 297 00:18:11,180 --> 00:18:18,500 vertebrates. So our head lice are a very special louse species 298 00:18:18,590 --> 00:18:23,330 that can only use us, and they live among the hair shafts of 299 00:18:23,330 --> 00:18:27,740 our head, and they eat little bits of dead skin that fall off 300 00:18:27,740 --> 00:18:31,520 of your head. They eat living skin, and they also sometimes 301 00:18:31,760 --> 00:18:35,330 eat our blood, and that's part of what causes the itching 302 00:18:35,360 --> 00:18:39,890 associated with having a head full of head lice, these little 303 00:18:39,920 --> 00:18:44,090 bugs eating the skin off of your scalp. Now, luckily, they're 304 00:18:44,090 --> 00:18:46,700 pretty easy to get rid of, but that doesn't mean they're not 305 00:18:46,700 --> 00:18:47,690 annoying while you have them. 306 00:18:47,000 --> 00:18:50,982 Jane: Human head lice and body lice have evolved alongside 307 00:18:51,059 --> 00:18:55,424 humans, so we've had lice for about as long as we've been 308 00:18:55,501 --> 00:19:00,019 human. Let's talk about some other things that like to make 309 00:19:00,096 --> 00:19:02,930 us itch: fleas, ticks and mosquitoes. 310 00:19:02,960 --> 00:19:07,783 Marlo: Hi, my name is Marlo. I am five years old. I live in 311 00:19:07,875 --> 00:19:14,090 Austin, Texas, and my question is, are fleas related to mosquitoes? 312 00:19:14,690 --> 00:19:18,860 Chelsea Wood: Distantly, but yes. Yeah, fleas are insects, 313 00:19:18,890 --> 00:19:23,870 just like mosquitoes are. But there's many, many thousands of 314 00:19:23,870 --> 00:19:28,790 years of evolution between the fleas and the mosquitoes. And 315 00:19:28,820 --> 00:19:35,660 their habits of drinking blood are things that have evolved 316 00:19:35,690 --> 00:19:39,980 independently in those two groups, so it's not a trait that 317 00:19:39,980 --> 00:19:43,310 they share way back in their evolutionary history, it is 318 00:19:43,310 --> 00:19:45,920 something that each group evolved independently. 319 00:19:46,760 --> 00:19:53,230 Lily: Hi, my name is Lily. I live in Maryland, and I am six 320 00:19:53,353 --> 00:20:01,044 years old. And my question is, why do fleas bite cats and dogs, 321 00:20:01,166 --> 00:20:02,510 not people? 322 00:20:02,000 --> 00:20:05,229 Chelsea Wood: Unfortunately, fleas do also bite people. If 323 00:20:05,303 --> 00:20:09,560 your dog or cat has fleas, you also can be bitten by their 324 00:20:09,633 --> 00:20:13,964 fleas. Now, the fleas prefer dogs and cats, so they're less 325 00:20:14,038 --> 00:20:18,588 likely to bite you than they are to bite your dog or your cat, 326 00:20:18,662 --> 00:20:22,993 but that doesn't mean that they won't bite you. In fact, my 327 00:20:23,066 --> 00:20:27,617 brother's dog had fleas a couple of months ago, and we all got 328 00:20:27,690 --> 00:20:30,260 bitten by her fleas, unfortunately. 329 00:20:30,710 --> 00:20:31,820 Jane: That is not fun. 330 00:20:32,870 --> 00:20:36,537 Cindy: My name is Cindy. I'm seven years old. I live in 331 00:20:36,613 --> 00:20:41,427 Ontario, and my question is, why is there such a thing as ticks 332 00:20:41,503 --> 00:20:42,650 and mosquitoes? 333 00:20:43,220 --> 00:20:46,318 Jane: Why is there such a thing as ticks and mosquitoes? We 334 00:20:46,377 --> 00:20:49,592 talked about fleas and mosquitoes. What about ticks and 335 00:20:49,651 --> 00:20:51,230 mosquitoes, any connection? 336 00:20:52,010 --> 00:20:55,250 Chelsea Wood: Yeah, they they are also related to one another, 337 00:20:55,250 --> 00:21:00,710 although distantly. And you know, the reason that they exist 338 00:21:00,710 --> 00:21:05,570 is the same reason why worms in our stomachs exist. Nature 339 00:21:05,690 --> 00:21:10,340 abhors a vacuum. Nature hates a vacuum. We're walking around big 340 00:21:10,340 --> 00:21:15,650 packages of blood, and blood is so nutrient rich it can sustain 341 00:21:15,800 --> 00:21:20,750 many, many flea and tick and mosquito lives. And so why 342 00:21:20,750 --> 00:21:24,920 wouldn't a species evolve to be able to use that food, to be 343 00:21:24,920 --> 00:21:29,330 able to use that resource? If they can manage to get at it, 344 00:21:29,570 --> 00:21:31,340 then they will absolutely use it. 345 00:21:32,380 --> 00:21:38,369 Theo: My name is Theo, and my age is three, and I live in 346 00:21:38,487 --> 00:21:45,416 Canada, Saskatchewan, and my question is, why do ticks bite 347 00:21:45,534 --> 00:21:48,940 you and also suck your blood? 348 00:21:50,890 --> 00:21:55,000 Lars: Hi, my name is Lars. I'm five years old. I live in 349 00:21:55,000 --> 00:21:59,950 Minneapolis, and my question is, why do ticks suck blood? 350 00:21:59,980 --> 00:22:03,130 Jasper: My name is Jasper. I live in Georgia, and my question 351 00:22:03,130 --> 00:22:05,710 is, why do ticks need blood to survive? 352 00:22:06,040 --> 00:22:08,470 Chelsea Wood: Ticks actually have a totally fascinating life 353 00:22:08,470 --> 00:22:12,670 cycle, usually involving three different stages. They're born 354 00:22:12,670 --> 00:22:17,440 out of eggs, and the eggs are laid underneath leaves, usually 355 00:22:17,440 --> 00:22:22,420 on the forest floor. Those eggs hatch out these teeny, tiny 356 00:22:22,480 --> 00:22:25,900 larvae, and they're so small that they're hard even to see on 357 00:22:25,900 --> 00:22:29,560 your skin with the naked eye. Typically, they're too small to 358 00:22:29,560 --> 00:22:32,440 ever be picked up by a person, because they're just like down 359 00:22:32,440 --> 00:22:35,620 underneath the leaves. So they'll usually feed on 360 00:22:35,620 --> 00:22:38,620 something small that's skidding around underneath that leaf 361 00:22:38,620 --> 00:22:42,400 litter, like a mouse. Once the larvae take that blood meal from 362 00:22:42,400 --> 00:22:46,270 a mouse, they drop off, and they do this thing called molting, 363 00:22:46,510 --> 00:22:50,230 which is where they shed their exoskeleton. They shed the outer 364 00:22:50,230 --> 00:22:55,660 layer of their body and grow into the next stage, which is 365 00:22:55,660 --> 00:23:01,000 called a nymph. The nymph is a little bit bigger, and it can 366 00:23:01,000 --> 00:23:04,810 feed on humans, but lots of other mammals and birds. It 367 00:23:04,810 --> 00:23:08,140 takes another blood meal, it drops off. It then goes through 368 00:23:08,140 --> 00:23:11,650 that period of molting, again, shedding its skin, and then it 369 00:23:11,650 --> 00:23:15,100 becomes an adult, which is a much bigger animal. Now the the 370 00:23:15,100 --> 00:23:17,680 adults, because they're bigger, have to take a bigger blood 371 00:23:17,680 --> 00:23:20,710 meal, which means that they need a bigger host, and so they'll 372 00:23:20,710 --> 00:23:25,690 typically feed on larger mammals like deer, and then they'll drop 373 00:23:25,690 --> 00:23:29,500 off. And once they've had that third and final blood meal, as 374 00:23:29,500 --> 00:23:33,700 an adult, they're able to mate and produce eggs, and the life 375 00:23:33,700 --> 00:23:37,540 cycle begins again. So at each stage of the ticks life cycle, 376 00:23:37,540 --> 00:23:41,080 it has to take a blood meal, and that blood meal is what fuels 377 00:23:41,080 --> 00:23:45,700 its ability to either molt or produce a batch of eggs. 378 00:23:46,780 --> 00:23:53,800 Holden: Hi, my name is Holden, and I'm from Elgin, Illinois and 379 00:23:54,160 --> 00:24:00,840 and I'm five, and my question is, how do ticks get Lyme 380 00:24:00,840 --> 00:24:05,520 disease in, and how do they spread it to other people? 381 00:24:05,750 --> 00:24:10,550 Jane: Many kids know that some ticks can make people sick. One 382 00:24:10,550 --> 00:24:13,610 of the diseases you can get from a tick is called Lyme disease, 383 00:24:13,610 --> 00:24:17,390 and there are others that the ticks cancarry and that humans 384 00:24:17,390 --> 00:24:22,160 can get. We have several kids that want to know how do ticks 385 00:24:22,190 --> 00:24:26,540 get Lyme disease or other diseases, and how do they spread 386 00:24:26,540 --> 00:24:28,820 it to other people? How do they make us sick? 387 00:24:28,870 --> 00:24:32,350 Chelsea Wood: Yeah, ticks are full of all kinds of different 388 00:24:32,590 --> 00:24:37,120 bacterial and viral parasites that they can pass on to people 389 00:24:37,150 --> 00:24:40,960 and other mammals. And that's part of the reason why it's 390 00:24:40,960 --> 00:24:43,900 really good to check yourself for ticks after you've been in a 391 00:24:43,900 --> 00:24:46,780 place where you know that they're hanging around, you want 392 00:24:46,780 --> 00:24:49,300 to pull them off before they're able to feed on your blood and 393 00:24:49,300 --> 00:24:53,590 transmit any of those viruses or bacteria to you. Now, for Lyme 394 00:24:53,590 --> 00:24:57,040 disease, that's typically transmitted to people in the 395 00:24:57,040 --> 00:25:00,640 bite of the black legged tick in the eastern part of North 396 00:25:00,640 --> 00:25:05,440 America, and then different species of tick here on the west 397 00:25:05,440 --> 00:25:09,340 coast. But all those ticks go through the kind of life cycle 398 00:25:09,340 --> 00:25:13,300 that I just described, where they're feeding on rodents like 399 00:25:13,330 --> 00:25:18,220 mice and and rats in their first larval stage, and then feeding 400 00:25:18,220 --> 00:25:21,520 on people only once they've molted and become nymphs, and 401 00:25:21,520 --> 00:25:26,020 that's where Lyme disease comes in, because mice are really, 402 00:25:26,020 --> 00:25:30,250 really good hosts for the Lyme disease bacterium. They can 403 00:25:30,250 --> 00:25:34,510 replicate tons and tons of that bacterium in their bodies. And 404 00:25:34,510 --> 00:25:37,750 so when they're fed on by a larval tick, the larval tick 405 00:25:37,750 --> 00:25:40,810 takes that blood into its body and it is now infected with the 406 00:25:40,810 --> 00:25:44,350 Lyme disease bacterium, and after it molts and becomes a 407 00:25:44,350 --> 00:25:47,890 nymph, it can now pass that bacterium onto the next host 408 00:25:47,890 --> 00:25:51,850 that it feeds on. Now the nymphs are the most dangerous for 409 00:25:51,850 --> 00:25:54,820 people, because they're still pretty small, and that means 410 00:25:54,820 --> 00:26:00,040 that most people who contract Lyme disease are getting it from 411 00:26:00,040 --> 00:26:03,850 a nymphal tick that's fed on a rodent and then on them, and 412 00:26:03,850 --> 00:26:06,100 they're not able to notice it before it's too late, because 413 00:26:06,100 --> 00:26:10,390 that nymph is too small and too difficult to notice. Now, Lyme 414 00:26:10,390 --> 00:26:13,120 isn't the only thing that can be transmitted to people in the 415 00:26:13,120 --> 00:26:15,700 bite of ticks, but that's generally how it works, where 416 00:26:15,850 --> 00:26:18,670 the ticks are picking up that virus or bacterium in their 417 00:26:18,670 --> 00:26:21,490 larval stage and then passing it along with their nymphs. 418 00:26:21,750 --> 00:26:26,430 Karen: Hi. My name is Karen, and I'm five years old. I live in 419 00:26:26,430 --> 00:26:31,800 Lewis, Delaware, and my question is, why do tick bites hurt or 420 00:26:31,800 --> 00:26:32,310 sting? 421 00:26:33,030 --> 00:26:35,820 Jane: That's a good question, because it seems like the tick 422 00:26:35,820 --> 00:26:38,850 would want to be more stealthy and not let you know that it's 423 00:26:38,850 --> 00:26:42,420 there by making... Same with a mosquito, like, why do they let 424 00:26:42,420 --> 00:26:44,520 you know that you've been bitten? 425 00:26:44,500 --> 00:26:47,645 Unknown: They don't want to. Ticks and mosquitoes and you 426 00:26:47,711 --> 00:26:51,774 know, all all biting arthropods have some strategies that they 427 00:26:51,840 --> 00:26:55,706 use to reduce the pain, or at least the initial pain of the 428 00:26:55,772 --> 00:26:59,704 bite, so that they can feed undetected. You know, mosquitoes 429 00:26:59,770 --> 00:27:03,833 have those delicate little feet so that when they land on you, 430 00:27:03,899 --> 00:27:08,159 they cause as little disturbance as possible. Ticks, their saliva 431 00:27:08,224 --> 00:27:12,156 is full of numbing agents that are intended to make the bite 432 00:27:12,222 --> 00:27:16,416 totally painless, but nothing's perfect. And they can still make 433 00:27:16,482 --> 00:27:20,414 mistakes and not have their chemicals perfectly tuned to the 434 00:27:20,480 --> 00:27:24,281 host's nervous system, their ability to sense that pain or 435 00:27:24,346 --> 00:27:27,885 that itchiness. And so the initial pain of the bite is 436 00:27:27,951 --> 00:27:31,818 often a mistake on the part of the arthropod. But then once 437 00:27:31,883 --> 00:27:35,750 it's done feeding, it doesn't care what you feel, right. It 438 00:27:35,815 --> 00:27:39,879 doesn't care if you're itchy or if the bite hurts because it's 439 00:27:39,944 --> 00:27:43,942 already had its blood meal and is off and safe, and so often, 440 00:27:44,008 --> 00:27:48,071 the itchiness or pain you feel of a bite after the mosquito or 441 00:27:48,136 --> 00:27:51,938 tick is done feeding is your immune system reacting to the 442 00:27:52,003 --> 00:27:56,132 fact that a foreign object has been pushed into your body. It's 443 00:27:56,197 --> 00:27:59,868 your immune system trying to protect you against all the 444 00:27:59,933 --> 00:28:04,062 stuff that's been introduced in the in the breach of your skin, 445 00:28:04,128 --> 00:28:04,980 in that bite. 446 00:28:05,400 --> 00:28:08,280 Jane: So maybe you should think of an itchy mosquito bite. The 447 00:28:08,280 --> 00:28:11,400 Itching is actually a good thing. That's your body going to 448 00:28:11,400 --> 00:28:16,920 work exactly. A lot of what we've been talking about sounds 449 00:28:16,920 --> 00:28:22,400 pretty scary, especially when we talk about human diseases and 450 00:28:22,400 --> 00:28:26,960 the idea that for every parasite, they are bad for the 451 00:28:26,960 --> 00:28:30,440 host species, should we be afraid of parasites? 452 00:28:30,600 --> 00:28:33,810 Unknown: Absolutely not. And I'm not afraid of parasites. I think 453 00:28:33,810 --> 00:28:36,390 parasites are amazing, and obviously, we should be doing 454 00:28:36,420 --> 00:28:39,900 everything that we can to get rid of our own parasites. If I 455 00:28:39,900 --> 00:28:43,170 had a tapeworm in my gut, I would definitely take medicine 456 00:28:43,170 --> 00:28:47,460 to get rid of it. But just because parasites are bad for 457 00:28:47,460 --> 00:28:51,750 their hosts doesn't mean that they're bad in general. Think 458 00:28:51,750 --> 00:28:55,470 about a predator, right? Like a lion stocking a gazelle on the 459 00:28:55,470 --> 00:29:00,090 savanna. That lion is very bad for the gazelle. If it manages 460 00:29:00,090 --> 00:29:03,360 to catch the gazelle. It is absolutely going to kill and eat 461 00:29:03,360 --> 00:29:06,090 it. That's a terrible day for the gazelle. But we don't think 462 00:29:06,090 --> 00:29:11,010 of lions as bad, because what they're doing in their ecosystem 463 00:29:11,190 --> 00:29:15,030 is keeping a cap on the abundance of gazelle. They serve 464 00:29:15,060 --> 00:29:17,580 a role in their ecosystem. They're doing something 465 00:29:17,610 --> 00:29:20,730 important that keeps the ecosystem in balance, and in 466 00:29:20,730 --> 00:29:24,690 exactly the same way, the parasites are also doing their 467 00:29:24,690 --> 00:29:28,590 part to keep ecosystems in balance, and that includes by 468 00:29:28,590 --> 00:29:33,900 making sure no one host species gets too abundant. The reason 469 00:29:33,900 --> 00:29:36,750 that we don't have more cockroaches and rats in the 470 00:29:36,780 --> 00:29:40,380 world is that their parasites keep a cap on their abundance, 471 00:29:40,860 --> 00:29:44,250 and we also know that parasites are really important for 472 00:29:44,280 --> 00:29:48,060 allowing predators to have enough food to eat. So 473 00:29:48,090 --> 00:29:52,050 parasites, while they might be bad for an individual host, are 474 00:29:52,050 --> 00:29:54,240 good for the ecosystem in which they occur. 475 00:29:54,510 --> 00:29:57,660 Jane: Yeah, in fact, you wrote a book for kids about parasites 476 00:29:57,660 --> 00:30:01,260 that's really cool. I read it, it's really. Fun, and one of the 477 00:30:01,260 --> 00:30:03,660 things that you say in your book is that without parasites, 478 00:30:03,930 --> 00:30:07,500 ecosystems would fall apart. And maybe you can give us the 479 00:30:07,500 --> 00:30:12,480 example of how a lot of our food, our crops, rely on 480 00:30:12,480 --> 00:30:16,140 parasites, like aphid killing wasps. 481 00:30:16,210 --> 00:30:19,420 Chelsea Wood: Yeah, there's this really interesting chapter in 482 00:30:19,420 --> 00:30:23,590 the book where I get to delve into parasitoids, which are a 483 00:30:23,590 --> 00:30:29,950 special class of parasite that kills their host, and nowhere is 484 00:30:29,980 --> 00:30:33,640 is there a better example of this than among the parasitoid 485 00:30:33,670 --> 00:30:37,030 wasps. There are tens of thousands of species of 486 00:30:37,030 --> 00:30:40,900 parasitoid wasps. They usually specialize in just one host 487 00:30:40,900 --> 00:30:46,630 species, and many of them tend to go after pests of our farms. 488 00:30:47,050 --> 00:30:51,760 Imagine something like an aphid, which is a kind of insect that 489 00:30:51,760 --> 00:30:56,290 sucks the juices out of plants. Some farmers spend their whole 490 00:30:56,290 --> 00:30:59,170 careers trying to get rid of aphids, because they can be so 491 00:30:59,170 --> 00:31:05,080 destructive for a crop like tomatoes or corn or wheat. 492 00:31:05,410 --> 00:31:08,950 Aphids are really, really dangerous, but the farmer, 493 00:31:09,310 --> 00:31:12,880 unbeknownst to him, is actually getting an assist from 494 00:31:12,880 --> 00:31:17,530 parasitoids, because there are some species of parasitoid wasps 495 00:31:17,710 --> 00:31:23,650 who find aphids and then they use this long ovipositor, which 496 00:31:23,650 --> 00:31:27,850 is basically like a spike on the butt of the wasp. And they use 497 00:31:27,850 --> 00:31:32,290 that ovipositor to stab the aphid and inject their larvae 498 00:31:32,320 --> 00:31:36,520 inside. And then the larvae grow up inside the aphid, munching on 499 00:31:36,520 --> 00:31:40,540 its innards until eventually they kill the aphid. Now, these 500 00:31:40,540 --> 00:31:44,410 parasitoids can actually be a really important control on the 501 00:31:44,410 --> 00:31:48,160 abundance of the aphids. Without the parasitoids, the aphids 502 00:31:48,160 --> 00:31:51,400 would grow totally out of control and ruin all of our 503 00:31:51,400 --> 00:31:55,030 crops. And so in that way, farmers really rely on 504 00:31:55,060 --> 00:31:59,170 parasitoids and other parasites to make sure that they still 505 00:31:59,170 --> 00:32:01,570 have a crop to harvest at the end of the season. 506 00:32:02,830 --> 00:32:06,250 Jane: Like a lot of things, parasites aren't really good or 507 00:32:06,250 --> 00:32:10,510 bad. I mean, they're bad for their hosts, but they're just a 508 00:32:10,510 --> 00:32:14,530 part of the cycle of life and our ecosystem, the same way all 509 00:32:14,530 --> 00:32:18,070 the other plants and animals and organisms play a role, so do 510 00:32:18,070 --> 00:32:22,570 parasites. Together, all the living organisms keep the world 511 00:32:22,600 --> 00:32:23,500 in balance. 512 00:32:24,260 --> 00:32:29,090 Thanks so much to Chelsea L. Wood. She's the author of Power 513 00:32:29,090 --> 00:32:32,420 to the Parasites. It's a book for kids, and it's full of 514 00:32:32,420 --> 00:32:35,900 interesting facts and stories about parasites. So if you found 515 00:32:35,900 --> 00:32:39,920 this episode interesting, you'll probably like that book. And I 516 00:32:39,920 --> 00:32:43,550 want to know, what do you think about parasites now? Do you feel 517 00:32:43,550 --> 00:32:47,390 differently than you did when I first introduced the episode? Do 518 00:32:47,390 --> 00:32:52,040 you feel better or worse about parasites? Let me know, and, of 519 00:32:52,040 --> 00:32:54,440 course, send a question if you've got one, we take 520 00:32:54,440 --> 00:32:57,770 questions on any topic, so have an adult record you if you're 521 00:32:57,770 --> 00:33:01,190 able. It's easy to do on a smartphone using an app like 522 00:33:01,190 --> 00:33:04,340 voice memos, then have your adult email the file to 523 00:33:04,370 --> 00:33:09,290 questions@butwhykids.org. And of course, if talking or using your 524 00:33:09,290 --> 00:33:12,500 voice isn't your thing, just have your adult email us your 525 00:33:12,500 --> 00:33:13,130 question. 526 00:33:14,110 --> 00:33:17,560 Oh, and guess what? We've got a new team member to introduce you 527 00:33:17,560 --> 00:33:22,060 to. Sarah Baik is our newest producer. If you follow. 528 00:33:22,120 --> 00:33:25,630 @Butwhy_kids on Instagram, You've seen some videos from her 529 00:33:25,630 --> 00:33:29,290 recent trip to Japan, and you can find her bio, where she 530 00:33:29,290 --> 00:33:33,010 describes who she is and what her history is on our website, 531 00:33:33,220 --> 00:33:37,570 butwhykids.org. By the way, if you go check out our bios, you 532 00:33:37,570 --> 00:33:41,410 can discover the favorite animal of everyone who works on But 533 00:33:41,410 --> 00:33:46,180 Why? So our show is produced by Melody Bodette, Sarah Baik and 534 00:33:46,180 --> 00:33:50,170 me, Jane Lindholm at Vermont Public, Joey Palumbo produces 535 00:33:50,170 --> 00:33:53,590 our video series. Our theme music is by Luke Reynolds, and 536 00:33:53,590 --> 00:33:57,880 we're distributed by PRX. We'll be back in two weeks with an all 537 00:33:57,880 --> 00:34:01,780 new episode. Until then, stay curious!