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Leeches (featuring Dr. Anna Phillips) · Daniel and Kelly’s Extraordinary Universe

0:05
Speaker 1: When most people think of leeches, they're immediately disgusted, or
0:10
Speaker 1: at least that's been my experience when I talk to
0:12
Speaker 1: people about leeches. But what is it about leeches that
0:16
Speaker 1: results in so much more disgust than we feel when
0:18
Speaker 1: we talk about other blood suckers like mosquitoes. Maybe it's
0:22
Speaker 1: that scene from Stand By Me or that scene from
0:24
Speaker 1: African Queen, or maybe it's something else altogether. And look, today,
0:30
Speaker 1: I'm sure we're not going to convince most of you
0:32
Speaker 1: that leeches are beautiful. But I hope that when you
0:35
Speaker 1: listen to this episode, Anna and I are able to
0:38
Speaker 1: convince you that leeches are Okay, fine, maybe they're disgusting,
0:41
Speaker 1: but they're all so fascinating and maybe they're even helpful
0:45
Speaker 1: to people. So, for example, you know, maybe you've heard
0:48
Speaker 1: that leeches used to be used to try to draw
0:50
Speaker 1: blood to treat just about any problem that humans used
0:54
Speaker 1: to have a long time ago, But did you know
0:56
Speaker 1: that leeches are still used in particular medical cases and
1:00
Speaker 1: they're actually helpful, and that leeches produce anti coagulants, which
1:04
Speaker 1: are these chemicals that make sure your blood doesn't clot
1:06
Speaker 1: up that are useful in a variety of medical settings,
1:10
Speaker 1: so understanding leeches can be helpful for human health as well.
1:14
Speaker 1: On today's episode, we have doctor Anna Phillips, who's the
1:18
Speaker 1: curator of earthworms and parasitic worms at the Smithsonian Natural
1:21
Speaker 1: History Museum in Washington, d C. And I can't think
1:24
Speaker 1: of a better person to talk to us today about leeches.
1:28
Speaker 1: So welcome to Daniel and Kelly's extraordinary and sometimes a
1:32
Speaker 1: little bit disgusting universe.
1:47
Speaker 2: Hi. I'm Daniel. I'm a particle physicist, and I've never
1:50
Speaker 2: been bitten by a particle.
1:52
Speaker 3: Hi.
1:52
Speaker 1: I'm Kelly Wienersmith. I'm a parasitologist and I've been bitten
1:56
Speaker 1: by leeches and it was okay, it was fine.
2:00
Speaker 2: Ends clearly they've infected you with some sort of brain
2:04
Speaker 2: disease that made you think it was okay.
2:06
Speaker 1: You know, we're gonna learn today the surprisingly they don't
2:09
Speaker 1: vector a lot of diseases. I'm like mosquitoes and ticks,
2:12
Speaker 1: they're not so bad. They're just hungry, which I get.
2:16
Speaker 2: I get that you've been brainwashed, you've been leech washed
2:18
Speaker 2: by leeches. I am not okay with being bitten by leeches.
2:22
Speaker 1: Well, I'm hoping that we can leech wash at least
2:24
Speaker 1: a few of our listeners today into thinking that leeches
2:27
Speaker 1: are maybe still gross, but that there's absolutely some fascinating
2:30
Speaker 1: stuff to learn from them.
2:31
Speaker 2: All right, well, then my question for you today, Kelly,
2:33
Speaker 2: is what is the grossest thing you have been bitten by?
2:37
Speaker 1: Oh? Gosh, the grossest thing I've been bitten by? I
2:40
Speaker 1: guess that's gotta be ticks.
2:42
Speaker 2: Ticks are the worst.
2:43
Speaker 1: I hate ticks. I really hate ticks. Like leeches. I'm
2:47
Speaker 1: okay with ticks, man, I hate them. You know. So
2:49
Speaker 1: you get a take, you pull it off, and you're like, oh, well,
2:52
Speaker 1: now should I send it in for testing? Do I
2:53
Speaker 1: have to worry that I got lime disease? What about
2:56
Speaker 1: you know, Rocky Mountain spotted fever? And whereas if you
2:59
Speaker 1: get bit by a leech, just like, oh I'm bleeding
3:01
Speaker 1: a little. That stinks, but you don't worry about what's
3:03
Speaker 1: going to happen afterwards, like that's the end of the encounter.
3:06
Speaker 1: And I get bit by ticks pretty often and it
3:08
Speaker 1: kind of freaks me out. I regularly spray my clothes
3:10
Speaker 1: with permethrin during the summer when I'm going to be
3:12
Speaker 1: going out in the woods, and like every member of
3:14
Speaker 1: our family has a set of permethrin treated clothes that
3:18
Speaker 1: they wear if they're going to be going out into
3:19
Speaker 1: the woods, because we've already had some lime in the
3:21
Speaker 1: family and we don't want anymore. What about you, what's
3:24
Speaker 1: the weirdest or gressest thing you've ever been bitten by?
3:26
Speaker 1: Not a particle.
3:29
Speaker 2: I was bitten by our pet rats once, so I
3:31
Speaker 2: have had a rat bite, and in their defense, my
3:35
Speaker 2: finger was covered with whipped cream and I stuck it
3:37
Speaker 2: in the cage and they got very enthusiastic. I don't
3:39
Speaker 2: think they were trying to bite my finger, but you know,
3:42
Speaker 2: how could you control yourself? It's whipped cream.
3:44
Speaker 1: I get it. I'm sorry. I understand the rats in
3:46
Speaker 1: that case. I've also been bit by a boa constrictor
3:49
Speaker 1: when I went to feed it a rat and I
3:51
Speaker 1: wasn't really careful about what I was doing with my hand.
3:54
Speaker 1: And then I also got bit once by an alligator
3:56
Speaker 1: gar Have you seen these?
3:58
Speaker 2: Is that like an alligator.
3:59
Speaker 1: It's a fit with an alligator like mouth. They're common
4:02
Speaker 1: in the South, but there's also some in Lake Eerie
4:05
Speaker 1: and I was doing a fish survey and I thought
4:07
Speaker 1: one had passed away, but even though it was very dry,
4:09
Speaker 1: it was still kicking. So I grabbed it by the
4:11
Speaker 1: tail and it turned around, and I was like, ah,
4:14
Speaker 1: I'm so.
4:14
Speaker 2: Sorry it's biting you and you're apologizing to it. Wow,
4:17
Speaker 2: you're so polite.
4:18
Speaker 1: I mean, if I were on the way out and
4:20
Speaker 1: somebody was harassing me, I would be grumpy about that too.
4:23
Speaker 1: I understood where it was coming from, but yeah, sorry.
4:25
Speaker 1: Your story reminded me of some of my other stories
4:27
Speaker 1: that how could I have forgotten?
4:28
Speaker 2: Well, your comment earlier about not being too grumpy about
4:31
Speaker 2: giving blood to leeches made me think about mosquitoes, because
4:35
Speaker 2: we recently had mosquitoes basically taking over southern California. When
4:39
Speaker 2: I moved here twenty years ago, there were almost no mosquitoes,
4:42
Speaker 2: and how their mosquitoes everywhere drives me crazy because I
4:46
Speaker 2: would happily give up a little bit of blood to
4:47
Speaker 2: mosquitoes if they didn't deposit the anesthetic that you then
4:51
Speaker 2: react to like it frustrates me endlessly. I would like
4:54
Speaker 2: set out a little pool of blood, you know, for
4:56
Speaker 2: them every day. If we could strike a deal with
4:58
Speaker 2: mosquitoes like stop giving me bites and drink my blood,
5:02
Speaker 2: I would happily give up blood to avoid mosquito bites.
5:05
Speaker 1: Oh, man, only we could have like a doctor Doolittle.
5:07
Speaker 1: But who could communicate with the mosquitos to set that
5:09
Speaker 1: kind of exchange up? That would be ideal. Why do
5:12
Speaker 1: you have so many more mosquitos? Has a new species
5:14
Speaker 1: moved in? Is it wetter? With more standing pools of water?
5:17
Speaker 1: Would change?
5:18
Speaker 2: I read this story once that claimed that they all
5:20
Speaker 2: came in one shipping container to Long Beach from China
5:24
Speaker 2: and they basically took over like it was a huge
5:27
Speaker 2: invasion of this Chinese tiny mosquito, not like the big
5:31
Speaker 2: American mosquitoes, but these little ones that also bite you
5:34
Speaker 2: multiple times, so you don't just get like one bite,
5:36
Speaker 2: you could like a series of bites. Oh really, not
5:38
Speaker 2: a fan?
5:39
Speaker 3: Wait?
5:39
Speaker 1: Why was China shipping us mosquitoes? They just accidentally got
5:42
Speaker 1: into a shipment? Is that the deal?
5:44
Speaker 2: Or somebody ordered mosquitos on Amazon and now we're all suffering?
5:48
Speaker 4: No?
5:48
Speaker 2: I think it was an accident. Yeah, there was some
5:50
Speaker 2: pool standing water in this shipping container and they survived
5:53
Speaker 2: the transit and they opened it up in Long Beach.
5:55
Speaker 2: Dot dot dot. My life is now terrible.
5:57
Speaker 1: That's the worst. I'm sorry. We've got an Asian longhorn
6:00
Speaker 1: and tick, which I think also accidentally got here, and
6:03
Speaker 1: it can reproduce without finding a mate. You get one,
6:05
Speaker 1: and then you've got ten, and then you've got hundreds.
6:07
Speaker 1: And there are cattle out here that are getting like exsanguinated.
6:12
Speaker 1: If they're not checked on regularly enough, they end up
6:14
Speaker 1: getting tons of them and then they don't have enough
6:15
Speaker 1: blood to do what they need to do.
6:16
Speaker 2: So anyway, exanguinated, my mental image is that you go
6:20
Speaker 2: out to check on your cow and it's just like
6:22
Speaker 2: a dry heap of skin and bones. Is that what
6:24
Speaker 2: we're talking about.
6:25
Speaker 1: I think they die before they look how you might
6:28
Speaker 1: imagine Dracula looks waking up in the morning. But yeah,
6:30
Speaker 1: I mean the dying from lack of blood. And I
6:32
Speaker 1: think there's some concern that there's a hemorrhagic fever in
6:35
Speaker 1: the native area that like could jump to here and
6:38
Speaker 1: now instead of in addition to lime, you'd have to
6:40
Speaker 1: worry about hemorrhagic fevers. And anyway, it's so great that
6:43
Speaker 1: we can ship stuff around the world, but it's got
6:45
Speaker 1: its downsides.
6:48
Speaker 2: All right, Well, today we're not just talking about what
6:50
Speaker 2: Daniel doesn't like to be bitten by, and what Kelly
6:52
Speaker 2: doesn't mind being bitten by. We're talking about all the
6:55
Speaker 2: exciting signs behind leeches.
6:57
Speaker 1: And so we asked you what is the first thing
7:01
Speaker 1: you think when you think of leeches? And I got
7:05
Speaker 1: to say, I got a couple answers that I expected,
7:07
Speaker 1: a couple that were very unexpected. And if you would
7:10
Speaker 1: like to be asked what you think about a topic
7:12
Speaker 1: we're going to talk about on the show, email us
7:14
Speaker 1: at questions at Daniel and Kelly dot org. So let's
7:17
Speaker 1: hear what our listeners had to say.
7:19
Speaker 3: A picture that I've seen of a black hole eating
7:23
Speaker 3: the material from a closely orbiting star.
7:26
Speaker 5: Honestly, they're just the wist and I can't think of
7:29
Speaker 5: anything more disgusting. The first thing I think of is
7:32
Speaker 5: medical grade leeches that are used to drain blood from hematomas,
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Speaker 5: bruises under the skin that have a lot of blood
7:41
Speaker 5: in them.
7:42
Speaker 6: The first thing I think of when I hear leeches
7:45
Speaker 6: is traveling down the Brasis River in Texas on a
7:48
Speaker 6: boy scout trip and on an inner tube and coming
7:52
Speaker 6: out with leeches stuck to the inner tube and a
7:55
Speaker 6: few to my legs. No fun.
7:58
Speaker 4: Watching the movie The African Queen with Katherine Hepburn and
8:01
Speaker 4: Humphrey Bogart, and they have to tow his boat through
8:04
Speaker 4: the swamp, waiting in the swamp, and when they get
8:07
Speaker 4: out there covered with leeches, and they have to spread
8:10
Speaker 4: salt on the leeches to get them off.
8:13
Speaker 7: Medieval medical practices where they were used for almost everything
8:19
Speaker 7: from headaches to ingrown toenails. I don't know conjunct to
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Speaker 7: fight us not all it being one of Dracula's favorite pets.
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Speaker 1: They've seen and stand by Me where they're swimming across
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Speaker 1: the swamp and they suddenly discover that they're covered in leeches.
8:36
Speaker 2: I think of the movie stand by Me.
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Speaker 6: Wasn't there an old black and white movie called Attack
8:42
Speaker 6: of Leeches?
8:43
Speaker 3: Or something seen from stand by Me?
8:46
Speaker 5: The third thing that comes to mind is the irs.
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Speaker 2: I think of the way they ribed and twisted.
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Speaker 1: When I discovered them as a kid, I thought it
8:53
Speaker 1: was swimming around my finger in a strange way.
8:55
Speaker 2: Then I pictured my mom screaming.
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Speaker 5: The barber surgeon from the Middle Ages applying them meditionally
9:02
Speaker 5: up with that in quotes.
9:03
Speaker 1: So I love that. The very first answer that hit
9:06
Speaker 1: my inbox was a picture that I've seen of a
9:09
Speaker 1: black hole eating the material from a closely orbiting star.
9:12
Speaker 1: I was like, Wow, in my world, that is not
9:15
Speaker 1: what you would expect the answer to be. But like,
9:18
Speaker 1: I see that, that's a fascinating answer. That was great.
9:20
Speaker 2: That's our audience right there. Physics biology crossover.
9:23
Speaker 1: Yeah, it's amazing. And then most of the other responses
9:26
Speaker 1: were like I expected people to mention stand by me,
9:29
Speaker 1: and I expected people to mention that one movie with
9:32
Speaker 1: Catherine Hepburn African Queen I think it was, and then
9:35
Speaker 1: mostly to be grossed out. And so that was more
9:38
Speaker 1: or less what I was expecting. What did you think?
9:40
Speaker 2: Yeah, these answers basically mimic my thoughts about leeches. I'm
9:44
Speaker 2: totally uninformed. I don't know anything about leeches compared to
9:47
Speaker 2: anything else except that I'm grossed out with anything bites me.
9:50
Speaker 2: So I'm curious to learn what is the science of leeches,
9:53
Speaker 2: what are leech scientists leechologists working on. What motivates somebody
9:57
Speaker 2: to get into leeches anyway, rather than basic any other
10:01
Speaker 2: field of science. So yeah, I want to meet your
10:04
Speaker 2: friend and hear all about leeches.
10:06
Speaker 1: Wait, wait, so would you say that this is at
10:07
Speaker 1: the bottom of the list of science jobs you would
10:09
Speaker 1: want studying leeches.
10:11
Speaker 2: It's not near the top, that's for sure. I wouldn't
10:14
Speaker 2: put it in the top fifty or one thousand science jobs.
10:17
Speaker 2: I mean, I think I'm pretty capable of getting interested
10:20
Speaker 2: in almost anything, but yeah, this is a bit of
10:22
Speaker 2: a gross out factor for me.
10:24
Speaker 1: I gotta say, if somebody said you could be the
10:26
Speaker 1: leech person at the Smithsonian Museum, I'd be like, I
10:30
Speaker 1: enjoyed studying space, but I'm studying leeches now, and I
10:32
Speaker 1: would make that jump. All right, So today we are
10:35
Speaker 1: talking to doctor Anna Phillips. She works for the Smithsonian
10:39
Speaker 1: Natural histor Museum in Washington, DC, and she is just
10:41
Speaker 1: delightful and she's going to tell us all about leeches.
10:44
Speaker 2: And wait for it, I'm going to make a connection
10:46
Speaker 2: between Kelly's two passions, space and leeches.
10:50
Speaker 1: Yeah, that was pretty clever at the end there, All right, enjoy.
10:55
Speaker 1: Doctor Anna Phillips is a research zoologist and curator of Klitalata,
11:00
Speaker 1: which is a class of anilid worms also known as
11:02
Speaker 1: earthworms and parasitic worms. At the Smithsonian Museum of Natural History.
11:06
Speaker 1: She studies biodiversity and the evolutionary history of parasitic worms
11:10
Speaker 1: and specializes in leeches and tapeworms. She's my hero in
11:15
Speaker 1: my world. She's a legend for doing her leech dance
11:17
Speaker 1: in a video for the BBC, which we're going to
11:19
Speaker 1: discuss later in the show. Welcome Anna, I I'm excited
11:24
Speaker 1: to be here. I'm excited to have you here. Did
11:27
Speaker 1: I say klitalada rte or did I say it wrong?
11:30
Speaker 3: Works for me?
11:32
Speaker 1: Nice? Oh man. I always love it when I get
11:34
Speaker 1: those slam dugs right from the beginning. So, you know,
11:37
Speaker 1: I think for a lot of people when we're growing
11:40
Speaker 1: up as kids, like I thought maybe I would study
11:42
Speaker 1: tigers or elephants, or you know, maybe anything other than
11:47
Speaker 1: worms living in the brains of fish. What was your
11:50
Speaker 1: path to getting excited about leeches.
11:53
Speaker 3: I was definitely not a five year old who thought
11:55
Speaker 3: I would grow up to study worms. It was a
11:57
Speaker 3: little bit of a winding road. When I was a kid,
12:00
Speaker 3: I was really excited about dinosaurs. They were sort of
12:05
Speaker 3: a good introduction into the scientific world for me. But
12:08
Speaker 3: as I got older, I realized there were a lot
12:11
Speaker 3: more other cool animals out in the world. And when
12:14
Speaker 3: I was an undergraduate, I applied for an internship through
12:18
Speaker 3: a program run by the National Science Foundation called Research
12:22
Speaker 3: Experience for Undergraduates, the RIU program, and it's funded by
12:27
Speaker 3: the National Science Foundation, and it's an opportunity for students
12:31
Speaker 3: to go work in science labs and working with me,
12:34
Speaker 3: a real scientist, and to work on projects and learn
12:37
Speaker 3: about the scientific research process. And there were many different projects.
12:43
Speaker 3: There were ones on scorpions and bats and bees and catfish,
12:46
Speaker 3: and there was one on leeches. And I thought, oh, no,
12:50
Speaker 3: one will apply for the one on leeches. I'll have
12:53
Speaker 3: better odds. That's amazing. Yeah, so I applied and it
12:58
Speaker 3: turns out six people applied. Oh, but I was selected.
13:02
Speaker 3: And that summer ended up being everything I thought science
13:05
Speaker 3: should be. There was work with specimens, there was field work.
13:08
Speaker 3: I went to a conference, got to work in a
13:10
Speaker 3: molecular lab, and we ended up being able to publish
13:13
Speaker 3: it nice. So then my advisor invited me back for
13:16
Speaker 3: a PhD to expand the project from my internship, and
13:21
Speaker 3: it was the rest is history.
13:23
Speaker 2: Do you think that you were lucky that you happened
13:25
Speaker 2: to stumble on a field you were fascinated by, or
13:28
Speaker 2: are you just the kind of person who can dig
13:29
Speaker 2: into anything and find the mysteries and the juicy questions,
13:33
Speaker 2: and that you just happened to end up in this field.
13:36
Speaker 3: I think there's a quality of researchers who like to
13:40
Speaker 3: dig in and find the juicy questions. So in some
13:43
Speaker 3: sense I could have ended up in other places and
13:45
Speaker 3: studying other animals, but leeches ended up being a really
13:50
Speaker 3: good fit for me. I had always found worms to
13:53
Speaker 3: be more interesting than like molluscs or insects or other things.
13:59
Speaker 3: It's also a good fit in the sense that, like,
14:01
Speaker 3: no matter where you go in the world, people know
14:03
Speaker 3: what leeches are. It's like the one worm that everyone
14:06
Speaker 3: You can say like all the bloodsucking worms, and you know,
14:09
Speaker 3: sort of point to your skin and people are like, oh,
14:11
Speaker 3: I know what that is. So even if they don't
14:13
Speaker 3: speak English, I think things worked out in a way.
14:16
Speaker 3: But yeah, I do kind of get distracted sometimes and
14:19
Speaker 3: find other things that I could dive in on and
14:22
Speaker 3: have to go no. No, remember parasites.
14:24
Speaker 1: So when students contact me and they say, oh, I
14:26
Speaker 1: want to go into marine biology, I'm like, Okay, I
14:29
Speaker 1: know you're excited about the dolphins, but an easier way
14:33
Speaker 1: in is the dolphin parasites Because fewer people are excited
14:36
Speaker 1: about those, and then you can become a marine biologist
14:39
Speaker 1: through the parasites. And I'm really hoping that they're going
14:42
Speaker 1: to get hooked on the parasites. And I have been
14:44
Speaker 1: surprised by how many students do get hooked on the
14:46
Speaker 1: parasites and then they're like, yeah, yeah, the dolphins are cool,
14:48
Speaker 1: but have you looked at the look at this worm.
14:50
Speaker 1: And I'm like, yes, we've hooked you exactly.
14:53
Speaker 3: Yeah. And this is what I tell a lot of
14:54
Speaker 3: students coming through is that it's good to have a
14:57
Speaker 3: goal and to be ambitious and to be aiming for something,
14:59
Speaker 3: but also flexibility, to have flexible interest, I would say,
15:04
Speaker 3: because like I said, I wanted to study dinosaurs and
15:05
Speaker 3: now I study worms and they don't even have fossils.
15:09
Speaker 3: But you know, it worked out. I'm pretty happy.
15:12
Speaker 1: I'm glad you're happy. So let's talk about where leeches
15:15
Speaker 1: are on the tree of life, so like what are
15:17
Speaker 1: their closest relatives, and then also like how many species
15:21
Speaker 1: of leeches do we think that there are? So, like
15:24
Speaker 1: you said in your intro, leeches are clidalate anaalids, so
15:28
Speaker 1: an analyta, these are the segmented worms with body cavities.
15:32
Speaker 3: So there's all the polykeets, which are the marine worms,
15:36
Speaker 3: which I don't focus on those because I don't work
15:38
Speaker 3: in marine environments very often. And then the other anelids
15:42
Speaker 3: are the clydalit anelids. This includes the oliga keats, which
15:45
Speaker 3: includes earthworms. It also includes brankie of deeladins, which are
15:50
Speaker 3: the crayfish worms, so they are symbiotic worms that live
15:53
Speaker 3: with crayfish. They're not parasitic, they're commensal organism. And then
15:58
Speaker 3: they're the leeches. With leeches, about half of them are
16:02
Speaker 3: blood feeding and the other half aren't.
16:04
Speaker 1: What are the other half doing?
16:05
Speaker 3: They're eating insect larvae, bacterial mats, just about anything and
16:10
Speaker 3: getting their mouths around. But they're not sucking blood, so
16:13
Speaker 3: they're not as interesting.
16:15
Speaker 2: So what are the big open science questions about leeches?
16:18
Speaker 2: I think it's fascinating that Kelly's first question is like,
16:21
Speaker 2: how do these relate to other living critters? Where do
16:23
Speaker 2: you put them on the tree of life? How do
16:25
Speaker 2: we organize them? Is that the motivating question? Is it,
16:27
Speaker 2: like all to try to understand how everything got here
16:30
Speaker 2: in the evolutionary history of it? Or are there still mysteries,
16:33
Speaker 2: but like, how do leeches accomplish this amazing thing they do?
16:35
Speaker 2: What are the sort of biggest open questions there in leeches?
16:39
Speaker 3: My research is with systematics and evolutions, so looking at
16:43
Speaker 3: the number of species, describing new species, how they're related
16:46
Speaker 3: to each other. So that's most of what my expertise is,
16:49
Speaker 3: and that's also what I find interesting. There are so
16:52
Speaker 3: many other aspects of leech biology that have many interesting questions.
16:57
Speaker 3: So for leeches, there's probably between eight hundred and a
17:00
Speaker 3: thousand species of leeches in the world, which compared to
17:04
Speaker 3: a lot of other worm groups, is pretty small. Like
17:07
Speaker 3: Nematodes has probably more than sixteen thousand species. So the
17:11
Speaker 3: order of tapeworms that I work in has more than
17:14
Speaker 3: thirty five hundred species, so eight hundred is pretty small.
17:18
Speaker 3: But what's really cool about leeches is to all the
17:20
Speaker 3: different evolutionary transitions within that group. In terms of the
17:25
Speaker 3: interesting questions it's looking at, like, wow, we have so
17:28
Speaker 3: many different feeding strategies. They occur in so many different environments.
17:31
Speaker 3: There's marine leeches, there's terrestrial leeches, there's burrowing leeches as
17:35
Speaker 3: well as the blood feeders, and so with all of
17:38
Speaker 3: these different evolutionary transitions. It's a more tractable group to
17:43
Speaker 3: explore those questions because you don't have to go through
17:45
Speaker 3: five hundred species. You can look at smaller groups with
17:49
Speaker 3: twenty or something, which is easier to approach. And then,
17:53
Speaker 3: like I said, they're pretty accessible. You can go to
17:56
Speaker 3: a lot of different places in the world and find
17:58
Speaker 3: leeches a lot of different habitats, and that can be
18:01
Speaker 3: easier than like studying things in the deep sea, for instance,
18:03
Speaker 3: where it's very expensive and revolves a lot of equipment
18:06
Speaker 3: and planning.
18:07
Speaker 1: So when we asked our audience what they think of
18:10
Speaker 1: when they think of leeches, a number of them noted
18:13
Speaker 1: that in like medieval times, leeches were used to treat
18:17
Speaker 1: like every single disease you could imagine, And so I
18:20
Speaker 1: was wondering if you could speak at all to the
18:23
Speaker 1: current use of leeches in medicine. I know that's not systematics,
18:26
Speaker 1: Is it okay to ask you about that?
18:28
Speaker 3: Sure? Yeah, yeah. This is actually one of the points
18:31
Speaker 3: of why leeches are important to the world because of
18:34
Speaker 3: their use in medicine, they've also been used as a
18:38
Speaker 3: model organism in a number of other fields, like neurology,
18:41
Speaker 3: and some importance in pharmacology and developmental biology studies. But
18:47
Speaker 3: when it comes to their use in medicine, yeah, they
18:49
Speaker 3: were really popular in the seventeen eighteen hundreds for blood letting.
18:53
Speaker 3: Prior to that, people would cut open arteries and veins
18:58
Speaker 3: to balance the humors and get some with the blood out.
19:01
Speaker 3: But leeches were an improvement on the situation because it's
19:04
Speaker 3: easier to get it to stop bleeding versus when you
19:08
Speaker 3: slice open artery in vain that it can be a challenge. Also,
19:12
Speaker 3: if you want to take more blood, you put more
19:14
Speaker 3: leeches on. If you want to take less blood, you
19:16
Speaker 3: take them off. It was a more controllable way of
19:19
Speaker 3: blood letting.
19:20
Speaker 1: Just to be clear, it wasn't helping anything, right, It
19:22
Speaker 1: was just like a less damaging way to damage your patient,
19:27
Speaker 1: and that was the benefit back then. Is that right?
19:29
Speaker 3: They thought it was helping. Okay, but now we know
19:33
Speaker 3: that leeches are only beneficial in certain cases. It's not
19:36
Speaker 3: going to cure your headache, it's not gonna to your hysteria,
19:40
Speaker 3: So the blood letting only helps certain situations. So today
19:44
Speaker 3: in modern medicine, leeches are still used. They were approved
19:47
Speaker 3: as a medical device in the US in two thousand
19:49
Speaker 3: and four, so they're not experimental. So what they're usedful
19:52
Speaker 3: in modern medicine is because leeches have antiquagulants in their saliva,
19:57
Speaker 3: so when they're abiding, they're exuding this ty wagulants blood
20:01
Speaker 3: thinner that's going locally into the wound, and it helps
20:04
Speaker 3: the leech because the wound continues to bleed and the
20:06
Speaker 3: anti wagulant prevents it from clotting, so that means that
20:10
Speaker 3: the leech can ingest the liquid blood easier. But once
20:13
Speaker 3: the leech has finished feeding and it leaves, that wound
20:16
Speaker 3: continues to bleed because those anti coagulants are in a tissue.
20:20
Speaker 3: We take advantage of this in medicine, so in cases
20:22
Speaker 3: where you have a skin graft that has been attached,
20:26
Speaker 3: or if digit reattachment so you cut your finger off
20:29
Speaker 3: and they put it back on. They can attach a
20:32
Speaker 3: lot of the small vessels that bring blood into the digit,
20:36
Speaker 3: but the veins that take the blood away are thinner walled.
20:39
Speaker 3: It's harder to attach those, and a lot of times
20:42
Speaker 3: they get the major vessels together, but they have to
20:45
Speaker 3: wait for those veins to regrow on their own. In
20:48
Speaker 3: the meantime, this means all the blood is rushing into
20:51
Speaker 3: this digit, it's swelling up, it's turning purple. It's painful.
20:54
Speaker 3: We can give anti coagulants and blood thinners systemically, like
20:58
Speaker 3: through the whole body, but you have a risk of
21:00
Speaker 3: major bleeding and it's kind of overkill when you just
21:03
Speaker 3: need to get it into that digit. So leeches have
21:06
Speaker 3: really tiny mouths and we can put them on the
21:09
Speaker 3: ends of fingers and noses and ears, and when they
21:13
Speaker 3: start feeding, that anti coagulant goes locally. It helps keep
21:17
Speaker 3: all of the blood flowing so there's no clotting, and
21:20
Speaker 3: then they're relieving that pressure by sucking the blood out
21:24
Speaker 3: and it encourages oxygenated blood to get into this damaged tissue.
21:28
Speaker 3: And so you can see within hours these fingers and
21:32
Speaker 3: toes go from being purple and swollen just suddenly looking
21:35
Speaker 3: much more normal and pink and healthy.
21:37
Speaker 1: Again, aside from all the leeches hanging off of it.
21:41
Speaker 3: Well, yeah, I mean they feed pretty quickly, so they're
21:45
Speaker 3: not going to be there too long.
21:46
Speaker 2: It almost sounds like you're recommending leeches.
21:49
Speaker 3: In certain cases. Wow, they can be a preferable option
21:54
Speaker 3: to other options. Yeah, we also have machines that you
21:57
Speaker 3: can put and suck out blood. But those you typically
22:01
Speaker 3: adhere better to broad surfaces like your back or your leg,
22:05
Speaker 3: But things like fingers and noses and ears have funny shapes,
22:09
Speaker 3: so leeches they attached better.
22:12
Speaker 2: That blows my mind. I think the pop side understanding
22:15
Speaker 2: of leeches, at least, you know, the superficial one that
22:17
Speaker 2: I have as a total non expert, is that, like,
22:20
Speaker 2: people used to use leeches back when they understood nothing
22:22
Speaker 2: about the body, and it was crazy, like drilling holes
22:25
Speaker 2: in your head. But now you're telling me that there
22:27
Speaker 2: are some scenarios where leeches can actually improve the outcome
22:30
Speaker 2: for a patient. And that makes me wonder, do you
22:33
Speaker 2: think those experiences one hundreds of years ago before we
22:35
Speaker 2: understood stuff, are what encouraged people to continue using them
22:38
Speaker 2: that sometimes they actually did help.
22:40
Speaker 3: I think there's a quality to that definitely. Like I said,
22:43
Speaker 3: they're not a cure all, but there were some cases
22:45
Speaker 3: that leeches are helpful.
22:48
Speaker 2: Wow.
22:48
Speaker 3: And then that also promoted a lot of research into
22:51
Speaker 3: why so as we developed more questions, part of that
22:56
Speaker 3: is looking at those anti coagulants and saying, like, well,
22:58
Speaker 3: what anti coagulants are using and can we take that
23:01
Speaker 3: into a pharmacology setting and you know, use those mechanisms
23:06
Speaker 3: without having to actually use the worms themselves. And what
23:09
Speaker 3: they found is that a lot of leeches have heuridin
23:13
Speaker 3: and this is an anti coagulant that's actually the most
23:16
Speaker 3: powerful anti coagulant known. In fact, we don't use it
23:20
Speaker 3: in modern medicine because it's too good. So one of
23:25
Speaker 3: the things about anti wagulants is that when it's causing
23:28
Speaker 3: the blood to continue flowing, we also want to have
23:30
Speaker 3: the ability to stop that. If you have an anti
23:33
Speaker 3: wagulant in your system and you have a major bleeding episode,
23:36
Speaker 3: we want to be able to stop that quickly. And
23:38
Speaker 3: heurdin is not the best for that. We have a
23:41
Speaker 3: hard time getting it to stop. So we have other
23:43
Speaker 3: options now, but it is something that's out there and
23:46
Speaker 3: the scientific community is working with understanding the mechanisms and
23:49
Speaker 3: the process to improve drug development.
23:52
Speaker 1: So mosquitoes and ticks also make anticoagulants. Why don't we
23:56
Speaker 1: use them when your finger falls off or leach is
23:59
Speaker 1: just even better or less creepy.
24:01
Speaker 3: In terms of why the leech anti coagulants would be preferable,
24:06
Speaker 3: I actually don't know.
24:08
Speaker 2: I refuse to believe the mosquitoes could do anything useful
24:11
Speaker 2: for anybody.
24:11
Speaker 1: They are purely even I'm not a fan either.
24:14
Speaker 3: A lot of people would agree with you. I think
24:16
Speaker 3: leeches are much more controllable versus mosquitoes and ticks, especially
24:20
Speaker 3: in a medical setting. And the other aspect is that
24:24
Speaker 3: leeches carry far fewer diseases than mosquitoes and ticks.
24:28
Speaker 1: Could you tell us more about that?
24:30
Speaker 3: So to this point, they've done a ton of research
24:34
Speaker 3: looking at our leeches vectors for bloodborne diseases, and some
24:39
Speaker 3: of the work that was done, especially in the nineties
24:41
Speaker 3: when people were really investigating HIV, to see if leeches
24:44
Speaker 3: were a vector for HIV. What they found is that
24:47
Speaker 3: when a leech feeds on a mouse, for instance, that's
24:51
Speaker 3: infected with these viruses, you can still isolate the virus
24:54
Speaker 3: from the blood meal inside leech. But when they fed
24:57
Speaker 3: the leech on the next mouse that didn't have those visviruses,
25:00
Speaker 3: it doesn't necessarily transmit. Okay, So if you're out getting
25:04
Speaker 3: bitten by leeches, you know, could you get viruses and
25:07
Speaker 3: bloodborn pathogens from that? It's possible, but it's a very
25:12
Speaker 3: very low chance. That's also a good thing about using
25:16
Speaker 3: leeches in modern medicine versus things like mosquitoes and ticks,
25:20
Speaker 3: which transmit a lot of really scary, dangerous viruses.
25:25
Speaker 1: And other hosts for leeches. There are a lot of
25:28
Speaker 1: leeches that, for example, specialize on turtles, Like do they
25:30
Speaker 1: transmit diseases between turtles or in general, are leeches just
25:34
Speaker 1: not good at transmitting diseases.
25:37
Speaker 3: Actually, it's great that you bring up leeches and turtles
25:39
Speaker 3: because there's a couple of cases of different types of
25:42
Speaker 3: blood born parasites between the turtles. So, for one, we
25:46
Speaker 3: know that they can transmit t for panasomes, which is
25:49
Speaker 3: the same organism that causes African sleeping sickness, but it's
25:52
Speaker 3: not making turtles sleepy. So we do know that leeches
25:55
Speaker 3: have been transmitting panisomes with turtles.
25:58
Speaker 1: Could you tell if a turtle with sleep they move
26:00
Speaker 1: pretty slow. Maybe it does make them sleepy and we
26:03
Speaker 1: just can't tell.
26:04
Speaker 3: Someone should look into it. The other thing is that
26:07
Speaker 3: they'll to transmit hemogregrons, which are our small blood worn pathogen,
26:11
Speaker 3: but as far as we know, it's not making the
26:13
Speaker 3: turtles sick. What we found is that turtles that have
26:18
Speaker 3: a small home range have fewer species of hemogregrans versus
26:23
Speaker 3: turtles that have a wider range encounter have more species,
26:28
Speaker 3: which means that they're encountering more leeches and more different
26:32
Speaker 3: types of bloodborn pathogens. But it means that the turtles
26:35
Speaker 3: that are wandering farther away, which we would assume would
26:38
Speaker 3: be they'd be healthier, they actually have a higher number
26:41
Speaker 3: of these blood parasites. So in this case it may
26:45
Speaker 3: indicate that the turtles are doing better. So maybe the
26:47
Speaker 3: blood parasites they don't hurt them that much, and so
26:51
Speaker 3: the healthy turtles are moving around a lot, and when
26:53
Speaker 3: they get blood parasites, they're like whatever, yeah, as far
26:56
Speaker 3: as we know, h Okay, interesting.
26:59
Speaker 1: Yeah, we're going to take a break, and then we
27:01
Speaker 1: are going to talk about other kinds of hosts that
27:04
Speaker 1: we find leeches on. Okay, so Anna, I'm generally interested
27:23
Speaker 1: in the different kinds of species that end up getting
27:26
Speaker 1: bitten by leeches, but I really want to know what
27:29
Speaker 1: is the weirdest place you've ever heard a leech found
27:32
Speaker 1: on an animal.
27:33
Speaker 3: Leeches will feed on a lot of different hosts, but
27:37
Speaker 3: it depends on the kind of leech. So some leeches
27:40
Speaker 3: have preferences and others don't really care. So in North
27:44
Speaker 3: America like Macrobdella decora, the North American medicinal leech, for instance,
27:48
Speaker 3: they just want vertebrate blood. It doesn't really matter. They'll
27:53
Speaker 3: go for frogs a lot of frog blood. But also
27:57
Speaker 3: they'll feed on fish mammals including humans. So some leeches
28:02
Speaker 3: doesn't really matter. Other leeches can be pretty specific, like
28:05
Speaker 3: they prefer turtles and maybe a fish, especially in the
28:10
Speaker 3: marine environments fish leeches they will actually prefer certain groups
28:15
Speaker 3: of fish. So yeah, it's all over the place, but
28:18
Speaker 3: it does depend on the type of leech and what
28:20
Speaker 3: their preferences are.
28:21
Speaker 2: Why would a leech evolve a preference. Isn't it better
28:24
Speaker 2: to be able to suck on lots of different kinds
28:25
Speaker 2: of stuff?
28:26
Speaker 3: You would think This kind of gets into like generalists
28:29
Speaker 3: versus specialists and biology and it's what's working for it.
28:34
Speaker 1: So most of our audience is physics and astronomy geeks.
28:38
Speaker 1: So could you just go into a little bit more
28:39
Speaker 1: detail on specialists in generalists?
28:41
Speaker 2: Do we understand in general why evolution produces both kinds
28:44
Speaker 2: of things? What would inspire one direction versus another, what
28:48
Speaker 2: causes it, and do we understand that at all.
28:51
Speaker 3: I'm not sure we do in leeches.
28:53
Speaker 1: Okay, so here I'm just going to spit ball for
28:55
Speaker 1: a second. I can imagine that it could be great
28:58
Speaker 1: to be able to drink the blood from any mammal
29:01
Speaker 1: you come across. It'd be easier to find food. But
29:04
Speaker 1: if you're a specialist, maybe you are more used to
29:08
Speaker 1: a particular kind of blood, so it's easier for you
29:10
Speaker 1: to extract resources or energy from it. Here's a question
29:14
Speaker 1: when leeches bite a host, is there anything in the
29:17
Speaker 1: host like that's an immune response that tries to attack
29:20
Speaker 1: and kill the leech or do leeches just get free
29:23
Speaker 1: meals everywhere they go? Because I can imagine if you
29:26
Speaker 1: specialize in a certain kind of host, maybe you get
29:28
Speaker 1: good at avoiding their ways of trying to kill you.
29:31
Speaker 1: But I guess do leaches just not have those kinds
29:33
Speaker 1: of problems.
29:34
Speaker 3: With other types of parasites That immune response is really important.
29:37
Speaker 3: And I agree in that point with leeches, because they're
29:40
Speaker 3: temporary ectoparasites, They're not there long enough to really have
29:44
Speaker 3: to deal with host immune system all that much. I
29:47
Speaker 3: don't know how much that's playing a role in their
29:51
Speaker 3: feeding preferences. I think it's probably more along the lines
29:56
Speaker 3: of how frequently they encounter good hosts. So, especially leeches
30:01
Speaker 3: and marine environments that are feeding on fish aren't always
30:05
Speaker 3: great swimmers, so when they get on a fish, they
30:09
Speaker 3: tend to stay there, and then there is the possibility
30:11
Speaker 3: that if that fish gets eaten by another fish, they
30:13
Speaker 3: may transfer at that point. But a lot of that
30:16
Speaker 3: is like very short distances that they can cross on
30:18
Speaker 3: their own. So maybe fish that occur in schools where
30:24
Speaker 3: there's many options and so the leech doesn't have to
30:27
Speaker 3: go very far. That would be an instance where being
30:31
Speaker 3: a specialist, you know, they can get by with it.
30:34
Speaker 3: But for a leach to this out in like a
30:36
Speaker 3: pond and may not have all that many individuals of
30:40
Speaker 3: a frog, for instance, they would then want to have
30:43
Speaker 3: more options available and so that they can go for
30:45
Speaker 3: the fish or the frogs or you know, a bird
30:48
Speaker 3: or the occasional person. So I think it's more about
30:52
Speaker 3: like how many different species they're encountering in the abundance
30:56
Speaker 3: of those species.
30:57
Speaker 1: Okay, cool, So when I look at leech, I always
31:01
Speaker 1: get frustrated when people say, oh, parasites, they're just these
31:03
Speaker 1: degenerate organisms, but like you know, they don't appear to
31:06
Speaker 1: be able to move around much and they don't seem
31:09
Speaker 1: to have a lot of sensory organs. How do leeches
31:12
Speaker 1: find and get to their hosts because they just look
31:14
Speaker 1: like these little blobs. How do they navigate their environment?
31:17
Speaker 3: There's a lot of questions about this. I will say
31:19
Speaker 3: this is a very well it should be an active
31:22
Speaker 3: area of research. So leeches have incredible senses. Many leeches
31:27
Speaker 3: have eyes, so there are little pigment cumps that detect light,
31:31
Speaker 3: dark and movements. They're not like our eyes that actually
31:34
Speaker 3: see images, but they don't like light because that means
31:37
Speaker 3: that they're exposed and they're easier to be eaten. So
31:40
Speaker 3: they want to kind of gravitate towards darkness. But at
31:43
Speaker 3: the same time, movement in a potential host is nearby,
31:46
Speaker 3: they want to go towards that. So they have eyes.
31:49
Speaker 3: They have sinsily on their bodies that these little pepili,
31:53
Speaker 3: these little bumps that when they're in the water, they
31:55
Speaker 3: can feel the vibrations and that helps them swim. Granted
32:00
Speaker 3: they're not the fastest swimmers, but they will swim in
32:04
Speaker 3: the direction of that movement. To go investigate and say, oh,
32:07
Speaker 3: is there something I can eat over here?
32:09
Speaker 2: Did they ever latch onto the wrong thing? Like they
32:11
Speaker 2: latch onto something they think is a person. They try
32:13
Speaker 2: to suck on it, and it's just like you know,
32:15
Speaker 2: a slimy blob of moss or something.
32:17
Speaker 3: Well, I don't know how much the slimy blob of
32:20
Speaker 3: moss is moving, but I don't know if they're trying
32:22
Speaker 3: to bite, But they definitely will investigate things they're moving.
32:26
Speaker 3: Something else about a lot of leeches that they like
32:28
Speaker 3: flat surfaces. It's easier for them to stick to, and
32:31
Speaker 3: so a lot of times when we're out, especially in
32:33
Speaker 3: places where there's a lot of debris and trash, they
32:36
Speaker 3: will stick to broad surfaces of things like bottles and
32:40
Speaker 3: pie plates and just any kind of flat debris. They'll
32:44
Speaker 3: just kind of hang out there. I don't think they're
32:46
Speaker 3: nicely looking for a host, but something you know, they
32:49
Speaker 3: can get underneath, and they can stick too easily.
32:51
Speaker 1: I've seen them on soda cans.
32:53
Speaker 3: Yeah, exactly. Yes, it was another part to your question.
32:56
Speaker 1: Well, so I was gonna interrupt and tell the story
32:58
Speaker 1: about like why in my world you are so famous,
33:01
Speaker 1: and it's because you got to be on the BBC
33:03
Speaker 1: once and you use the fact that they respond to
33:07
Speaker 1: vibrations or movements in the water and you danced in
33:10
Speaker 1: a BBC video to attract the leeches. Is that usually
33:14
Speaker 1: how you attract the leeches. Does that mean that they're
33:16
Speaker 1: biting you for you to get them or tell us
33:18
Speaker 1: about collecting leeches and then we'll get back to the
33:20
Speaker 1: sensory stuff.
33:22
Speaker 3: Yeah. So one of the things that we have done,
33:25
Speaker 3: those of us who have been trying to collect as
33:27
Speaker 3: many leeches as we can for our research, is to
33:30
Speaker 3: use ourselves as bait. This obviously only works in the
33:33
Speaker 3: blood feeders, but when we go out into a pond,
33:36
Speaker 3: we want to get out and look everywhere. So this involves,
33:39
Speaker 3: you know, getting into the water about knee deep. We
33:43
Speaker 3: look through plants, submerge debris like I was talking about,
33:47
Speaker 3: but it's also like tree limbs and rocks and anything
33:51
Speaker 3: that a leech could be hiding under. And while we're
33:53
Speaker 3: doing all of that, we're making a fair bit of
33:55
Speaker 3: you know, motion in the water and we're disturbing it
33:58
Speaker 3: a lot. For the BBC interview, we were specifically interested
34:01
Speaker 3: in the Macrobdella leeches that I was talking about earlier
34:04
Speaker 3: the North American medicinal leeches. So when we got out
34:08
Speaker 3: into the water, one thing we were doing was trying
34:10
Speaker 3: to make a lot of movement, a lot of disturbance
34:12
Speaker 3: to try and to track the leeches. Is kind of
34:14
Speaker 3: like a leech dance, trying to just get as many
34:18
Speaker 3: ripples in the water as possible so that when they
34:20
Speaker 3: do detect that motion, they'll swim closer. But they're not
34:23
Speaker 3: super fast and so it takes some time. So we
34:26
Speaker 3: get in, we make some ripples in the water. You know,
34:28
Speaker 3: everybody has their own style, Like some people are more consistent,
34:31
Speaker 3: you know, up and down, so people are side to side.
34:34
Speaker 3: A lot of room for individuality here. But do you
34:37
Speaker 3: do that and then you kind of let everything quiet
34:39
Speaker 3: down so the leeches, you know, can swim closer, and
34:43
Speaker 3: then you have to kind of go again because they
34:45
Speaker 3: take a minute.
34:45
Speaker 1: Because they're slow. Can you see them coming towards you
34:48
Speaker 1: and catch them in a net or do you not
34:50
Speaker 1: know until they've bit you that Like I have a
34:52
Speaker 1: specimen for the museum now.
34:54
Speaker 3: I like to try and see and get them before
34:57
Speaker 3: they're attaching, because when they're attaching, they're going to try
34:59
Speaker 3: and bite, probably because they're hungry, that's why they're seeking
35:02
Speaker 3: out a host. But many leashes, you'll see them swimming
35:05
Speaker 3: across the surface of the water and you can use
35:07
Speaker 3: a net or you can use your hands and grab them.
35:08
Speaker 3: But some leeches are more sneaky and they kind of
35:11
Speaker 3: dive down and then you don't know. So when you're
35:14
Speaker 3: doing the leech dance and you're making all these ripples
35:16
Speaker 3: in the water, you have to stop periodically and also
35:18
Speaker 3: do a leg check foot check to make sure they
35:21
Speaker 3: haven't gotten somewhere that you can't see because it's below
35:24
Speaker 3: the water. And if you do get them before they bite,
35:27
Speaker 3: then that's a bonus. But if you don't, sometimes you
35:30
Speaker 3: find the leach when it's already bitten and it's being
35:32
Speaker 3: worst case scenarios. You pull your leg out of the
35:34
Speaker 3: water and it's already bleeding and the leach is gone.
35:36
Speaker 1: Oh yes, as a scientist, that is a bummer. I've
35:39
Speaker 1: never seen Daniel make this space before, to be honest,
35:42
Speaker 1: and Daniel and I have been working together for a while.
35:46
Speaker 2: Well you know, I'm a particle physicist and I've never
35:48
Speaker 2: been bitten by a particle, and I don't really have
35:50
Speaker 2: to worry about that. I have to like take one
35:52
Speaker 2: for the team for science. Is this a regular thing?
35:55
Speaker 2: Like how many times have you been bitten by leeches?
35:58
Speaker 2: Is it like so many times you can't even count?
36:00
Speaker 3: Imagine exactly I've lost count. I mean, actually I try
36:04
Speaker 3: to avoid getting bitten me too. Yeah, open wounds, and
36:10
Speaker 3: you know, muddy water can invite other problems that I'd
36:13
Speaker 3: like to avoid. But also a lot of people over time,
36:17
Speaker 3: you know, if you do this for your whole career,
36:19
Speaker 3: you know, so thirty years of getting bitten by leeches,
36:21
Speaker 3: some people develop an allergy to it, and I'd like
36:23
Speaker 3: to avoid that. The other possibility is that you can
36:27
Speaker 3: always wear waiters broad surface the leech will attach to,
36:30
Speaker 3: so you make the movement, but it's less fun.
36:34
Speaker 2: You make it sound like anybody wearing anti leech protection
36:37
Speaker 2: is like a wimp or something you could if you
36:40
Speaker 2: have to.
36:41
Speaker 3: Oh well, I actually have converted to waiters recently. So
36:44
Speaker 3: the only problem with waiters is they get hot.
36:46
Speaker 1: So hot, and then you're sweaty and you stink the
36:49
Speaker 1: rest of the day. And sometimes they get a leak
36:52
Speaker 1: and then it's hard to walk because your feet are heavy.
36:55
Speaker 1: And I totally get not wanting to go in with waiters.
36:58
Speaker 2: It's not even a question from me. So much rather
37:01
Speaker 2: be hot and stinky than bitten by leeches.
37:04
Speaker 1: Like I've talked to people who study mosquitos and to
37:08
Speaker 1: keep the mosquito colony alive, you know, they can get
37:10
Speaker 1: blood bags, but sometimes if they know that they're not
37:12
Speaker 1: infected by anything, they'll feed them with their arms. Does
37:15
Speaker 1: stuff like that ever happen with leeches where you're like, oh,
37:18
Speaker 1: these need to stay alive for another week or two,
37:21
Speaker 1: but I don't have anything other than my arm, or
37:24
Speaker 1: does that just kind of not happen with leeches. How
37:25
Speaker 1: do we feed the medical leeches.
37:27
Speaker 3: I actually don't know how they're feeding them in the labs,
37:29
Speaker 3: But for leeches for my research, I'll bring them back
37:33
Speaker 3: live a lot of times. And I like to show
37:35
Speaker 3: people leeches because I work at the Natural History Museum,
37:37
Speaker 3: so we have a lot of visitors and if we
37:39
Speaker 3: have the opportunity, I like to keep live leeches around
37:42
Speaker 3: to show off. But they don't need to eat all
37:46
Speaker 3: that often, so they can survive for several months without eating.
37:52
Speaker 1: Wow, that's convenient.
37:54
Speaker 3: It's very convenient, especially because it can be a little
37:58
Speaker 3: bit of a process to feed them. Like you said,
38:00
Speaker 3: you know, getting bags of blood leeches. You can't just
38:02
Speaker 3: pour the blood in the water. They can't like absorb it.
38:04
Speaker 3: They have to suck it out of something. So usually
38:07
Speaker 3: we'll get blood from a biological company or the butcher
38:11
Speaker 3: and put it in a nitroplastic glove focohole so the
38:14
Speaker 3: leeches know what's in there and then they will go
38:16
Speaker 3: for it.
38:17
Speaker 2: I was sure you were going to say interns. They
38:19
Speaker 2: use you higher summer interns and use those to feed
38:21
Speaker 2: the leaches.
38:23
Speaker 3: Way too much paperwork.
38:25
Speaker 8: This is the federal government, but it has happened occasionally
38:30
Speaker 8: where everybody's kind of you know, in the break room
38:32
Speaker 8: on a Friday evening and they're like, hey, anna bring
38:34
Speaker 8: the leeches. So, but it's hard to get them to
38:38
Speaker 8: feed in that kind of setting because when they're feeding,
38:41
Speaker 8: they use all of the muscles in their body just
38:43
Speaker 8: suck the blood out and then they move the blood
38:45
Speaker 8: through their body with.
38:47
Speaker 3: All of their muscles. That means they're really vulnerable to
38:50
Speaker 3: predators during that time. So when they're feeding, they need
38:53
Speaker 3: to feel super safe. So if it's dark, if it's quiet,
38:57
Speaker 3: and that is not necessarily the break room afternoon.
39:01
Speaker 1: But if you turn down the lights and you sing
39:02
Speaker 1: it a nice song, sometimes it works out.
39:06
Speaker 3: Yeah, sometimes exactly, and if they're hungry enough. But no
39:09
Speaker 3: one here has ever fed leeches. I believe you one
39:13
Speaker 3: hundred percent.
39:14
Speaker 1: Do we know anything about the evolution to get from
39:16
Speaker 1: earthworms to blood sucking leeches? Do we know anything about
39:20
Speaker 1: the steps in between? Like how do you get from
39:23
Speaker 1: one strategy to another?
39:24
Speaker 3: It's a great question. That's something that we have been
39:26
Speaker 3: debating for over one hundred years with leeches, especially because
39:31
Speaker 3: the closest relatives are the brank you of deladens the
39:33
Speaker 3: crayfish worms, and they're commensals, so they're not necessarily feeding
39:37
Speaker 3: on blood. Now, what's interesting is that the crayfish gets injured,
39:41
Speaker 3: like it loses a leg or a claw comes off,
39:43
Speaker 3: and there's break you of deleadens nearby. They will all
39:46
Speaker 3: go to that wound and start feeding on the crayfish blood.
39:49
Speaker 1: Huh.
39:50
Speaker 3: But they won't necessarily make the wound themselves.
39:53
Speaker 1: Okay, So that seems like it could be like a
39:55
Speaker 1: step on the way, Like you live with the crayfish,
39:58
Speaker 1: and then you feed on it when it gets hurt,
40:00
Speaker 1: and then you eventually have the ability to hurt them
40:03
Speaker 1: and suck their blood.
40:04
Speaker 3: Yeah, but the branci ofb delins, there aren't any parasitic
40:06
Speaker 3: branchib deeldins. And then with leeches, there's been this long
40:09
Speaker 3: debate about the ancestral leech was a blood feeding or not,
40:14
Speaker 3: And we still don't know the answer to that because
40:16
Speaker 3: it happened so long ago. Our molecular data, the DNA
40:19
Speaker 3: sequences haven't kept that signature very strong in the data,
40:24
Speaker 3: so we still kind of debate about that. Within certain groups,
40:27
Speaker 3: we can tell that yes, there was a blood feeding ancestor.
40:31
Speaker 3: So for instance, in the group that I have spent
40:33
Speaker 3: the most time working on, the jawed leeches, they have jaws,
40:37
Speaker 3: they have teeth, they make little bites, and then they
40:40
Speaker 3: suck blood out of that wound. But there's also species
40:43
Speaker 3: that don't feed on blood. They still have teeth though,
40:46
Speaker 3: and that's usually it helps them to chew up their
40:48
Speaker 3: earth farms as they're eating them, or to chew of
40:51
Speaker 3: the insect larvae as they consume it. And what's interesting
40:54
Speaker 3: about that group is it does look like the ancestor
40:57
Speaker 3: of that group was a non blood feeding leech. And
41:01
Speaker 3: then there was a transition to blood feeding within the group,
41:03
Speaker 3: but there's also been several independent transitions back to non
41:07
Speaker 3: blood feeding. Huh, So it seems like something that does change,
41:10
Speaker 3: you know, depending on the group and what environment they're
41:13
Speaker 3: found in. Yeah, there's a lot of different feeding strategies.
41:16
Speaker 1: It doesn't seem like it's a hard strategy to transition
41:19
Speaker 1: to if it's happening multiple times.
41:21
Speaker 3: Right.
41:22
Speaker 1: Interesting. I would have guessed that processing blood would be
41:25
Speaker 1: way different than eating an earthworm.
41:27
Speaker 3: It should be, Yeah, but these leeches have found a
41:31
Speaker 3: way to maximize where they are, and once that transition occurs,
41:35
Speaker 3: you know, there's several species that will maintain that. Yeah,
41:37
Speaker 3: it seems to be relatively plastic. I would say, Okay,
41:40
Speaker 3: all right.
41:41
Speaker 1: Well let's take another break and we'll come back and
41:43
Speaker 1: talk more about some weird leeches. Okay, so we're back,
42:03
Speaker 1: and I have to ask you about something that I
42:05
Speaker 1: heard once over drinks with friends, but I am not
42:08
Speaker 1: actually sure that it was a real fact. And it
42:11
Speaker 1: is that there is a leech that specializes specifically on
42:15
Speaker 1: hippo butts. So the only way you would find this
42:17
Speaker 1: leech is if you were searching hippo butts. Is it
42:21
Speaker 1: true that there is a hippo butt leech.
42:22
Speaker 3: You are correct, there is Placodilla's yeager school die. It
42:27
Speaker 3: is typically found in the rectum of hippos.
42:30
Speaker 1: In the rectum of hippos, that's an even more extreme environment.
42:33
Speaker 1: So that leech needs to not just find a hippo,
42:36
Speaker 1: but it needs to find a hippo, and then it
42:38
Speaker 1: needs to figure out which end is the back end.
42:40
Speaker 1: And that sounds like a difficult search problem for a
42:43
Speaker 1: tiny little leech. But this also sounds like a hard
42:45
Speaker 1: thing to study because hippos are very dangerous. Do we
42:47
Speaker 1: know how those leeches figure out which end of the
42:50
Speaker 1: hippo is the right end?
42:51
Speaker 3: It's a good question. I don't know. But there are
42:54
Speaker 3: other leeches that tend to gravitate towards certain areas of
42:57
Speaker 3: the body. So this is something that several types of
43:00
Speaker 3: leeches have to figure out. So there's a lot of
43:04
Speaker 3: leeches that feed on orifices, and that probably is because
43:09
Speaker 3: they have fewer teeth and so it's harder to get
43:11
Speaker 3: through the skin, and they're looking for areas with thinner
43:14
Speaker 3: tissue and more blood vessels, so like inside mouths and
43:17
Speaker 3: up noses, and so that's probably what the hippo butt
43:20
Speaker 3: leach is doing is that, you know, hippo's skin is
43:22
Speaker 3: pretty tough. They can't bite through that, so they're looking
43:24
Speaker 3: for an area that is softer, softer tissue that they
43:29
Speaker 3: can bite through. And unfortunately for the hippos, I would
43:32
Speaker 3: guess I'm not sure their opinions on this, but yeah,
43:37
Speaker 3: it's softer in there, so that's what they're going for.
43:39
Speaker 1: What was the second part of your question, I've got
43:41
Speaker 1: distracted by a more important question.
43:43
Speaker 2: How did anybody discover this? Were they looking for something
43:46
Speaker 2: else up the butt of a hippo or tell us
43:48
Speaker 2: the story?
43:49
Speaker 1: Right?
43:49
Speaker 3: So hippos can be very dangerous, and so who ever
43:52
Speaker 3: discovered this, I don't remember who it was, but I
43:56
Speaker 3: guess they were looking for other things in the hippo wrecks.
44:01
Speaker 3: I'm guessing it was a parastologist.
44:03
Speaker 2: They lost their keys or something.
44:07
Speaker 3: He had a reason, I'm sure, And then they found
44:10
Speaker 3: a bunch of leeches.
44:10
Speaker 1: For the species name. The species part that you said
44:13
Speaker 1: sounded like someone's last name. Is it someone's last name?
44:15
Speaker 1: Is that the person who found it?
44:16
Speaker 3: I don't know if it was the person who found it,
44:18
Speaker 3: Probably not, because when we name species after people, it's
44:21
Speaker 3: typically not the person describing it, so I don't know
44:25
Speaker 3: that person's association with that species, but it was in
44:28
Speaker 3: honor of someone.
44:29
Speaker 1: I would love to have a parasite named after me,
44:31
Speaker 1: but it hasn't happened yet. One day, maybe I'll be
44:33
Speaker 1: that important.
44:34
Speaker 3: I'm not sure what this individual thought of having a
44:37
Speaker 3: hippo butt leach named after them.
44:39
Speaker 2: Kelly, it seems like the path is clear. You just
44:40
Speaker 2: got to look up the butts of lots of weird
44:42
Speaker 2: animals until you find your parasite.
44:44
Speaker 1: Well, but Anna just said that you usually don't get
44:47
Speaker 1: to name a species after you, you can name it
44:49
Speaker 1: after someone you know. So I need to become friends
44:51
Speaker 1: with the people who are checking animal butts. And I
44:54
Speaker 1: thought that I was doing a good job of becoming
44:56
Speaker 1: friends with the right kinds of people, but it just
44:57
Speaker 1: hasn't happened yet. But I'm going to keep my fingers.
45:00
Speaker 2: I'm not in that group. Yeah, your friendship with me
45:02
Speaker 2: is not getting you any closer to that for sure.
45:04
Speaker 1: Well, you're going to name a particle after me, probably right,
45:07
Speaker 1: the Smith particle, I hope.
45:10
Speaker 3: So I think there's a good chance, Kelly. I think
45:12
Speaker 3: with your crowd.
45:13
Speaker 1: There's a good chance of this in the future, I'm hoping. Okay,
45:16
Speaker 1: so you're more likely to find leeches and highly vascularized
45:19
Speaker 1: thin skin areas. And so I've seen leeches on like
45:24
Speaker 1: fish sides with scales, Like, do they have ways to
45:27
Speaker 1: get under the scales? I guess that's pretty easy to do.
45:30
Speaker 1: You just kind of move them aside.
45:31
Speaker 3: Yeah, they have very small mouths. And also there's a
45:34
Speaker 3: lot of turtle leeches, and so you know, turtles have
45:36
Speaker 3: scales and then they also have their shells. But on
45:38
Speaker 3: the turtles, you know, they have different scuts in different
45:41
Speaker 3: plates on the shells, and the leeches go for the
45:44
Speaker 3: seams in between them. So they're not going to try
45:47
Speaker 3: and feed through the skewed because it's keratonized it's hard,
45:50
Speaker 3: but they'll go for the scenes in between because they
45:52
Speaker 3: can get to the blood vessels easier there. But with
45:55
Speaker 3: turtles especially, they're going for places where the turtle can't
45:57
Speaker 3: scratch them off. So it's going up like around the neck,
46:00
Speaker 3: behind the arms, underneath their legs, places that they can't
46:03
Speaker 3: either scratch them off or go find a tree or
46:06
Speaker 3: a rock to scrape them off.
46:08
Speaker 1: Okay, so I tell people I study parasites and they're like, well,
46:11
Speaker 1: that's gross, And then I try to get them excited
46:14
Speaker 1: by being like, Okay, I'm not going to change your
46:16
Speaker 1: mind about them being gross. That's fine, But like these
46:19
Speaker 1: tiny little sacks of fluid, they're able to figure out,
46:22
Speaker 1: like where the soft parts of people are, and they're
46:25
Speaker 1: able to find them, and like they do do all
46:28
Speaker 1: of these amazing things. They've like evolved these anticoagulants that
46:31
Speaker 1: help them with their feeding. So when you tell people
46:34
Speaker 1: I study leeches and they go uugh, do you have
46:38
Speaker 1: like a speech that you give them to try to
46:39
Speaker 1: be like okay, but they're gross but fascinating or are
46:42
Speaker 1: you just like this is a lost cause. How do
46:45
Speaker 1: you try to turn people into leech fans?
46:49
Speaker 3: I think it depends on the individual. Okay, So I've
46:51
Speaker 3: definitely been at places when people realize what I do,
46:54
Speaker 3: they say, Okay, you don't get to talk for the
46:56
Speaker 3: rest of the evening, and I go, oh, it's not
46:58
Speaker 3: the best dinner conversation. But for people who are interested,
47:02
Speaker 3: I mean, I agree, like bloodsucking worms can be gross.
47:05
Speaker 3: I get it. I mean that's just a reality that
47:09
Speaker 3: you have to face. But if we can admit that
47:11
Speaker 3: there's a cool side to it and that there's a
47:14
Speaker 3: lot that we can learn from leeches about their anticoagulants,
47:17
Speaker 3: about where they occur in nature, how they're associated with
47:20
Speaker 3: different verbrate hosts. We can learn a lot from them,
47:23
Speaker 3: and that's I think the more important point. Trying to
47:26
Speaker 3: appreciate them for what they're doing and that they're serving
47:30
Speaker 3: an important role learn our ecosystems that hasn't always.
47:34
Speaker 1: Been recognized is the angle that usually works best. They're
47:38
Speaker 1: medicinally helpful and they're teaching us about anticoagulants. I'm guessing
47:42
Speaker 1: that's the most convincing.
47:44
Speaker 3: Yeah, that's a strong point with leeches. Also because they're
47:47
Speaker 3: commercially traded, leeches have played a important role in conservation
47:51
Speaker 3: as well. So the rudo medice analysis is the European
47:55
Speaker 3: medicinal leech. This was the leech that was collected the
47:57
Speaker 3: most in the seventeen to eighteen hundreds from a dismal
48:00
Speaker 3: purposes and for blood letting, and this species was also
48:04
Speaker 3: one of the first species to have conservation measures put
48:07
Speaker 3: in place about its collecting. So in Germany, especially in France,
48:12
Speaker 3: the number of leeches that were collected for blood letting
48:15
Speaker 3: purposes was astronomical. There were millions of leeches collected and exported,
48:21
Speaker 3: and very quickly the governments realized that this is a
48:24
Speaker 3: huge number that needs to be tracked, not just for
48:26
Speaker 3: economic purposes. But then later as they started tracking the
48:29
Speaker 3: populations the natural populations is seeing that, oh, there's not
48:33
Speaker 3: as many leeches as you used to be. So they
48:35
Speaker 3: started putting regulations in place to say, you know, you
48:38
Speaker 3: can collect leeches, but there's only so many you can export,
48:40
Speaker 3: and there's only so many that you can collect today.
48:43
Speaker 3: And actually the root of minus analysis is considered vulnerable
48:48
Speaker 3: because of the number of leeches that were collected back
48:51
Speaker 3: in the seventeen eighteen hundred, so those populations still have
48:53
Speaker 3: not recovered to this point. So today the modern species
48:58
Speaker 3: that is used in blood letting is Rudo verbana. It's
49:01
Speaker 3: another species rudo that's found farther east in Europe, and
49:05
Speaker 3: that is the commercially traded leech. So today, if you
49:08
Speaker 3: say that you have brudo and you're sending it to
49:11
Speaker 3: different places, one of the first things they want to
49:13
Speaker 3: ask is is it rudomus analyis because we need to
49:16
Speaker 3: be careful about that because it's considered vulnerable as a
49:18
Speaker 3: conservation status of being vulnerable or is it hrud of
49:22
Speaker 3: verbana and we need to track it because it's a
49:24
Speaker 3: commercially traded quantity.
49:27
Speaker 1: So like when the Rudo Mets analyis, was I really
49:32
Speaker 1: rocked that? I'm sure I didn't. So when those numbers
49:34
Speaker 1: started to go down, did anything noticeable happen in the ecosystems,
49:39
Speaker 1: Like were we able to identify that they had played
49:40
Speaker 1: an important role and when they fall down, like maybe
49:44
Speaker 1: the animals that ate them, their numbers go down or
49:46
Speaker 1: was there nothing obvious at the time.
49:48
Speaker 3: I don't think anyone was looking at that necessarily. Yeah,
49:52
Speaker 3: I'm unaware of work on that. A lot of people
49:55
Speaker 3: when they would study this would look at the leeches
49:57
Speaker 3: themselves and not necessarily how it played roles in the ecosystems.
50:02
Speaker 3: But I think this is something about parasitology in general
50:04
Speaker 3: that we're realizing how much more important that is. These days,
50:08
Speaker 3: scientists are starting to include parasites in looking at ecosystem questions,
50:13
Speaker 3: more so than ever has been in the past, because
50:16
Speaker 3: they are connecting different trophic levels and different parts of
50:18
Speaker 3: the food web, and parasites are doing a lot more
50:21
Speaker 3: in our ecosystems than I think we've ever recognized before,
50:25
Speaker 3: especially when you think about ecosystem decline and changing climate scenarios.
50:31
Speaker 3: That parasites can be a canary in the coal mine
50:34
Speaker 3: because they are connecting so many different points, and so
50:37
Speaker 3: when the parasites aren't able to make those connections, we
50:39
Speaker 3: can start to see perturbations and disturbances in these ecosystems
50:43
Speaker 3: and parasites long before we see the effect in the
50:47
Speaker 3: larger macrofauna.
50:49
Speaker 2: So do you think parasites or leaches more specifically, serve
50:52
Speaker 2: an essential, an inevitable role in an ecosystem. Let me
50:56
Speaker 2: put it to you in a different context that maybe
50:59
Speaker 2: you've never been asked before. Or say, we land on
51:01
Speaker 2: an alien planet and we observe an alien ecosystem, do
51:04
Speaker 2: you expect to find some form of leeches on that
51:07
Speaker 2: alien planet? Are there alien leeches? It's my question.
51:11
Speaker 3: I like the possibility of alien leeches. I would definitely
51:15
Speaker 3: expect there to be a parasite or many parasites, probably,
51:19
Speaker 3: but I don't know if they would take the form
51:21
Speaker 3: of leeches necessarily. The reason I say this is because
51:25
Speaker 3: parasitism is the most common life mode on the planet.
51:29
Speaker 3: Oh wow for eukaryotic organisms, right, yes, yes, of ukryonic organisms,
51:34
Speaker 3: it's ubiquitous. As long as there have been organisms, there's
51:38
Speaker 3: probably been something parasitizing it. Wow.
51:40
Speaker 2: Am I talking to the first astro parasitologists.
51:44
Speaker 3: I think you may be the first astro paristologists.
51:48
Speaker 1: There's so many cool parasites left to study here on Earth.
51:51
Speaker 1: When people are like, Kelly, would you move to Mars?
51:53
Speaker 1: And I'm like, there are still parasitic worms left to
51:55
Speaker 1: describe your people. Why would anybody go to Mars. There's
51:59
Speaker 1: too much work to do.
52:02
Speaker 3: Yeah, it's daunting and there's not enough of us doing it.
52:05
Speaker 3: So yeah, we got to pick up the pace.
52:07
Speaker 1: That's right.
52:08
Speaker 2: And I don't think the idea of getting sucked on
52:10
Speaker 2: by alien leeches is going to make somebody more likely
52:13
Speaker 2: to go to Mars or venture on to another planet.
52:16
Speaker 2: So it's not exactly doing a sales job.
52:18
Speaker 1: I mean, I think space is bad enough at selling
52:21
Speaker 1: space as it is, but I'm a bit biased and
52:24
Speaker 1: I know lots of people who disagree with me. So
52:26
Speaker 1: on that note, I have had so much fun. Thank you, Anna.
52:30
Speaker 1: Do you want to end by telling us what your
52:31
Speaker 1: favorite leech.
52:32
Speaker 3: Is I have to pick just one? I know they're
52:35
Speaker 3: like children.
52:35
Speaker 1: Now do you pick just one?
52:36
Speaker 3: I don't know exactly. I have a special affinity for
52:41
Speaker 3: the Macrobdella leeches in North America. Macro because they're large
52:45
Speaker 3: and bidella is a name for leech. They're big, they're
52:49
Speaker 3: brightly colored and since they're all agreed with orange polka dots,
52:52
Speaker 3: and I mean big is that there's several inches and
52:54
Speaker 3: a lot of people encounter them and they're pretty. It
52:58
Speaker 3: was one of the first groups that I studied as
52:59
Speaker 3: an intern long ago, so still hold a special place.
53:02
Speaker 1: In my heart. They sound wonderful and I bet a
53:05
Speaker 1: lot of our listeners have encountered them, and maybe they'll
53:07
Speaker 1: appreciate them more now.
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