Leeches (featuring Dr. Anna Phillips)

Daniel and Kelly chat with Dr. Anna Phillips about the disgusting and fascinating world of leeches. 

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Episode Transcript

Speaker 1 (00:05):
When most people think of leeches, they're immediately disgusted, or
at least that's been my experience when I talk to
people about leeches. But what is it about leeches that
results in so much more disgust than we feel when
we talk about other blood suckers like mosquitoes. Maybe it's
that scene from Stand By Me or that scene from
African Queen, or maybe it's something else altogether. And look, today,

(00:30):
I'm sure we're not going to convince most of you
that leeches are beautiful. But I hope that when you
listen to this episode, Anna and I are able to
convince you that leeches are Okay, fine, maybe they're disgusting,
but they're all so fascinating and maybe they're even helpful
to people. So, for example, you know, maybe you've heard
that leeches used to be used to try to draw

(00:50):
blood to treat just about any problem that humans used
to have a long time ago, But did you know
that leeches are still used in particular medical cases and
they're actually helpful, and that leeches produce anti coagulants, which
are these chemicals that make sure your blood doesn't clot
up that are useful in a variety of medical settings,
so understanding leeches can be helpful for human health as well.

(01:14):
On today's episode, we have doctor Anna Phillips, who's the
curator of earthworms and parasitic worms at the Smithsonian Natural
History Museum in Washington, d C. And I can't think
of a better person to talk to us today about leeches.
So welcome to Daniel and Kelly's extraordinary and sometimes a
little bit disgusting universe.

Speaker 2 (01:47):
Hi. I'm Daniel. I'm a particle physicist, and I've never
been bitten by a particle.

Speaker 3 (01:52):
Hi.

Speaker 1 (01:52):
I'm Kelly Wienersmith. I'm a parasitologist and I've been bitten
by leeches and it was okay, it was fine.

Speaker 2 (02:00):
Ends clearly they've infected you with some sort of brain
disease that made you think it was okay.

Speaker 1 (02:06):
You know, we're gonna learn today the surprisingly they don't
vector a lot of diseases. I'm like mosquitoes and ticks,
they're not so bad. They're just hungry, which I get.

Speaker 2 (02:16):
I get that you've been brainwashed, you've been leech washed
by leeches. I am not okay with being bitten by leeches.

Speaker 1 (02:22):
Well, I'm hoping that we can leech wash at least
a few of our listeners today into thinking that leeches
are maybe still gross, but that there's absolutely some fascinating
stuff to learn from them.

Speaker 2 (02:31):
All right, well, then my question for you today, Kelly,
is what is the grossest thing you have been bitten by?

Speaker 1 (02:37):
Oh? Gosh, the grossest thing I've been bitten by? I
guess that's gotta be ticks.

Speaker 2 (02:42):
Ticks are the worst.

Speaker 1 (02:43):
I hate ticks. I really hate ticks. Like leeches. I'm
okay with ticks, man, I hate them. You know. So
you get a take, you pull it off, and you're like, oh, well,
now should I send it in for testing? Do I
have to worry that I got lime disease? What about
you know, Rocky Mountain spotted fever? And whereas if you
get bit by a leech, just like, oh I'm bleeding
a little. That stinks, but you don't worry about what's

(03:03):
going to happen afterwards, like that's the end of the encounter.
And I get bit by ticks pretty often and it
kind of freaks me out. I regularly spray my clothes
with permethrin during the summer when I'm going to be
going out in the woods, and like every member of
our family has a set of permethrin treated clothes that
they wear if they're going to be going out into
the woods, because we've already had some lime in the
family and we don't want anymore. What about you, what's

(03:24):
the weirdest or gressest thing you've ever been bitten by?
Not a particle.

Speaker 2 (03:29):
I was bitten by our pet rats once, so I
have had a rat bite, and in their defense, my
finger was covered with whipped cream and I stuck it
in the cage and they got very enthusiastic. I don't
think they were trying to bite my finger, but you know,
how could you control yourself? It's whipped cream.

Speaker 1 (03:44):
I get it. I'm sorry. I understand the rats in
that case. I've also been bit by a boa constrictor
when I went to feed it a rat and I
wasn't really careful about what I was doing with my hand.
And then I also got bit once by an alligator
gar Have you seen these?

Speaker 2 (03:58):
Is that like an alligator.

Speaker 1 (03:59):
It's a fit with an alligator like mouth. They're common
in the South, but there's also some in Lake Eerie
and I was doing a fish survey and I thought
one had passed away, but even though it was very dry,
it was still kicking. So I grabbed it by the
tail and it turned around, and I was like, ah,
I'm so.

Speaker 2 (04:14):
Sorry it's biting you and you're apologizing to it. Wow,
you're so polite.

Speaker 1 (04:18):
I mean, if I were on the way out and
somebody was harassing me, I would be grumpy about that too.
I understood where it was coming from, but yeah, sorry.
Your story reminded me of some of my other stories
that how could I have forgotten?

Speaker 2 (04:28):
Well, your comment earlier about not being too grumpy about
giving blood to leeches made me think about mosquitoes, because
we recently had mosquitoes basically taking over southern California. When
I moved here twenty years ago, there were almost no mosquitoes,
and how their mosquitoes everywhere drives me crazy because I
would happily give up a little bit of blood to
mosquitoes if they didn't deposit the anesthetic that you then

(04:51):
react to like it frustrates me endlessly. I would like
set out a little pool of blood, you know, for
them every day. If we could strike a deal with
mosquitoes like stop giving me bites and drink my blood,
I would happily give up blood to avoid mosquito bites.

Speaker 1 (05:05):
Oh, man, only we could have like a doctor Doolittle.
But who could communicate with the mosquitos to set that
kind of exchange up? That would be ideal. Why do
you have so many more mosquitos? Has a new species
moved in? Is it wetter? With more standing pools of water?
Would change?

Speaker 2 (05:18):
I read this story once that claimed that they all
came in one shipping container to Long Beach from China
and they basically took over like it was a huge
invasion of this Chinese tiny mosquito, not like the big
American mosquitoes, but these little ones that also bite you
multiple times, so you don't just get like one bite,
you could like a series of bites. Oh really, not

(05:38):
a fan?

Speaker 3 (05:39):
Wait?

Speaker 1 (05:39):
Why was China shipping us mosquitoes? They just accidentally got
into a shipment? Is that the deal?

Speaker 2 (05:44):
Or somebody ordered mosquitos on Amazon and now we're all suffering?

Speaker 4 (05:48):
No?

Speaker 2 (05:48):
I think it was an accident. Yeah, there was some
pool standing water in this shipping container and they survived
the transit and they opened it up in Long Beach.
Dot dot dot. My life is now terrible.

Speaker 1 (05:57):
That's the worst. I'm sorry. We've got an Asian longhorn
and tick, which I think also accidentally got here, and
it can reproduce without finding a mate. You get one,
and then you've got ten, and then you've got hundreds.
And there are cattle out here that are getting like exsanguinated.
If they're not checked on regularly enough, they end up
getting tons of them and then they don't have enough
blood to do what they need to do.

Speaker 2 (06:16):
So anyway, exanguinated, my mental image is that you go
out to check on your cow and it's just like
a dry heap of skin and bones. Is that what
we're talking about.

Speaker 1 (06:25):
I think they die before they look how you might
imagine Dracula looks waking up in the morning. But yeah,
I mean the dying from lack of blood. And I
think there's some concern that there's a hemorrhagic fever in
the native area that like could jump to here and
now instead of in addition to lime, you'd have to
worry about hemorrhagic fevers. And anyway, it's so great that
we can ship stuff around the world, but it's got

(06:45):
its downsides.

Speaker 2 (06:48):
All right, Well, today we're not just talking about what
Daniel doesn't like to be bitten by, and what Kelly
doesn't mind being bitten by. We're talking about all the
exciting signs behind leeches.

Speaker 1 (06:57):
And so we asked you what is the first thing
you think when you think of leeches? And I got
to say, I got a couple answers that I expected,
a couple that were very unexpected. And if you would
like to be asked what you think about a topic
we're going to talk about on the show, email us
at questions at Daniel and Kelly dot org. So let's
hear what our listeners had to say.

Speaker 3 (07:19):
A picture that I've seen of a black hole eating
the material from a closely orbiting star.

Speaker 5 (07:26):
Honestly, they're just the wist and I can't think of
anything more disgusting. The first thing I think of is
medical grade leeches that are used to drain blood from hematomas,
bruises under the skin that have a lot of blood
in them.

Speaker 6 (07:42):
The first thing I think of when I hear leeches
is traveling down the Brasis River in Texas on a
boy scout trip and on an inner tube and coming
out with leeches stuck to the inner tube and a
few to my legs. No fun.

Speaker 4 (07:58):
Watching the movie The African Queen with Katherine Hepburn and
Humphrey Bogart, and they have to tow his boat through
the swamp, waiting in the swamp, and when they get
out there covered with leeches, and they have to spread
salt on the leeches to get them off.

Speaker 7 (08:13):
Medieval medical practices where they were used for almost everything
from headaches to ingrown toenails. I don't know conjunct to
fight us not all it being one of Dracula's favorite pets.

Speaker 1 (08:29):
They've seen and stand by Me where they're swimming across
the swamp and they suddenly discover that they're covered in leeches.

Speaker 2 (08:36):
I think of the movie stand by Me.

Speaker 6 (08:38):
Wasn't there an old black and white movie called Attack
of Leeches?

Speaker 3 (08:43):
Or something seen from stand by Me?

Speaker 5 (08:46):
The third thing that comes to mind is the irs.

Speaker 2 (08:49):
I think of the way they ribed and twisted.

Speaker 1 (08:51):
When I discovered them as a kid, I thought it
was swimming around my finger in a strange way.

Speaker 2 (08:55):
Then I pictured my mom screaming.

Speaker 5 (08:57):
The barber surgeon from the Middle Ages applying them meditionally
up with that in quotes.

Speaker 1 (09:03):
So I love that. The very first answer that hit
my inbox was a picture that I've seen of a
black hole eating the material from a closely orbiting star.
I was like, Wow, in my world, that is not
what you would expect the answer to be. But like,
I see that, that's a fascinating answer. That was great.

Speaker 2 (09:20):
That's our audience right there. Physics biology crossover.

Speaker 1 (09:23):
Yeah, it's amazing. And then most of the other responses
were like I expected people to mention stand by me,
and I expected people to mention that one movie with
Catherine Hepburn African Queen I think it was, and then
mostly to be grossed out. And so that was more
or less what I was expecting. What did you think?

Speaker 2 (09:40):
Yeah, these answers basically mimic my thoughts about leeches. I'm
totally uninformed. I don't know anything about leeches compared to
anything else except that I'm grossed out with anything bites me.
So I'm curious to learn what is the science of leeches,
what are leech scientists leechologists working on. What motivates somebody
to get into leeches anyway, rather than basic any other

(10:01):
field of science. So yeah, I want to meet your
friend and hear all about leeches.

Speaker 1 (10:06):
Wait, wait, so would you say that this is at
the bottom of the list of science jobs you would
want studying leeches.

Speaker 2 (10:11):
It's not near the top, that's for sure. I wouldn't
put it in the top fifty or one thousand science jobs.
I mean, I think I'm pretty capable of getting interested
in almost anything, but yeah, this is a bit of
a gross out factor for me.

Speaker 1 (10:24):
I gotta say, if somebody said you could be the
leech person at the Smithsonian Museum, I'd be like, I
enjoyed studying space, but I'm studying leeches now, and I
would make that jump. All right, So today we are
talking to doctor Anna Phillips. She works for the Smithsonian
Natural histor Museum in Washington, DC, and she is just
delightful and she's going to tell us all about leeches.

Speaker 2 (10:44):
And wait for it, I'm going to make a connection
between Kelly's two passions, space and leeches.

Speaker 1 (10:50):
Yeah, that was pretty clever at the end there, All right, enjoy.
Doctor Anna Phillips is a research zoologist and curator of Klitalata,
which is a class of anilid worms also known as
earthworms and parasitic worms. At the Smithsonian Museum of Natural History.
She studies biodiversity and the evolutionary history of parasitic worms

(11:10):
and specializes in leeches and tapeworms. She's my hero in
my world. She's a legend for doing her leech dance
in a video for the BBC, which we're going to
discuss later in the show. Welcome Anna, I I'm excited
to be here. I'm excited to have you here. Did
I say klitalada rte or did I say it wrong?

Speaker 3 (11:30):
Works for me?

Speaker 1 (11:32):
Nice? Oh man. I always love it when I get
those slam dugs right from the beginning. So, you know,
I think for a lot of people when we're growing
up as kids, like I thought maybe I would study
tigers or elephants, or you know, maybe anything other than
worms living in the brains of fish. What was your
path to getting excited about leeches.

Speaker 3 (11:53):
I was definitely not a five year old who thought
I would grow up to study worms. It was a
little bit of a winding road. When I was a kid,
I was really excited about dinosaurs. They were sort of
a good introduction into the scientific world for me. But
as I got older, I realized there were a lot
more other cool animals out in the world. And when

(12:14):
I was an undergraduate, I applied for an internship through
a program run by the National Science Foundation called Research
Experience for Undergraduates, the RIU program, and it's funded by
the National Science Foundation, and it's an opportunity for students
to go work in science labs and working with me,
a real scientist, and to work on projects and learn

(12:37):
about the scientific research process. And there were many different projects.
There were ones on scorpions and bats and bees and catfish,
and there was one on leeches. And I thought, oh, no,
one will apply for the one on leeches. I'll have
better odds. That's amazing. Yeah, so I applied and it

(12:58):
turns out six people applied. Oh, but I was selected.
And that summer ended up being everything I thought science
should be. There was work with specimens, there was field work.
I went to a conference, got to work in a
molecular lab, and we ended up being able to publish
it nice. So then my advisor invited me back for
a PhD to expand the project from my internship, and

(13:21):
it was the rest is history.

Speaker 2 (13:23):
Do you think that you were lucky that you happened
to stumble on a field you were fascinated by, or
are you just the kind of person who can dig
into anything and find the mysteries and the juicy questions,
and that you just happened to end up in this field.

Speaker 3 (13:36):
I think there's a quality of researchers who like to
dig in and find the juicy questions. So in some
sense I could have ended up in other places and
studying other animals, but leeches ended up being a really
good fit for me. I had always found worms to
be more interesting than like molluscs or insects or other things.

(13:59):
It's also a good fit in the sense that, like,
no matter where you go in the world, people know
what leeches are. It's like the one worm that everyone
You can say like all the bloodsucking worms, and you know,
sort of point to your skin and people are like, oh,
I know what that is. So even if they don't
speak English, I think things worked out in a way.
But yeah, I do kind of get distracted sometimes and

(14:19):
find other things that I could dive in on and
have to go no. No, remember parasites.

Speaker 1 (14:24):
So when students contact me and they say, oh, I
want to go into marine biology, I'm like, Okay, I
know you're excited about the dolphins, but an easier way
in is the dolphin parasites Because fewer people are excited
about those, and then you can become a marine biologist
through the parasites. And I'm really hoping that they're going
to get hooked on the parasites. And I have been
surprised by how many students do get hooked on the

(14:46):
parasites and then they're like, yeah, yeah, the dolphins are cool,
but have you looked at the look at this worm.
And I'm like, yes, we've hooked you exactly.

Speaker 3 (14:53):
Yeah. And this is what I tell a lot of
students coming through is that it's good to have a
goal and to be ambitious and to be aiming for something,
but also flexibility, to have flexible interest, I would say,
because like I said, I wanted to study dinosaurs and
now I study worms and they don't even have fossils.
But you know, it worked out. I'm pretty happy.

Speaker 1 (15:12):
I'm glad you're happy. So let's talk about where leeches
are on the tree of life, so like what are
their closest relatives, and then also like how many species
of leeches do we think that there are? So, like
you said in your intro, leeches are clidalate anaalids, so
an analyta, these are the segmented worms with body cavities.

Speaker 3 (15:32):
So there's all the polykeets, which are the marine worms,
which I don't focus on those because I don't work
in marine environments very often. And then the other anelids
are the clydalit anelids. This includes the oliga keats, which
includes earthworms. It also includes brankie of deeladins, which are
the crayfish worms, so they are symbiotic worms that live

(15:53):
with crayfish. They're not parasitic, they're commensal organism. And then
they're the leeches. With leeches, about half of them are
blood feeding and the other half aren't.

Speaker 1 (16:04):
What are the other half doing?

Speaker 3 (16:05):
They're eating insect larvae, bacterial mats, just about anything and
getting their mouths around. But they're not sucking blood, so
they're not as interesting.

Speaker 2 (16:15):
So what are the big open science questions about leeches?
I think it's fascinating that Kelly's first question is like,
how do these relate to other living critters? Where do
you put them on the tree of life? How do
we organize them? Is that the motivating question? Is it,
like all to try to understand how everything got here
in the evolutionary history of it? Or are there still mysteries,
but like, how do leeches accomplish this amazing thing they do?

(16:35):
What are the sort of biggest open questions there in leeches?

Speaker 3 (16:39):
My research is with systematics and evolutions, so looking at
the number of species, describing new species, how they're related
to each other. So that's most of what my expertise is,
and that's also what I find interesting. There are so
many other aspects of leech biology that have many interesting questions.
So for leeches, there's probably between eight hundred and a

(17:00):
thousand species of leeches in the world, which compared to
a lot of other worm groups, is pretty small. Like
Nematodes has probably more than sixteen thousand species. So the
order of tapeworms that I work in has more than
thirty five hundred species, so eight hundred is pretty small.
But what's really cool about leeches is to all the
different evolutionary transitions within that group. In terms of the

(17:25):
interesting questions it's looking at, like, wow, we have so
many different feeding strategies. They occur in so many different environments.
There's marine leeches, there's terrestrial leeches, there's burrowing leeches as
well as the blood feeders, and so with all of
these different evolutionary transitions. It's a more tractable group to
explore those questions because you don't have to go through

(17:45):
five hundred species. You can look at smaller groups with
twenty or something, which is easier to approach. And then,
like I said, they're pretty accessible. You can go to
a lot of different places in the world and find
leeches a lot of different habitats, and that can be
easier than like studying things in the deep sea, for instance,
where it's very expensive and revolves a lot of equipment

(18:06):
and planning.

Speaker 1 (18:07):
So when we asked our audience what they think of
when they think of leeches, a number of them noted
that in like medieval times, leeches were used to treat
like every single disease you could imagine, And so I
was wondering if you could speak at all to the
current use of leeches in medicine. I know that's not systematics,
Is it okay to ask you about that?

Speaker 3 (18:28):
Sure? Yeah, yeah. This is actually one of the points
of why leeches are important to the world because of
their use in medicine, they've also been used as a
model organism in a number of other fields, like neurology,
and some importance in pharmacology and developmental biology studies. But
when it comes to their use in medicine, yeah, they

(18:49):
were really popular in the seventeen eighteen hundreds for blood letting.
Prior to that, people would cut open arteries and veins
to balance the humors and get some with the blood out.
But leeches were an improvement on the situation because it's
easier to get it to stop bleeding versus when you
slice open artery in vain that it can be a challenge. Also,

(19:12):
if you want to take more blood, you put more
leeches on. If you want to take less blood, you
take them off. It was a more controllable way of
blood letting.

Speaker 1 (19:20):
Just to be clear, it wasn't helping anything, right, It
was just like a less damaging way to damage your patient,
and that was the benefit back then. Is that right?

Speaker 3 (19:29):
They thought it was helping. Okay, but now we know
that leeches are only beneficial in certain cases. It's not
going to cure your headache, it's not gonna to your hysteria,
So the blood letting only helps certain situations. So today
in modern medicine, leeches are still used. They were approved
as a medical device in the US in two thousand

(19:49):
and four, so they're not experimental. So what they're usedful
in modern medicine is because leeches have antiquagulants in their saliva,
so when they're abiding, they're exuding this ty wagulants blood
thinner that's going locally into the wound, and it helps
the leech because the wound continues to bleed and the
anti wagulant prevents it from clotting, so that means that

(20:10):
the leech can ingest the liquid blood easier. But once
the leech has finished feeding and it leaves, that wound
continues to bleed because those anti coagulants are in a tissue.
We take advantage of this in medicine, so in cases
where you have a skin graft that has been attached,
or if digit reattachment so you cut your finger off
and they put it back on. They can attach a

(20:32):
lot of the small vessels that bring blood into the digit,
but the veins that take the blood away are thinner walled.
It's harder to attach those, and a lot of times
they get the major vessels together, but they have to
wait for those veins to regrow on their own. In
the meantime, this means all the blood is rushing into
this digit, it's swelling up, it's turning purple. It's painful.

(20:54):
We can give anti coagulants and blood thinners systemically, like
through the whole body, but you have a risk of
major bleeding and it's kind of overkill when you just
need to get it into that digit. So leeches have
really tiny mouths and we can put them on the
ends of fingers and noses and ears, and when they
start feeding, that anti coagulant goes locally. It helps keep

(21:17):
all of the blood flowing so there's no clotting, and
then they're relieving that pressure by sucking the blood out
and it encourages oxygenated blood to get into this damaged tissue.
And so you can see within hours these fingers and
toes go from being purple and swollen just suddenly looking
much more normal and pink and healthy.

Speaker 1 (21:37):
Again, aside from all the leeches hanging off of it.

Speaker 3 (21:41):
Well, yeah, I mean they feed pretty quickly, so they're
not going to be there too long.

Speaker 2 (21:46):
It almost sounds like you're recommending leeches.

Speaker 3 (21:49):
In certain cases. Wow, they can be a preferable option
to other options. Yeah, we also have machines that you
can put and suck out blood. But those you typically
adhere better to broad surfaces like your back or your leg,
But things like fingers and noses and ears have funny shapes,

(22:09):
so leeches they attached better.

Speaker 2 (22:12):
That blows my mind. I think the pop side understanding
of leeches, at least, you know, the superficial one that
I have as a total non expert, is that, like,
people used to use leeches back when they understood nothing
about the body, and it was crazy, like drilling holes
in your head. But now you're telling me that there
are some scenarios where leeches can actually improve the outcome
for a patient. And that makes me wonder, do you

(22:33):
think those experiences one hundreds of years ago before we
understood stuff, are what encouraged people to continue using them
that sometimes they actually did help.

Speaker 3 (22:40):
I think there's a quality to that definitely. Like I said,
they're not a cure all, but there were some cases
that leeches are helpful.

Speaker 2 (22:48):
Wow.

Speaker 3 (22:48):
And then that also promoted a lot of research into
why so as we developed more questions, part of that
is looking at those anti coagulants and saying, like, well,
what anti coagulants are using and can we take that
into a pharmacology setting and you know, use those mechanisms
without having to actually use the worms themselves. And what

(23:09):
they found is that a lot of leeches have heuridin
and this is an anti coagulant that's actually the most
powerful anti coagulant known. In fact, we don't use it
in modern medicine because it's too good. So one of
the things about anti wagulants is that when it's causing
the blood to continue flowing, we also want to have

(23:30):
the ability to stop that. If you have an anti
wagulant in your system and you have a major bleeding episode,
we want to be able to stop that quickly. And
heurdin is not the best for that. We have a
hard time getting it to stop. So we have other
options now, but it is something that's out there and
the scientific community is working with understanding the mechanisms and
the process to improve drug development.

Speaker 1 (23:52):
So mosquitoes and ticks also make anticoagulants. Why don't we
use them when your finger falls off or leach is
just even better or less creepy.

Speaker 3 (24:01):
In terms of why the leech anti coagulants would be preferable,
I actually don't know.

Speaker 2 (24:08):
I refuse to believe the mosquitoes could do anything useful
for anybody.

Speaker 1 (24:11):
They are purely even I'm not a fan either.

Speaker 3 (24:14):
A lot of people would agree with you. I think
leeches are much more controllable versus mosquitoes and ticks, especially
in a medical setting. And the other aspect is that
leeches carry far fewer diseases than mosquitoes and ticks.

Speaker 1 (24:28):
Could you tell us more about that?

Speaker 3 (24:30):
So to this point, they've done a ton of research
looking at our leeches vectors for bloodborne diseases, and some
of the work that was done, especially in the nineties
when people were really investigating HIV, to see if leeches
were a vector for HIV. What they found is that
when a leech feeds on a mouse, for instance, that's

(24:51):
infected with these viruses, you can still isolate the virus
from the blood meal inside leech. But when they fed
the leech on the next mouse that didn't have those visviruses,
it doesn't necessarily transmit. Okay, So if you're out getting
bitten by leeches, you know, could you get viruses and
bloodborn pathogens from that? It's possible, but it's a very

(25:12):
very low chance. That's also a good thing about using
leeches in modern medicine versus things like mosquitoes and ticks,
which transmit a lot of really scary, dangerous viruses.

Speaker 1 (25:25):
And other hosts for leeches. There are a lot of
leeches that, for example, specialize on turtles, Like do they
transmit diseases between turtles or in general, are leeches just
not good at transmitting diseases.

Speaker 3 (25:37):
Actually, it's great that you bring up leeches and turtles
because there's a couple of cases of different types of
blood born parasites between the turtles. So, for one, we
know that they can transmit t for panasomes, which is
the same organism that causes African sleeping sickness, but it's
not making turtles sleepy. So we do know that leeches
have been transmitting panisomes with turtles.

Speaker 1 (25:58):
Could you tell if a turtle with sleep they move
pretty slow. Maybe it does make them sleepy and we
just can't tell.

Speaker 3 (26:04):
Someone should look into it. The other thing is that
they'll to transmit hemogregrons, which are our small blood worn pathogen,
but as far as we know, it's not making the
turtles sick. What we found is that turtles that have
a small home range have fewer species of hemogregrans versus
turtles that have a wider range encounter have more species,

(26:28):
which means that they're encountering more leeches and more different
types of bloodborn pathogens. But it means that the turtles
that are wandering farther away, which we would assume would
be they'd be healthier, they actually have a higher number
of these blood parasites. So in this case it may
indicate that the turtles are doing better. So maybe the
blood parasites they don't hurt them that much, and so

(26:51):
the healthy turtles are moving around a lot, and when
they get blood parasites, they're like whatever, yeah, as far
as we know, h Okay, interesting.

Speaker 1 (26:59):
Yeah, we're going to take a break, and then we
are going to talk about other kinds of hosts that
we find leeches on. Okay, so Anna, I'm generally interested

(27:23):
in the different kinds of species that end up getting
bitten by leeches, but I really want to know what
is the weirdest place you've ever heard a leech found
on an animal.

Speaker 3 (27:33):
Leeches will feed on a lot of different hosts, but
it depends on the kind of leech. So some leeches
have preferences and others don't really care. So in North
America like Macrobdella decora, the North American medicinal leech, for instance,
they just want vertebrate blood. It doesn't really matter. They'll
go for frogs a lot of frog blood. But also

(27:57):
they'll feed on fish mammals including humans. So some leeches
doesn't really matter. Other leeches can be pretty specific, like
they prefer turtles and maybe a fish, especially in the
marine environments fish leeches they will actually prefer certain groups
of fish. So yeah, it's all over the place, but

(28:18):
it does depend on the type of leech and what
their preferences are.

Speaker 2 (28:21):
Why would a leech evolve a preference. Isn't it better
to be able to suck on lots of different kinds
of stuff?

Speaker 3 (28:26):
You would think This kind of gets into like generalists
versus specialists and biology and it's what's working for it.

Speaker 1 (28:34):
So most of our audience is physics and astronomy geeks.
So could you just go into a little bit more
detail on specialists in generalists?

Speaker 2 (28:41):
Do we understand in general why evolution produces both kinds
of things? What would inspire one direction versus another, what
causes it, and do we understand that at all.

Speaker 3 (28:51):
I'm not sure we do in leeches.

Speaker 1 (28:53):
Okay, so here I'm just going to spit ball for
a second. I can imagine that it could be great
to be able to drink the blood from any mammal
you come across. It'd be easier to find food. But
if you're a specialist, maybe you are more used to
a particular kind of blood, so it's easier for you
to extract resources or energy from it. Here's a question

(29:14):
when leeches bite a host, is there anything in the
host like that's an immune response that tries to attack
and kill the leech or do leeches just get free
meals everywhere they go? Because I can imagine if you
specialize in a certain kind of host, maybe you get
good at avoiding their ways of trying to kill you.
But I guess do leaches just not have those kinds
of problems.

Speaker 3 (29:34):
With other types of parasites That immune response is really important.
And I agree in that point with leeches, because they're
temporary ectoparasites, They're not there long enough to really have
to deal with host immune system all that much. I
don't know how much that's playing a role in their
feeding preferences. I think it's probably more along the lines

(29:56):
of how frequently they encounter good hosts. So, especially leeches
and marine environments that are feeding on fish aren't always
great swimmers, so when they get on a fish, they
tend to stay there, and then there is the possibility
that if that fish gets eaten by another fish, they
may transfer at that point. But a lot of that

(30:16):
is like very short distances that they can cross on
their own. So maybe fish that occur in schools where
there's many options and so the leech doesn't have to
go very far. That would be an instance where being
a specialist, you know, they can get by with it.
But for a leach to this out in like a

(30:36):
pond and may not have all that many individuals of
a frog, for instance, they would then want to have
more options available and so that they can go for
the fish or the frogs or you know, a bird
or the occasional person. So I think it's more about
like how many different species they're encountering in the abundance

(30:56):
of those species.

Speaker 1 (30:57):
Okay, cool, So when I look at leech, I always
get frustrated when people say, oh, parasites, they're just these
degenerate organisms, but like you know, they don't appear to
be able to move around much and they don't seem
to have a lot of sensory organs. How do leeches
find and get to their hosts because they just look
like these little blobs. How do they navigate their environment?

Speaker 3 (31:17):
There's a lot of questions about this. I will say
this is a very well it should be an active
area of research. So leeches have incredible senses. Many leeches
have eyes, so there are little pigment cumps that detect light,
dark and movements. They're not like our eyes that actually
see images, but they don't like light because that means

(31:37):
that they're exposed and they're easier to be eaten. So
they want to kind of gravitate towards darkness. But at
the same time, movement in a potential host is nearby,
they want to go towards that. So they have eyes.
They have sinsily on their bodies that these little pepili,
these little bumps that when they're in the water, they
can feel the vibrations and that helps them swim. Granted

(32:00):
they're not the fastest swimmers, but they will swim in
the direction of that movement. To go investigate and say, oh,
is there something I can eat over here?

Speaker 2 (32:09):
Did they ever latch onto the wrong thing? Like they
latch onto something they think is a person. They try
to suck on it, and it's just like you know,
a slimy blob of moss or something.

Speaker 3 (32:17):
Well, I don't know how much the slimy blob of
moss is moving, but I don't know if they're trying
to bite, But they definitely will investigate things they're moving.
Something else about a lot of leeches that they like
flat surfaces. It's easier for them to stick to, and
so a lot of times when we're out, especially in
places where there's a lot of debris and trash, they
will stick to broad surfaces of things like bottles and

(32:40):
pie plates and just any kind of flat debris. They'll
just kind of hang out there. I don't think they're
nicely looking for a host, but something you know, they
can get underneath, and they can stick too easily.

Speaker 1 (32:51):
I've seen them on soda cans.

Speaker 3 (32:53):
Yeah, exactly. Yes, it was another part to your question.

Speaker 1 (32:56):
Well, so I was gonna interrupt and tell the story
about like why in my world you are so famous,
and it's because you got to be on the BBC
once and you use the fact that they respond to
vibrations or movements in the water and you danced in
a BBC video to attract the leeches. Is that usually
how you attract the leeches. Does that mean that they're
biting you for you to get them or tell us

(33:18):
about collecting leeches and then we'll get back to the
sensory stuff.

Speaker 3 (33:22):
Yeah. So one of the things that we have done,
those of us who have been trying to collect as
many leeches as we can for our research, is to
use ourselves as bait. This obviously only works in the
blood feeders, but when we go out into a pond,
we want to get out and look everywhere. So this involves,
you know, getting into the water about knee deep. We

(33:43):
look through plants, submerge debris like I was talking about,
but it's also like tree limbs and rocks and anything
that a leech could be hiding under. And while we're
doing all of that, we're making a fair bit of
you know, motion in the water and we're disturbing it
a lot. For the BBC interview, we were specifically interested
in the Macrobdella leeches that I was talking about earlier

(34:04):
the North American medicinal leeches. So when we got out
into the water, one thing we were doing was trying
to make a lot of movement, a lot of disturbance
to try and to track the leeches. Is kind of
like a leech dance, trying to just get as many
ripples in the water as possible so that when they
do detect that motion, they'll swim closer. But they're not
super fast and so it takes some time. So we

(34:26):
get in, we make some ripples in the water. You know,
everybody has their own style, Like some people are more consistent,
you know, up and down, so people are side to side.
A lot of room for individuality here. But do you
do that and then you kind of let everything quiet
down so the leeches, you know, can swim closer, and
then you have to kind of go again because they
take a minute.

Speaker 1 (34:45):
Because they're slow. Can you see them coming towards you
and catch them in a net or do you not
know until they've bit you that Like I have a
specimen for the museum now.

Speaker 3 (34:54):
I like to try and see and get them before
they're attaching, because when they're attaching, they're going to try
and bite, probably because they're hungry, that's why they're seeking
out a host. But many leashes, you'll see them swimming
across the surface of the water and you can use
a net or you can use your hands and grab them.
But some leeches are more sneaky and they kind of
dive down and then you don't know. So when you're
doing the leech dance and you're making all these ripples

(35:16):
in the water, you have to stop periodically and also
do a leg check foot check to make sure they
haven't gotten somewhere that you can't see because it's below
the water. And if you do get them before they bite,
then that's a bonus. But if you don't, sometimes you
find the leach when it's already bitten and it's being
worst case scenarios. You pull your leg out of the
water and it's already bleeding and the leach is gone.

Speaker 1 (35:36):
Oh yes, as a scientist, that is a bummer. I've
never seen Daniel make this space before, to be honest,
and Daniel and I have been working together for a while.

Speaker 2 (35:46):
Well you know, I'm a particle physicist and I've never
been bitten by a particle, and I don't really have
to worry about that. I have to like take one
for the team for science. Is this a regular thing?
Like how many times have you been bitten by leeches?
Is it like so many times you can't even count?

Speaker 3 (36:00):
Imagine exactly I've lost count. I mean, actually I try
to avoid getting bitten me too. Yeah, open wounds, and
you know, muddy water can invite other problems that I'd
like to avoid. But also a lot of people over time,
you know, if you do this for your whole career,
you know, so thirty years of getting bitten by leeches,

(36:21):
some people develop an allergy to it, and I'd like
to avoid that. The other possibility is that you can
always wear waiters broad surface the leech will attach to,
so you make the movement, but it's less fun.

Speaker 2 (36:34):
You make it sound like anybody wearing anti leech protection
is like a wimp or something you could if you
have to.

Speaker 3 (36:41):
Oh well, I actually have converted to waiters recently. So
the only problem with waiters is they get hot.

Speaker 1 (36:46):
So hot, and then you're sweaty and you stink the
rest of the day. And sometimes they get a leak
and then it's hard to walk because your feet are heavy.
And I totally get not wanting to go in with waiters.

Speaker 2 (36:58):
It's not even a question from me. So much rather
be hot and stinky than bitten by leeches.

Speaker 1 (37:04):
Like I've talked to people who study mosquitos and to
keep the mosquito colony alive, you know, they can get
blood bags, but sometimes if they know that they're not
infected by anything, they'll feed them with their arms. Does
stuff like that ever happen with leeches where you're like, oh,
these need to stay alive for another week or two,
but I don't have anything other than my arm, or
does that just kind of not happen with leeches. How

(37:25):
do we feed the medical leeches.

Speaker 3 (37:27):
I actually don't know how they're feeding them in the labs,
But for leeches for my research, I'll bring them back
live a lot of times. And I like to show
people leeches because I work at the Natural History Museum,
so we have a lot of visitors and if we
have the opportunity, I like to keep live leeches around
to show off. But they don't need to eat all
that often, so they can survive for several months without eating.

Speaker 1 (37:52):
Wow, that's convenient.

Speaker 3 (37:54):
It's very convenient, especially because it can be a little
bit of a process to feed them. Like you said,
you know, getting bags of blood leeches. You can't just
pour the blood in the water. They can't like absorb it.
They have to suck it out of something. So usually
we'll get blood from a biological company or the butcher
and put it in a nitroplastic glove focohole so the

(38:14):
leeches know what's in there and then they will go
for it.

Speaker 2 (38:17):
I was sure you were going to say interns. They
use you higher summer interns and use those to feed
the leaches.

Speaker 3 (38:23):
Way too much paperwork.

Speaker 8 (38:25):
This is the federal government, but it has happened occasionally
where everybody's kind of you know, in the break room
on a Friday evening and they're like, hey, anna bring
the leeches. So, but it's hard to get them to
feed in that kind of setting because when they're feeding,
they use all of the muscles in their body just
suck the blood out and then they move the blood

(38:45):
through their body with.

Speaker 3 (38:47):
All of their muscles. That means they're really vulnerable to
predators during that time. So when they're feeding, they need
to feel super safe. So if it's dark, if it's quiet,
and that is not necessarily the break room afternoon.

Speaker 1 (39:01):
But if you turn down the lights and you sing
it a nice song, sometimes it works out.

Speaker 3 (39:06):
Yeah, sometimes exactly, and if they're hungry enough. But no
one here has ever fed leeches. I believe you one
hundred percent.

Speaker 1 (39:14):
Do we know anything about the evolution to get from
earthworms to blood sucking leeches? Do we know anything about
the steps in between? Like how do you get from
one strategy to another?

Speaker 3 (39:24):
It's a great question. That's something that we have been
debating for over one hundred years with leeches, especially because
the closest relatives are the brank you of deladens the
crayfish worms, and they're commensals, so they're not necessarily feeding
on blood. Now, what's interesting is that the crayfish gets injured,
like it loses a leg or a claw comes off,
and there's break you of deleadens nearby. They will all

(39:46):
go to that wound and start feeding on the crayfish blood.

Speaker 1 (39:49):
Huh.

Speaker 3 (39:50):
But they won't necessarily make the wound themselves.

Speaker 1 (39:53):
Okay, So that seems like it could be like a
step on the way, Like you live with the crayfish,
and then you feed on it when it gets hurt,
and then you eventually have the ability to hurt them
and suck their blood.

Speaker 3 (40:04):
Yeah, but the branci ofb delins, there aren't any parasitic
branchib deeldins. And then with leeches, there's been this long
debate about the ancestral leech was a blood feeding or not,
And we still don't know the answer to that because
it happened so long ago. Our molecular data, the DNA
sequences haven't kept that signature very strong in the data,

(40:24):
so we still kind of debate about that. Within certain groups,
we can tell that yes, there was a blood feeding ancestor.
So for instance, in the group that I have spent
the most time working on, the jawed leeches, they have jaws,
they have teeth, they make little bites, and then they
suck blood out of that wound. But there's also species
that don't feed on blood. They still have teeth though,

(40:46):
and that's usually it helps them to chew up their
earth farms as they're eating them, or to chew of
the insect larvae as they consume it. And what's interesting
about that group is it does look like the ancestor
of that group was a non blood feeding leech. And
then there was a transition to blood feeding within the group,
but there's also been several independent transitions back to non

(41:07):
blood feeding. Huh, So it seems like something that does change,
you know, depending on the group and what environment they're
found in. Yeah, there's a lot of different feeding strategies.

Speaker 1 (41:16):
It doesn't seem like it's a hard strategy to transition
to if it's happening multiple times.

Speaker 3 (41:21):
Right.

Speaker 1 (41:22):
Interesting. I would have guessed that processing blood would be
way different than eating an earthworm.

Speaker 3 (41:27):
It should be, Yeah, but these leeches have found a
way to maximize where they are, and once that transition occurs,
you know, there's several species that will maintain that. Yeah,
it seems to be relatively plastic. I would say, Okay,
all right.

Speaker 1 (41:41):
Well let's take another break and we'll come back and
talk more about some weird leeches. Okay, so we're back,

(42:03):
and I have to ask you about something that I
heard once over drinks with friends, but I am not
actually sure that it was a real fact. And it
is that there is a leech that specializes specifically on
hippo butts. So the only way you would find this
leech is if you were searching hippo butts. Is it
true that there is a hippo butt leech.

Speaker 3 (42:22):
You are correct, there is Placodilla's yeager school die. It
is typically found in the rectum of hippos.

Speaker 1 (42:30):
In the rectum of hippos, that's an even more extreme environment.
So that leech needs to not just find a hippo,
but it needs to find a hippo, and then it
needs to figure out which end is the back end.
And that sounds like a difficult search problem for a
tiny little leech. But this also sounds like a hard
thing to study because hippos are very dangerous. Do we
know how those leeches figure out which end of the
hippo is the right end?

Speaker 3 (42:51):
It's a good question. I don't know. But there are
other leeches that tend to gravitate towards certain areas of
the body. So this is something that several types of
leeches have to figure out. So there's a lot of
leeches that feed on orifices, and that probably is because
they have fewer teeth and so it's harder to get
through the skin, and they're looking for areas with thinner

(43:14):
tissue and more blood vessels, so like inside mouths and
up noses, and so that's probably what the hippo butt
leach is doing is that, you know, hippo's skin is
pretty tough. They can't bite through that, so they're looking
for an area that is softer, softer tissue that they
can bite through. And unfortunately for the hippos, I would
guess I'm not sure their opinions on this, but yeah,

(43:37):
it's softer in there, so that's what they're going for.

Speaker 1 (43:39):
What was the second part of your question, I've got
distracted by a more important question.

Speaker 2 (43:43):
How did anybody discover this? Were they looking for something
else up the butt of a hippo or tell us
the story?

Speaker 1 (43:49):
Right?

Speaker 3 (43:49):
So hippos can be very dangerous, and so who ever
discovered this, I don't remember who it was, but I
guess they were looking for other things in the hippo wrecks.
I'm guessing it was a parastologist.

Speaker 2 (44:03):
They lost their keys or something.

Speaker 3 (44:07):
He had a reason, I'm sure, And then they found
a bunch of leeches.

Speaker 1 (44:10):
For the species name. The species part that you said
sounded like someone's last name. Is it someone's last name?
Is that the person who found it?

Speaker 3 (44:16):
I don't know if it was the person who found it,
Probably not, because when we name species after people, it's
typically not the person describing it, so I don't know
that person's association with that species, but it was in
honor of someone.

Speaker 1 (44:29):
I would love to have a parasite named after me,
but it hasn't happened yet. One day, maybe I'll be
that important.

Speaker 3 (44:34):
I'm not sure what this individual thought of having a
hippo butt leach named after them.

Speaker 2 (44:39):
Kelly, it seems like the path is clear. You just
got to look up the butts of lots of weird
animals until you find your parasite.

Speaker 1 (44:44):
Well, but Anna just said that you usually don't get
to name a species after you, you can name it
after someone you know. So I need to become friends
with the people who are checking animal butts. And I
thought that I was doing a good job of becoming
friends with the right kinds of people, but it just
hasn't happened yet. But I'm going to keep my fingers.

Speaker 2 (45:00):
I'm not in that group. Yeah, your friendship with me
is not getting you any closer to that for sure.

Speaker 1 (45:04):
Well, you're going to name a particle after me, probably right,
the Smith particle, I hope.

Speaker 3 (45:10):
So I think there's a good chance, Kelly. I think
with your crowd.

Speaker 1 (45:13):
There's a good chance of this in the future, I'm hoping. Okay,
so you're more likely to find leeches and highly vascularized
thin skin areas. And so I've seen leeches on like
fish sides with scales, Like, do they have ways to
get under the scales? I guess that's pretty easy to do.
You just kind of move them aside.

Speaker 3 (45:31):
Yeah, they have very small mouths. And also there's a
lot of turtle leeches, and so you know, turtles have
scales and then they also have their shells. But on
the turtles, you know, they have different scuts in different
plates on the shells, and the leeches go for the
seams in between them. So they're not going to try
and feed through the skewed because it's keratonized it's hard,
but they'll go for the scenes in between because they

(45:52):
can get to the blood vessels easier there. But with
turtles especially, they're going for places where the turtle can't
scratch them off. So it's going up like around the neck,
behind the arms, underneath their legs, places that they can't
either scratch them off or go find a tree or
a rock to scrape them off.

Speaker 1 (46:08):
Okay, so I tell people I study parasites and they're like, well,
that's gross, And then I try to get them excited
by being like, Okay, I'm not going to change your
mind about them being gross. That's fine, But like these
tiny little sacks of fluid, they're able to figure out,
like where the soft parts of people are, and they're
able to find them, and like they do do all
of these amazing things. They've like evolved these anticoagulants that

(46:31):
help them with their feeding. So when you tell people
I study leeches and they go uugh, do you have
like a speech that you give them to try to
be like okay, but they're gross but fascinating or are
you just like this is a lost cause. How do
you try to turn people into leech fans?

Speaker 3 (46:49):
I think it depends on the individual. Okay, So I've
definitely been at places when people realize what I do,
they say, Okay, you don't get to talk for the
rest of the evening, and I go, oh, it's not
the best dinner conversation. But for people who are interested,
I mean, I agree, like bloodsucking worms can be gross.
I get it. I mean that's just a reality that
you have to face. But if we can admit that

(47:11):
there's a cool side to it and that there's a
lot that we can learn from leeches about their anticoagulants,
about where they occur in nature, how they're associated with
different verbrate hosts. We can learn a lot from them,
and that's I think the more important point. Trying to
appreciate them for what they're doing and that they're serving
an important role learn our ecosystems that hasn't always.

Speaker 1 (47:34):
Been recognized is the angle that usually works best. They're
medicinally helpful and they're teaching us about anticoagulants. I'm guessing
that's the most convincing.

Speaker 3 (47:44):
Yeah, that's a strong point with leeches. Also because they're
commercially traded, leeches have played a important role in conservation
as well. So the rudo medice analysis is the European
medicinal leech. This was the leech that was collected the
most in the seventeen to eighteen hundreds from a dismal
purposes and for blood letting, and this species was also
one of the first species to have conservation measures put

(48:07):
in place about its collecting. So in Germany, especially in France,
the number of leeches that were collected for blood letting
purposes was astronomical. There were millions of leeches collected and exported,
and very quickly the governments realized that this is a
huge number that needs to be tracked, not just for
economic purposes. But then later as they started tracking the

(48:29):
populations the natural populations is seeing that, oh, there's not
as many leeches as you used to be. So they
started putting regulations in place to say, you know, you
can collect leeches, but there's only so many you can export,
and there's only so many that you can collect today.
And actually the root of minus analysis is considered vulnerable
because of the number of leeches that were collected back

(48:51):
in the seventeen eighteen hundred, so those populations still have
not recovered to this point. So today the modern species
that is used in blood letting is Rudo verbana. It's
another species rudo that's found farther east in Europe, and
that is the commercially traded leech. So today, if you
say that you have brudo and you're sending it to

(49:11):
different places, one of the first things they want to
ask is is it rudomus analyis because we need to
be careful about that because it's considered vulnerable as a
conservation status of being vulnerable or is it hrud of
verbana and we need to track it because it's a
commercially traded quantity.

Speaker 1 (49:27):
So like when the Rudo Mets analyis, was I really
rocked that? I'm sure I didn't. So when those numbers
started to go down, did anything noticeable happen in the ecosystems,
Like were we able to identify that they had played
an important role and when they fall down, like maybe
the animals that ate them, their numbers go down or
was there nothing obvious at the time.

Speaker 3 (49:48):
I don't think anyone was looking at that necessarily. Yeah,
I'm unaware of work on that. A lot of people
when they would study this would look at the leeches
themselves and not necessarily how it played roles in the ecosystems.
But I think this is something about parasitology in general
that we're realizing how much more important that is. These days,

(50:08):
scientists are starting to include parasites in looking at ecosystem questions,
more so than ever has been in the past, because
they are connecting different trophic levels and different parts of
the food web, and parasites are doing a lot more
in our ecosystems than I think we've ever recognized before,
especially when you think about ecosystem decline and changing climate scenarios.

(50:31):
That parasites can be a canary in the coal mine
because they are connecting so many different points, and so
when the parasites aren't able to make those connections, we
can start to see perturbations and disturbances in these ecosystems
and parasites long before we see the effect in the
larger macrofauna.

Speaker 2 (50:49):
So do you think parasites or leaches more specifically, serve
an essential, an inevitable role in an ecosystem. Let me
put it to you in a different context that maybe
you've never been asked before. Or say, we land on
an alien planet and we observe an alien ecosystem, do
you expect to find some form of leeches on that
alien planet? Are there alien leeches? It's my question.

Speaker 3 (51:11):
I like the possibility of alien leeches. I would definitely
expect there to be a parasite or many parasites, probably,
but I don't know if they would take the form
of leeches necessarily. The reason I say this is because
parasitism is the most common life mode on the planet.
Oh wow for eukaryotic organisms, right, yes, yes, of ukryonic organisms,

(51:34):
it's ubiquitous. As long as there have been organisms, there's
probably been something parasitizing it. Wow.

Speaker 2 (51:40):
Am I talking to the first astro parasitologists.

Speaker 3 (51:44):
I think you may be the first astro paristologists.

Speaker 1 (51:48):
There's so many cool parasites left to study here on Earth.
When people are like, Kelly, would you move to Mars?
And I'm like, there are still parasitic worms left to
describe your people. Why would anybody go to Mars. There's
too much work to do.

Speaker 3 (52:02):
Yeah, it's daunting and there's not enough of us doing it.
So yeah, we got to pick up the pace.

Speaker 1 (52:07):
That's right.

Speaker 2 (52:08):
And I don't think the idea of getting sucked on
by alien leeches is going to make somebody more likely
to go to Mars or venture on to another planet.
So it's not exactly doing a sales job.

Speaker 1 (52:18):
I mean, I think space is bad enough at selling
space as it is, but I'm a bit biased and
I know lots of people who disagree with me. So
on that note, I have had so much fun. Thank you, Anna.
Do you want to end by telling us what your
favorite leech.

Speaker 3 (52:32):
Is I have to pick just one? I know they're
like children.

Speaker 1 (52:35):
Now do you pick just one?

Speaker 3 (52:36):
I don't know exactly. I have a special affinity for
the Macrobdella leeches in North America. Macro because they're large
and bidella is a name for leech. They're big, they're
brightly colored and since they're all agreed with orange polka dots,
and I mean big is that there's several inches and
a lot of people encounter them and they're pretty. It

(52:58):
was one of the first groups that I studied as
an intern long ago, so still hold a special place.

Speaker 1 (53:02):
In my heart. They sound wonderful and I bet a
lot of our listeners have encountered them, and maybe they'll
appreciate them more now.

Speaker 3 (53:08):
I hope.

Speaker 1 (53:09):
So all right, thanks Nanna. Daniel and Kelly's Extraordinary Universe
is produced by iHeartRadio.

Speaker 3 (53:22):
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Speaker 2 (53:25):
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