Oh, my god.
Whoa.
That's huge!
Is he biting all the way through there?
A blood sucking parasite that's been used medicinally for millennia.
The bane of every tropical pond swimmer.
There's another one!
Oh man, they're everywhere!
These guys have mostly evolved to quietly suck blood without alerting their prey,
but in some cases they can kill their host.
This is not what I signed up for.
Tonight at the leech restaurant, I'm what's on the menu.
Hi, I'm Danielle Dufault and you're watching Animalogic.
Today's the day that I become leech food.
Leeches are the epitome of parasites.
Their name can be used as a verb, meaning to take without giving anything in return.
And for the most part they have earned their reputation.
About three-quarters of the 680 known species are bloodsuckers.
This guy was trying to get into my pants.
Most of them live in freshwater, but there are also marine and terrestrial leeches.
Oh my god.
Some of the terrestrial parasites have a taste for human blood,
as our trusty producers found out firsthand.
Last year, we traveled to the great Otway National Park in Australia to film koalas.
While walking the trails, Andres and Dylan both began feeling a little itchy.
After checking their socks they found multiple guests, Australian land leeches.
Oh, he's squirming around.
There's one coming towards you.
There is nothing behind.
But it was like that.
Oh my god.
Whoa, that's huge!
Is he biting all the way through there?
This is insane!
I haven't gotten any on me, but Dylan and Andres have been covered.
Andres just plucked off about five of them.
Smells delicious.
The sucky boys wait patiently on vegetation,
and when a mammal walks by they look for the warmest spot, attach themselves, and then bite.
Can I see your bite?
The thing about leeches they have three big teeth.
Oh, so I can't really see where it bit you but you might have a cool bite.
Unlike other blood suckers, like mosquitoes, these leeches have jaws,
and when they bite they make a v-shaped incision.
Leeches hold on by using both suction as well as three really powerful,
very hook-like teeth in their mouth.
So you can always identify a leech bite by the shape of those incisions.
A very sci-fi creature, you know?
Leeches inject an anticoagulant called hirudin.
It's one of the world's greatest blood thinners and makes it easier to absorb the blood.
Most of their hosts don't even notice the initial bite.
There's another one!
Here.
Oh man, they're everywhere!
Oh my god.
In our case, we didn't even notice until probably hours after they first bit us.
I got another one.
Ah, okay.
Oh, he's just crawling right up you, see?
He's got your hand.
Listen, he smells your blood okay?
I need to get checked now.
They're probably falling all over me too.
This is not what I signed up for.
After the leech is full, it detaches.
Because of the hirudin, the host can bleed for hours, if not days, afterwards.
Back where I live in Ontario, we don't have terrestrial leeches,
we just have aquatic ones that you find in all the river sides, and all of our lakes.
But here, they will just wait on a big blade of grass, stretch out
and grasp on to you, seeking out your warm hot blood.
But of course, the vast majority of leeches are found in water.
They've evolved to occupy ecological niches on all seven continents, including Antarctic waters.
And like their terrestrial cousins, most of them are bloodsuckers.
Here in North America, we have about 80 freshwater leech species.
They're so common that they're often used as fish bait.
Researchers at the Royal Ontario Museum are even still finding new species.
Since I worked there as a scientific illustrator, I got to go and catch up with
the leading leech expert who recently discovered a new species of leech.
So my name is Sebastian Kvist.
I am the curator of invertebrate zoology,
which means that I take care of all the animals that lack a backbone.
Things like these guys, like smaller worms.
I deal with the jellyfish, crustaceans, and everything like that.
It was time to feed his lab's leeches, so naturally, I volunteered to be their snack.
Tonight at the leech restaurant I'm what's on the menu.
It took a couple of tries, but after a little while, one bit.
These are Macrobdella Decora, North American medicinal leeches.
They're usually found in slow-moving rivers and ponds.
They usually consume small vertebrate's blood, as well as frog eggs.
They also readily feed on human blood.
So I definitely felt this guy bite, but it was such a tiny sensation.
He just kind of latches onto your skin with his teeth and makes sure that he can hang on,
as he is right now, so that he can suck into my blood for a good 45 minutes to get full.
He can grow up to 10 times his regular size.
Once he's gorged himself on enough blood.
In this case, I was happy to feed her, but what if you wanted to remove one from your body?
Leeches, as far as we know, don't spread any diseases.
But one of the things that can happen is that they throw up a bit of the blood
into the wound, and it brings with it a bunch of bacteria.
You might get a minor infection.
And a good way to get a leech to do that is to stress it.
This means don't put lime or salt on them, it stresses them out.
There's a safer way.
Yeah, basically you go in with your fingernail right by the mouth,
and you lift it off really quickly.
Oh, okay.
That's a good way of getting a leech off of you.
But don't worry about me, a single leech would be completely harmless.
So a leech like this will consume about 5 to
10 millilitres of blood in about 45 minutes in a complete feeding.
So, roughly 200 leeches might be a problem, but one of these?
It's nothing.
You can spare five to ten millilitres, you know?
Once they're connected, they don't care about anything else.
They have two nervous centres, one around each sucker.
But while they bite, all their energy goes to their feeding end.
The rest of their body goes on autopilot.
It's like, have you ever tickled a leech because I'm tickling a leech.
You might also notice that they seem to get wet as they feed.
That's because they're only interested in red blood cells.
All the plasma gets separated and excreted through their skin.
Amazing, right?
Now it's time to let this little guy digest.
Having a leech attached to your skin is not really on many people's bucket list.
But for hundreds of years they've been used to treat a huge range of ailments.
In Europe and Asia, leeches of the genus Hirudo Medicinalis,
A.K.A medicinal leeches, are used to treat pain, inflammation, and other health issues.
In the wild, these pretty ladies feed mostly on ungulates and other mammals,
so they're happy to stick to human skin.
They make an incision with their toothy jaw and suck for about an hour.
Because of their powerful anticoagulants, the wound often bleeds for several hours afterwards.
More recently, leeches have been used to help patients with limb reattachment.
Their anticoagulants stimulate blood flow and accelerate healing.
They've been especially useful for finger reattachments.
So, thank you leeches!
Your blood-sucking prowess is a testament to the power of evolution.
Not all leeches are parasites.
Some are full-time predators and swallow their prey whole.
Of course, their prey is usually very small.
Some other predatory leeches don't swallow their prey
but use a proboscis to suck the bodily fluids out of their prey.
A similar method to the spider's or True bug's hunting strategy.
Some species in the Glossiphoniidae family
are escargot specialists and only eat snail bodily fluids.
They're also known to be amazing parents, carrying their eggs in a pouch on their underside.
When they hatch the babies attach to their parents, sometimes sucking them dry.
All leeches are hermaphrodites, so any two sexually mature leeches of the same species
can fertilize each other's eggs, which are then laid in a cocoon.
And in this family's case, they always win parent of the year.
The scariest leeches are probably the ones that feed in mammal mucus membranes.
The newly discovered Tyrannobdella rex, named after the t-rex because of
its relatively huge teeth, is known to swim up people's noses and feed there for days.
Despite using them for millennia,
we're only starting to understand the biodiversity of leeches.
There are likely hundreds of species yet to be discovered.
But I promise you, if Sebastian discovers another one you'll be
the first to know through this channel right here.
Please let me know in the comments and be sure to subscribe for new episodes every week.
Thanks for watching and see ya!