Editor's Note: The video of leeches used in surgery is a bit bloody — especially after the 2-minute mark.
Leeches get a bad rap — but they might not deserve it.
Yes, they're creepy crawly blood-suckers. And they can instill an almost primal sense of disgust and revulsion. Humphrey Bogart's character in the 1951 film The African Queen even went so far as to call them "filthy little devils."
But the humble leech is making a comeback. This critter is increasingly playing a key role as a sidekick for scientists and doctors, simply by being its bloodthirsty self.
Distant cousins of the earthworm, most leech species are parasites that feed on the blood of animals and humans alike. They are often found in freshwater and navigate either by swimming or inching themselves along, using two suckers — one at each end of their body — to anchor themselves. Most species range from about a quarter inch to three inches in length.
Upon reaching an unsuspecting host, a leech will surreptitiously attach itself and begin to feed. It uses a triangular set of three teeth to cut in, and secretes a suite of chemicals to thin the blood and numb the skin so its presence goes undetected.
Some leech species can also live on land, thriving in humid environments like the forests of southern Asia. Biologists recently reported that leeches in that region can provide a valuable snapshot of which animals are present in a particular area: The parasites carry their host's blood, and DNA, within their gut after each meal.
"They find things you don't find," said Michael Tessler, a postdoctoral scholar at the American Museum of Natural History in New York. As an added bonus (depending on your perspective), leeches are also attracted to humans as potential blood meals, he said. Thus, the creatures do not shy away from researchers, making sample collection quick and easy.
Tessler and several colleagues gathered 750 terrestrial leeches in the genus Haemadipsa from Cambodia, Bangladesh and southern China. Then, they analyzed the DNA from each inch-long leech's meal to identify the unwitting blood donors. With this analysis, the scientists were able to identify wild and domestic animals common in those areas, including some species of concern for conservation.
The study also revealed a few surprises. Some leech meals had come from a few bird species, and one came from a bat. "Clearly these things get around," Tessler said.
Beyond their utility in field biology, leeches have an important role to play in a surgeon's medical kit.
The association between doctors and leeches dates back to the ancient Egyptians and ancient Greeks. According to Greek philosophers, illness was the result of an imbalance in bodily fluids, or humors. They believed that applying leeches to patients would help restore a proper balance. Leeches were widely used as a cure-all for an array of ailments, especially in medieval Europe.
These practices were relegated to the status of quackery by the advent of modern medicine in the 20th century as doctors developed new, more effective treatments. Nowadays, however, medical leeches are experiencing a renaissance as their bloodsucking ability is tuned to a more scientific purpose.
Leeches come in handy during reconstructive surgeries, such as those to reattach fingers, according to Dr. Rudolf Buntic, a hand surgeon and director of microsurgery for California Pacific Medical Center in San Francisco. During such a procedure, surgeons repair small arteries that carry blood into the severed digit. However, the tiny veins that carry blood back out may be too damaged or too small to repair, leaving blood to stagnate in the finger.
That's when Hirudo medicinalis comes in.
"The leech acts as a vein," said Buntic.
It draws stale blood out of the reattached finger as it feeds, allowing fresh, oxygenated blood to come in. Chemicals in the leech's saliva also help prevent blood clots from forming in the damaged tissue. Doctors apply fresh leeches over the course of about ten days. This provides enough time for new, tiny veins to regrow and create channels for blood to leave the patient's finger on its own, Buntic said.
Throughout the treatment, surgeons order leeches from the pharmacy, just as they would any other medicine.
If these little guys still give you the heebie-jeebies, don't worry: They probably won't be showing up at your local drugstore anytime soon, as they're primarily used in hospitals.
You might run into them in some research labs, however. David Weisblat, a biologist at the University of California, Berkeley, has been studying leech development and evolution for more than 40 years. He's recently started a project to learn more about leech behavior and neurobiology.
This involves placing the leeches onto a checkerboard of sorts, made of sandpaper. The squares alternate between rough and smooth grains. Many of the leeches, small snail-hunters in the genus Helobdella, have a strong preference for the smoother squares, moving in strictly diagonal patterns.
"It's like a little pawn on the chessboard that's gone crazy," Weisblat said.
Though leeches may have an unimpressive nervous system by vertebrate standards, they are still capable of using information from their environment to make decisions, said Weisblat. And figuring out how this process works is easier in a leech than in the nervous system of mice or rats. In understanding how leeches find their way around with so few neurons, we can begin to understand how the nervous system processes and encodes information, Weisblat said.
Capturing the way leeches sense and move through their environment could also one day translate to bioengineering applications, like designing small, exploratory robotics, said Weisblat. "Leeches can go on glass surfaces, crawling with their suckers, and exploring all sorts of different ways," he said.
"It's pretty amazing, when you think about how simple they are."
Emma Hiolski is a freelance science journalist and intern with KQED's Deep Look video series. Her work has appeared in Science, Chemical & Engineering News and The San Jose Mercury News. You can find her on Twitter @EHiolski.
How to set up a leech habitat for pregnant leeches and to be able to breed leeches at home on a small scale.
If you’ve been a having a dream about having a leech farm been able to multiply breed keep leeches and do various things with leeches in as much natural environment for them as possible, then this tutorial is for you.
And lets get started. I have a box, its just plastic see through box that you will need in order to set up your leech habitat.
Now the reason that I’ve used a clear plastic is because anything that has to do with leeches has to be clear and see through. Trust me you don’t want to take anything that’s opaque or solid and keep leeches in. The reason is because you always gonna have to keep an eye on your leeches and they has to be very clearly visible.
Don’t buy any supplies for leeches that are not see through.
Leech.com has the best supplies and it has the best leeches as well so you can’t go wrong visiting and getting all your supplies from there.
You can also find the same supplies probably in your local Walmart Cameart or grocery store or whatever supplies home supplies store.
I’ve put almost three quarters cold water from the tap from the sink into this crate (into this container).
The container has to have a lid.
And when I close the lid its sort of snaps close although. Its a it could some leeches could escape because they are escape artist and they can get through any little hole.
You can also set up a peace of fabric on top, like a scarf or just peace of cotton or gauze.
Well actually gauze is not good because it is too porous it's got big holes.
So when you have something like this you can then tie it with an elastic and this will prevent the leeches from escaping.
What you need is just an elastic band to go around.
You need the elastic to go all the way around, to make it very tight.
And you can also use the fabric and the lid at the same time. This way it will prevent allot of the leeches from escaping hopefully all of them. The idea is to keep all the leeches in and not let any of them out.
So lets continue with the tutorial on how to set up your bedding.
Now what you’ll need is leech moss. You will find it on leech.com. Leech moss will be available here year round.
So back to my collection of leeches. I am using a leech bucket for them and this bucket of leeches is not set up for pregnant leeches or for breading purposes. My leeches are very very lively.
My leeches are from leech.com - they are all over the place although I haven’t changed their water in a couple of days but they are starting to come out already and you will see that there are holes in the lid. One two three four five six seven eight nine ten eleven twelve thirteen fourteen fifteen sixteen seventeen eighteen nineteen twenty twenty one holes...! Twenty one holes and I keep made holes on my buckets because I don’t want leeches escaping, and I don’t want to put fabric on top of my bucket and so I am not using fabric on top of my bucket where i keep my collection of leeches. I am using a lid, solid lid. I find that the lid if far more effective because it keeps them in and doesn’t let them escape.
The leech forceps the leech handling tool which you will also find online in leech.com
This is what you’ll need to do:
I have purchased leech moss and a lot of them will escaping while I do this but thats just the nature of leeches. They will run. So the leech moss that I purchased from Leech.com is probably about one two three four five six six or seven portions of it. When you buy one portion you will going to get about a hand full. You will probably be able to keep about thirty leeches in it. So about thirty leeches.... and with all of the moss I have, you will be able to keep hundreds and hundreds of leeches. Each portion is about two hundreds grams.
All right so, my leeches are so robust and lively. They are just unbelievable. And they are very clean and very beautiful and I love them. Some of my leeches are really really big. I have one really huge leach.... and I am sure I have pregnant leeches already because they mate in a very warm temperature.
So but back to our set up, what we’ll need is because we have pregnant leeches as I said I take out all of my moss and I will make sure that the moss is placed in the water in a propped up fashion.
So lets see how this will work. Now this would not be so good because there is no water in the moss and this is a styrofoam box but if I use more that one styrofoam box in fact I have another one. And you can use a plastic box or anything with holes in it. There holes in my boxes.
All right so I am going to place another box on top of the first one.
This will clearly allow for the pregnant leeches to crow in and out of.
My leeches they are all over the place!
And I am submerging these boxes under water.
They are made of Styrofoam, so they will float.
So you might want to get other kind of boxes not Styrofoam.
But the idea is to have the leech moss be half way wet and half way dry.
So what will happen is now that I have the moss set up, it will stay half dry and half wet.
And if I can keep it submerged under water like this without it floating up so you might want to put some heavy weights like rocks / stones. So make sure to keep everything submerged.
So that the moss stays half way wet half way under water and half way above that’s the idea.
Now I also have a little bit of wild moss which is available here in England and as you can see its almost identical to the purchased moss and I’ll just put all the moss that I have in my habitat.
And of course my leeches are all over the place again....!
Now I’ll be very busy collecting them afterwords but the leeches are everywhere.
So whats going to happen is I am going to keep the boxes submerged.
I’ve actually gone outside and I found some weighing devices - I’ve got two bricks.
My bricks are going to keep my Styrofoam well under water and this is just perfect perfect habitat for the leeches.
This is this is giving them enough moss and its also affording them to be in wet in swimming in water.
So on both sizes I have plenty of room for swimming.
The inside of the two boxes sort of box stuck together gives them a dark dark space as well and then the moss which is half wet half dried will give the leech the opportunity to lay their cocoons.
The pregnant leeches will lay cocoons.
So I’ve had I bought some eggs just to demonstrate.
These are not leech eggs.
These are not leech cocoons.
These are just regular eggs that I’ve purchased what will happen with your leech breading habitat.
This is how you’ll find leech cocoons on top of moss in the dry.
Because leech cocoons cant be submerged under water.
Maybe they can half way be submerged but not completely.
So then I’ll place this lid on and then I will use my poking device to make holes just like I have with my leech bucket.
Where I keep my leech collection.
I am going to make a few holes so lets find some easier.
That’s one hole two , three, four.
I’ve only done five just to demonstrate but you can actually cover this in holes.
I would say about thirty holes will be great maybe even more.
And so, now that I’ve set up my leech habitat I can easily transfer my leeches.
And of course leeches are all over the place.
But I’ve got some bigger leeches and smaller leeches.
I will I will pick out some of the bigger leeches.
They are probably pregnant.
Leeches do breed in a warm temperature in the spring time.
Leech will actually made in the spring but leech will lay cocoon probably end of spring beginning of summer.
Although I’ve heard Leeches.com has customers that’ve reported that when they bought pregnant leeches, that the leeches have actually given birth to cocoons in winter.
So my friend Lisa has reported that.
She bought from leeches.com and her leeches delivered I think tree leech cocoons if I am not mistaken and hundreds of baby leeches inside.
So here leeches absolutely loving this environment.
This is the right moss this is the right set up for leeches.
This is perfect for leeches.
So now some of leeches are actually goes swimming in the water.
Some of the leeches will launch around on top of the dry moss.
Some of the Leeches will find the box, box space inside just swim around in dark.
Or to launch around or just sleep.
And so this is this is offering tree different kinds of environment for the leech.
Cold water, dark water and dry half dry half dry moss for leeches to breed on to lay cocoons on and to for the leech cocoon to hatch and for the little baby to hatchlings for the little baby leeches to come out of.
Each leech cocoon going to be very spongy egg, egg looking cocoon.
Its going to be a bit smaller that this or this size and it its going to be a bit smaller that this or this size and its going to be like sponge.
And you can actually even open it although I don’t recommend you opening leech cocoon because the hatchling inside, the babies that are going to be inside they are going to wait for the right time…
Look leeches are trying to bite me.
Oh no, they are going to wait for the right time to hatch out of this cocoon.
So its not up to you or anybody else to determine when leeches going to be hatching .
The little babies determination when this is going to take place.
And as you can see I have leeches everywhere.
This is the most lively bunch I’ve ever seen that I’ve gone all over the place.
But the all and up in this leech habitat after all and I am gonna to prepare to breed leeches this spring.
And so another way to breed leeches is to set up the same kind of habitat like this one but just for two leeches.
So you can put a male and female.
In fact leeches are hermaphrodite.
So any two leeches that you take, this one and this one for example you can put them in a habitat like this one exactly.
And just have the two of them here and they will eventually made.
And they will eventually one leech will get pregnant and will deliver cocoons.
So that’s how the process works.
Once baby leeches are hatched and they start swimming in the water and everything leeches will want to eat and the leeches eat by drinking blood.
That’s leech only food.
Leech don’t swallow worms or leech don’t do anything else.
Leeches just drink water, uh water, leeches just drink blood.
So what you can do is feed leeches here on your veins.
You can feed leeches on very very delicate places in your body.
To make sure that the little babies because leech cant bite everywhere.
Leeches can only bite in very delicate places.
So what I’ve seen people do is they will put the mother and the father leech on the finger and have them sucking from the finger.
Feeding leeches on the finger.
And then they will put the baby leeches in water and they will put that same finger in the water and the baby leeches will actually feed from the wound from the bite from the mother and the father leech.
So the baby leeches will have easy way of latching.
Otherwise leeches wount be able to.
And I think this cover just about everything as you can see all the leeches that I put in here they either starting to swim or leeches are actually are hiding because leeches love the dark.
Right now this is too bright for leeches.
And leeches already starting to find dig holes and find their way into the moss.
As I said heaven heaven for leeches its perfect.
I hope you’ve learned allot.
If you have any questions whats so ever on leech breading, on pregnant leeches on anything concerning leech habitats or feeding leeches or anything else, check out my other videos I’ve done close to sixty at this point where I teach you veryest different aspects of keeping leeches and also leech therapy.
And don’t forget to subscribe to my leech channel which is very important so you can follow all my videos automatically as they come out every week and you’ll get to learn allot.
Leech keeping and leech therapy takes a life time to learn so its important for you to get started right away on learning all the different veryest aspects of leeches.
Thank you for watching.
I hope you enjoy this video.
Please give it thumbs up, please subscribe below and I’ll see you next week on the next video.
From me Tsetsi and sunny London good bye.