10 Juicy Facts About Leeches

Ian Cook
Ian Cook

Leeches get a bad rap, but they’re actually pretty cool once you get to know them—and we're finding out more about them, even today. Recently, a team led by Anna Phillips, curator of parasitic worms at the Smithsonian National Museum of Natural History, discovered a new species of medicinal leech (pictured above) in a Maryland swamp. We asked parasite expert and curator at the American Museum of Natural History Mark E. Siddall to share some surprising facts about the worms we love to hate. 

1. Not all leeches suck blood.

Hematophagous, or blood-feeding, species are only one type of leech. “The vast majority of species are [hematophagous],” Siddall tells Mental Floss, “but it depends on the environment. In North America, there are probably more freshwater leeches that don’t feed on blood than there are blood-feeders.” And even among the hematophagous species, there are not too many who are after you. “Very few of them are interested in feeding on human blood,” Siddall says. “Certainly they’ll do it, if they’re given the opportunity, but they’re not what they’re spending most of their time feeding on.” 

2. Leeches are everywhere.

Japanese leech on a log
Pieria, Wikimedia Commons // Public Domain

“Every continent on the planet has leeches, with the exception of Antarctica,” Siddall says. “And even then there are marine leeches in Antarctic waters.” Humans have co-existed with leeches for so long, according to Siddall, that just about every language has a word for leech. 

3. Leeches have made a comeback in medicine.

Bloodletting for bloodletting’s sake has fallen out of favor with Western physicians, but that doesn’t mean medicinal leeches are enjoying a cushy retirement. Today, surgeons keep them on hand in the operating room and use them as mini-vacuums to clean up blood. “That is a perfectly sensible use of leeches,” Siddall says. Other uses, though, are less sensible: “The more naturopathic application of leeches in order to get rid of bad blood or to cure, I don’t know, whatever happens to ail you, is complete hooey,” he says. How on Earth would leeches take away bad blood and leave good blood? It’s silly.” 

4. Novelist Amy Tan has her own species of leeches.

Land-based leeches made an appearance in Tan’s 2005 book Saving Fish from Drowning, a fact that instantly put the author in leech researchers’ good graces. “There are not a lot of novels out there with terrestrial leeches in them,” Siddall says. So when he and his colleagues identified a new species of tiny terrestrial leeches, they gave the leech Tan’s name. The author loved it. “I am thrilled to be immortalized as Chtonobdella tanae,” Tan said in a press statement. “I am now planning my trip to Queensland, Australia, where I hope to take leisurely walks through the jungle, accompanied by a dozen or so of my namesake feeding on my ankles.”

5. Leeches can get pretty big.

The giant Amazon leech (Haementeria ghilianii) can grow up to 18 inches and live up to 20 years. And yes, this one’s a blood-feeder. Like all hematophagous species, H. ghilianii sticks its proboscis (which can be up to 6 inches long) into a host, drinks its fill, and falls off. Scientists thought the species was extinct until a zoologist found two specimens in the 1970s, one of whom he named Grandma Moses. We are not making this up.

6. Leeches make good bait.

Many walleye anglers swear by leeches. “A leech on any presentation moves more than other types of live bait," pro fisher Jerry Hein told Fishing League Worldwide. "I grew up fishing them, and I think they're the most effective live bait around no matter where you go." There’s an entire leech industry to provide fishers with their bait. One year, weather conditions kept the leeches from showing up in their typical habitats, which prevented their collection and sale. Speaking to CBS news, one tackle shop owner called the absence of leeches “the worst nightmare in the bait industry.”

7. Leech scientists use themselves as bait.

Siddall and his colleagues collect and study wild leeches. That means hours of trekking through leech territory, looking for specimens. “Whether we’re wandering in water or traipsing through a bamboo forest,” Siddall says, “we are relying on the fact that leeches are attracted to us.” Do the leeches feed on them? “Oh my god, yes. We try to get them before they feed on us … but sometimes, obviously, you can’t help it.”

8. Leech sex is mesmerizing.

Like many worms, leeches are all hermaphroditic. The specifics of mating vary by species, but most twine themselves together and trade sperm packets. (The two leeches in the video above are both named Norbert.)

9. Some leech species make surprisingly caring parents. 

“There’s a whole family of leeches that, when they lay their eggs, will cover them with their own bodies,” Siddall says. “They’ll lay the eggs, cover them with their bodies, and fan the eggs to prevent fungus or bacteria from getting on them, and then when the eggs hatch, they will attach to the parent. They’re not feeding on the parent, just hanging on, and then when the parent leech goes to its next blood meal it’s carrying its offspring to its next blood meal. That’s pretty profound parental care, especially for invertebrates.”

10. You might be the next to discover a new leech species. 

Despite living side-by-side with leeches for thousands of years, we’ve still got a lot to learn about them. Scientists are aware of about 700 different species, but they know there are many more out there. “I’ll tell you what I wish for,” Siddall says. “If you ever get fed on by a leech, rather than tearing off and burning it and throwing it in the trash, maybe observe it and see if you can see any color patterns. Understand that there’s a real possibility that it could be a new species. So watch them, let them finish. They’re not gonna take much blood. And who knows? It could be scientifically useful.”

This Smart Accessory Converts Your Instant Pot Into an Air Fryer

Amazon
Amazon

If you can make a recipe in a slow cooker, Dutch oven, or rice cooker, you can likely adapt it for an Instant Pot. Now, this all-in-one cooker can be converted into an air fryer with one handy accessory.

This Instant Pot air fryer lid—currently available on Amazon for $80—adds six new cooking functions to your 6-quart Instant Pot. You can select the air fry setting to get food hot and crispy fast, using as little as 2 tablespoons of oil. Other options include roast, bake, broil, dehydrate, and reheat.

Many dishes you would prepare in the oven or on the stovetop can be made in your Instant Pot when you switch out the lids. Chicken wings, French fries, and onion rings are just a few of the possibilities mentioned in the product description. And if you're used to frying being a hot, arduous process, this lid works without consuming a ton of energy or heating up your kitchen.

The lid comes with a multi-level air fry basket, a broiling and dehydrating tray, and a protective pad and storage cover. Check it out on Amazon.

For more clever ways to use your Instant Pot, take a look at these recipes.

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Researchers Just Unearthed ‘Lost’ Footage of the Extinct Tasmanian Tiger—Watch It Here

A Tasmanian tiger, or thylacine, in captivity circa 1930.
A Tasmanian tiger, or thylacine, in captivity circa 1930.
Topical Press Agency/Hulton Archive/Getty Images

For 85 years, the last known footage of the now-extinct Tasmanian tiger sat forgotten in the National Film and Sound Archive of Australia (NFSA), until it was recently unearthed by researchers from a Facebook group called the Tasmanian Tiger Archive.

The NFSA’s newly digitized 21-second clip is part of a nine-minute travelogue called Tasmania the Wonderland from 1935, presumed to be the work of Brisbane filmmaker Sydney Cook (though the film is missing its credits, so that remains unconfirmed). It shows a striped, dog-like creature named Benjamin—the last of his kind ever in captivity—pacing his cage at Tasmania’s Beaumaris Zoo, which shut down in 1937.

Tasmanian tigers aren’t actually tigers—they’re carnivorous marsupials called thylacines. TreeHugger reports that the species died out in mainland Australia about 2000 years ago, but they managed to survive in Tasmania until the 20th century. Though thylacines were officially declared extinct after Benjamin died from suspected neglect in September 1936, the status has been highly contested to this day.

“Do I think the animal is extinct?” Neil Waters of the Thylacine Awareness Group of Australia told HowStuffWorks. “No, because I have seen two and been coughed/barked at by one in South Australia in 2018. There have been more than 7000 documented sightings of thylacines (or animals that appear to be thylacines), with the majority of those sightings on mainland Australia.”

Considering that fewer than a dozen known clips—a total of just over three minutes—of film footage showing thylacines exist today, Benjamin’s 21 seconds of fame in Tasmania the Wonderland is a monumental rediscovery. And, since thylacines were exhibited in zoos in Washington, New York, Sydney, Berlin, and other cities after the advent of film, the NFSA is optimistic that more footage could turn up in time.

[h/t TreeHugger]