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The Crazy World of Leeches


Photo: Christian Fischer / Wikimedia Commons / CC BY-SA 3.0


I’m about to unlock a childhood memory: You’re a kid on a hot summer day. You’re playing in the water, having the time of your life, when you notice something. Just a little something on your leg. Next thing you know, you’re running out of the water and screaming “LEECH!” at the top of your lungs.


Most of us have had this experience as a child. I know I have, on more than one occasion. If your parents were anything like mine, they probably told you to calm down and that it was just a tiny bloodsucker. They probably headed off to come to the rescue with a saltshaker. A sprinkle of salt, an uncomfortable wiggle from the leech, and it was off your leg. All was right with the world…or WAS IT?


As it turns out, putting salt on a leech isn’t a very good idea. You’re much better off to let the leech just fall off on its own because the discomfort of the salt may make it VOMIT INTO YOU. Urgh, thanks, MOM. There is a lot more to the leech that meets the eye. For example, did you know it’s a worm? The leech is a water worm and a pretty amazing one at that. Here are just a few facts you might not have known about the amazing water worm we call a leech:

  • Leeches have 9 pairs of testicles, 10 stomachs, 32 brains, several hundred teeth. We are pretty sure there’s a joke in there somewhere, but we’re going to leave it alone.

  • Leeches take a two for the price of one approach to reproduction, literally! Leeches are actually a type of hermaphroditic (having both male and female parts) worm.

  • Leeches have been in medicine for over 2500 years! Their analgesic, anesthetic and anticoagulant virtues make them a great resource in healing wounds. Doctors have been using them for literal ages. People used to have jobs that entailed baring their legs and wandering in marshes in order to catch leeches to sell to medical practices. Today, there is a leech farm in the UK that supplies medical practices all over the world. Leeches are even FDA approved!

  • Leeches can predict the weather! Ok, maybe not exactly BUT in the 1800s, a scientist made an accurate storm prediction machine using leeches, due to their agitation before storms.

  • Bloodsucking super spies! Scientists also use leeches to spy on animals that are rare or shy. They provide a picture of what species are in an environment. No need for stake out or trap cameras, just catch a few leeches and they will rat out the neighbourhood by virtue of what’s in their system.

  • Leeches eat worms, snails and insect larvae and are in turn eaten by fish, ducks, and turtles.

  • Leeches are a fisherman’s friend, but it’s not the healthiest friendship (for the leech). Anglers worldwide adore this water worm as bait.

You’ve got to hand it to them, leeches are surprisingly complex little worms. They’re an important part of the food web, modern medicine, and science! Take some time and Google leeches for more interesting facts. Hopefully knowing more about these little guys will help us to know there is nothing to fear from our fellow lake residents and we can all get along swimmingly.

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