Leeches are segmented worms that belong to the phylum Annelida and comprise the subclass Hirudinea. Like the oligochaetes, such as earthworms, leeches share a clitellum and are hermaphrodites. Nevertheless, they differ from the oligochaetes in significant ways. For example, leeches do not have bristles and the external segmentation of their bodies does not correspond with the internal segmentation of their organs. Their bodies are much more solid as the spaces in their coelom are dense with connective tissues. They also have two suckers, one at each end.
How is that for an intro? Let’s loosen it up a little bit:
Leeches get a bad rap, but they’re actually pretty cool once you get to know them. Parasite expert, curator at the American Museum of Natural History. There are some interesting facts about leeches according to self-described Leech Guy Mark Siddall.
1. They Don’t All Suck Blood
Hematophagous, or blood-feeding, species are only one type of leech. While the vast majority of species are blood-feeding, it actually depends on the environment. In North America, there are probably more freshwater leeches that don’t feed on blood than there are blood-feeders. 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. They’re Everywhere
3. They’ve 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
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. They Can Get Pretty Big
The giant Amazon leech (Haementeria ghilianii) can grow up to 18 inches (approx 45cm) 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 (approx 15cm) 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.
(Just so horrifying…..)
6. They Make Good Bait
Many walleye anglers swear by leeches as apparently a leech on any presentation moves more than other types of live bait. 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. Their 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 apparently both named Norbert. Why Bono is involved? Who knows…
8. Some Species Make Surprisingly Caring Parents
A whole family of leeches Will cover their eggs with their bodies after laying them. 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…
9. 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,” Siddall says. “We try to get them before they feed on us … but sometimes, obviously, you can’t help it.”
10. You Might Be The Next To Discover A New 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.”
And I found another one that might or might not be true: