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A new species of bloodsucking leech with three jaws has been found in Maryland

Anna Phillips, the curator of parasitic worms at the Smithsonian's National Museum of Natural History, holds a new species of leech.
Anna Phillips, the curator of parasitic worms at the Smithsonian's National Museum of Natural History, holds a new species of leech. (Smithsonian National Museum of Natural History)

What has three jaws, 56 to 59 teeth in each, no thumbs and was first discovered in Charles County?

No, this is not a story about Chessie, the monster who definitely lives at the bottom of the Chesapeake Bay along with the unedited footage of Stanley Kubrick’s staged moon landing.

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Rather, this is about gross, bloodsucking leeches and how a team led by a researcher at the Smithsonian’s National Museum of Natural History discovered a new species.

Anna Phillips, who led the team and is the museum’s curator of parasitic worms, said the group began researching a type of common “medicinal leech” — called Macrobdella decora — found throughout the country in 2015 to see whether it could find any geographic differences in genetics and DNA.

When she and others collected some leeches in the swamps of Charles County off Route 224, Phillips said, nothing stood out about the specimen to the naked eye.

But after researchers found significant differences in their DNA compared with the more common species in late 2016 or early 2017, she said, the team knew it had stumbled onto an unexpected discovery.

“We only found it in Maryland,” she said. “It was definitely sort of a signal that we need to look at these specimens closer.”

So after further research, the team determined it was an undocumented species of leech and has had its discovery published in this month’s Journal of Parasitology, naming it Macrobdella mimicus, or “Mac Mimi” for short (not really, but it should).

Phillips said it’s important to note how close to an urban area the discovery was made, as Charles County is less than 50 miles outside Washington, D.C.

“This has been right here, so there’s been a lot of unrecognized diversity and biodiversity right next to home,” she said.

As for the species itself, while it’s still gross like any other leech and has some scary-sounding characteristics — including the three jaws that contain 56 to 59 teeth each — Phillips said it’s still a relatively harmless leech, like most others.

The leech can fit in the palm of your hand, has microscopic teeth and there’s nothing about its makeup that make it more dangerous than other species, Phillips said.

But there are also unanswered questions as to the origins of the leech, as Phillips said there was a high concentration of the species in Southern Maryland, but less so in Northern Virginia.

She said there are still swaths of the country where researchers have not collected detailed data on the region’s leeches, like the Pine Barrens region of northwestern New Jersey.

Which is gross to think about for more than a few seconds.

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