A New Bloodsucking Leech Species Found Hiding Outside Washington, D.C.

With an olive-green body encasing three jaws, each lined with more than 50 teeth, it looks like a cigarette-sized relative of the skin-crawling creature from the Alien films. Actually, it's far less sinister: a new species of a bloodsucking leech.

Anna Phillips, the curator of parasitic worms at the Smithsonian's National Museum of Natural History in Washington, D.C., led the team that recently discovered Macrobdella mimicus in almost their own backyard.

Uncovered in the swamps of Charles County in Maryland, it's the first species of medicinal leech discovered in North America since 1975, Phillips says.

Their superficial likeness to the common species known as Macrobdella decora, found across the northern U.S., has allowed them to go undetected for so long, leading the team to name the new species "mimicus," after the Greek word meaning "imitator."

DNA tests ultimately led the team to identify the leech as a new species. Parasitologists look to the arrangement of pores on the bottom of leeches' bodies to help distinguish species. The researchers noticed a slight discrepancy in the arrangement of the leeches' accessory pores — pores that secrete mucus to allow mating leeches to latch together.

"It's been here this whole time," Phillips said in a press release from the Smithsonian Institution. "We just hadn't looked at it in this new way."

But once the scientists ventured into the new species' native habitat, it didn't take much for Phillips' team to catch the specimens — or rather, for the specimens to catch them.

"Our collection method is to roll up our pants, wear water sandals, and wade in about knee-deep, make a little bit of movement, stir up the vegetation and the mud and — they come to us," Phillips said in an interview with NPR's Weekend Edition.

Phillips says humans shouldn't necessarily fear their bite alone.

But when leeches are harmed — whether yanked, burned or salted — Phillips says, they can regurgitate the bacteria that sits in their intestines to facilitate their digestion into the wound, leading to infection.

Leeches, parasitic worms that feed on the blood of animals and humans, have an ancient history in medical quackery due to the belief that bloodletting helped purge the "tainted" human body of various ailments.

In recent years, however, medicinal leeches are making a comeback in hospitals and scientists' labs.

The anticoagulants found in their saliva can facilitate blood flow, preventing blood clots from forming in damaged tissue. Surgeons also use the critters during reconstructive procedures, such as finger reattachment, to replace stale blood with fresh, leech-drawn, oxygenated blood.

NPR's Peter Breslow and Melissa Gray produced and edited this story for broadcast. Emma Bowman produced this story for Web. [Copyright 2019 NPR]