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First New Species of Medicinal Leech Discovered Since 1975

Journal of Parasitology – In an international collaboration between researchers from the US, Canada and Mexico, a new species of medicinal leech has been discovered in the Eastern United States. Part of a larger study, researchers were originally searching for genetic variation within the North American medicinal leech species Macrobdella decora. What researchers didn’t expect is that they would uncover an entirely new species, Macrobdella mimicus, which they named after its close resemblance to M. decora.

“This species (M. decora) is very broadly distributed in North America, from the East coast to almost the Rocky Mountains and from Canada to the Southern U.S.,” said Anna J. Phillips, one of the authors of this study. “This is a suspiciously broad distribution especially for a freshwater leech. We wanted to investigate this further and collect specimens from as many places as possible to see if they actually are all the same species, and through this collecting, we came across the specimens in Maryland.”

Members of Macrobdella family are known for their olive-green dorsum with black flecks and red-orange spots. What distinguishes the M. mimicus from M. decora is that while they both have 4 pores arranged in two rows in two columns, the female gonopore’s location slightly differs. This discovery is significant because M. decora is a well-documented species with many M. mimicus previously mislabeled as M. decora.

Field samples along with samples from the National Museum of Natural History, the North Carolina Museum of Natural Sciences and the Virginia Museum of Natural History were used to identify the wide spread nature of M. mimicus.

“Being able to go to museum collections and have not only specimens collected from field work that were good for molecular study but being able to look at historical specimens and looking back in time to see that this species has been here for years was really valuable,” said Anna J. Phillips. “It really increased our understanding and led to targeting additional localities to start to create a more comprehensive approach to understanding this species.”

First published in the Journal of Parasitology, this study quickly gained publicity was picked up by many large media outlets including Newsweek, Inside Science, Smithsonian,, Popular Science and more.

“I think we’ve all been surprised by how much the public has been interested in leeches,” said Anna J. Phillips. “I thought that people might be interested in it a little, but it’s definitely been surprising to all of us.”

While steps have been made to further advance inclusion within the society, the presidential address outlines steps for future improvement. This includes publishing a diversity and inclusion statement on the website, pushing for a broader scope in the Society’s award nominations, collecting demographic data to test trends of diversity in ASP and setting up daycares and hosting special socials and workshops at annual meetings.

While the American Society for Parasitologists is by no means alone in its need for more diversity, conversations like this help to propel the society into a more inclusive future.

Full text of the article "hylogenetic Position and Description of a New Species of Medicinal Leech from the Eastern United States," Journal of Parasitology, Vol. 105, No. 4, 2019, is available here.


About Journal of Parasitology
The Journal of Parasitology is the official journal of the American Society of Parasitologists (ASP). The journal reports on all aspects of animal and human parasites, and is widely recognized for publishing content that has a long-term impact on the field of parasitology. The journal is intended for all with interests in basic or applied aspects of general, veterinary, medical parasitology, and epidemiology. For more information, visit

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Dominique Scanlan
Allen Press, Inc.
800/627-0326 ext. 226

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