Medicinal Leech

European Medicinal Leech Genome Sequenced

Researchers have for the first time mapped the genome of the European medicinal leech (Hirudo medicinalis), one of the most prominently used medicinal species.

The European medicinal leech (Hirudo medicinalis). Image credit: Sebastian Kvist.

Today, two leech species — Hirudo medicinalis and Hirudo verbana — are used for healing practices based soundly in science, primarily for the replantation of digits or skin grafting surgery.

Their saliva contains the strongest anticoagulants (blood thinners) known to medicine and can relieve the buildup of blood after surgery and promote the healing of blood vessels.

However, the full complement of compounds in medicinal leech saliva that achieve this outcome was not known until now.

Dr. Sebastian Kvist, an evolutionary biologist at the University of Toronto and curator of invertebrate zoology at the Royal Ontario Museum, and his colleagues focused on the diversity of anticoagulants contained within the leech genome.

“Incredibly, the leech uses 15 different proteins known to negatively affect the blood-clotting mechanism in vertebrates, and 17 other proteins that are likely also part of the same anti-clotting process,” Dr. Kvist said.

“This is far more than we anticipated, and the insights generated by this research will allow medical professionals to better understand how and when to use leeches in their practice.”

“As only the third leech genome ever sequenced, Hirudo medicinalis provides important comparative data for understanding the evolution of bloodfeeding in leeches,” added co-author Dr. Mark Siddall, curator of annelida and protozoa at the American Museum of Natural History.

“It is astonishing that the most utilized, well-known and famous leech species in the world had not been investigated at this level,” he added.

“This research provides critical insight into the evolution of bloodfeeding in leeches and will play an important role in future research.”

The findings were published in the journal Scientific Reports.

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S. Kvist et al. 2020. Draft genome of the European medicinal leech Hirudo medicinalis (Annelida, Clitellata, Hirudiniformes) with emphasis on anticoagulants. Sci Rep 10, 9885; doi: 10.1038/s41598-020-66749-5