(Credit: Mai Fahmy)

Videos Reveal This Bloodsucking Parasite Doing Something Odd That Settles a Century-Old Debate

New research has revealed surprising behavior in a species of terrestrial leech, which has been captured on video displaying an unexpected ability that settles more than a century of debate among scientists.

The new videos, part of a research effort led by scientists with the American Museum of Natural History in cooperation with Fordham University and City University of New York’s Medgar Evers College, reveal the first convincing proof that leeches can jump.

The new findings, detailed in a new study by lead author Mai Fahmy and colleagues, confirm previous accounts of these small parasitic creatures leaping that were roundly dismissed by researchers, who maintained that they merely attached themselves to passersby.

Above: Video obtained in Madagascar in 2017 shows a Chtonobdella leech taking a small jump followed by a big leap to the ground (Credit: Mai Fahmy). 

The discovery was made during expeditions to Madagascar in 2017 and 2023, during which Fahmy successfully obtained footage of leeches from the genus Chtonobdella exhibiting jumping capabilities. The unusual behavior is achieved by leeches coiling backward from their position on a leaf to produce momentum that propels them forward in a motion somewhat similar to a “back bending cobra.”

The surprising behavior, which has been speculated about for more than a century based on anecdotal accounts, represents a significant departure from the accepted inchworm-like locomotion leeches are known to utilize.

“Essentially, it executes a graceful jump but with a seemingly hard landing,” said Michael Tessler, the recent study’s co-author.

The new research also introduces the species Chtonobdella fallax to a broader context of worm-like invertebrates that also exhibit jumping abilities, including gall midges, Mediterranean fruit fly larvae, skipper flies, and several varieties of caterpillars.

“We believe this is the first convincing evidence that leeches can jump and do so with visible energy expenditure,” Fahmy said.

However, until now there was little in the way of concrete evidence that terrestrial leeches possessed jumping abilities, despite observations that have been reported over the decades.

“There have been previous accounts of leeches jumping, including onto people, but those reports were often explained away as leeches just attaching to passerby as they brushed against shrubs or dropping from a branch above,” Fahmy said in a statement.

“This study dispels that argument.”

Fahmy and Tessler’s study, “A jumping terrestrial leech from Madagascar,” appeared in the journal Biotropicaon June 20, 2024.

Micah Hanks is the Editor-in-Chief and Co-Founder of The Debrief. He can be reached by email at micah@thedebrief.org. Follow his work at micahhanks.com and on X: @MicahHanks.