FOLLOW THE BLOOD: Researchers are using the DNA stored in leeches’ meals to study animal biodiversity.© AMNH/L. BERNIKERIn 2009, a leech made headlines after it helped catch a criminal in Australia. Two burglars had assaulted and robbed a 71-year-old woman in her isolated home in the Tasmanian forest, where the bloodsuckers are widespread. The leech, which had latched onto one of the thieves to feed, plopped off at the scene of the crime in 2001. Investigators extracted the perpetrator’s DNA from the invertebrate and cracked the case nearly eight years later, when the robber’s blood showed up as a match after he was arrested for an unrelated offense.
But leeches aren’t just useful at crime scenes. These creatures’ sanguineous appetites have also come in handy for scientists, who are hoping to use them to solve another mystery: the diversity of animals, particularly those hidden deep within forest habitats around the world. “Contrary to popular opinion, [leeches] don’t just suck,” says Mark Siddall, an invertebrate zoologist at the American Museum of Natural History’s Sackler Institute for Comparative Genomics.
Leeches are a group of segmented worms primarily found in freshwater habitats, although a few species live in the oceans and on land. Despite their reputation, many don’t feed on blood, instead eating earthworms, snails, and other invertebrates. The bloodsucking (hematophagous) leeches inhabit a number of biodiversity-rich regions, such as the rainforests of Southeast Asia, Australia, ...
