Just how hungry is a leech? As an undergraduate at Brown University in the early 1980s, Michael Dickinson devised a clever way to find out. After getting hooked on neuroethology—the study of the neural mechanisms underlying animal behavior—Dickinson joined the lab of Charles Lent, a biologist who worked with the legendary bloodsuckers. One problem they were addressing was how the animal regulates its feeding—a key question when it comes to the medicinal leeches used, for example, to restore blood flow to transplanted digits. “It sounds so trivial,” says Dickinson. “But how can you measure whether a leech is hungry? How do you quantify that?”
The solution Dickinson came up with involved a warm cylinder wrapped in a bit of waxed paper. “A hungry leech will bite the surface of the object just because it’s warm,” he says. “It’ll bite, it’ll stop, and it’ll bite again. Afterward, you can unroll the ...
