Leeches

Most people think of leeches as little creatures that lurk in the bottom of rivers waiting to suck their blood. But there are over 650 different types of leeches and many of them don't suck blood. Leeches can eat over five times their body weight. They have special chemicals in their saliva that keeps their prey from feeling their bite and keeps their blood from clotting. People used to think that they could cure diseases by letting leeches suck their blood. That's not true, but doctors are still trying to find a way to use leeches to help make people well.