ZoOLogy > What's This? Leeches

Did you know that some blood-sucking leeches have three jaws in their mouths? Each jaw has a row of fine, sharp teeth. Can you see the fine cuts in the corner photo? The leech made these in the skin of its host by moving its jaws back and forth.

Using the muscular outer rim of its mouth, the leech then creates a firm seal around the wound. Now it can suck the blood into its gut. A yummy leech blood meal!

In just 30 minutes, leeches can swallow more than five times their body weight in blood.

After this heavy meal, leeches don't need to feed again for a few months. They'll usually hide under rocks or sticks to slowly digest this meal.

Why doesn't the blood of the host animal clot as the leech is feeding? It's because leech saliva contains anticoagulants, compounds that stop blood from clotting.

Humans have long known the value of these anticoagulants and have been using leeches in medicine for over 2000 years.

Today, scientists are also studying the anticoagulant of the American Medicinal Leech (Macrobdella decora) to see if it can be used to treat diseases.

There are many types of leeches. Some leeches are bloodsuckers. They live and feed on vertebrate animals such as turtles, fish, frogs, and even humans.

Some leeches suck the body fluids of other invertebrate animals, such as worms and insect larvae. The leech pictured is using its proboscis, a needle-like muscular tube, to feed on a snail.

Some leeches even eat other small invertebrates whole!

Some people may think that all leeches are black. But they come in an amazing diversity of colors and patterns.

Take a look at these two leeches found in the forests of Madagascar . One is bright orange with an intricate brown chain mail pattern. The other has a brilliant lime and turquoise line down its back.

Even though they look quite different, they're actually color variations of the same leech species, Malagobdella vagans.

Leeches live in all kinds of environments - in the open ocean, in freshwater, and in humid jungles.

To collect leeches for research, scientists travel all over world, including the high mountains of Bolivia and the thick jungles of Madagascar.

How do they find leeches? They use themselves as bait! Once the leech is done feeding, it lets go and falls into the collection bag.