Freshwater Leech

Macrobdella decora

The Freshwater Leech, also known as "North American Leech" or the "American Medicinal Leech," is a worm that grows over two inches long. It lives in lakes, marshes, and slow-moving streams.

This leech is brownish-green with black and red spots, and it has a round, sucker-shaped mouth. They also have five pairs of eyes.

The Freshwater Leech is a parasite that feeds on the blood of fish, frogs, turtles, and mammals. It should not be confused with other leeches, most of which prey only on insects, snails, and small creatures.

Freshwater Leeches spend the day under rocks or leaves on the lake or stream bottom. They detect their prey by the vibrations it makes in the water. The leech, which is an excellent swimmer, then comes out of its hiding place and attaches to the host animal. It can attach with its mouth or another sucker on its tail.

The mouth sucker has sharp teeth, which the leech uses to cut into the skin of the host animal. It releases a special chemical, called an enzyme, which has two jobs. First, the enzyme is an anesthesia, which means it numbs the area where the leech is feeding so the host does not feel it. Second, the enzyme is an anti-coagulant, which means it helps blood flow freely. The Freshwater Leech drinks blood until it is about five times its normal weight. Then it releases its grip and finds a new hiding place. The enzyme will cause the host to keep bleeding, even after the leech is gone, until it wears off.

Freshwater Leeches do not need to eat often. They can even go a year or two without a meal.

Leeches, just like their earthworm cousins, are hermaphrodites. This means that after they mate, both leeches can lay eggs. The leeches lay eggs inside small coccoons in the muddy bottom. Young leeches hatch from the coccoons when they are ready. It is not known how long Freshwater Leeches live, but it is for several years at least.

 

If a leech wants to move around, it can swim quickly or crawl on the bottom like an inchworm. Freshwater Leeches are often seen on the legs of snapping turtles, one of their favorite hosts.

Besides their hosts, these leeches will somtimes feed on amphibian eggs or snails.

Predators of Freshwater Leeches include fish, turtles, crayfish, and water birds.

Relationships in Nature:

PREY/FOOD
PREDATORS
SHELTER
OTHER

Common Snapping Turtle

Largemouth Bass

Common Duckweed

Eastern Painted Turtle H

Eastern Painted Turtle

Channel Catfish

Yellow Pond Lily

Common Snapping Turtle H

Bullfrog

Bluegill

Common Cattail

Bullfrog H

Channel Catfish

Yellow Perch

Pickerelweed

Muskrat H

Muskrat

Crayfish

Arrow Arum

Beaver H

Beaver

Black Crappie

Common Reed

Human H

Human

Mallard

Tussock Sedge

Raccoon H

Raccoon

Green Darner

Lizard's Tail

White-tailed Deer H

White-tailed Deer

Common Snapping Turtle

Marsh Bulrush

Striped Skunk H

Wood Frog

Eastern Painted Turtle

Green Frog

Northern Water Snake

Stagnant Pond Snail

Wood Duck

Striped Skunk

Yellow Bullhead

Spotted Salamander

Eastern Mosquitofish

Southern Leopard Frog

Northern Hog Sucker

Green Hydra

Relationship to Humans:

Freshwater Leeches can be annoying and they often gross people out. They do no real harm, however, since they do not take enough blood to cause problems. In the past, doctors even used these leeches to drain blood from people on purpose! Today, fishermen use leeches for bait.

SCIENTIFIC CLASSIFICATION

KINGDOM
Animal
PHYLUM
Annelid
CLASS
Hirudinea
ORDER
Gnathobdellida
FAMILY
Hirudinidae
GENUS
Macrobdella
SPECIES
Macrobella decora

QUICK LINKS

Organism Menu
Home
Glossary
Student Activities
Relationships
Classification Info
How to Use This Site
Bibliography