1. Phylum Annelida
Segmented Worms

2. Class Oligochaeta (‘few bristles’)

3. About 170 N.A. species
Each segment has small bundles of tiny chaetae
Most live in silt and mud in ponds, lakes, etc.
As deposit feeders, feces deposited atop the bottom; helps keep surface aerobic
Some are very tolerant of low oxygen; Tubifex worms are long and red; can build up very high densities (8,000/m2)

4. Class: Hirudinea (Leaches)

5. Leeches Primarily aquatic (~69 species in N.A.); only a few marine
Many are highly colored (but fade in alcohol)
Body: soft, muscular, flattened; 34 segments
Two suckers: one anterior (includes the mouth), one posterior

6. Natural History
Most live in shallow waters with much plants, debris, or stones; in suitable habitat, can reach density of 700/m2
Move inchworm-style; many can swim
All feed on fluids from other organisms either as piercer-predator or as external parasite
Most feed on invertebrates
Blood suckers have 3-toothed jaws and secrete hirudinin, an anticoagulant; most feed on frogs, turtles, or fish
May not feed again for two years
Always reproduce sexually; some make cocoons;
Many require years to reach maturity
Are both predators and prey