This class includes about 3,500 species of earthworms and freshwater worms.
Oligochaetes occur in a variety of habitats throughout the world.
Most are burrowers in the soil, but the class also includes worms that inhabit wells, marshes, and swamps. Other species live under rocks on the seashore, in the leaves of tropical trees and vines, on the surface of glaciers, or on the gills of freshwater crayfish. Oligochaete Anatomy Like the polychaetes, oligochaetes have bodies divided into segments. However, they lack parapodia and, with a few exceptions, have relatively few and inconspicuous setae. The setae of an earthworm may be felt as a roughness if one rubs a finger along its side.