Diversity of Oligochaetes

3100 species.

Many species live in freshwater. (all types of freshwater habitats)

Aquatic forms are smaller than terrestrial forms.

Dero 

4 pairs of ciliated body projection.

Stylaria

well-developed sense organs & slender, long, flexible setae 

useful in swimming.

Branchiura

 long digitate dorsal & ventral projections in their posterior body.

Tubifex

 lack gills.

Pheratima

The terrestrial oligochaetes live in moist soil.

They are larger than aquatic forms.

10-30cm in length.