Number of species about 100. In freshwater of NWE, one species:
Troglochaetus beranecki Delachaux, 1921
Description
An artificial group of relatively small polychaetes (Fauchald, 1977). Their simple anatomical structure, apparently the result of small size, has been responsible for erroneous speculations on their phylogenetical primitivism.
Distribution
Cosmopolitan.
Ecology
Mainly marine, in interstitial water.
Reproduction
Both sexual and asexual ways known.
Literature
Fauchald, 1977: 152.