Chaetonotus is a gastrotrich and belongs to the phylum Gastrotrichia.

This is a relatively small phylum of unsegmented, worm-like aquatic invertebrates. Gastrotrichs are found in the interstitial waters of fine sediments, or on overlying detritus. Most are less than a mm in length, although a few reach sizes up to 3mm.

They are covered with cilia and use it for their means of locomotion. Because of this, they are sometimes confused with ciliates (protozoans). The animal is capable of reversing its ciliary beat in order to withdraw from an unpleasant stimulus.

The body is elongated and ventrally flattened. It has a distinct head, and typically two or more caudal organs of adhesion. The tail frequently divides into two, forming a distinctive bifid tail. The head has a mouth, pharynx, photo and chemo receptors.

Chaetonotus feed on protozoa and micro-organisms including bacteria and invertebrates. Food is sucked into the mouth by the powerful pumping pharynx.