New records, neotype designation and DNA sequences of three species of Chaetonotus (Gastrotricha: Chaetonotidae) from Brazil.

Gastrotrichs are aquatic microinvertebrates (less than 1 mm long) commonly found in freshwater and marine environments worldwide. The taxonomy of gastrotrichs is mainly based on external morphological characters, such as body shape and size of the different body regions, presence and distribution of adhesive tubules, or the microstructure of the external cuticle (e.g.