The entoprocta are a small phylum of minute, solitary or colonial, sessile, aquatic animals. About 150 species have been described worldwide, with only one species occurring in freshwater. The colonial species encrust stones, shells and algae, and species have been described from all oceans. The solitary species are mostly associated with water-current-producing hosts, such as polychaetes, sponges and bryozoans; these species are not conspicuous and most of the reported distributions reflect specialists' searches.