Within the class Polychaeta, the subclass Errantia regroups the ‘wandering’ worms, in contrast to the sedentary worms that belong to the subclass Sedentaria. All mobile worms are aquatic, and the vast majority are found in the marine environment, all around the world and at every depth.
Worms within the subclass Errantia are mobile, with paired muscular bristle-bearing appendages used in locomotion, sensation and/or respiration – called parapodia – and a differentiated head, often complete with eyes and teeth.
