The Polychaeta are a huge group of marine worms, also known as the bristle worms or polychaetes. They are among the most common marine organisms.
Polychaetes are multi-segmented worms living in all environments in the world's oceans. Most polychaete body segments bear a pair of parapodia (flat, lobelike outgrowths) with a dense cluster of tiny bristles and hooks called chaetae. The name polychaete actually means 'many bristles'.
Polychaetes are divided informally into two groups; the errantia, or free-moving forms, and sedentaria, or tube-dwelling forms which are normally in a fixed location (imobile).
