Polychaete Worms

Polychaeta () is a paraphyletic class of generally marine annelid worms, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia which bear many chitinous bristles called chaetae, hence their name.

More than 10,000 species have been described in this diverse and widespread class; in addition to inhabiting all of the world's oceans, polychaetes occur at all ocean depths, from planktonic species living near the surface, to a small undescribed species observed through a ROV at the deepest region in the Earth's oceans, Challenger Deep. In addition, many species live on the abyssal plains, coral reefs, parasitically, and a few within fresh water.