A marine polychaete or bristle worm. Most polychaetes are ocean dwellers. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Photo by Alexander Semenov.

A marine polychaete or bristle worm. Most polychaetes are ocean dwellers. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin. Photo by Alexander Semenov.