Sand Worms Clam Worms and Tubeworms: Polychaeta

Clam worms, sand worms, and tubeworms are found in every ocean habitat from warm tropical seas to cold polar waters. They swim in open water or crawl along the seashore or sea bottom. Many species dig in muddy or sandy ocean bottoms to establish temporary or permanent burrows and tubes. Others are found among mussel beds on rocks or pilings, rocky reefs, or on corals. Some of these species live under rocks. Others live inside tubes made of sand or lime attached to rocks and corals. Some species are able to live in water that is less salty than the ocean. They live in estuaries (EHS-chew-AIR-eez), or areas where rivers meet the sea, and even in some freshwater habitats.

Some species live on the bodies of crustaceans (krus-TAY-shuns), or water-dwelling animals that have jointed legs and a hard shell but no backbone. The worms do not harm the crustaceans, but actually help them by keeping their breathing organs clean of organisms. Other species live inside the bodies of mussels, clams, oysters, and unsegmented worms as parasites (PAIR-uh-sites). Parasites live on or inside another animal and depend on them for food for their entire lives.