Sand Worms Clam Worms and Tubeworms: Polychaeta

Some clam worms, sand worms, and tube-worms live in dense groups. Others live alone. Many species avoid light. They quickly take shelter under rocks or retreat inside their tubes or burrows when disturbed.

Most species of these worms require males and females to reproduce. Some will form temporary pairs during the breeding season. Males and females release their sperm and eggs into the water where fertilization takes place. Fertilization (FUR-tih-lih-ZAY-shun) is the joining of the egg and sperm to start development. After the eggs are fertilized, the pairs will become very aggressive and may eat each other. In other species, fertilization happens inside the body. The eggs are then released into the water, attached to some object, or kept inside the body until they hatch.

The larvae (LAR-vee), or animals in an early stage that change form before becoming adults, usually develop in open water. As they develop, additional segments are formed behind a special growth zone. Their lifespan can range from a few weeks to several years.