Echiurans: Echiura

To feed, some echiurans extend the sticky proboscis out of the burrow and onto the surrounding sea bottom. The tip of the proboscis gathers particles of food and covers them with a sticky coat of mucus. The cilia move the particles back toward the mouth. Other species are filter feeders. Fat innkeeper worms, Urechis caupo, build a sticky net of mucus and place it near the opening of their U-shaped burrow. Both ends of the burrow open to the water. As they flex their body trunks, water is drawn through the burrow, trapping bits of food and small organisms in the net. The worm eventually gathers and eats the food, net and all.

Both males and females are required for reproduction. Most species release eggs and sperm into the water. Fertilization (FUR-teh-lih-ZAY-shun) takes place in the water. In one group the eggs are fertilized inside the female's body. Developing echiurans first go through a larval stage. The unsegmented larvae (LAR-vee) are free-swimming and covered with cilia. They drift with other plankton, or microscopic water-dwelling plants and animals, for up to three months, eventually developing into young worms and settling on the bottom.