14 Annelids: World of Worms-Mid

Annelids: World of Worms FOCUS Question How does a worm's body help it live in its habitat?

Wriggly Worms You're digging in the garden when you discover something squirming in the soil. It's an earthworm! Earthworms belong to a group of worms called annelids The bodies of annelids. are organized into small segments, or sections. Segmented worms also include bristle worms and leeches. Annelids have long, flexible bodies. They are invertebrates, which means they don't have a backbone. They have no arms or legs, either. Worms are found in just about every habitat on Earth. They live on land and in water—even in ice!

Digging in the Dirt An earthworm's name says it all—these segmented worms make their homes in the soil. Earthworms dig, burrow, and make tunnels in their earthy habitat. They live anywhere that has damp soil conditions. Many of them live in rainy forests or in places with lots of muck and mud. Earthworms breathe through their smooth, slimy skin. Their skin produces a slippery substance called mucus (MYOO-kuss). This coating of mucus helps keep their body moist. It also allows the worms to glide easily through the soil.

Earthworms also have tiny bristles on each segment that help them move through the soil. These bristles are called setae (SEE-tee). To burrow, an earthworm moves its setae in and out so it can grip the ground. The worm's muscles then push its body forward. As it tunnels, an earthworm takes in soil, dead leaves, and decaying plant roots through its mouth. Then the worm breaks down the leftover living material and returns the nutrients to the soil as waste. Earthworms are helpful decomposers. Math Moment If an earthworm has 26 setae on one segment. and 100 segments how many setae does it have?

Bristles All Over Bristle worms are also known as polychaete (PAH-lee-keet) worms. Many swim in the open ocean or live on the ocean floor. Some live in fresh water. Others burrow in the sand on beaches. Bristle worms have a pair of parapodia (pare-uh-POH-dee-uh) on each segment of their body. These structures look like small legs. Each one has bristles on it. Parapodia help bristle worms move and survive in different kinds of environments. Word Wise Polychaete comes from the Greek language. Poly- means "many," and chaete means "bristles."

Adapting to Every Environment The Pompeii worm lives in a tube near very hot deep-sea vents. The water is heated underground and enters the sea through openings on the ocean floor. The Pompeii worm's fuzzy body is covered with bacteria. The bacteria insulate the worm and protect it from the heat. This bristle worm has small parapodia. It uses them to move water around and get more oxygen into its tube home. The clam worm lives in shallow water, where it swims and crawls using its large, curved parapodia and often burrows in the mud. Clam worms eat other invertebrates and algae with their strong jaws.