Section 2

Nematoda and Rotifera

• The phylum Nematoda consists of roundworms. Most roundworms are free-living, but some are parasites of plants and animals.

• Nematodes are pseudocoelomates. They have a hollow, fluid-filled cavity called a pseudocoelom between the mesoderm and the endoderm. They also have a digestive tract with an anterior mouth and posterior anus.

• Ascarid worms infect people who consume food or water containing eggs of the genus Ascaris. The eggs develop into larvae that migrate through the body and mature in the intestines.

• Hookworm larvae in the soil burrow through a person's feet. The larvae migrate through the body and mature in the intestines.

• Trichina worms infect people who consume undercooked meat containing cysts of the genus Trichinella. The cysts release larvae that burrow into the intestinal wall and develop into adults.

• Pinworms live in the lower intestine and lay eggs on the skin around the anus. After being transmitted by the hands to other objects, the eggs may be ingested. They then hatch in the intestine, where the worms mature.

• Filarial worms include species that live in the human lymphatic system. Their larvae are transmitted between hosts by mosquitoes.

• Rotifers are pseudocoelomates, and most rotifers are free-living in fresh water. The cilia surrounding a rotifer's mouth sweeps food into its digestive tract.

Vocabulary roundworm (p. 695) cuticle (p. 695) hookworm (p. 696)

trichinosis (p. 697) pinworm (p. 697) filarial worm (p. 697)

elephantiasis (p. 697) rotifer (p. 698) mastax (p. 698)

cloaca (p. 698) parthenogenesis (p. 698)

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