Nematode Worm (Nematoda) Videos
Nematodes are worms belonging to the phylum Nematoda -- a group distinct from Annelida, the phylum to which earthworms and leeches belong. They range in size from microscopic to seven meters (about 23 feet) long, the largest being the parasitic forms found in whales. They have elongated bodies, usually tapered at both ends, and have a bilateral symmetry. They also possess a fluid-filled body cavity between the digestive tract and the body wall, called a pseudocoel.
One of the most abundant animals on Earth, many species of these transparent, microscopic worms are parasites, causing important diseases of plants, animals, and humans. Other nematodes exist as free-living forms in soil and aquatic environments and some even live in food products such as beer and vinegar.
Most species have separate sexes, but some are hermaphroditic. Nematode parasites of animals occur in almost all organs of the body, but the most common sites are in the digestive, circulatory, and respiratory systems. Common names for these worms are hookworm, lungworm, pinworm, threadworm, whipworm, and eelworm. Nematodes can cause a variety of diseases, including filariasis, ascariasis, and trichinosis.