nematoda notes. phylum nematoda these worms live in soil, animals, both freshwater and marine...
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Phylum Nematoda
• These worms live in soil, animals, both freshwater and marine environments.
• Some are free-living, but many are parasites.
Nematoda
• Roundworms are tapered at both ends.
• They have a thick outer covering, which they shed 4 times as they grow.
Nematoda
• This covering protects them in harsh environments.
• They lack circular muscles but have lengthwise muscles.
Nematoda
• Roundworms have a pseudocoelom (which means “false coelom”) and have bilateral symmetry.
• Roundworms have 2 body openings: a mouth and an anus.
• The free-living species have well-developed sense organs, such as eyespots.
A. Roundworm Parasites of Humans
• Infection by Ascaris is the most common roundworm infection in humans.
• It occurs mostly in tropical areas. • Children become infected more
often than adults.
A. Roundworm Parasites of Humans
• The Ascaris eggs are found in soil and enter a human’s body through the mouth.
• The eggs hatch in the intestines, move into the bloodstream, and eventually to the lungs, where they are coughed up, swallowed, and begin the cycle again.
Human Roundworms
• Pinworms are the most common roundworm found in the United States.
• The highest incidence of infection is in children.
• These worms are highly contagious because eggs can survive for up to 2 weeks on surfaces.
Human Roundworms
• Its life cycle begins when live eggs are ingested.
• They mature in the host’s intestinal tract.
• Female pinworms exit the host’s anus and lay eggs on nearby skin.
• These eggs fall onto bedding or other surfaces.
Human Roundworms• Trichinella causes a disease called
trichinosis. • This roundworm can be ingested in
raw or undercooked pork, pork products, or wild game.
Human Roundworms
• Hookworm infections are common in humans in warm climates where they walk on contaminated soil in bare feet.
• These cause people to feel weak and tired due to blood loss.
B. Roundworm Parasites of Other Organisms
• About 1200 species of nematodes cause diseases in plants.
• Nematodes can infect and kill pine trees, cereal crops, and food plants such as potatoes.