Phylum Nematoda

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Chapter 34

• Section 2
• Phylum Nematoda Rotifera

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Phylum Nematoda

• Roundworms (pseudocoelomates)
• Bilaterally symmetrical
• 1mm-120mm (4 feet)
• Digestive tract with two openings (mouth anus)
• Cuticle- protective covering

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Phylum Nematoda

• Most are parasites and more than 50 species are
  parasites in humans
• Common roundworm studied by scientists in
  developmental biology is C. elegans

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Ascaris

• Genus of roundworm parasites that live in pigs,
  horses, and humans
• Feed on food in intestines of host
• Females produce 200,000 eggs per day

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Hookworms

• Hookworm- intestinal parasite
• Have cutting plates that clamp onto the
  intestinal wall
• Feed on hosts blood
• Cause anemia
• Like Ascaris, hookworms release eggs

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Trichinella

• Form cysts in muscle of host
• Found in undercooked meat
• Trichinosis- disease causes muscle pain
  stiffness
• Farmers no longer feed meat to hogs and freeze
  meat

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Other Parasitic Roundworms

• Pinworm- most common roundworm parasite in the
  USA
• School age children
• Does not cause serious damage
• Found in feces

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Other Parasitic Roundworms

• Filarial worms- disease-causing roundworms that
  infect over 250 million people in tropical
  countries
• Causes elephantiasis- limbs become swollen and
  skin hardens and thickens

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Other Parasitic Roundworms

• Dogs cats
• T. canis and T. cati
• Live in the heart and large arteries of the lungs
• Heartworm disease

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Phylum Rotifera

• Rotifers
• Transparent, free-living animals that live in
  freshwater
• Cilia surrounds the mouth- helps sweep food in-
  algae, bacteria, protozoa

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Phylum Rotifera

• Food moves from mouth to mastax- muscular organ
  that breaks down food
• Food is absorbed then passes from intestines to
  cloaca- common hole which reproduction,
  digestion, and excretory systems empty

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Phylum Rotifera

• Rotifer reproduction
• Parthenogenesis- unfertilized eggs develop into
  adult females
• Other eggs form into males and the males
  fertilize other eggs with sperm

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REVIEW!!!

• Identify two characteristics of the Phylum
  Nematoda and the Phylum Rotifera.
• What is the name of the most common roundworm
  studied by scientists in developmental biology?
• What type of worm causes elephantiasis?