36-2 Nematoda and Rotifera

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36-2 Nematoda and Rotifera

• Both phylum have bilateral symmetry
• Both have fluid filled space which serves 4
  functions
• 1. Holds internal organs
• 2. Serves as storage area for eggs and sperm
• 3. Supports body
• 4. Provides structure against which muscles
  can contract

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Phylum Nematoda

• Roundworms (transps. 134,135,158)
•  Long slender bodies that taper at each end
•  Known as pseudocoelomates
• hollow fluid-filled cavity that is lined by
  mesoderm on outside, and endoderm on the inside
• 1 mm to 120cm in length

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Phylum Nematoda

•  Have digestive tract with 2 openings
  anterior end is mouth and posterior end is anus.
  Food goes in mouth and moves in only 1 direction.
  This is better than a gastrovascular cavity.
• Separate sexes
•  Protective noncellular covering called
  cuticle
• Free living on land and in salt water or
  fresh water
• Some are parasites

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1. Genus Ascaris

•   Parasitic in intestines of pigs, horses and
  humans (fig. 36-7 p.716)
•   1 ft. in length
• 1 female produces 200,000 eggs/day

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Life Cycle

•  Fertilized eggs in feces of hosts
•  New host ingests contaminated food or water
• Eggs develop in intestines. Larvae form, go
  through bloodstream to lungs to throat. Coughed
  up and swallowed and returned to intestines.

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2. Hookworms

• Always parasitic
•  Feed on hosts blood
•  Life cycle similar to Ascaris
• Affect 400 million people. Especially in the
  tropical regions

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3. genus Trichinella

•  Parasitic in walls of hosts intestines
•  Larvae go to muscles and form cysts
• Get by eating raw meat (usually pork). Called
  trichinosis. Pretty rare in the USA.

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Other Parasitic Roundworms

• 1. Pinworm
•  Most common in the USA
•  Causes no serious disease 

• 2.  Filarial worms
•  Parasitic
•  Usually in the tropics
•  Larvae develop in the mosquito
• a.Elephantiasis limbs accumulate excess
  water and swell
• b. heartworm disease clogs arteries and
  heart of dogs (and some cats

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Pinworm
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Elephantiasis
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Heartworm Disease
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Phylum Rotifera

•  Called rotifers
•  Free living and transparent and in fresh
  water
• Can survive without water for a long time. They
  dry up and when wet conditions return, they
  resume life

•  Separate sexes
•  Draw and label fig. 36-10 p. 718
•  Define or explain purpose
• cilia
• mastax
• cloaca

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Rotifera