Phylum Nematoda
The Roundworms
Characteristics
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12,000 species named
Live everywhere
Often parasites
Pseudocoelomates
Cylindrical shape
Most less than 5 cm
Can be microscopic to
1 meter in length
More Characteristics
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Nonliving (noncellular) cuticle
Longitudinal muscles only
No circular muscles
Alimentary canal: mouth to anus
Important in decomposition and soil nutrients
Classification
Phylum Nematoda
The Roundworms
Class Rhabditea
Class Enoplea
Major Parasites
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Ascaris
Hookworm
Pinworm
Trichina
Whipworm
Filarial worms
Ascaris
• An intestinal
roundworm
• Common infection in
horses, humans, and
pigs.
• May lay 200,000 eggs
per day
• Abdominal symptoms
Hookworm
• Curved anterior
resembles a hook
• Hook to intestines
• Causes anemia in
patient
• Found in soil, burrow
through skin, most
commonly foot
Hookworm
Hookworm larvae
Hookworm eggs
Pinworm
• Most common parasite in
the United States
• Lives in large intestine
and cecum.
• Females lay eggs in anal
area at night
• Eggs develop within 6
hours, resulting in itching.
If swallowed, mature in
large intestine
Pinworm egg
Trichina
• Produces trichinosis
• Adult worms burrow
in small intestine and
produce live young
• Juveniles enter blood
vessels and are carried
to muscles
Whipworm
• Common in North
America in humans
• Intestinal infection
• Occurs through
contaminated food or
unhygienic habits
Filarial Worms
• At least 8 species that
infect humans
• Includes Elephantiasis,
river blindness, dog
heartworm
• Worms live in the
lymphatic system
• Carried by mosquitoes
Dog Heartworm