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Characteristics
• 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• Nonliving (noncellular) cuticle• Longitudinal muscles only • No circular muscles• Alimentary canal: mouth to anus• Important in decomposition and soil nutrients
Classification
C la ss R h ab d itea C la ss E no p lea
P h ylum N e m ato daT h e R o u n dw o rm s
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
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