Phylum Nematoda The Roundworms

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

Major Parasites 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