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Phylum: Nematoda. “thread-like”, commonly called roundworms, found just about everywhere Examples: ascaris , pinworms, hookworms, trichina worms. Traits . Round bodies. Traits . Non-segmented. Traits . Bilateral symmetry. Traits . cephalized. Traits .
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Phylum: Nematoda • “thread-like”, commonly called roundworms, found just about everywhere • Examples: ascaris, pinworms, hookworms, trichina worms
Traits • Round bodies
Traits • Non-segmented
Traits • Bilateral symmetry
Traits • cephalized
Traits • Tube-in-a-tube (complete) digestive system – 2 openings
Traits • Longitudinal muscles only
Traits • Flame cells
Advantages of a complete digestive system • Can eat continuously • Can eliminate wastes without losing good food
Why are worms so long? • Since they have a straight G.I. tract, they must be long in order to have a tract long enough to digest and absorb food before it reaches the anus
Excretory system • Flame cells collect waste and force them out through a series of tubes with one common exit
Reproduction • Most are dioecious
Two categories: Free living Parasitic
Freeliving • More abundant than the parasitic nematodes • Live in soil and water (fresh and salt)
Freeliving Nematodes • Bacterial feeders • Fungal feeders • Many are beneficial in helping to control disease and cycle nutrients in the soils
Size = average 1 mm in length • Larger one consuming smaller parasitic ones
Plant parasitic nematodes • Form cysts on the roots
Parasites • Live in another organism
A few main types… Ascaris Pinworms Hookworms Trichina worms Filarial worms
Ascaris • Studied a lot because they are big and cheap
Ascaris life cycle • Adults live in pig intestines, mate, eggs leave with feces • Pigs ingest contaminated food or water, start over • Since the cycle is simple, it’s hard to break
Ascaris Mouth
Pin worms • Most common nematode parasite in humans
Pin worm life cycle • Adults live in human intestines, mate, females crawl out the anus and lay eggs on the surrounding skin • Kid scratches self, then eats without washing hands, starts over
Cure • Easy, oral medicine goes directly to them and are flushed out with feces
Prevention • Wash hands, especially after using the bathroom
Hook worms • Intestinal parasites of humans, suck blood
Hook worm life cycle • Adults live in intestines, mate, eggs leave with feces • Hatch into larvae which bore through bare feet and eventually enter the lungs • Crawl up trachea, are swallowed, start over
Symptoms • Abdominal pain, severe diarrhea, anemia
Prevention • Wear shoes • good sewage system
Trichina worms • Cause trichinosis, can be fatal Red swollen eyes Fatigue and diarrhea Brain swelling Heart failure
Trichina worm life cycle • Adults live in pigs intestines, mate, eggs immediately hatch into larvae which bore through intestines into blood stream • Eventually lodge and form cysts in the muscles, another animal eats it, start over
Prevention • Cook meat well • Inspect meat • Don’t feed pigs raw meat
Filarial worms • Cause elephantitis by clogging lymph nodes so they can’t drain fluids from the limb
Filarial worm life cycle • Live and mate in fluids of body tissues, larvae are sucked out by mosquitoes and injected into another animal
Prevention • Kill mosquitoes