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

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 larvae

Ascaris Mouth

Ascaris in Pig Intestines

Pinworms

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

Pinworm in Colon

Cure Easy, oral medicine goes directly to them and are flushed out with feces

Prevention Wash hands, especially after using the bathroom

Hookworms

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

Hookworm larvae tracks

Symptoms Abdominal pain, severe diarrhea, anemia

Prevention Wear shoes good sewage system

Trichina worms

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

Meat infested with Trichina worm

Prevention Cook meat well Inspect meat Don’t feed pigs raw meat

Filarial worms

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