Flatworms

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Flatworms

• Phylum Platyhelminthes

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Common Name

• drifters

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Symmetry

• Bilateral
• No backbone

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Characteristics

• One digestive opening
• Flattened, soft bodies
• Parasitic and free-living
• 3 layers of tissue
• Organ system

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Examples

• Planarians (3mm to 30cm)
• Tapeworms (can grow 10-12m)
• Flukes

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Dugesia lives in freshwater, mostly a scavenger
but can also feed on protists
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Schistosoma mansoni - multiple host Primary
host human Intermediate host snail Causes
Schistosomiasis -in humans decays lungs liver,
spleen, or intestines, occurs in tropical areas
with poor sanitation/sewage.
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19 foot tapeworm being removed
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Tongue Worm- type of fluke
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Basic body plan of Tremotoda fluke worm
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Fluke worm
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Liver Fluke
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Round Worms

• Phylum Nematoda

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Symmetry

• Bilateral
• No backbone

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Characteristics

• Digestive system with 2 openings (mouth and anus)
• Parasitic
• Round bodies that taper at the ends
• Separate sexes
• Largest phylum of worms
• Most are free living

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Examples

• Hookworms
• Heartworms
• Ascaris
• Trichinella

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Roundworms Disease Trichinosis (trichinella
worm) - cysts within the muscles are consumed
(undercooked food) -- worm grows in intestine--
forms cysts in the muscles of the new host --
symptom terrible pain in muscles
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Filarial Worms - found in Tropical regions of
Asia -- usually transmitted by mosquitoes--
causes elephantiasis
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Hook worm mouth
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Hookworm
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Ascaris Worms
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Ascarid Worms (common roundworm) - lives in
intestine- eggs are passed out in the feces
Most roundworms infect dogs, but occasionally
they find their way into human hosts
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Ascaris Mouth
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Trichinella Worm Mouth
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