Flatworms

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Flatworms

• Phylum Platyhelminth

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Endoparasite
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Exoparasite / Ectoparasite
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Life cycles

• Most parasitic worms have more than one organism
  in their life cycle
• An intermediate host (the first), usually a
  mollusk
• Sometimes there are multiple intermediate hosts
• A final (definitive host), usually a vertebrate
• These hosts are where sexual reproduction occurs

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Clonorchis
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Flatworms

• Name means flat worm

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Flatworm advancements

• First animals to show bilateral symmetry
• First animals to have 3 well defined germ layers
  (called tripoblastic)
• Are considered acoelomate (no body cavity)
• Simple sense organs with eye spots in some

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Advancements, continued

• First animals to show cephalization having a
  clear and defined head with most of the important
  structures found there
• First to have an excretory system
• First to have a circulatory system with blood

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Characteristics

• Oral and genital structures found mostly on the
  ventral surface
• Digestive system incomplete
• Simple sense organs
• Nervous system with a central processor (brain)
• Most organisms monoecious, some with complicated
  life cycles

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Class Turbellaria

• Planarians
• Free living
• Most often found in fresh water
• Eyespots sense light

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Some can split asexually by fission
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Planarian
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Planarian

• Pharynx is responsible for obtaining food
• Extends out and releases proteolytic enzymes
  (breaks down protein)
• External digestion

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Class Trematoda

• Parasitic flukes
• Generally endoparasites
• Poorly developed sense organs
• Generally have suckers but no hooks

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Life cycle of the liver fluke
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Fluke
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Paragonimus westermani

• The lung fluke parasite
• Causes paragonimiasis

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Clonorchis
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Clonorchis

• Common in the Orient
• Can cause cirrhosis of the liver

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Schistosomiasis
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Schistosomiasis

• Blood fluke
• 200 million people infected
• Causes severe dysentery, anemia, bladder
  inflammation and brain damage
• There is also a kind that infects birds that
  causes swimmer itch a rash

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Class Cestoda

• Tapeworms
• Long flat bodies made up of an attachment head
  with hooks and suckers, called scolex
• The scolex is followed by MANY reproductive
  segments called proglottids

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Tapeworms

• Completely lack a digestive system and sense
  organs
• Generally have more than one host

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Tapeworm cyst in the liver
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Beef Tapeworm

• Larvae shed from the human host are eaten by
  cattle
• Larvae hatches and encysts in the muscle
• People eat un- or undercooked meat and the larvae
  hatches in the intestines

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Dog Tapeworm
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Pork Tapeworm - Taenia solium
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Question

• What is the world's longest parasite?
• The world's longest parasite is the tapeworm so
  the next question is 'What is the world's longest
  tapeworm?'
• The longest tapeworm ever removed from a human
  came out of Sally Mae Wallace on September 05,
  1991.
• In all, doctors pulled 37 feet of tapeworm out of
  Sally Mae Wallace's body
• If you find all of this disgusting, be glad
  you're not a whale as tapeworms in whales can
  grow up to 120 feet long.

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You need

• Planaria digestive or plain
• Clonorcis
• Schistosome
• Taenia