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Cestodes

Question Answer Article
Fill in the missing words about cestodes A cestode (tapeworm) is a chain (strobila) of progressively maturing reproductive units called proglottids anchored at one end to the intestinal wall by a hold-fast organ called the scolex. Link to Answer Article
What species of Taenia occur in dogs?
  • Taenia ovis
  • Taenia hydatigena
  • Taenia pisiformis
  • Taenia multiceps
  • Taenia serialis
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What are the more obvious morphological features of the scolex of a cyclophyllidean tapeworm?
  • Four suckers
  • Rostellum with rows of large hooks
  • Unsegmented neck (behind the scolex) which gives rise to new segments
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Describe the features of a cysticercus
  • Fluid filled bladder, containing a single invaginated head (protoscolex) - seen as a white blob on the wall of the cyst
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In which host(s) would you expect to find the cysticercus of T. hydatigena and where in the host might it be found?
  • Sheep (mostly)'
  • Cattle
  • Pigs
  • Found in the peritoneal cavity
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What is the difference between a coenurus and a cysticercus?
  • A coenurus is a fluid filled bladder with multiples (dozens) of inverted head attached to the wall
  • Whereas the cysticercus has only a single inverted scolex.
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How does the distribution of hydatid cysts differ in sheep, horses and humans?
  • Sheep = most are in the lungs with smaller numbers in the liver
  • Horses = nearly all are in the liver
  • Hymans = most are in the liver, with some in the lungs and a few elsewhere
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Summarise complex metamorphosis and give an example of a species of insect which uses it
  • Larva emerges from egg
  • Larva grows and moults
  • Larva pupates
  • Adult emerges from pupa
  • Flies
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