Introduction to the Platyhelminthes

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Introduction to the Platyhelminthes Life in two
dimensions. . .

• The simplest animals that are bilaterally
  symmetrical and composed of three fundamental
  cell layers
• Acoelomate FLAT!
• Lack an anus, the same pharyngeal opening both
  takes in food and expels waste

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• first creature to develop a head, brain, paired
  senses and a tail, the first to move forward and
  thus the first to hunt for food and mates
• 20,000 kinds of flatworms are alive and well
  today
• fresh and salt-water environments and other nice
  damp niches, like the insides of other animals.
• Fossil Record Platyhelminths have practically no
  fossil record (except eggs)

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• Platyhelminthes Taxonomy
• Turbellaria- mostly free-living, includes the
  planarian (e.g. Dugesia), these are found in the
  oceans, in fresh water, and in moist terrestrial
  habitats, and a few are parasitic.
• Trematoda- flukes, all parasitic, and have
  complex life cycles specialized for parasitism in
  animal tissues. Members of one major taxon of
  flukes, the Digenea, Schistosoma -- which
  includes the human lung fluke
• Cestoda- tapeworms (Taenia), are intestinal
  parasites in vertebrates, and they also show
  anatomical and life history modifications for
  parasitism

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• Review of Morphology of Common Flatworm
• Bilaterally symmetrical with a head and a tail
• Centralized nervous system
• Three tissue layers
• No body cavity, no circulatory system and no hard
  skeleton
• Colored (e.g. marine flatworms)
• With eyespot

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Flatworms have both male and female sex organs in
the one animal. If you think about it, that's a
great way to be. If you're rare and you're
looking for a mate and you're traveling alone,
you don't have to meet another female or another
male. You just have to meet another one. --
Leslie Newman
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Philippine Flatworms Area Malapascua Island,
Philippines
Pseudoceros sp.
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Philippine Flatworms Area Cebu Island, Moalboal,
Philippines
Maritigrella sp.
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Pseudoceros sp.
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Pseudoceros sp.
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Philippine Flatworms Area Puerto Galera,
Philippines
Pseudoceros sp.
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Philippine Flatworms Area Batangas, Philippines
Pseudoceros sp.
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Cycloporus sp.
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Pseudoceros sp.
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• Class Trematoda
• The image is a fluke (possibly a species of
  Probolitrema). Flukes, like other parasitic
  flatworms, have complex life cycles often
  involving two or more host organisms.
• Lung Fluke

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