Department of Environmental Conservation

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Flatworms (Platyhelminthes)

General Information about Flatworms or Planaria (Platyhelminthes)
Life history Different kinds of flatworms may reproduce sexually, or by dividing, depending on the environmental conditions. Some kinds will live from weeks to a few months; others that reproduce by dividing can live indefinitely.
Diversity There is one class (Tricladida) of freshwater flatworms in North America.
Soft un-segmented body; head is somewhat triangular with two eye spots; no segmented legs. They can be gray, brown, or black with stripes, spots, or mottled.
Habitat & Feeding Flatworms may be found in springs, streams, ditches, marshes, ponds, lakes, and puddles. Flatworms are predators and collector-gatherers; they have no teeth, so they get on top of their prey and use their feeding tube to suck out the prey's fluids, or to eat chunks, or eat the prey whole.
Water quality indicator status Flatworms are tolerant of low dissolved oxygen; high numbers of them may indicate that the water is impacted by organic or nutrient pollution.
Fun facts
  • Flatworms can regenerate; if cut into several pieces, each piece will grow into an individual flatworm.
  • Some kinds of flatworms divide every 5-10 days.