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Planaria: Facts & Anatomy

Instructor: Gretchen Baumle
Planaria, also called flatworms, are found in both salt water and fresh water environments and even damp places on land. They're amazing creatures with some unbelievable tricks for survival - they've been on this planet for over a half a billion years!

Anatomy of a Flatworm

Planaria are commonly called flatworms, and many species can be found in many different environments. For example, a flatworm called Giardia is a common parasite found in contaminated drinking water that, if consumed, can cause diarrhea and severe dehydration. Red planaria are flatworms that can damage coral reefs in the ocean. Dugesia is another common planarian, although it's not parasitic. Dugesia is found in bodies of freshwater and is a typical resident of most ponds and streams. Their bodies have an almost arrow-like shape with a long, flat body and a triangular head with two eye spots. They're called eye 'spots' because they're not as advanced as an eye would be - typically they can only detect light and dark shadows. This seems to work well for them, however, because they've been on earth since before the dinosaurs and will probably be here long after we're gone!

All flatworms are referred to as acoelomates, which is a fancy way of saying their bodies are so flat there isn't room for internal body cavities. They're solid throughout. (Animals with body cavities, like humans, are called coelomates.) This is actually great for the planaria because things like oxygen and carbon dioxide can move into and out of their bodies right through their skin. No need for lungs! They also have a super simple nervous system, with a cluster of nerve cells in their head that serves the purpose of a very basic brain.

Dugesia

Flatworm Regeneration

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