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.
They swim through the water using a smooth, wave-like motion of their bodies. Planaria are carnivores, believe it or not, which means they eat meat instead of plants. And they consume this meat through a tube-shaped mouth on the underside of their bodies. They're very well adapted to their habitats and employ unique ways of survival, like the ability to regrow lost body parts. In fact, if a planarian is cut in half, it will grow into two distinct worms! Cut it into five pieces, get five new worms! Pretty neat, huh?
Planaria are fascinating little animals known to most people as flatworms. They're so flat they don't have internal body cavities like humans do, making them acoelomates (vs. those animals with body cavities, called coelomates). With their remarkable ability to regenerate missing or damaged body parts, they may hold the key to immortality, essentially living forever!
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