No bones. No brains. But what a sting!
The sting of some "jellies," such as this sea nettle (left), can be deadly. Others are harmless to humans.
They look like blobs when washed up on the beach. But in the water jellies are graceful. They range in size from about 1 inch (2 1/2 centimeters) to 200 feet (61 meters) long. They have been drifting through the world's oceans for more than 650 million
years.
Jellyfish are not fish at all. They are invertebrates, relatives of corals and sea anemones (uh-NEH-muh-neez). A jelly has no head, brain, heart, eyes, nor ears. It has no bones, either. But that's no problem! To capture prey for food, jellies have a net of tentacles that contain poisonous, stinging cells. When the tentacles brush against prey (or, say, a person's leg), thousands of tiny stinging cells explode, launching barbed stingers and poison into the victim.
Where there's water—from icy polar seas to tropical Pacific shores—there are jellies. Scientists estimate there may be 2,000 species of jellyfish.
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