Jellyfish are probably some of the most unusual and mysterious creatures that you'll ever encounter. Jellyfish have very simple bodies -- they don't have bones, a brain or a heart. With their gelatinous bodies and dangling tentacles, they look more like something from a horror movie than a real animal. But if you can get past the weirdness - and the fact that getting too close to one results in a nasty sting -- you'll discover that jellyfish are pretty fascinating. They don't seek out people to attack -- their nervous system is too simple to do that. Their sting is both a defense mechanism and a way to capture their prey. Though a jellyfish can kill a small aquatic animal, its sting is not usually fatal to humans. It tends to cause pain, skin rashes, fever and muscle cramps. An adult jellyfish is a medusa (plural: medusae), named after Medusa, the mythological creature with snakes for hair who could turn humans to stone with a glance.

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