They can be bioluminescent, too, which means they produce their own light! Jellyfish have no brain, heart, bones or eyes. They are made up of a smooth, bag-like body and tentacles armed with tiny, stinging cells. These incredible invertebrates use their stinging tentacles to stun or paralyse prey before gobbling it up.<br /><br />Jellyfish are over 600 million years old. Before the dinosaurs, trees, or even fungi, there were jellyfish. <br />There could be 300,000 species of jellyfish.<br />They have no brain and are 98% water. <br />One species may be immortal. <br />In their ecosystem, jellyfish are effective predators<br />
