Electric Eels

Despite their name, electric eels are not true eels. They belong to a group of fish called knifefish and live in the muddy rivers and streams of South America. Most of an electric eel's long body is filled with special organs made up of thousands of cells that work like tiny batteries. When these cells release their charge at the same moment, the eel can produce a shock of several hundred volts.

Electric eels use electricity in more than one way. Because the water they live in is often too dark and muddy to see through, they constantly send out weak electric pulses. By sensing how these pulses are disturbed, they can detect objects and other animals nearby. When they find prey, they switch to powerful high-voltage shocks that make the prey's muscles tighten, so that it cannot escape.

In 2016, the biologist Kenneth Catania described an even more surprising behavior. When it is threatened by a larger animal, an electric eel may leap partly out of the water and press its chin against the attacker. This allows the electricity to flow directly into the attacker's body instead of spreading out through the water.