Electric eels can send send up to 600 volts of electricity coursing through the water. Those predators aren't just sending zaps of electricity out into the environment willy-nilly, however, Ed Yong writes for National Geographic. The electric eels have specialized, battery-like cells and can use electricity to remotely control their victims' movements.
As Yong describes, the predator's hunting methods are only just now being discovered because few researchers have taken the time to study how electric eels snag their prey. But when Vanderbilt University's Kenneth Catania took a closer look at the electric eels' behavior, he found that they essentially have a "reveal yourself" and a "freeze" command, both of which prey are defenseless against. Yong writes:
To work out what the pulses were doing, Catania presented eels with zombie prey—lobotomised and anaesthetised fish that were hooked up to a device for measuring forces. An agar barrier prevented the eel from reaching the morsels but allowed its discharges to pass. This macabre set-up confirmed that the eels’ high-voltage pulses force the fish’s muscles to involuntarily contract.
The eel had two different types of attacks, Catania found. First, a double pulse of electricity forces prey to reveal itself. Next, the eel emits a series of quick electric pulses—about 400 per second—to freeze its prey in place for easy eating.
Catania was quite impressed with the findings. As he told Yong, "This is one of the most amazing things I’ve encountered in studying animals, and I’ve seen a lot of unusual things."