In a recent Science article, the mechanism electric eels use to incapacitate their prey was found to work via a mechanism surprisingly similar to Tasers.
First, some background. The electric eel is not a true eel, but an electric fish. (Eel themselves are a type of fish, but the electric eel is a different type of fish. Confusing! One difference that true eels have dorsal fins and electric eels do not).
A large portion of the electric eel's body is made of electric organs which contain flat disk-shaped cells called electrocytes. As their name suggest, these cells each produce a small voltage, about one-tenth of a volt. In total however, the electric organs can produce up to 600 V in certain species. The ability to discharge electrical shocks is the basis for their prey-hunting capabilities.
When the electric eel has its prey in range, it discharges a high-frequency volley of electric shocks. Do you imagine a animal jerking around from all the electricity? Don't! Turns out that the discharge frequency completely immobilizes the animal. Basically, the pulses come fast enough that they contract all the muscles in the prey's body, so it remains completely still, and the electric eel can attack. This is how Tasers work! However, the Tasers deliver about 19 pulses per second, while the electric eels discharge around 400 per second.
But how does the electric eel locate its food in the first place? It turns out that the discharge is under fine control. If the eel wants to locate potential near-by but hidden prey, it lets off two pulses, or doublets, that cause the prey animal to "jerk" or "jump". Now the hiding place of the prey animal has been compromised, and the electric eel can employ its high frequency discharge to attack.
To summarize: To locate hiding prey, the electric eel lets off two pulses that make the prey "jump." To immobilize said prey, the electric eel lets off a high frequency volley of electric shocks and then eats the still, floating, fish.
This work comes out of Vanderbilt from a fantastic researcher named Ken Catania (although at the time of this posting his website has not been updated to reflect the electric eel publication). I've had the honor of hearing him speak and his work is truly an original and creative exploration of animal behavior.
If you want to know more, this research has been reported all over the internet. Check out this video from Slate, or these reports from the NYT, BBC or National Geographic. You can find a link to the original research here, (click on the Science link on the right) but you need a Science subscription to access it.