Electric eels deliver Taser-like shocks

The electric eel - a scaleless Amazonian fish that can deliver an electrical jolt strong enough to knock down a full-grown horse - possesses an electroshock system uncannily similar to a Taser, scientists say.
Researchers studied the way in which the electric eel uses high-voltage electrical discharges to locate and incapacitate its prey.
The research was conducted by Vanderbilt University Stevenson Professor of Biological Sciences Kenneth Catania who equipped a large aquarium with a system that can detect the eel's electric signals and obtained several eels, ranging up to four feet in length.
Catania discovered that the eel's movements are incredibly fast. They can strike and swallow a worm or small fish in about a tenth of a second.

He recorded three different kinds of electrical discharges from the eels: low-voltage pulses for sensing their environment; short sequences of two or three high-voltage millisecond pulses (called doublets and triplets) given off while hunting; and volleys of high-voltage, high-frequency pulses when capturing prey or defending themselves.
He found that the eel begins its attack on free-swimming prey with a high-frequency volley of high-voltage pulses about 10 to 15 milliseconds before it strikes.

The fish were completely immobilised within three to four milliseconds after the volley hit them. The paralysis was temporary: If the eel didn't immediately capture a fish, it normally regained its mobility and swam away.

Catania said he was struck by the similarity between the eel's volley and a Taser discharge. A Taser delivers 19 high-voltage pulses per second while the electric eel produces 400 pulses per second.
The Taser works by overwhelming the nerves that control the muscles in the target's body, causing the muscles to involuntarily contract.
To determine if the eel's electrical discharges had the same effect, Catania walled off part of the aquarium with an electrically permeable barrier.
He placed a pithed fish on other side of the barrier from the eel and then fed the eel some earthworms, which triggered its electrical volleys. The volleys passed through the barrier and struck the fish, producing strong muscle contractions.

To determine whether the discharges were acting on the prey's motor neurons or on the muscles themselves, he placed two pithed fish behind the barrier: one injected with saline solution and other injected with curare, a paralytic agent that targets the nervous system.
The muscles of the fish with the saline continued to contract in response to the eel's electrical discharges but the muscle contractions in the fish given the curare disappeared as the drug took effect.
This demonstrated that the eel's electrical discharges were acting through the motor neurons just like Taser discharges.
The study was published in the journal Science.