Electric Eels Can Set Charge to Buzz or Stun

The electric eel is one of those animals that can strike fear into people's hearts, even though it lives a relatively peaceful life in the tepid waterways of South America. Now scientists have figured out how it uses its electric shock to both detect and stun its prey -- a brand new finding for an animal that has been a curiosity of science since the 18th century.

It turns out the eel emits a low-level charge that takes over the nervous system of any nearby animal, say a frog or a fish, and causes it to involuntarily twitch. This twitch alerts the eel that it has found live prey (and not a rock or branch).

After detecting its prey, the eel uses volleys of high-voltage pulses combined with a suction strike to kill its prey -- the hapless fish is gobbled up by the eel's enormous mouth.

Kenneth Catania, professor of biology at Vanderbilt University, presented this finding in this week's journal Science. Catania is an expert in mammal sensory systems and brain organization. He is known for his work on star-nose moles, the cute/ugly critters who use big, fleshy appendages on their nose to find their way underground.

After writing a book chapter on animal behavior, he recently got interested in electric eels and began photographing their behavior in his lab's aquarium.

"They have two modes," Catani said. "If they are hunting for hidden prey and don't know where it is, they give out a little blip of the electricity just briefly, and the animal twitches. It's a perfect way to cause the prey to reveal themselves."

The second mode remotely activates the prey's muscles.

"You would have maximal muscle contractions, it completely immobilizes you," Catania said. "The eel can catch you when normally you could escape."

Most of the electric eel's body is composed of electrocytes, which are muscle-derived biological batteries, that can provide a combined discharge of up to 600 volts.

"It's the same way the Taser acts," he said. "When someone gets Tased, they are not getting stunned by brain activity; their peripheral nervous system is being activated."

Catania says the electric eel lives only in South America and can reach two meters (nearly 7 feet). He's checked existing records and could find no human deaths, although they likely have given cattle and other large mammals a pretty bad shock.

"I would imagine that the eel would be able to inactivate anything it would fit in its mouth," he said. Some of them get quite big. I have a four-foot one that is as big around as my leg."

Eels were used in early attempts to understand electricity and more recently, eels were important for identifying acetylcholine receptors and for providing insights into the evolution of electric organs.

Read more at Discovery News