Talk about a shock—electric eels use their built-in "taser" to stun prey from a distance, a new study reveals.
Strong, fast pulses delivered remotely by the fish Electrophorus electricus cause its victim's muscles to contract, essentially paralyzing it. Then, the electric eel can swim over and slurp up its prize in one easy gulp.
The discovery is the first time scientists have found that an animal can remotely control its prey with electricity. (See pictures of other fish that use electricity to sense their environments.)
Vanderbilt University biologist Kenneth Catania made the find while recording captive electric eels with a high-speed camera.
"Fish are amazing escape artists. If the electric eel didn't have this capability, it would have a really hard time catching something to eat," said Catania, whose paper was published December 4 in the journal Science. "The mechanism is the same as a taser."
James Albert, an ichthyologist from the University of Louisiana at Lafayette who was not involved in the research, called it "a truly amazing piece of work."
"It's one of these 'oh duh' discoveries. The answers were sitting right in front of us, but Ken was the only one who bothered to look."
Shock to the System
Despite their name, electric eels are not a true eel—they're a type of knifefish native to the Amazon and Orinoco Rivers in South America.
Along their abdomens, electric eels have a series of three organs used to send and receive pulses of electricity. (See "Electric Fish Engage in 'Shocking' Mating Ritual, Study Finds.")
Two of the organs deliver low-voltage pulses, which scientists already knew act as a sixth sense. Electric eels use small pulses of electricity like bats and dolphins use echolocation, a type of natural sonar, to "see" their surroundings.
A third organ supplies high-voltage pulses that the eel uses to cripple its prey in three milliseconds, Catania said.
"This [is] extremely fast, and I wanted to know how the eel was able to do it," said Catania.
Since he couldn't find any information on the eel's strategy in the research literature, he decided to investigate the phenomenon himself.
Don't Tase Me!
Catania anesthetized a fish whose brain had been incapacitated but whose muscle fibers remained intact and able to contract. He then placed an electric eel in a tank with the fish and measured muscle contractions in the prey fish.
When the eel sent out high-frequency electric pulses, the fish's muscles contracted strongly, effectively paralyzing the fish. Catania observed that the eel was not physically touching the prey.
Before an eel can immobilize its prey, however, it has to find it. Further experiments by Catania revealed that pairs of low-voltage electric pulses known as doublets caused involuntary muscle twitches in nearby fish. (Watch video: "Catching Electric Eels.")
Electric eels can sense the resulting water movements, which reveal the location of their prey.
Catania also went one step further-he showed that the high-voltage electric pulses from the electric eels matched the electric pulses from the fish's own nervous system.
This allows the eel to effectively hijack its prey's nervous system to force it to reveal its location or remain paralyzed for the predator to eat.
The University of Louisiana's Albert noted that the electric eel has likely evolved this behavior over millennia. (See a photo gallery of real eels.)
"It never occurred to me that [electric eels] were doing remote control behavior," he added.
Now we just need to hope that the remote control abilities of electric eels don't extend to our television sets.