When it comes to unleashing their trademark zaps, electric eels employ an impressive and sophisticated set of tactics.
These dangerous denizens of the muddy waterways of South America's Amazon and Orinoco basins can double the voltage of their jolts by curling their serpentine bodies to adjust the position of the positive and negative poles of their electric organ, according to a study unveiled Wednesday.
Researchers also described how the eels use electrical pulses: both as a radar system to track prey and to immobilize it by causing strong, involuntary muscle contractions in an electrifying form of remote control.
Vanderbilt University neurobiologist Kenneth Catania said electric eels sometimes have been viewed as unsophisticated, primitive creatures with a single tool in the toolbox, shocking their prey to death. In reality, they manipulate their electric fields in complex ways that only now are being appreciated.
The new study, published in the journal Current Biology, reveals how the eels use a unique maneuver to ratchet up their jolt when attacking large or difficult prey.
The eel first bites the prey. It then curls its body around the prey in a way that places the negative pole – its electric organ, located in the tail – close to the positive pole, located in its head.
With the prey trapped in between the poles, the eel more than doubles the voltage inflicted upon the prey. This causes rapid, involuntary fatigue in the prey's muscles, enabling the eel to thwart any escape.
"What I like about these findings is they are inevitable and yet incredible," Catania said.
"We know from basic physics that bringing two electrical poles together concentrates the electric field, and we know from basic muscle physiology that running a muscle too fast for too long causes exhaustion. But I would never have imagined an electric eel could produce the same results."
Electric eels reach lengths of 1.8 to 2.5 meters or 6 to 8 feet. They possess electric organs with specialized cells called electrocytes that can generate a discharge of up to 600 volts to subdue prey or ward off predators.
In a separate study last week in the journal Nature Communications, Catania showed the eels also employ their electrical powers as a radar system to track fast-moving prey.
The study showed the eels used feedback from their high-voltage volleys to pinpoint the position of prey.