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 A new study shows that the eels use it to exert a form of remote
control over their victims, causing fish that may be hiding to
twitch, thus exposing their location, or inducing involuntary muscle
contraction to incapacitate their prey.
"Apparently, eels invented the Taser long before humans," said
biologist Kenneth Catania of Vanderbilt University in Nashville,
Tennessee, who conducted the research published on Thursday in the
journal Science.
The study reveals precisely what an eel's zap does to its victim. In
laboratory experiments, Catania showed how the electrical discharges
remotely activate the prey's neurons, or nerve cells, that control
the muscles.
While hunting, the eels periodically give off two high-voltage
pulses separated by a 2 millisecond pause, causing a massive
involuntary twitch in nearby hidden prey, the study found. The eels,
highly sensitive to water movements, can detect motion caused by the
twitch, learning the other fish's location.
 The eel then delivers a full blast of a longer, high-voltage shock
to immobilize the prey through involuntary muscle contraction - much
like a Taser - enabling easy capture.
"I have spent much of my career examining extreme animal adaptations
and abilities. I have seen a lot of interesting stuff, but the eel's
abilities are astounding, perhaps the most amazing thing I have ever
observed," Catania said.
"After all, they can generate hundreds of volts - that by itself is
incredible. But to use that ability to essentially reach into
another animal's nervous system and activate their muscles is a
pretty good trick," Catania added.
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Electric eels, with serpentine bodies and flattened heads, can reach
lengths of 6 to 8 feet (1.8 to 2.5 meters), prowling the Amazon and
Orinoco river basins. They possess electric organs with specialized
cells called electrocytes that serve as biological batteries and can
generate an electric discharge of up to 600 volts to subdue prey or
defend against predators.
"Although they are not known to kill people, they are capable of
incapacitating humans, horses and obviously fish during their
electric discharge," Catania said.
Catania said the eels also use electricity in a third way,
periodically giving off a low-voltage pulse that seems to work as
sort of a radar system for navigating dark and murky water.
(Reporting by Will Dunham; Editing by Sandra Maler)
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