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Just When Science Has Electric Eels Figured Out, This Happens

National Geographic

A new study suggests that electric eels do more than just stun prey with their high-voltage charge.

The electric eel was once thought of as a primitive species that evolved over the millennia by using a high-voltage electric shock to stun their prey before seeking it out and eating it. Now, it appears that just the opposite may be true.

Now researchers are saying that the eel’s electric charge evolved first as a way to sense the environment around to help them find their prey, and that its use as a weapon came later. While the moniker “eel” is a bit misleading for this member of the knifefish family, scientists are now saying that these animals will use their shock waves as much to track their prey as to stun it.

As challenging as it is to simply capture one of these creatures that dwell in the remote Amazon River Basin, it’s even more of a challenge to study them. They are known to grow as big as 8 feet in length and are capable of generating a charge of 600 volts.

Ken Catania, a neurobiologist at Vanderbilt University found a previously hidden feature to their hunt. Catania said, “The eel can use its electric attack simultaneously as a weapon and a sensory system. It’s sort of a science-fiction-like ability”

The unique feature of the electric eel that allows it to be one of the few animals on earth to control such an electrical current is thousands of specialized cells called electrocytes. These cells are capable of storing the energy like a battery and then discharging it to disable fish and other prey.

What was unclear to scientists was how the eel could locate stunned prey after shocking it in the murky waters it calls home especially since it is mainly a nocturnal hunter. One good way to describe the issue is this: think of taking a successful passing shot on a bird and how its momentum causes it to continue falling past the point where it was shot.

Society for Science
Society for Science

Much the same can happen to an eel that stuns a fish in the dark. The prey could move out of the range of the eel even though it has been shocked into submission. Neurobiologist Catania was successful in recreating an eel attack in the lab by making an anesthetized fish flinch thereby causing the eel to discharge its electrical shock, but the fish was also wrapped in enough plastic to block the eel’s electroreceptors.

The result was that the eel lunged toward the movement, but didn’t attempt to eat the fish. Was it the plastic or did the eel just not know where the fish was?

Catania then placed an electrically conductive carbon rod in the tank. After inducing an attack on another fish Catania realized that the eel would move towards it, but then change course and head straight for where the rod was placed. It seemed like the eel was seeing the fish in two places at once.

“The eel turns on its high-voltage as a way to deactivate the fish,” Catania said, “but at the same time, it’s also using that high-voltage as a way to track where the fish is”

An eel’s electrolocation and a bat’s echolocation are similar, but Aaron Corcoran, a post-doctoral researcher at Wake Forest University and an expert in sonar says “Of course, bats don’t stun their prey. That electric eels are electrolocating prey as they stun them is at once astonishing and intriguing”

Catania said that he used to think electric eels were fairly primitive. “Now that I’ve gotten into the details,” he says, “(I think it’s) one of the most sophisticated predators out there.”


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Just When Science Has Electric Eels Figured Out, This Happens