November 01, 2015

Electric Embrace: Eels Curl Up to Supercharge Shocks

It's kind of like walking straight into an electric fence, or getting shot with a stun gun. That's how one biologist describes the experience of getting zapped by an electric eel.

"You wouldn't voluntarily do it over and over again," said Kenneth Catania, a professor of biological sciences at Vanderbilt University in Nashville, Tennessee, and author of a new study about the electric eels' shocking behavior.

Catania has been zapped a few times since he began studying the electric eel (Electrophorus electricus), a fish that's indigenous to the murky waters of the Amazon. Endowed with three electricity-producing organs, E. electricus can send a pulse, or volley, of high-voltage electricity through the water toward prey items. These shocks aren't meant to kill the prey, just demobilize it so the eel can more easily consume its victims, Catania told Live Science. [Video: Watch an Electric Eel Curl Around Its Prey]

To envision how the eel uses its electric charge, try picturing the critter's long, thin body as a skinny magnet. Like a magnet, the eel has two ends, or poles. When the animal sends out an electric pulse, most of the charge comes from its head, which Catania calls the "positive pole." The eel's tail serves as the "negative pole," sending out a much weaker electric pulse than the head, Catania said.

Most of the time, E. electricus just needs the charge from its head to demobilize prey. However, the tail end of the eel is actually quite important, Catania's new study shows. By bringing its tail around toward its head, an electric eel can double the strength of the electric pulse it sends out into the water, allowing it to demobilize larger prey items, the study found.

To measure the energy output of a curling eel, Catania rigged up a sort of eel chew toy by attaching a dead fish to a piece of wire. The fish was fitted with electrodes that could measure the voltage produced by the eel. Then, Catania stuck the chew toy in the tank with the eel and wiggled the toy around, simulating struggling prey. Sure enough, the eels tended to wrap themselves around the fish, and when they did so, they delivered at least twice their usual zap of electricity, Catania found.

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