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Posts Tagged ‘electric eel’

Paving the road toward celebrating Earth Day on April 22, I’ll be posting about some of Earth’s fascinating creatures and their ‘WOW!” adaptations to surviving in the world. Let’s begin with the electric eel.

Electric-eel2

The electric eel has many uses for its electrical power. Wikimedia Commons

Unless you live in the country side of South American nations such as Brazil, Suriname, Venezuela, Colombia, Ecuador, or Peru, and like to roam on slow-moving bodies of water of the Amazon and Orinoco Rivers, you are not in immediate danger of being shocked by an electric eel. (Of course, zoo keepers of this eel, beware)

Nevertheless, this intriguing fish may spark your attention because, unlike other fish, electric eels need to surface to breathe air. They can grow to be as long as an 8-foot man is tall and they can discharge about 600 volts. This is five times the discharge of one electric socket in US households, and about 3 times the power in electric sockets in other countries’ homes.

Scientists have been fascinated by the eels’ ability to manipulate electricity to aid its survival. And some scientists let their curiosity make them do truly weird experiments.

The eel scientist

Meet Ken Catania. He studies strange-looking creatures, such as the star-nosed mole and its unusual way to smell its underwater environment (more on that in a future post). More recently, Catania has been focusing on electric eels, and their ‘shocking’ abilities.

He discovered that eels can control how much electricity they put out. They use low voltage pulses to sense for prey, and they can turn up the power to make prey (think of fish) twitch and reveal its hiding location. An eel also can discharge a stream of high-voltage pulses to paralyze prey and easily suck it into its mouth in a flash. Fascinating!

But then, one day Catania was standing by the electric eels aquarium in his lab holding a net in his hand. He was going to use the net, which had a metallic rim and handle, to transfer eels from one tank to another.

As he submerged the net in the water, some of the eels swam away from it, but others zoomed toward it. In an instant, an eel leapt up and climbed along the net’s handle, firing a racket of high voltage pulses. Then, it dropped into the water. Catania was not hurt by the electric shocks because he was wearing insulating gloves, but he was very ‘shocked’ by what had just happened.

“Under no other circumstances were eels observed to leap out of the water,” he said.

Of old tales and leaping eels

Just when scientists thought they knew all there was to know about electric eels, here comes a serendipitous observation that makes them wonder. Why would eels jump out of the water? Catania had to solve the mystery.

He began by researching the scientific literature and came across an odd South American story from famous explorer Alexander von Humboldt. Humboldt wrote of eels jumping out of the water, attacking a group of horses that had stepped into a pool where the eels lived.

“The aggressive behavior of the eels, taking the offensive against the horses, seemed the most fantastic and questionable part of the story,” Catania said.

But he had observed the jumping behavior with his own eyes, so he decided to test it in the lab and measure the eels’ electric output when (if) they jumped. What advantage would the eels gain by jumping out of the water?

Catania knew that when eels swim emitting electrical discharges, an electric field forms around them. If a predator on the surface reaches toward an eel through the water, it won’t feel much of an electric charge. Would this be different if the eel jumped out of the water? And here comes the seemingly weird, but very illustrative design part of his experiments.

Catania used props shaped like alligator heads and human arms that were equipped with electric sensors that lit up when electricity flowed through them. He also carried out experiments using his own arm shielded by an insulating glove. With these tools he tested his eels’ ability to jump as Humboldt’s eels allegedly did, and measured their electric power.

The eels did not disappoint. These eels can jump! As they rose above the water touching the props, they discharged enough electric power to lit the sensors. That power, Catania estimated, also would be enough to cause intense pain in an predator trying to catch the eel. Discouraged and in pain, the predator would leave the eels alone and most likely will remember the experience next time it comes across a pond.

About two hundred years after Humboldt told the story of the jumping eels, Kenneth Catania not only confirmed his observations, but also revealed another amazing adaptation of the most powerful electric fish.

I invite you to see this short video showing some of Catania’s experiments and an 1800’s illustration of Humboldt’s story.

Thank you for reading and I hope you visit again!

Ana Maria

Ana Maria S. Rodriguez

Interested in reading the original sources describing Catania’s work?

  1. Catania, K. Leaping eels electrify threats, supporting Humboldt’s account of a battle with horses, PNAS,
  2. Catania, K. The shocking predatory strike of the electric eel, Science, 2014, Vol. 346, Issue 6214, pp. 1231-1234. (This link only provides an abstract of the work. Request the complete article via your public library).

More information about eels:

The Electric Eel, Smithsonian’s National Zoo & Conservation Biology.

 

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My website: Ana Maria Rodriguez 

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