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SCIENCE
 

Electric eels can amp up power to zap their prey

An electric eel curls its body to deliver higher-voltage shocks to stun its prey.
An electric eel curls its body to deliver higher-voltage shocks to stun its prey. Wikimedia Commons

Eels are a snake-like fish that live underwater. Some have a special power. They can zap their prey with a burst of electricity that knocks them out.

Now it turns out eels use a clever trick to make the electricity they produce even stronger. They bend their bodies into a curved shape like the letter 'U.' Doing that more than doubles the strength of the electric shock.

Scientist Kenneth Catania made the new discovery.

“Even an animal that’s been studied for centuries may be doing amazing things that we were unaware of,” said Catania.

Electric Powers Surprise Scientist

Catania has been studying electric eels for a while. Earlier, he discovered another surprising way they use their electric powers. Eels can send out a wave of electricity through the water. The shock forces hidden fish to jerk, which shows the eel where they are.

After eels shock their prey, they briefly release it. They quickly move the fish to line up lengthwise with their mouth. Then, they swallow it whole.

The only chance the fish has to escape is during the short moment after the eel releases it. Of course, it can get away only if it has not been completely knocked out by the electricity.

Catania began to notice something odd as he was studying electric eels. Many of them curled up their bodies when zapping a future meal. They brought their head toward their tail with the fish in between.

Younger Eels Curl Up More Often

Catania noticed that younger, smaller eels curled up frequently during their electric attacks. Young eels have much less shock power because of their small size.

Bigger, older eels almost never bothered to curl up. The only time they did was when they were attacking a particularly large fish. Such prey take extra power to knock out. It also takes extra time to move them before they can be swallowed. The extra time could allow a fish to escape if it has not been zapped strongly enough.

Catania thought he knew why the curling he saw might be happening. Perhaps the eels were curling their bodies so as to strengthen their electric power.

Eels have an organ inside their bodies that produces electricity. One end is the positive pole and the other is the negative pole, just like a magnet. The positive end is at the head and the negative end is in the tail.

If head and tail are brought close together perhaps the eel's electric force is strengthened, Catania thought. The two ends might be able to work together. Perhaps they can send out a much stronger shock then one end alone can.

Horseshoe Magnet Is Stronger, Too

Something like that can be seen with a curved horseshoe magnet. The magnetic field is stronger in a horseshoe magnet than in a straight bar magnet because the positive and negative poles are close together. The two ends work together. They produce a stronger magnetic force than one end alone could.

Catania decided to design an experiment to test his idea. He took a fish and put it near an eel as bait. The fish had electrodes attached to it, which allowed Catania to measure how much electricity passed through it.

Then, he measured the strength of the electric shock each time the eel attacked. Sure enough, the fish received more than double the amount of electricity when the eel curled its body.

Catania still wants to explore one very puzzling question. How do eels avoid shocking themselves?

Scientists have no idea how eels protect their own brain and muscles from being damaged by electricity, Catania said. "It’s pretty much an open question.”

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1
Anchor 3: People, Events & Ideas

Based on the article, why is curling important to younger eels?

A

It allows them to swallow their prey whole.

B

It allows them to create more electricity.

C

It causes them to use less electricity.

D

It causes them to move faster.

2
Anchor 5: Text Structure

How does the quote from the introduction [paragraphs 1-4] contribute to the article?

“Even an animal that’s been studied for centuries may be doing amazing things that we were unaware of,” said Catania.

A

It explains why Catania wants to continue studying eels.

B

It shows that Catania thinks others should be studying eels.

C

It shows that Catania thinks he should study a different fish.

D

It explains why Catania thinks he should be studying other animals too.

3
Anchor 3: People, Events & Ideas

Based on the article, why do younger eels curl up more often than older eels?

A

Younger eels curl to help them move their prey.

B

Younger eels can bend more than older eels.

C

Younger eels curl to increase their shock power.

D

Younger eels curl because they are not as big as older eels.

4
Anchor 5: Text Structure

Fill in the blank in the sentence below.

Overall the article is organized around .......

A

explaining why Catania thinks it is important that people study eels.

B

explaining what Catania observed and how he tested his idea.

C

explaining how what Catania has learned will help humans.

D

explaining how what Catania has learned relates to what others have learned.

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