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Electric Eels!A Reading A–Z Level U Leveled Book

Word Count: 1,262

Writing Compare another fish to the electric eel using a Venn diagram. Write a paragraph explaining how they are alike and different.

Science and Art Research to learn more about electric eels. Design a poster about electric eels to share with your class. Include a diagram and important facts.

Connections

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LEVELED BOOK • U

O•R•U

Written by Racheal Rice

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What is an electric eel?

Focus Question

Written by Racheal Rice

Photo Credits:Front cover, back cover: VPC Animals Photo/Alamy Stock Photo; title page: © George Grall/National Geographic Creative; page 3: © Norbert Wu/Minden Pictures; page 4: © ullstein bild/ullstein bild/Getty Images; page 5: Electric eel/Private Collection/Bridgeman Images; page 6: © Bil ly Hustace/Corbis Documentary/Getty Images; page 7: Amazon-Images/Alamy Stock Photo; page 9 (left): Jeff Rotman/Alamy Stock Photo; page 9 (top right): © Sue Daly/NPL/Minden Pictures; page 9 (bottom right): © Ryu Uchiyama/Nature Production/Minden Pictures; page 10 (battery): © iStock.com/ShowVectorStudio; page 11: © Elenathewise/iStock/Thinkstock; page 14: © Adalbertus/Dreamstime.com; page 15: © yourth/iStock/Thinkstock

Illustration Credits:Pages 8, 10: Laszlo Veres/© Learning A–Z

Editor’s note: Many of the photographs in this book show electric eels in aquariums or labs. Electric eels l ive in murky water, so photographing them in their natural habitat produces muddy results.

Words to Know

amplify electric electric currents immune internal navigate

organs shocks stun top predators tributaries volts

Electric Eels!Level U Leveled Book© Learning A–ZWritten by Racheal Rice

All rights reserved.

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CorrelationLEVEL U

Q4040

Fountas & PinnellReading Recovery

DRA

3

Table of Contents

Legendary Shocker . . . . . . . . . . . . . . . . . . . . . . . . . 4

It’s a Fish! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

It’s Electric! . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Stunning Attack . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Don’t Swim There! . . . . . . . . . . . . . . . . . . . . . . . . 13

Future Energy Source . . . . . . . . . . . . . . . . . . . . . 15

Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Electric Eels! • Level U 4

Legendary Shocker

In 1800, German naturalist Alexander Humboldt went searching for electric eels in what is now Venezuela . He knew electric eels and their shocking abilities could help him if only he could catch some alive . Live eels could help him solve some mysteries of the little-understood force of electricity . He knew it was too dangerous to touch the eels with his bare hands . Their shocks could cause violent pain throughout a person’s body . He asked local fishermen if they could help .

Humboldt spent five years (from 1799 to 1804) exploring South America.

5

Shocking Fish StoryHumboldt didn’t have modern materials or equipment

that would have made catching electric eels safer. His account of fishing for eels with horses became legendary among scientists. Only recently did a scientist confirm that electric eels do rise up out of the water to protect themselves, as Humboldt observed. Before that, some scientists thought Humboldt’s story might be exaggerated, like any fish story.

Humboldt watched as the fishermen guided about thirty horses into a murky, shallow pond . He described how the thick snakelike eels rose up out of the water . The eels delivered hundreds of shocks to the horses before the fishermen could catch five of them . Humboldt studied the eels and learned much from them .

A picture made from Humboldt’s writing about fishing for eels with horses shows the power of electric eels.

Electric Eels! • Level U 6

It’s a Fish!

Electric eels are actually long, cylinder-shaped, gray-brown fish that are often yellow or orange below their heads and on their throats . They are more closely related to catfish than to other eels, but their body shape makes them look more like eels . They are classified in the scientific order commonly called knifefish, which all have some ability to use electricity . Electric eels can grow as long as 2 .1 to 2 .75 meters (7–9 ft .) and weigh as much as 20 to 22 kilograms (44–48 .5 lb .) . That means they can be about as big around as an average adult human’s thigh . Male and female electric eels are much the same in color and size, so it can be difficult for scientists to tell them apart .

Electric Eel FactsScientific Name Electrophorus electricusAnimal Type Fish

Diet Fish, crustaceans, and amphibians

Length 2.1 to 2.75 meters (7–9 ft.)

Weight 20 to 22 kilograms (44–48.5 lb.)

7

Unlike most other fish, electric eels breathe air through their mouths . They have gills like other fish, but their gills mostly help them breathe out . Electric eels open their mouths at the water’s surface, and oxygen from the air goes into their bodies through special organs in their mouths . The waste air they breathe out goes through their mouths and gills . Electric eels need to breathe air every few minutes and can drown if they get trapped underwater .

Electric eels breathe air through their mouths.

Electric Eels! • Level U 8

Shocking FactElectric eels can regenerate the tail parts of their bodies

if they’re cut off, similar to some lizards and worms.

Like most other fish, electric eels have fins . They have small fins on either side of their heads and one long fin along their bellies . Electric eels’ belly fins run the length of their bodies . They also have backbones that run the length of their bodies and help them move . Electric eels wave their belly fins in a kind of rippling S-shape to swim through the water . They mostly move slowly, except when they attack .

9

Other Electric Fish

Shocking Medical HistoryDon’t try this at home! Ancient Greeks and Romans held live

electric rays to people’s foreheads to cure headaches. A ray’s shock can cause numbness in humans, so it might have worked.

It’s Electric!

An electric eel’s ability to use electricity sets it apart from other fish . It is Planet Earth’s most electric fish . Scientists know that electric eels can protect themselves, navigate, hunt, and stun or kill prey using their bioelectricity . Bioelectricity is the action of electric currents in a body . Scientists have identified other knifefish and some skates, rays, and catfish that use weak electrical abilities to navigate, communicate, or protect themselves, but none have the powerful attack shock of an electric eel .

electric catfish

electric ray

clearnose skate

Electric Eels! • Level U 10

Shocking FactIf an electric eel curls its body around its prey, connecting

its head and tail, it can increase its shocking power.

Three electric organs make up most of an electric eel’s insides and give it its powerful shocking abilities . The electric organs start just behind the eel’s head, going down its back and on both sides through its tail . An electric eel’s body is two-thirds electric organs . The organs are designed to send out shocks from the eel’s body, which can be compared to a battery with a positive and a negative end . The positive end is at the eel’s head, and the negative end is at its tail .

Three Electric OrgansThe electric eel’s three electric organs are named main, Hunter’s, and Sachs’.

Main

Hunter’s

Sachs’

11

An electric eel’s electric organs can shock prey with up to 650 volts of electricity, which is enough to kill small animals and stun large ones . Anything in the water within 8 .5 meters (28 ft .) of the eel can feel the shock . For comparison, an electric eel produces a shock with five times the volts of a typical U .S . wall socket, which can be dangerous to humans .

Electric eels are immune to their own shocks, but scientists aren’t sure why . It might have something to do with their size compared to the size of their prey, how quickly the shock moves away from their bodies, or internal structures scientists don’t understand fully . Scientists do know that electrocytes are the special cells in an eel’s electric organs that help it shock prey, and that an eel’s electrocytes line up in long rows . When an eel uses its bioelectricity, each of the electrocytes delivers a tiny shock at nearly the same time . The stacking of electrocytes and the nearly simultaneous shock by each one combine to amplify those tiny shocks into one large, stunning ZAP!

Electric Eels! • Level U 12

Stunning Attack

Before the attack zap happens, electric eels have to find their prey . These fish live in murky water, and they have poor eyesight . They are also nocturnal, or most active at night . Electric eels don’t use their eyes to hunt, relying on bioelectricity instead . They have a similar ability to bats and owls that find prey based on how sound bounces off objects . Electric eels send out about fifty low-volt pulses, or repeating beats of electricity, every second . Plants, animals, and nearby objects interrupt the pulses, showing the electric eels what’s around them .

When an electric eel thinks prey is nearby, it quickly sends out a group of two or three high-volt pulses . The shocks make an animal clench and twitch its muscles involuntarily, which means it can’t stop moving . The muscle movement reveals the prey’s exact location . Then the electric eel sends out a high-volt shock, which stops the prey’s twitching and sometimes kills it . The electric eel moves quickly and sucks the prey through its mouth directly into its stomach . The prey doesn’t have time to recover and swim away . Adult electric eels mostly eat small fish, crustaceans, and amphibians . Young eels mostly eat worms, insect larvae, and small fish .

13

Don’t Swim There!

Electric eels are top predators and are common in their environments, which are usually muddy or sandy slow-moving rivers . Scientists have found them in the Amazon and Orinoco Rivers and their tributaries in northern South America . Because electric eels prefer slow-moving or calm fresh water, they can also be found in swamps, creeks, and ponds or along the edges of lakes in tropical plains or forests . Because they breathe air, electric eels can survive in water with little oxygen and even out of water for hours as long as their skin stays wet .

Electric Eel HabitatATLANTIC

OCEAN

PACIFICOCEAN

SOUTHAMERICA

Amazon River

Orinoco River

Electric Eel Habitat

Electric Eels! • Level U 14

Electric eels mostly mate in small ponds . Male eels build nests by creating bubbles with their saliva, and female eels lay hundreds of eggs in the bubbles . Male eels guard the nests and the hatched baby eels until they are about 10 centimeters (3 .9 in .) long . Then the baby eels have to start defending themselves with their shocking abilities, which aren’t as powerful as an adult’s . Young electric eels are vulnerable to animals, such as crocodiles, that might risk preying on them before they grow larger .

Black caimans, which are relatives of crocodiles, are one of the few predators that will chance trying to eat an electric eel.

15

Future Energy Source

Scientists understand more about electric eels now than Humboldt did, but researchers are not yet done learning . Scientists at Yale University are looking at electrocytes as a model for cells to replace batteries in medical devices—such as pacemakers, which keep a human heart beating . Pacemaker batteries contain chemicals that could poison a patient if the device breaks . Researchers want a battery that won’t harm the insides of a human body and won’t run out of power .

What Humboldt wrote more than two hundred years ago could still apply today: “We are, doubtless, very far from having discovered all the secrets of the electrical action of fishes .” What will electric eels help scientists understand next?

Electric Eels! • Level U 16

Glossary

amplify (v.) to make larger in amount, strength, or importance (p . 11)

electric (adj.) charged with, powered by, or producing energy that is created by moving charged particles (p . 4)

electric currents (n.)

movements of electric charge through matter (p . 9)

immune (adj.) protected from or resistant to something (p . 11)

internal (adj.) of, relating to, or occurring on the inside of something (p . 11)

navigate (v.) to find one’s way over a long distance; to steer a course toward a destination (p . 9)

organs (n.) parts of an organism that have specific functions, such as the kidneys or lungs (p . 7)

shocks (n.) sharp jolts experienced when electric current touches or travels through a body (p . 4)

stun (v.) to knock unconscious or into a dazed state (p . 9)

top predators (n.)

predators at the top of a food chain that no other animal eats (p . 13)

tributaries (n.) rivers or streams that flow into a larger river (p . 13)

volts (n.) units of measure for the amount of force that gets an electric current moving (p . 11)