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The secrets of slime: how gooey mucus keeps animals alive.

A shark swims through the Pacific Ocean, searching for its next meal. It spots a hagfish, an eel-like animal, resting on the seafloor.

The shark moves in. It bites into the hagfish. But then something goes wrong. The shark's mouth suddenly fills with a thick, gooey substance. The hagfish has released its secret weapon: slime. The shark gags and swims away, leaving the hagfish alone.

In a fraction of a second, a hagfish can make about 1 liter (4 cups) of slime, making it one of the slimiest creatures on Earth. But it's far from the only one that uses this gooey substance to survive. Many animals--including humans--make slime, which scientists call mucus.

Animals use slime to move around, to defend themselves, and even to communicate. By studying slime, scientists hope to learn how its special properties can help people too.

Masters of Slime

Douglas Fudge is a biologist at the University of Guelph in Canada. He studies hagfish.

"Hagfish make ridiculous amounts of slime in a very short amount of time," says Fudge. This adaptation protects the animal from predators.

When a hagfish is attacked, it flexes its muscles. This squeezes mucus out of special glands in the animal's body. The glands also release \ tiny silk-like fibers that expand in the I water. They mix with the mucus and seawater to form a sticky slime y that predators can't swallow.

Hagfish have a trick to keep from getting stuck in their own slime. They twist their flexible bodies into a knot, then slide through the knot to wipe themselves clean.

On the Move

Hagfish use slime to defend themselves. So does an animal called the parrotfish, which cloaks itself in mucus to deter predators while it sleeps.

Other creatures, like slugs and snails, are covered in mucus all the time. The slimy coating keeps their bodies from drying out, says Christopher Viney. He's a materials scientist at the University of California, Merced.

Mucus also helps slugs and snails move around their environment. The slippery substance lubricates their undersides, allowing them to glide over rough surfaces like gravel or tree bark. Viney has even seen a slug climb across razor blades without getting hurt. "I think the slug enjoyed having its belly rubbed," he says.

Slime has unique properties, says Viney. It flows like a liquid to help a slug move. But it's also tough, like a solid material. If a slug climbs a window, its slime is strong and sticky enough to keep it from sliding down.

Slugs can even use slime to communicate. If a slug comes across another slug's slime trail, chemicals in the mucus tell it when the other slug was there and which way it went.

Slimy Future

Slime's properties are useful to many animals--including people (see Your Slimy Self, below). The same properties are also inspiring new technology.

For example, researchers at the Massachusetts Institute of Technology have developed a robotic snail. It uses a slime-like substance to crawl up walls and across ceilings, which most robots can't do.

Fudge and his team study the tough fibers in hagfish slime. The silk-like structures could inspire new fibers for clothing, says Fudge. Fabric made from these fibers wouldn't be slimy. But it would break down easily once the clothes are thrown out, making the material environmentally friendly.

Scientists study mucus for one more reason: because it's fun, says Fudge. He's been working with slimy hagfish for 18 years. "I didn't think I would continue studying them," he says, "but the slime just kept getting more and more interesting."

words to know

mucus--a thick, slimy substance produced by an animal's body

adaptation--a change in the body or behavior of a species over many generations, making it better able to survive

gland--an organ in the body that releases a particular substance

lubricate--to reduce friction and allow smooth movement

WATCH A VIDEO /superscience

BONUS SKILLS SHEET /superscience

Your Slimy Self

Wild animals aren't the only ones that need slime to survive. Mucus also helps the human body function.

You're probably familiar with the mucus in your nose--also known as snot. When you have a cold, your body pumps out extra snot to fight invading germs. But this mucus helps you when you're healthy too. When you inhale, the sticky substance traps tiny particles from the air.

"It prevents dust and debris from reaching your lungs," says Dr. Roy Benaroch, a pediatrician in Atlanta, Georgia.

Your mouth, ears, and eyes have a protective mucus coating too. A mucus lining in your stomach keeps the acid that breaks down food from leaking into the rest of your body.

As gross as it is, slime keeps you alive. "It's very, very important," says Benaroch.


Learn about the properties of slime and how animals use slime to survive.


Print Edition:

Lexile Level 870

Guided Reading Level T

Online Leveling Tool:

Lexile Level 620

Guided Reading Level L


NGSS: LS4.C: Adaptation

NSES: The characteristics of organisms: regulation and behavior

Common Core:

Writing: 2. Write informative/ explanatory texts to examine a topic and convey information clearly.

DIGITAL FEATURES: /superscience

Video: Learn why humans and other animals produce mucus and why scientists are studying slime.

Web Link: Watch a video about why banana slugs produce slime: ww2.kqed .org/science/2015/02/17 /banana-slugs-secret-of-the-slime.

Lesson Plan


1. Obtain three 8-ounce bottles of Elmer's clear glue, a mixing bowl, yellow and green food coloring, a measuring cup, warm water, borax, a teaspoon, a plastic spoon, and 12 Dixie cups.

2. Squeeze all three bottles of glue into the bowl. Then fill each glue bottle with water, shake it, and add the water to the bowl. Add she drops of green food coloring and three drops of yellow.

3. Put 1 1/2 cups of warm water in the measuring cup. Stir in 3 teaspoons of borax. Add the borax solution to the bowl. Mix it all together to create slime.

4. Divide the slime among the Dixie cups for student use. (You can also use the slime for this issue's hands-on experiment, "Ooze-a-Palooza," about why slugs make slime. That experiment is on page 7 of the student issue.)


1. Divide students into groups of two or three. Give each group a cup of slime. Have students manipulate the slime for a few minutes. Then have them write down properties of the slime. Ask:

* What are the properties of your slime? (green, sticky, wet, shiny, slippery)

* Is slime a solid, a liquid, or a gas? (Slime has qualities of a liquid and a solid.)

2. Explain that slime is a special substance that doesn't fit into any of the three usual states of matter. It's categorized as "non-Newtonian fluid." Other non-Newtonian substances include toothpaste and ketchup.


* Name three reasons that animals produce slime. (Animals make slime to move more easily, to communicate, and to defend against predators.)

* How does mucus in the nose help humans? (Mucus prevents dust and debris from reaching our lungs.)

SKILLS SHEETS available at

Snot Signals (T3): Answer questions about a chart showing the properties of snot.

No-Sweat Bubble Test (T10): Complete a multiple-choice reading comprehension test.

Slime Solution (online only): Describe an invention that uses slime to solve a problem.
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Title Annotation:life science
Author:Grunbaum, Mara
Geographic Code:1USA
Date:Oct 1, 2015
Previous Article:Gobs of gum.
Next Article:Ooze-a-Palooza.

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