Curious Kids: What in the world is a slime eel?

Researchers pour a barrel of hagfish into a holding tank aboard a research vessel about 20 miles off the coast of Portsmouth, New Hampshire. AP/Steven Senne

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.


What is a slime eel? - Minti F., Ashfield, Massachusetts, 12

A “slime eel” is a very special blind aquatic animal that lives at the bottom of the ocean.

The correct name for these fish is actually hagfish – although the name “slime eel” catches a lot more attention! They have been called the most disgusting creatures in the ocean. Why? Hagfish can burrow into dead or dying animals by entering through mouths or even skin to devour them, sometimes from the inside out.

I am an exotic animal veterinarian especially fascinated by reptiles and other unusual animals. This species has always caught my attention due to their incredible characteristics.

Hagfish play a vital role in the ocean ecosystem and are found around 300 to 600 feet down on the ocean floor. They grow to be about 18 inches long and have tentacles around their mouths.

In 2017, a car got slimed with hagfish after a truck carrying them overturned.

In humans, sweat, tears and saliva are released from glands, but hagfish release something very unusual from their body through two different types of glands. One gland type produces a complicated coiled mucus thread that is estimated to be about six inches long. The other gland type produces something like a slime bubble. This slime can clog the gills of other fishes and protects the hagfish from predators.

On average, a hagfish can produce about one quart (picture two Ben & Jerry’s ice cream pints) of slime. In some cases, a single hagfish can fill a 5-gallon bucket with its slime! This large amount of mucus helps these fish literally slip away from their predators.

In some Asian countries like Japan and Korea, slime eels are considered a delicious food. In South Korea, they are often grilled in markets and sold to eat.

Because they are popular to eat, some hagfish populations are fished too much. Fishermen in the United States catch them and send them overseas to be eaten. The U.S. government has created rules to limit the number of slime eels fishermen can catch.

While they may be called disgusting, I find them fascinating creatures that cover an important role in marine ecosystems.

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