What Is Hagfish Slime, and Why Is It So Powerful?

Undersea animals are some of the most interesting on Earth, and hagfish are no exception. These fish resemble eels and produce slime that protects them from predators. Their slime is unique, valuable, and strong, giving them distinct advantages in the wild.

In a video of the hagfish on YouTube, shared by Ocean Wise, you can see the gray and pink fish stretched out snake-like as it swims in water. A hand reaches out to grab the fish, which is much smaller than you might expect—the hand is able to grasp the entire fish at once.

But the most interesting part of the video occurs around the 0:20 mark, when the person lifts the hagfish out of the water tank. Their hands are covered in a clear, sticky slime produced by the hagfish. The person pulls out sheets of slime from the hagfish, demonstrating just how much goo this animal produces.

In the caption, Ocean Wise wrote, “Hagfish have the outstanding ability to defend themselves by producing an incredible slime when touched. It comes from the glands along the side of their body, and within minutes, literally liters of it can be produced.”

“Despite being one of the most primitive vertebrates alive, this rare species is certainly strange and wonderful!” they added. “Our oceans harbor amazing species that, despite being a bit weird, are still worth protecting.”

How Does a Hagfish Produce Slime?

Hagfish produce their slime from 100 glands on both sides of their bodies. They can deploy their slime in less than half a second, expanding up to 10,000 times its ejected volume. Talk about a cool skill to have!

This slime is less like Nickelodeon slime and more like a thick, sticky, milky, fibrous mucus. It’s composed almost entirely of seawater, along with mucus and silk-like proteins. Hagfish produce slime at different times, such as when eating, burrowing, or escaping from predators.

The slime contains threads that are 100 times thinner than a strand of hair. It is strong, robust, and durable, and research has shown that slime threads are similar to spider silks when stretched. Some reports have even found that hagfish slime is 100,000 times softer than Jell-O. And they make a lot of it. Two 2-foot-long hagfish can fill a 5-gallon bucket with slime.  

What Are the Benefits of Hagfish Slime?

Slime helps hagfish in several ways. The hagfish can tie itself into an overhand knot from head to tail, a movement made easier by the smooth slime. This position helps the hagfish avoid being eaten by predators and allows it to remove excess slime, which can suffocate it if it accumulates.

Their slime also helps hagfish squeeze through openings that are less than half of their body width. If a fish gets close enough to try to eat the hagfish, the slime can clog the predator’s gills, deterring the attack. Hagfish can also shoot jets of slime into a predator’s mouth to choke it.

Some people eat hagfish, which are often skinned and then grilled or stir-fried. In Korea, hagfish slime is considered a delicacy and is sometimes used as a substitute for egg whites. Other animals also recognize the benefits of this slime. The hokku clam, for example, will seek out hagfish slime to line its burrow.

Hagfish Live in Every Ocean

This fish is considered a primitive species, meaning it hasn’t changed its anatomy significantly in its 300 million years on Earth. Hagfish are found in most of the world’s oceans, especially in cold saltwater regions such as the North Pacific, Atlantic, and Southern oceans.

When feeding, they use their rasping tongues and rows of teeth to pull prey into their mouths, including bottom-dwelling worms and fish. They are also scavengers, feeding on animal carcasses on the ocean floor by burying their faces and eating from the inside out. They have no stomachs but absorb nutrients through their skin. Hagfish help keep the seafloor clean by consuming decaying animal matter, playing an important role alongside other scavengers and decomposers in ocean ecosystems.

Predators like marine mammals and diving birds can often attack hagfish without getting caught up in their slime. However, hagfish also have to worry about human predators. Hagfish are often hunted for their skin, which is marketed as “eel leather” and used to make wallets, purses, and belts, particularly in South Korea and Japan.

This is one reason why a significant proportion of the approximately 80 hagfish species are considered at risk of extinction, with recent estimates suggesting about 20% may be threatened. Overfishing and habitat loss are among the biggest threats to hagfish. If hagfish were lost, it would disrupt ocean ecosystems. That’s why it’s important to support deep-sea creatures like hagfish.