What Is a Hagfish? And Why Is It So Slimy?

Mark Conlin, Alamy

It's Hagfish Day! We're sure you want to celebrate, but maybe you first want to know: What the heck is a hagfish?

We talked to Andrew J. Clark, hagfish researcher at the College of Charleston, for the lowdown on these wonderfully icky creatures.

Don't Call Him an Eel

The hagfish is sometimes called the slime eel. It's not a true eel, but the "slime" part of that name is right on the money: The hagfish has the unique ability to produce astonishing quantities of disgusting goop.

"They have slime glands that run along the length of their bodies," says Clark. And the stuff is more interesting than just some kind of snot: The glands exude a substance that forms a sort of a netting around water at a molecular level.

How much slime can one hagfish make? Here's Clark's recipe: Take a five-gallon bucket full of salt water and one adult hagfish. Gives its tail a little pinch and stir the water a bit. In just a few seconds, the whole bucket will be full of slime.

Of course, the hagfish didn't evolve this ability so it could fill buckets — it's a defense mechanism. When a predator grabs one, its mouth will be filled almost instantaneously with a huge cloud of nasty slime. With its gills full of gunk that keeps it from breathing, the attacker is likely to spit the hagfish out and try its luck elsewhere.

No Skeleton? No Problem

Despite its nickname, the slime eel,  the hagfish is indeed a fish,  but not a very conventional one. "Hagfish have a lot of primitive traits that are not typical of our general vision of what fish should be," says Clark. "They don't have scales, they don't have eyes, they don't have jaws."

In fact they don't even really have a skeleton — just a few bits of cartilage in the head and tail. This is a little confusing for the human who thinks of fish as vertebrates — animals with backbones — but it's no problem for the hagfish. "Hagfish get by just fine without vertebrae," says Clark. "If they had vertebrae there'd be some impediments to some of the most phenomenal things they can do in the wild."

What kind of phenomenal things would that be? Well, how about this: The hagfish can tie itself into knots.

Awesome, sure — but why do they want to? It has to do with the way they eat. Hagfish are primarily scavengers, so they need to be able to bite chunks off a big carcass. Think of some more familiar animals that eat food bigger than they are, says Clark — like those nature films where you see a crocodile grabbing a zebra and doing that "death roll." That's actually a way of dismembering their prey. "It's effectively increasing how hard they can bite," says Clark, and the knot lets the hagfish do the same thing.


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