For a start, it’s not sticky. If there wasn’t so damn much of it, you’d be able to wipe it off your skin with ease. The hagfish themselves scrape the slime off their skin by tying a knot in their bodies and sliding it from head to tail.

The slime also “has a very strange sensation of not quite being there,” says Fudge. It consists of two main components—mucus and protein threads. The threads spread out and entangle one another, creating a fast-expanding net that traps both mucus and water. Astonishingly, to create a liter of slime, a hagfish has to release only 40 milligrams of mucus and protein—1,000 times less dry material than human saliva contains. That’s why the slime, though strong and elastic enough to coat a hand, feels so incorporeal.

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Indeed, it’s one of the softest materials ever measured. “Jell-O is between 10,000 and 100,000 times stiffer than hagfish slime,” says Randy Ewoldt from the University of Illinois at Urbana-Champaign, who had to invent new methods for assessing the substance’s properties after conventional instruments failed to cope with its nature. “When you see it in a bucket, it almost still looks like water. Only when you stick your hand in and pick it up do you find that it’s a coherent thing.”

The proteins threads that give the slime cohesion are incredible in their own right. Each is one-100th the width of a human hair, but can stretch for four to six inches. And within the slime glands, each thread is coiled like a ball of yarn within its own tiny cell—a feat akin to stuffing a kilometer of Christmas lights into a shoebox without a single knot or tangle. No one knows how the hagfish achieves this miracle of packaging, but Fudge just got a grant to test one idea. He thinks that the thread cells use their nuclei—the DNA-containing structures at their core—like a spindle, turning them to wind the growing protein threads into a single continuous loop.

A microscope image of a hagfish’s coiled slime thread (Courtesy of Douglas Fudge)

Once these cells are expelled from the slime glands, they rupture, releasing the threads within them. Ewoldt’s colleague Gaurav Chaudhury found that despite their length, the threads can fully unspool in a fraction of a second. The pull of flowing water is enough to unwind them. But the process is even quicker if the loose end snags on a surface, like another thread, or a predator’s mouth.

Being extremely soft, the slime is very good at filling crevices, and scientists had long assumed that hagfish use it to clog the gills of would-be predators. That hypothesis was only confirmed in 2011, when Vincent Zintzen from the Museum of New Zealand Te Papa Tongarewa finally captured footage of hagfish sliming conger eels, wreckfish, and more. Even a shark was forced to retreat, visibly gagging on the cloud of slime in its jaws.

“We were blown away by those videos,” Fudge says, “but when we really looked carefully, we noticed that the slime is released after the hagfish is bitten.” So how does the animal survive that initial attack? His colleague Sarah Boggett showed that the answer lies in their skin. It’s exceptionally loose, and attaches to the rest of the body at only a few places. It’s also very flaccid: You could inject a hagfish with an extra 40 percent of its body volume without stretching the skin. The animal is effectively wearing a set of extremely loose pajamas, Fudge says. If a shark bites down, “the body sort of squishes out of the way.”