Ingredients of hagfish slime revealed

But knowing the recipe only deepens the puzzle

Scientists have now figured out the recipe for what might be the most repulsive slime this side of a movie screen; the goo released by annoyed hagfish. Too bad knowing the recipe isn’t enough to control the stuff.  

EXTREME SLIME A long, skinny hagfish defends itself by releasing substances that react with seawater to make a sudden blob of smothering slime. To collect slime, researchers anesthetize the fish out of water and milk the mucus. Timothy Winegard

When seized by a predator, or even just    agitated, the Atlantic hagfish and its relatives release an odd substance that instantly reacts with seawater to become a huge slippery mass of goo. A hagfish can bloop out a liter or so in less than a second, says marine biologist Douglas Fudge of the University of Guelph in Canada.

“It’s hard to exaggerate about hagfish slime,” Fudge says. Glands in the fish spurt out a mix of little disc-shaped containers, or vesicles, and skeins of wound-up protein fiber that’s finer than spider silk. On contact with seawater, the vesicles burst. At the same time, the skeins unwind, a single cell’s filament stretching as long as 10 centimeters. The slime mix traps remarkable amounts of seawater and quickly swells.

The deployed slime ends up being mostly seawater, which is why first-timers plunging a hand into a bucket of the stuff are surprised, Fudge says. “If you blew your nose for a year — it’s not like that.” Instead it’s less gooey and tastes — Fudge says he’s relying on secondhand information — like seawater.

He and his colleagues have now analyzed the contents of the Atlantic hagfish slime’s fluid component, they report online March 12 in the Journal of Experimental Biology. The ingredients include high concentrations of a type of organic compound known as methylamines.

Finding methylamines in hagfish slime was exciting, says Fudge, because it had the potential to answer a puzzling question. For years, Fudge has wanted to know how vesicles avoid bursting prematurely inside the fish, an insight that might lead to better stabilizing compounds for keeping research stocks of slime in the laboratory fridge. So Fudge and his colleagues embarked on studies to determine the precise ingredients and stabilizing powers of Atlantic hagfish slime’s fluid component.

Analyzing the fluid parts of what the fish releases, Fudge and his colleagues found high concentrations of intriguing methylamines such as trimethylamine oxide. It’s familiar to fish physiologists as one of the substances that enriches the tissues of sharks and rays and keeps saltwater from drawing their body fluids out through osmosis. The researchers thought they had found one of the secret stabilizing ingredients.

But experiments with an artificial soup made by following the hagfish slime recipe and with naturally exuded fluid — the researchers anesthetize hagfish and gently milk their glands into air — still produced spontaneous slime explosions, the researchers report. “Maybe the gland is pressurized,” Fudge muses.

“Hagfish are rather fond of trashing reasonable hypotheses,” comments Frederic Martini of the University of Hawaii at Manoa, another researcher who has studied them.

“Doug will sort it out eventually,” Martini says. “But hey, people have been trying to figure out hagfish reproduction for 400 years, and we still haven’t done so.”  

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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