World's Slimiest Animal Makes Goo That Can Expand 10,000 Times In 0.4 Seconds

As one driver found out the hard way when a truckload of hagfish landed on their car.


Rachael Funnell


Rachael Funnell

Digital Content Producer

Rachael is a writer and digital content producer at IFLScience with a Zoology degree from the University of Southampton, UK, and a nose for novelty animal stories.

Digital Content Producer

hagfish slime

Mess with the hags, you get slime in bags. Image credit: Dirtsailor2003 via flickr, CC BY-ND 2.0 cropped

Nobody does slime better than hagfish. Also known as slime eels, these slippery Myxiniformes have evolved to use goo as a defense mechanism by clogging the gills of predators in less than a second. They’re considered to be the slimiest animals on the planet, capable of producing mucus that expands to 10,000 times its size in 0.4 seconds.

Videos demonstrate how effective hagfish slime is in putting off prospective predators. A particularly good example shows a shark going in for the kill only to instantly abort, presumably with the taste of regret mixed among the ball of gloop stuck in its mouth.



Hagfish slime is formed when seawater interacts with two different ingredients secreted by their slime glands. They include mucin vesicles that rapidly swell and burst in seawater, forming a gloopy net of mucus strands, and threads that are rich in a type of fiber called an intermediate filament (IF). 

These individual IF threads are only 12 nanometers in width but up to 15 centimeters (6 inches) in length. They’re arranged in yarn-like bundles called skeins which consist of conical layers of loops.

To unravel the mystery of hagfish slime and how it explodes into the water so rapidly, researchers on a 2019 paper took a closer look at how the thread cells behave when making contact with seawater. They saw that skeins began unraveling within the time frame of a predator attack (between 100 and 400 milliseconds) and that this can be even faster if the skein is pinned to a surface – like the mouth of a predator.


The skeins can expand to 10,000 times their initial size in this time, creating a generous network of unraveling threads that mucous vesicles can gather on to create a truly troubling ball of gill-invading goo. Exposure to seawater triggers the transformation because it dissolves the protein glue that keeps the bundles held together, releasing the elastic energy stores.

This transforms a mere teaspoon of slime into a beaker full of the stuff in just a few seconds, and you can see one such skein unraveling in the below video that featured in the 2019 paper.


A big problem for predators looking to suck down some eels, then, but on rare occasions, it can present an unexpected threat to humans, too. In 2017, a woman happened to be driving behind a truck transporting 3,400 kilograms (7,500 pounds) of hagfish when something terrible happened.


A traffic cop signaled the truck driver to stop, but the maneuver resulted in a transfer of weight that caused one of the containers to come loose, slide onto the road, and tip over, spilling onto the highway. This included the hagfish.

As you’d expect, the hagfish’s defense mechanism kicked in as they went skidding across the smooth surfaces of the cars piled-up behind the crash, with driver Kim Randall getting most of them.

Goo that expands to 10,000 its original size in 0.4 seconds must sure be something when it’s spilling all over your car roof.

[H/T: Popular Science]


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