How hagfish launch slime missiles that swell 10,000 times in size By Erika K. CarlsonJan. 15, 2019 , 7:01 PM When a hagfish runs into a hungry shark, the eellike creature squirts out a dollop of goo that—in just a few tenths of a second—expands into a slimy mess 10,000 times its original size, choking the shark and chasing it away. Now, a new study suggests hagfish can’t take all the credit for this gooey defense. Motions in seawater might be the reason the slime can spread into a large cloud so quickly.Hagfish slime is made up of microscopic pockets of mucus and tightly wound bundles of stringy fiber dubbed “skeins.” When a drop of goo hits the water (above), the skeins inside can unravel into strings several centimeters long in less than half a second.Researchers took a skein from a hagfish and pulled at one end of the thread, watching it unravel under a microscope. Based on the force needed to pull apart the skein, they calculated how quickly it would unravel under different scenarios. Drag forces from motions in water alone can unravel skeins fast enough to explain the hagfish’s speedy slime defense, the researchers report today in the Journal of the Royal Society Interface. Understanding how hagfish slime expands so quickly, the researchers say, could help us develop novel materials and technologies—though perhaps not asphyxiating nets of goo.