A Hagfish Can Make a Bucket of Slime in Less Than Half a Second

On July 13, 2017, a flatbed truck on U.S. Route 101 in Oregon braked too hard, lost a 7,500-pound load of live hagfish, and turned a stretch of highway into a translucent, snot-grey field that took the state DOT and a bulldozer the rest of the day to clear. The hagfish were not unwell. They were doing what hagfish do.

A hagfish is a primitive, jawless, eel-shaped fish that has been refining the same defensive trick for roughly 300 million years. When it senses a predator's bite, slime glands along its flanks eject a packet of mucin and tightly coiled protein threads. The threads, made from variants of keratin, are stored as compact bundles called skeins. The instant they hit seawater they unspool — each skein contains roughly 15 cm of thread — and bind enormous amounts of water around them. The packet inflates by a factor of about 10,000 in 0.4 seconds, which means a teaspoon of slime concentrate becomes several liters of viscous mesh almost instantly.

What that mesh does is suffocate. Footage from labs in British Columbia and Washington shows sharks and pollock biting a hagfish, releasing it within a second, and then thrashing as the slime clogs their gill rakers. The hagfish, indifferent, ties itself in an overhand knot and slides the knot tail-to-head along its body to wipe its own gills clean before swimming off.