By studying the mucus of hagfish under the microscope, and by building a mathematical model, researchers now understand the mechanisms that allow the viscous substance emitted by the fish to swell in a few tenths of a second to reach 10,000 times its initial size.
We already know the clever ploy of the cuttlefish and aquatic mollusks that escape its predators by plunging them into a black ink mist. But here is another animal with a similar talent: hagfish. Resembling an eel, it is able to defend itself by projecting into the water not ink, but a viscous mucus that allows it to obstruct the gills of its attackers.
A few years ago, researchers managed to seize the anguilliform animal in action. But the precise mechanism allowing the mucus to "swell" in just a tenth of a second - to reach up to 10,000 times its initial size - remained an enigma.That was before the work of American researchers, who managed to build a mathematical model reproducing the expansion of the "slime" projected by the hagfish
As they explain in a publication published in the Journal of the Royal Society Interface, scientists devoted themselves to the study of hydrodynamic processes related to the spectacular deployment of small balls of mucus projected into the water by the hagfish . And to their surprise, they discovered - under the lens of a microscope - some amazing secrets related to the mechanism.
Well hidden secrets
At the heart of the mucus hides tiny fibrous clumps - called "skeins" - which expand and take the form of cords several inches long in less than half a second. The secret of the mucous inflation of the hagfish finally uncovered!
It remained to researchers to determine if the forces related to the movements of water - turbulence - could alone explain the uncoiling of the skeins. And that's where mathematics came to the rescue of scientists.
Balls of mucus that unfold like tape
By building their model, the researchers were able to simulate the process of the small unfurling balls of mucous. "Our model revolves around the idea of a small element that hangs at first, and [that is] then pulled. Imagine a roll of tape. To begin unrolling the ribbon of a new roll, you may have to look for the beginning, and take off with your fingernail. But if there is already an accessible end, it's easy to catch it with a few things and start [unfolding the ribbon],” says Jean-Luc Thiffeault, professor of mathematics at the University of Wisconsin in Madison.
The forces generated by the movements of water are thus sufficient to unroll the tiny fibrous clusters, and thus to swell the balls of mucus up to 10,000 times their initial size. "When a shark closes its mouth, it actually causes turbulence. This creates faster flows, the kind of stuff that provides [the spark] needed for this kind of thing to happen,” concludes Jean-Luc Thiffeault. The unstoppable mucus of hagfish now has no secrets for us! For the shark, however, there will always be an inextricable trap.
Check out the video above for more on the intriguing hagfish...