Anyone who has ever gone to the trouble of untangling computer cables or tangled Christmas garland knows that untying these bags of knots takes far more time than creating them. However, there is an animal species that achieves this miracle in less time than it takes to utter it.
The earthworm ball disintegrates within milliseconds
THE Lumbriculus variegatus are worms about ten centimeters long that live in the fresh waters of North America and Europe. They are found mainly in the muddy sediments of ponds and lakes and in wet swampy areas.
To preserve moisture and heat, these earthworms like to roll up and form balls with tens of thousands of individuals. But while it takes them minutes to form these compact bowls of living spaghetti, the presence of a predator or threat in their vicinity will cause them to disintegrate in milliseconds!
American scientists analyzed this phenomenon on the pages of the magazine Science by combining ultrasound imaging, computer simulations and theoretical analyses. This allowed them to develop a model to explain the topological dynamics during this almost instantaneous collective disintegration.
Their work was done on “blobs” of about twenty individuals, which they embedded in gelatin so that they would move less and the dispersion would be more easily observed. Then they startled the worms with electric shocks or flashes of UV light and filmed the result, carefully recording the movements of each member of the myriad.
Joint “corkscrew dance”
If the mechanism seems chaotic at first glance, it turns out that each earthworm adopts an ultra-fast spiral rotation, turning very quickly to the left and then to the right to get rid of its partners and cause the structure to dislodge.
Like a sort of collective “corkscrew dance” that allows each worm to detach from its acolytes. If this dance is more like a languid slow “blob” formation and lasts several minutes, it turns into frenetic rock for several tens of milliseconds as soon as danger appears.
In addition to elucidating a fascinating biological phenomenon, the researchers believe their work could have resonance in other fields. For example, it helps to understand how our DNA molecules compact inside our cells. Or enable the development of new materials, such as dressings that change as a wound heals, or soft robotic systems capable of instantly changing shape.