The ultra-fast trap of an aquatic carnivorous plant

This marsh seems quiet, but terrible things take place underwater. Stagnant waters are poor in nutrients. Once there, you’ve got to live by your own means [wits]. What use could these little bags be, stuck to bladderwort’s roots? This is a bladderwort’s leaf. It does some favour to the carnivorous plant… But let’s leave the water for a more comfortable place, and take a fragment carrying such small bladder-shaped leaves. A high-speed camera is needed, because … Even slowed down ten times, this remains quick. Let’s slow down much more … The prey comes closer, and … The capture only lasted one millisecond. This small freshwater crustacean is still moving, but the digestive enzymes of the plant are already at work. In a few hours, only its skeleton will be left. And the [carnivorous] plant will be enjoying its precious nutrients. Well, “enjoying”, not always… Small glands pump water to the outside, which creates a depression inside. [The] trap needs around one hour to set. Like in a bow, elastic energy is stored in the deformed material, until both sides almost touch. Here it is, the trap is set, ready to catch its prey! Just touch its sensitive hairs, and it reacts. This is the fastest known underwater trap. Door is the key. When depression inside the bladder is important enough even the smallest perturbation can trigger inversion. Here also, a simulation helps understanding the deformation of the door. It first inverts its curvature and as soon as the doorstep is passed, water flows in the depressed bladder which forces a wide opening. It’s like with this rubber popper toy. [The] curvature inversions can generate very swift movements. Once water has flowed into the bladder, [the door folds back], back to outward curvature ; then the trap is watertight again. Who is the next victim?

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