The carnivorous Aldrovanda vesiculosa, also known as the waterwheel plant, snaps its "trap" shut ten times faster than the flytrap. As it is quite rare in the wild, the plant's mechanism has not previously been studied in great detail. It is thought that the waterwheel and the flytrap may share a common ancestor. However there is no fossil evidence for what this ancestor might have looked like.
"This is one of the main questions in the carnivorous plant community," says Dr Simon Poppinga, an author on the study. "Snap traps evolved only once in plants. There are two different mechanisms. Which one was first?"
Using a camera recording at 1000fps, researchers triggered the traps using an electrical stimulus. "It's very, very small and it's very, very fast, and this puts you basically to the limits of optical resolution," Westermeier told BBC News.
They realised that the plant's traps are in a constant state of "pre-stress" - tensed to snap shut much like a bear trap - and when triggered by prey they quickly release and close. The team noted that the action of the traps is due to a combination of hydraulics and the release of this pre-stress. At just 2-4mm, the traps are about a tenth the size of a Venus flytrap's, but they close in a remarkable 0.02 to 0.1 seconds.
Researchers hope to do further work investigating the waterwheel's prey spectrum to determine what it feeds on. It is currently thought to have a diet of small crustaceans like water fleas, possibly extending to tadpoles and small fish.
http://www.bbc.com/news/science-environment-44041587
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