How do Venus flytraps snap shut catching prey in seconds?

A Venus flytrap is a meat-eating plant that catches its own food.

Their leaves look a bit like tiny jaws. Inside each leaf are tiny hairs. If an insect, fly or even small frog brushes against the hairs twice in a short time, the trap snaps shut very quickly - usually in less than a second.

For years scientists wondered exactly what made the trap shut so quickly.

Now new research has shed light on the natural wonder of the Venus flytrap.

"When scientist Charles Darwin saw these plants move so fast, he was convinced that the plant had a muscle inside, but plants do not have muscles and they do not have nerves," said Dr Yoël Forterre, a physicist at the French National Centre for Scientific Research (CNRS) and Aix-Marseille University, lead author of the research.

For a long time, many scientists thought the trap might close because water moved and shifted around inside the plant's leaf.

The idea was that, after the hairs were touched, water would shift from one side of the leaf to the other.

That would make one side puff up and the other side become smaller, a bit like a squishy toy changing shape when you squeeze it.

Scientists thought that if this happened fast enough, the leaf could bend and shut.

But a team of scientists wanted to test that idea.

They measured how quickly water can move through a Venus flytrap leaf. They found it takes about 30 to 60 seconds for water to travel from one side to the other.

Which is far too slow for how quickly the leaf snaps shut.

A Venus flytrap does not take half a minute to close. It usually snaps shut in under a second.

Now the scientists think water movement through the leaf cannot be the only way the leaf is able to close so quickly.

While the trap is open, different parts of the leaf are pulling in different directions. If one part suddenly becomes less stiff, the leaf can quickly flip into a new shape.

The scientists think that when an insect touches the tiny hairs, the plant sends a very fast electrical signal across the leaf.

This is like a quick message telling the rest of the trap that something has landed on it.

As soon as that message arrives, the outside of the leaf becomes less stiff. The inside stays firmer. That difference helps the trap to snap shut very quickly.

Dr Forterre said: "Plants are just amazing. It makes you realise how all plants can sense their surroundings, transport information, react, defend themselves [and] feed."