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The Venus Flytrap Countdown

Biologists confirm that Venus flytraps can count to 20.

a close-up image of a Venus Flytrap

Photo: Konstatin Lazorkin (Flickr)

Dionaea muscipula is commonly known as a Venus flytrap.

The Venus flytrap is a carnivorous plant. As a species, it evolved to survive in nutrient-deficient environments by trapping and digesting insects and arachnids to obtain sufficient levels of nutrients such as nitrogen and phosphorus.

When a creature lands inside the flytrap’s jaws, how does it know to clamp down on its dinner? According to experiments undertaken by biologists in Germany: counting is the key.

Electrochemical Signals

While these plants don’t have a nervous system the way that animals do, they don’t think or remember, they certainly sense and respond to stimuli in complex ways. The Venus flytrap’s leaves have trigger hairs that, when touched, transmit an electrochemical signal.

Scientists found the trap would close only when its hairs were triggered twice or more within twenty seconds. If the hairs were triggered twice with a delay longer than twenty seconds, the trap wouldn’t shut. Interestingly, the flytrap’s counting isn’t over once it traps an insect.

Dinner Is Served

It requires at least two more signals. Presumably, they’re from when the insect struggles. An idea is that these signals confirm the catch is food, and once dinner is confirmed, it’s to start releasing digestive enzymes.

Biologists noted the more the trigger hairs were activated, the more digestive enzymes the flytrap produced to dissolve its prey. Counting allows the Venus flytrap to use energy more efficiently by helping it avoid closing its trap for a false alarm.

Doing this also helps it to avoid wasting digestive enzymes, a sensible strategy for a plant that evolved to be carnivorous to survive.

Thank you to Richard Hangarter of Indiana University for reviewing this episode.

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