News Animals

These brainless jellyfish use their eyes and bundles of nerves to learn

The animals haven’t been shown to change their behavior based on past experiences, until now

A photo of a Caribbean box jellyfish on a dark background.

Fingernail-sized Caribbean box jellyfish use their 24 eyes to spot and dodge mangrove roots that might damage their fragile bodies.

J. Bielecki

By Maria Temming

For Caribbean box jellyfish, learning is literally a no-brainer.

In a new experiment, these animals learned to spot and avoid obstacles despite having no central brain, researchers report September 22 in Current Biology. This is the first evidence that jellyfish can make mental connections between events — such as seeing something and running into it — and change their behavior accordingly.