Popular Science reports on a study from the University of Copenhagen, revealing that Caribbean box jellyfish can actually learn from previous experiences without the need for a brain.
Caribbean box jellyfish can learn without a brain. (Illustrative image).
The brain is a collection of nerve cells that controls the body and is typically encased within a skull. Although the structure of this collection varies significantly among different species, particularly in invertebrates, which often possess a very simple structure known as a ganglion, most animals have some form of nervous center.
Jellyfish are among the few species that lack such a collection, alongside sea cucumbers, sea urchins, corals, and a few other marine animals. However, a research team from the University of Copenhagen found that Caribbean box jellyfish can actually learn from past experiences without needing a brain. They utilize their learning ability in conjunction with a complex visual system to navigate through dark mangrove swamps.
The team created a tank with white and gray stripes simulating the roots of mangrove trees. Initially, the jellyfish swam close to the stripes and frequently collided with the tank walls, but after several encounters, they seemed to associate the gray stripes with the pain of collision and learned to swim away from them. The jellyfish demonstrated a rapid learning capability.
To gain further insights, the team isolated one of the jellyfish’s visual centers known as the rhopalium. Each visual center contains six eyes that generate electrical signals to coordinate movement; when encountering obstacles, they emit multiple signals prompting the jellyfish to change direction.
Neuroscientist Jan Bielecki from the University of Kiel commented that this discovery is significant as it demonstrates that the capacity for learning is an essential aspect of nervous function, which may have evolved very early on and has been preserved across many different species.
According to Bielecki, an organism that cannot alter its behavior based on past experiences is likely to end up in life-threatening situations. Jellyfish are among the oldest creatures on Earth, having existed for over 500 million years.
