Remarkable Discovery: Jellyfish Can Learn Without a Brain, Scientists Find

Humans, with our big, meaty brains, often take the concept of learning for granted. We learn to read, tie our shoes, and even gather less practical knowledge, like facts about jellyfish. But here's a fascinating new tidbit: jellyfish can learn too. This revelation may come as a surprise because these seemingly simple sea creatures lack a conventional brain. However, a recent study has unveiled that jellyfish can adapt their behavior based on past experiences.

Jellyfish stand in stark contrast to more complex organisms like vertebrates and mollusks. Even compared to most multicellular life forms, they are exceptionally basic—only sea sponges are less advanced. Instead of a centralized brain, jellyfish, such as the minuscule Caribbean box jellyfish (Tripedalia cystophora), possess scattered neurons throughout their transparent bodies. These neurons are concentrated near their eye-like structures called rhopalia, serving as processing centers for visual information. The groundbreaking study suggests that learning might be an inherent function of these neurons, taking place in jellyfish despite the absence of a conventional brain.

In a study published in the journal Current Biology, Jan Bielecki and a team from Kiel University placed Caribbean box jellyfish in tanks with patterned walls to observe changes in their behavior. Some jellyfish were put into tanks with black and white striped walls, mimicking mangrove roots that jellyfish might encounter in their natural habitat. Their natural instinct is to avoid colliding with these roots, as such collisions could harm their delicate bodies. In contrast, other jellyfish were placed in tanks with fainter gray stripes, imitating more distant obstacles.

As expected, the researchers observed that the jellyfish in the boldly striped tank never touched the walls, perceiving them as immediate threats. However, those in the tank with fainter stripes initially drifted into the walls frequently. Intriguingly, after just a few minutes, the behavior of the jellyfish in the latter tank began to change. They started swimming 50% farther away from the walls and turned around more frequently. It became evident that they had learned that these obstacles (the walls) were much closer than initially perceived.

According to the researchers, this fascinating outcome indicates that the jellyfish learned that their instinct was inaccurate and adapted their behavior accordingly. Although using the term "mind" might not be entirely appropriate in this context, the research team conducted experiments where they extracted visual neurons from jellyfish. They exposed these neurons to faintly striped patterns while applying electric pulses to simulate collisions. Astonishingly, within minutes, these neurons began signaling the detached animal to turn around in response to the image.

These findings not only shed light on the remarkable capabilities of jellyfish but also have implications for our understanding of more complex life forms. Scientists believe that this line of investigation could help uncover the biological origins of learning, a process that has played a pivotal role in humanity's rise as the dominant form of life on Earth."