Title: Jellyfish Rewrite the Book on Learning Abilities, Challenging Traditional Neuroscience Notions
Subtitle: Study reveals advanced learning capabilities in jellyfish, defying the need for centralized brains
Date: September 22, 2023
In a groundbreaking study published in the journal Current Biology, scientists have discovered that jellyfish possess advanced learning abilities comparable to those of humans, mice, and flies, challenging long-held beliefs about neural learning processes. The research, conducted by a team from Kiel University in Germany and the University of Copenhagen in Denmark, sheds light on the evolutionary origins of learning and memory.
Contrary to their seemingly basic nature, Caribbean box jellyfish (Tripedalia cystophora) possess a sophisticated visual system with 24 eyes embedded in their bell-shaped bodies. Living in murky mangrove swamps, these tiny creatures use their extraordinary vision to navigate around underwater tree roots and capture prey. The researchers successfully trained the jellyfish to recognize and avoid obstacles, demonstrating their capacity for associative learning.
Jan Bielecki, the study’s first author from Kiel University, emphasized the significance of leveraging the animal’s innate behavior to optimize learning outcomes. Bielecki stated, “Learning is the pinnacle performance for nervous systems,” highlighting the importance of aligning training methods with the natural tendencies of the animal.
To recreate the jellyfish’s natural environment, the researchers designed a circular tank adorned with gray and white stripes, resembling distant mangrove roots. Over a 7.5-minute observation period, the jellyfish gradually improved their ability to avoid collisions with the tank’s walls. By the end of the experiment, the jellyfish had increased its average distance to the wall, quadrupled successful pivots to evade obstacles, and halved contact with the wall.
Anders Garm, senior author of the study from the University of Copenhagen, believes that studying the relatively simple nervous systems of jellyfish provides a unique opportunity to unlock fundamental details about complex structures and behaviors. Garm remarked, “Looking at these relatively simple nervous systems in jellyfish, we have a much higher chance of understanding all the details and how it comes together to perform behaviors.”
The researchers also sought to decipher the mechanisms underlying jellyfish’s associative learning. They focused on the animal’s visual sensory centers called rhopalia, which house six eyes and generate pacemaker signals that govern pulsing motions. By exposing the rhopalia to moving gray bars, mimicking the approach of objects, and applying weak electric stimulation during the approach, the researchers found that the structure began to generate obstacle-dodging signals in response to light gray bars. This experiment demonstrated the role of combining visual and mechanical stimuli in jellyfish’s associative learning and identified the rhopalia as a learning center.
The next steps for the research team involve delving deeper into the cellular interactions of jellyfish nervous systems to unravel the mechanisms behind memory formation. Additionally, they plan to investigate the functionality of the bell’s mechanical sensor to gain a comprehensive understanding of jellyfish’s associative learning capabilities.
Anders Garm expressed astonishment at the speed at which jellyfish learn, comparing it to that of more advanced animals. He suggests that even the simplest nervous systems may possess advanced learning abilities, indicating a fundamental cellular mechanism that emerged in early stages of nervous system evolution.
This groundbreaking study not only challenges conventional beliefs about neural learning but also provides a new perspective on the potential for learning and intelligence in simple organisms. The implications of these findings extend far beyond the aquatic realms, pushing scientists to rethink the complexities of the brain and the nature of learning itself.
For more information on this study, refer to “Associative learning in the box jellyfish Tripedalia Cystophora,” published in Current Biology on September 22, 2023.
This research was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), the Danish Research Council (DFF), and the Villum Foundation.