|Sea anemone with a starry appearance. Photographer: Gaelle Botton-Amiot
A recent study conducted by a group of biologists - two from the University of Fribourg in Switzerland and one from Universitat de Barcelona in Spain - has revealed that a particular type of Cnidaria is capable of associative learning. The researchers behind the study, Gaelle Botton-Amiot, Simon Sprecher, and Pedro Martinez, published their findings in the Proceedings of the National Academy of Sciences.
The concept of associative learning was first discovered by Ivan Pavlov, who observed dogs salivating at the sound of a bell after being trained with treats. Humans also demonstrate associative learning through examples such as avoiding touching a hot stove. This type of learning involves memory and a response to certain stimuli. While associative learning has been observed in various creatures, it was previously believed that a brain was necessary for such learning to occur.
The researchers behind this study questioned whether the brain was a necessary component for associative learning. As the Cnidaria phylum lacks a brain and any known organ responsible for processing neural activity, the researchers decided to focus on starlet sea anemones - a sea creatures with light-responsive organs and retractable tentacles that react to stimuli.
|A starlet sea anemone's head. Photographer: Gaelle Botton-Amiot
In order to explore whether these creatures were capable of associative learning, the researchers gathered several specimens and brought them to their laboratory for observation. The anemones were exposed to a bright light and/or an electric shock, with some receiving both stimuli simultaneously while others received them independently.
Over time, the anemones that received both the light and shock simultaneously learned to associate them as a single event and responded accordingly. The researchers were able to demonstrate this by exposing the anemones to light without applying the shock and observing whether they would still retract their tentacles. The results showed that 72% of the anemones responded as expected, indicating that they were able to remember the association between sudden bursts of light and electric shocks and respond accordingly by retracting their tentacles.
More information: Gaelle Botton-Amiot et al, Associative learning in the cnidarian Nematostella vectensis, Proceedings of the National Academy of Sciences (2023). DOI: 10.1073/pnas.2220685120