Despite simple brains, jellyfish are smarter than we thought

Jellyfish are more evolved than previously thought, according to a new study.

This study demonstrated that the Caribbean box jellyfish, despite having only 1,000 neurons and no centralized brain, can learn at a much more complex level than previously imagined.

This discovery could change our fundamental understanding of the brain and enlighten us about our own mysterious brains.

After more than 500 million years on Earth, there’s no denying that jellyfish have been a huge evolutionary success. Yet we have always thought of them as simple creatures with very limited learning abilities.

The general opinion is that a more advanced nervous system equates to a more advanced learning ability in animals. Jellyfish and their relatives, collectively known as cnidarians, are among the earliest modern animals to have developed nervous systems, and are thought to have very simple nervous systems and no centralized brain. I am.

For more than a decade, neurobiologist Anders Garm has been studying box jellyfish, a group of jellyfish commonly known as one of the world’s most poisonous organisms.

“It was once thought that jellyfish could only manage the simplest forms of learning, including habituation, the ability to get used to certain stimuli, such as a certain sound or a certain touch. Now, jellyfish are much more sophisticated. “We found that they have an excellent learning ability and can actually learn from their mistakes, and in doing so change their behavior,” says Garm, an associate professor in the Department of Biology at the University of Copenhagen.

One of the most sophisticated properties of the nervous system is its ability to change behavior as a result of experience – its ability to remember and learn. Researchers led by Garm Bielecki and Jan Bielecki at Kiel University set out to test this ability in box jellyfish.

The discovery will be published in a magazine current biology.

Scientists studied box jellyfish in the Caribbean. Tripedaria cystophora, a fingernail-sized medusa that lives in the mangrove swamps of the Caribbean Sea. Here, they use their excellent visual system, including their 24 eyes, to search for small copepods among the mangrove roots. While root nests are great hunting grounds, they can also be dangerous for soft jellies.

So when a small box jellyfish approaches a mangrove root, it turns around and swims away. If you change direction too quickly, you won’t have time to catch copepods. But if you turn too late, you run the risk of hitting the roots and damaging the gelatinous body. Therefore, assessing distance is very important for them. As the researchers discovered, contrast is key here.

“Our experiments show that jellyfish use contrast – how dark the roots are relative to the water – to assess the distance to the roots, allowing them to swim away at the right time. What’s even more interesting is that the relationship between distance and contrast changes from day to day due to rainwater, algae, and wave action.

“We find that each time a new hunting day begins, the box jellyfish learns from the current contrast by combining visual impressions and sensations during unsuccessful avoidance maneuvers. This means that only 1,000 neurons Even though there are not (there are about 100 billion of them in our brains), neurons are able to link the temporal convergence of different impressions and learn associations (so-called associative learning). They learn as quickly as advanced animals like fruit flies and rats.”

The new findings shatter previous scientific understanding of the capabilities of animals with simple nervous systems.

“For basic neuroscience, this is pretty big news. It provides a new perspective on what can be done with simple nervous systems. “This suggests that it may have been an evolutionary advantage,” Garm says.

The researchers also determined where learning is occurring in these box jellyfish. This gave them a unique opportunity to learn how to study the precise changes that occur in neurons involved in advanced learning.

“We hope this will become a supermodel system for observing cellular processes in advanced learning in all kinds of animals. We are currently investigating which cells are involved in learning and memory formation. “We’re trying to determine exactly what happens in the cell, so we can look at what structural and physiological changes occur within the cell as learning occurs.” .

Once scientists can identify the exact mechanism involved in learning in jellyfish, the next step will be to find out whether it applies specifically to jellyfish or whether it is found in all animals.

“Eventually, we plan to investigate the same mechanisms in other animals to see if memory works in general,” the researchers say.

This type of breakthrough knowledge could be used for a variety of purposes, Garm says.

“Understanding something as mysterious and so complex as the brain is in itself absolutely amazing. But there are so many useful possibilities that we can’t even imagine. The big questions for the future are: Definitely different forms of dementia.

“I’m not saying we’ve found a cure for dementia, but if we can better understand what memory is, which is the central problem in dementia, we can lay the foundation for a deeper understanding of dementia. “and perhaps counteract it,” the researchers conclude.

Source: University of Copenhagen

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