Are Jellyfish Smarter Than We Think?


Dessa: Today is Science Friday. I’m Dessa.

The rest of the time is two stories about the wonderful world of jellyfish. The jellyfish is often admired for his translucent, ethereal beauty and hypnotic movements, but not for his intelligence. He’s not a Scrabble partner. But researchers have discovered that even though these fragile creatures don’t actually have brains, they can learn and change their behavior in response to past mistakes.

Joining me today to talk about this discovery is Dr. Anders Garm. He is an associate professor of marine biology at the University of Copenhagen and one of the authors of a paper on the findings published in the journal Current Biology. Welcome to Science Friday.

Anders Garm: Thank you.

Dessa: So jellyfish don’t have brains. what do they have?

Anders Garm: Oh, they have a lot of stuff. The jellyfish introduced here is a very special jellyfish. They are the jellyfish we call box jellyfish, or box jellyfish. Below the bell there are suspended structures, there are actually four of them, but we call them roparia. And there we have a kind of central nervous system, albeit a very simple one. Therefore, each of these four structures has approximately 1,000 neurons. The nervous system is still there, although not as much.

Dessa: So can you give us a little bit of background here? How many are 1,000 neurons? How many can you find in something as simple as a mouse or a fruit fly?

Anders Garm: Yes, there are many others. Take Drosophila, one of the model systems we use to study the brain, which has 200,000 to 300,000 neurons. There’s a lot more when you pick up the mouse. That’s hundreds of millions. In other words, 1,000 is a very small number.

Dessa: So, could you describe the experiment that you conducted and tell us a little bit about the results?

Anders Garm: Yes. The first thing we did was a series of behavioral experiments. What we really wanted to make sure here is that we were testing natural behavior. That is, these jellyfish are found in the mangroves of the Caribbean and live between the roots of the supports of mangrove trees. So we copied their natural habitat, the mangrove root area, into the laboratory of our setup. There you can change the look of the route imitation you were using.

Even if you’re close, it can give you a low contrast that shows you’re far away. You can let them know they’re nearby with high contrast, just as they are. Alternatively, you can remove contrast completely. And by combining these three different types of root imitations, we were able to combine this low-contrast visual impression that appears close but far away, and only when you hit a root. . When subjected to mechanical stress from a collision, lower contrast actually means closer proximity, and it will learn to avoid it.

Dessa: Okay. There they learned that the gray sticks in the aquarium did not mean distant roots. Were they obstacles that the jellies had to avoid?

Anders Garm: That’s right. So we were tricking them into learning by giving them imitations that appeared farther away than they actually were.

And the other two setups were control experiments. High-contrast roots that never hit showed that when you remove a mechanical stimulus, the mechanical stress of hitting an object, they don’t learn and don’t change their behavior. Conversely, when we used a uniform gray wall with no contrast and found that the animals were constantly bumping into the wall, meaning they received many stress signals from it, visual input Since there was no, the animals did not change or change their behavior. Don’t learn not to avoid walls.

Once again, we see that a combination of visual input, low contrast, and mechanical stress enables learning. This is called associative learning or operant conditioning.

Dessa: So how long did it take them to learn how to avoid these painted stripes?

Anders Garm: That surprised us. I mean, I have to admit that we expected them to learn because it makes a lot of sense that they can learn this in their habitat. However, I was quite surprised at how quickly I learned. Because just repeating these false avoidances and receiving mechanical stimulation would require 3, 4, or 5 or even 6 times, but 3 to 6 times is enough. Because it turns out that

Then they learned the distance contrast and began to avoid it. And this low number of repetitions is essentially comparable to many other animals that are classic in learning experiments, such as flies, crabs, and mice.

Dessa: Once they make the association, yeah – you see these stripes. I’ve learned to avoid it. Because if you don’t, you’ll run into a wall – how long did they retain that information?

Anders Garm: Well, I’m not completely sure. We haven’t yet investigated whether it’s just short-term memory or some kind of long-term memory. But what we can guess is that it doesn’t make sense to them, so they don’t remember it for very long. This is because you need to get the latest information as the water changes. So this is expected to last maybe 30 minutes or 1 hour, after which a re-study will be required.

Dessa: Wow. If you look at the changes in the water, it’s like, if the water is really murky, you need to adjust the level of contrast between things near and far. If you’re a jellyfish, does that mean you have to constantly update it?

Anders Garm: Yes, that’s right. yes.

Dessa: Okay. Now, can you distinguish between this kind of learning and reflexive behavior? Is the jellyfish meant to avoid these obstacles?

Anders Garm: These are different actions. So what’s important about learning is that it’s one of the main mechanisms behind plasticity and behavior. So it’s basically not just a response to a stimulus. This can be said to be a clever or intelligent way of responding to stimuli that relies on past experience. And that’s what distinguishes learning from others. It is not a reflex as it requires prior experience.

Dessa: At the beginning, I said that there is no central system like the brain. There are approximately 1,000 of these neurons throughout the jellyfish’s body. Does that mean that without a centralized processing center, certain parts of the jellyfish can learn things that other parts don’t know?

Anders Garm: Yes. I’d like to make a slight correction here. So they have more than 1,000 neurons, but in the center where they’re learning, he has 1,000 neurons, which he calls part of the rhopalium nervous system. And because this rhopalium can be removed from the animal, we were able to show it in a really nice experiment. And the interesting thing about this is that for simple animals like this, you can take out a body part and then you don’t actually notice that it’s no longer a body part. That’s it. So it still behaves as if you were on top of the jellyfish.

And we have a neural activity fingerprint of this avoidance behavior. So we can actually directly measure what this part of the nervous system is trying to tell the animal whether or not we want it to do that behavior. And that’s how we were actually able to show that that’s happening in these 1,000 neurons.

But you are completely right. The almost philosophical question here is that along the bell he repeats this four times, so if these four roparia are learning, he of that roparia will pass what one has learned to his other The question is whether you can convey this to the four Rhopalia. This is a very interesting question and I would love to explore it. And these are actually future plans that we want to realize.

DESSA: Speaking of future plans, what are the next steps? In your own research, does this lead to the next big question of how jellyfish function in the wild?

Anders Garm: Yes. So what you actually want to do is get it out of the jellyfish. Because we think this jellyfish provides a very good model system for understanding some of the fundamental processes that occur when cells and neural circuits learn, some of the cellular processes.

So using these 1,000 neurons, and this is what we’re doing now, we can create a complete circuit of these 1,000 neurons (what’s called a connectome) and figure out how these neurons We want to be able to map exactly what it looks like and where it is. It is located in the body and how it communicates with synapses.

Once we have this diagram, we can identify which parts of the circuit are most likely involved in these learning processes, depending on how they are connected. We then examine these neurons using both molecular and physiological methods, comparing naïve neurons to neurons that are part of this learning process and determining what actually changes, both at the cellular level. It can be detected whether Even at the circuit level. In this way, we hope to gain a deeper understanding of advanced learning such as associative learning and operant conditioning.

Dessa: Okay. Speaking of associative learning and modifying behavior from past mistakes, the Caribbean box jellyfish is poisonous. Have you ever been stung by a jellyfish yourself during an exam?

Anders Garm: I’ve been stung by many different jellyfish. One of the reasons we chose this very jellyfish, Tripedalia cystophora (commonly known as Tripedalia cystophora), is that it is a copepod eater. And in jellyfish, there is a very close relationship between prey size and venom strength.

And because copepods are very small animals, this animal is almost as poisonous as the common moon jellyfish. And this actually means you have to kiss it to actually feel the poison. Because that’s one of the places where there’s living skin that’s sensitive enough.

Dessa: Oh, I hope you don’t feel that way. Thank you very much for joining us today. That person was Dr. Anders Garm, associate professor of marine biology at the University of Copenhagen in Denmark. Thank you for your time.

Anders Garm: Thank you.

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