Even with no brains, jellyfish can learn from their mistakes


Image of a nearly transparent jellyfish with relatively thick tentacles.
Expanding / They don’t have brains, but they still have some smarts.

They have no brain or spinal cord. They seem to be drifting aimlessly. Jellyfish don’t have a central nervous system, but these gelatinous creatures show once again that they may be thinking more than we realize.

Jellyfish, or jellyfish, belong to the phylum Cnidaria, whose members are already known to be capable of associative learning. This allows them to maintain awareness of their surroundings (and potential predators). Now, an international team of scientists has discovered that cnidarians are capable of a more advanced type of associative learning known as operant conditioning. This requires remembering the positive or negative effects of previous actions. Despite lacking a brain, the Caribbean box jelly (Tripedaria cystophora) can learn from their mistakes to avoid potentially disastrous consequences.

damage control

T. cystophora About the size of a human fingernail, it has a visual system that is far less complex than humans and other vertebrates, but still quite sophisticated for a jellyfish. Jelly has her 24 eyes around the body and needs them. They live in mangrove swamps and bumping into long roots in murky water is almost inevitable, and in such encounters the jellies can cause severe damage to their delicate bodies. Its vision helps it navigate between roots and is especially helpful in avoiding those nasty tangles.

This inspired Jan Bielecki and his research team at the University of Kiel in Germany to simulate that environment in the lab and see how jellyfish cope. More specifically, they wanted to determine whether the jelly could learn from its mistakes.

“There are several mechanisms that shape behavioral plasticity, but the influence of past experience, or memory formation and learning, is arguably the most important,” Bielecki and colleagues recently published in Current Biology. stated in a study conducted.

To test the jellies’ obstacle avoidance behavior (OAB), the researchers covered the walls of a round aquarium with stripes that resembled the roots of the creatures’ natural habitat. White stripes imitated nearby roots, and gray stripes appeared. As if you were far away. From the jellyfish’s perspective, the gray stripes seem like something they don’t need to worry about right away, even though they’re the same distance away as the white stripes.

The jelly got off to a bad start, frequently crashing into the wall in the gray striped area. In just seven and a half minutes, the situation changed dramatically. At that point, the jelly remained 50% farther from the gray stripes than it was initially. The jellies tended to pulsate through the water at a faster rate when faced with visible obstacles, and they swam faster when gray stripes were visible. This suggested operant conditioning.

Look, mama, I don’t have a head.

Since a real brain doesn’t help jellyfish understand their environment, something else needed to guide them, so the researchers dissected the jellyfish and studied its nervous system to find out what it was. .

Jellyfish do not have brains, but they do have structures called rhopalia. Six eyes are connected to each of these visual sensory centers, giving the jelly a sense of the rhythm of its movement.

Although the isolated rhoparia were unable to move, the researchers placed a gray bar in front of each rhoparia, as if the nerves were still attached to the moving jellyfish and pointed toward the obstacle. moved. In in vitro experiments, weak electrical shocks were sent into the rhopalium to stimulate actual collisions. Roparia soon began emitting warning signals of its own. The scientists considered this response to be further evidence that the jellyfish had learned from the collisions in the aquarium. If the rest of the body were attached, these signals would have told the jellyfish to deflect and flee.

Operant conditioning is expected behavior in bilateral animals such as arthropods, molluscs, and vertebrates. This is the first time this condition has been observed in a non-symmetrical animal. However, although cnidarians have fundamentally different nervous systems, the cnidaria and birataria groups are actually siblings. This may provide further insight into the evolution of more complex nervous systems like ours.

“[The relationship between these two groups] “This suggests the intriguing possibility that high-level neural processes such as operant conditioning are fundamental properties of all nervous systems,” the researchers wrote in the same study.

Further research may reveal more complex structures within the seemingly simple nervous systems of jellyfish and other cnidarians.Humans may be proud of their huge and complex brains, but jelly-like T. cystophora It may help us understand how our brain evolution began.

Current Biology, 2023. DOI: 10.1016/j.cub.2023.08.056



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