Why Don’t Jellyfish Have Brains? Exploring the Unique Nervous Systems of Jellyfish

KOMPAS.com – Jellyfish are planktonic marine members of the class Scyphozoa (phylum Cnidaria), which is a group of invertebrate animals consisting of around 200 species.

Jellyfish have several unique features. One of them is that this soft animal does not have a brain, which is an important organ for living creatures.

Most animals have some kind of centralized nerve center, aka a brain, although many only have simple versions called ganglia or concentrations of nerves that control other nerves around them. So, why don’t jellyfish have brains?

Jellyfish don’t have brains, but they still have nerves

Reporting from PBS Nature, jellyfish do not have a central nerve, but jellyfish have two nervous systems.

Also read: What Does the Oldest Jellyfish Fossil Ever Found Look Like?

Jellyfish have large nerve nets that control their swimming ability and small nerve nets that control all other behavior.

Tiny nerve networks throughout the jellyfish’s body allow the animal to know where parts of its body are and act according to that knowledge, for example a jellyfish can use a single tentacle to move prey to its mouth.

Meanwhile, the large nerve net covers the rhopalia, finger-like structures on the edge of the jellyfish’s “bell.” It contains crystals that allow the jellyfish to sense up and down movements and tiny pigment spots that may allow the jellyfish to sense light, chemicals, or a combination of both.

Each rhopalium helps coordinate swimming movements so it is not surprising that most of them are located near the swimming muscles.

Also read: Is it true that jellyfish don’t have hearts?

Rebecca Helm, a researcher at the Woods Hole Oceanographic Institute, said jellyfish have a network of cooperative nerve bundles that communicate with each other and several centralized nerve sacs, but do not have a main controller.

According to Helm, this is good for the jellyfish when, for example, a turtle bites off part of its body. The reason is, that is not the end of everything because jellyfish can still live even if they lose part of the server.

So far, scientists can only speculate why jellyfish did not evolve a nerve center or brain.

Helm explained that the ancestors of jellyfish branched to one side of the tree of life, so it is possible that the evolution of a centralized nervous system occurred early on on the branch where humans are located, but jellyfish are not included in it.

Also read: What Does the Newly Discovered Strange Jellyfish with 24 Eyes Look Like?

However, the simple nervous system that jellyfish have helps these animals survive well, Helm said.

It’s also important to remember that even though jellyfish don’t have brains like most other living creatures, they still have nerves.

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2023-09-09 11:00:00
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