Researchers from the California Institute of Technology have genetically modified a jellyfish to allow them to view the neural activity of the creature in order to understand how its brain works, according to a peer-reviewed paper published in the journal Cell on Wednesday.
The research was conducted on a Clytia hemisphaerica, a jellyfish that is only about one centimeter in diameter when fully grown. The researchers genetically modified the jellyfish so that its neurons individually glowed when activated. They were then able to watch the neural activity of the transparent creature as it behaved naturally.
The researchers were interested in studying jellyfish brain activity because they are an extreme outlier in laboratories. Worms, flies, fish and mice are more commonly used as they are all most closely related, genetically.
"Jellyfish are an important point of comparison because they're so distantly related," said Brady Weissbourd, the first author on the study and a postdoctoral scholar, according to Caltech. "They let us ask questions like, are there principles of neuroscience shared across all nervous systems? Or, what might the first nervous systems have looked like?"
Weissbourd stressed that a broad study of nature could aid the discovery of useful biological innovations.
Jellyfish brains, unlike human brains, are distributed throughout their entire bodies, with each body part seeming to act autonomously. A jellyfish mouth removed surgically can continue to "eat" even without the rest of the animal's body.
The scientists wondered how this decentralized nervous system manages to coordinate and orchestrate behavior. They began by observing the neural behavior when the jellyfish eats.
When the jellyfish snags a brine shrimp, it folds its body to bring the tentacle to its mouth while also bending its mouth towards the tentacle, raising the question of how it manages to do this with a brain that seems to be unstructured and radially symmetric.
After observing the neural activity, the team determined that a subnetwork of neurons that produces a particular neuropeptide, a molecule produced by neurons, is responsible for the folding of the body. The observation of the system also helped the researchers realize that the neuron network was actually surprisingly organized.
"Our experiments revealed that the seemingly diffuse network of neurons that underlies the circular jellyfish umbrella is actually subdivided into patches of active neurons, organized in wedges like slices of a pizza," said David Anderson, director of the Tianqiao and Chrissy Chen Institute for Neuroscience at Caltech, according to the university.
"Importantly, this level of neural organization is completely invisible if you look at the anatomy of a jellyfish, even with a microscope," he said. "You have to be able to visualize the active neurons in order to see it – which is what we can do with our new system."
Weissbourd added that they have only scratched the surface of what they can learn about jellyfish behavior and nervous systems in general. "The ultimate goal is not only to understand the jellyfish nervous system but to use it as a springboard to understand more complex systems in the future."