How does the hydra feel after decapitation and how does it respond to stimuli

Even the simplest creatures seem extremely complicated from the surface
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Fortunately, Hydra makes this part easy

Jacob Robinson, an electrical and computer engineer at Rice University, and Krishna Badhiwala, the lead author and alumnus of the Brown School of Engineering at the university, are using the transparency of this animal to complete the hardest part, manipulating these in almost every possible way.

Very flexible little creatures to understand how they perceive touch

They published a comprehensive analysis of hydras in the open-access journal eLife.

Working with University of California biologist Celina Juliano and University of California graduate student Abby Primack is a small step towards understanding neural networks in all living things

Ordinary polyps (Hydra vulgaris), a freshwater snail that looks like a miniature jellyfish polyp, expand and contract when swimming in the environment, but they can also be prompted to do so by giving them a poke
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In the past ten years, the Rice Lab has developed highly specialized equipment to achieve this, temporarily confining animals to the channels of microfluidic devices to simultaneously capture images and data detailing their muscle and neural responses

There, the hydra can be physically stimulated with a controlled force to make it contract
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In this new study, researchers genetically modified Hydra to express a green fluorescent protein when related neurons are activated, and then remove a group of neurons-even body parts-to see how the network is The reaction when poking an animal

Their goal is to build a model of how internal states and external stimuli shape the behavior of organisms with highly dynamic neural structures
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Robinson said: "We need to establish a foundation for how animals like hydra work from a neurobiological perspective, so that we can start to compare with truly diverse animals
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I can see that in five or ten years, we will There are many very interesting questions to answer, and now we have established some foundations

Neurons in the Hydra are concentrated in the mouth area (near the tentacles) and the distal mouth area (around the feet), but the researchers found two different types of neurons-"mechanical reactivity" and the previously discovered "contraction burst" nerve Yuan-distributed throughout the body
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This helps explain the different discharge patterns they found, depending on whether the hydra contracted spontaneously or triggered mechanically

The researchers also found that both the mouth and the distal mouth area play a role in spontaneous contraction
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The oral area, also known as the suboral plate, is more pronounced; because it seems to coordinate the motor response, they learned that removing the suboral plate completely can significantly reduce the response of the Hydra to stimuli

The distal mouth area, also known as the stalk, seems to contain a high concentration of motor neurons involved in contraction.
This can be demonstrated by the calcium network, which is activated from the feet when triggered by the suboral plate or stimulated by the "headless" polyp
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The most interesting evidence is that when one or the other neural network of the Hydra is removed or cut in half, the remaining neurons pick up the slack to maintain at least the basic function and/or regenerate the lost part
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Robinson said: "When we started to study Hydra, we wanted to understand as much as possible about how it works, its similarities and differences compared to other animals
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One thing we don't know is a specific kind of neural structure
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Especially.
It’s because Hydra has a distributed neural network.
We want to know whether a specific area of ​​an animal processes information in a centralized manner, or whether all neurons are the same
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It turns out that the mouth and far mouth networks are quite different in the way they control different aspects of hydra
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But there seems to be some redundancy and sensory information processing.
We have also seen this in other animals.
This redundant idea is very important to the survival of animals, so it will appear many times no matter where we see it
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Although the radiative nervous system of the hydra is fundamentally different from the neural network of bilateral organisms such as mammals, there are similarities in the way all these systems share the workload when necessary
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Robinson said: "I like to think of it this way: Let's look at all the crazy things that the nervous system has evolved from the same starting point
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This may allow us to determine basic principles that are hard to find in rodents and humans.
In rodents and humans, over time, these principles may be obscured by other things we develop
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Robinson said that neuroscientists who are going beyond traditional small model organisms—rodents, nematodes, zebrafish, and fruit flies—will be most interested in the results of the hydrops
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It is recognized that we do need a diversified selection of the animals we study
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This has also had an impact on scientific initiatives outside of the animal kingdom
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This particular type of nervous system can be fully restored, which makes me think that there are some principles related to the stability of the network
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Inspired by nature, these technologies can be used to stabilize the power grid or the Internet"

Krishna N Badhiwala, Abby S Primack, Celina Juliano, Jacob T Robinson.
Multiple neuronal networks coordinate Hydra mechanosensory behavior.
eLife, 2021; 10 DOI: 10.
7554/eLife.
64108