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A discovery that ‘truly changed the textbook’

Finding that

Behold, Gar’s brain. In the microscope image, the left hemisphere of the brain glows green and the right side glows magenta. But at the bottom of the picture one can see nerves of both colors that connect to both hemispheres. This shows that Gar’s two eyes are connected to the same brain as the human eye. Credit: Reprinted with permission from RJ Vigouroux et al. Science 372: eabe7790 (2021).

The network of nerves that connect our eyes to our brains is complex, and researchers have now shown that they develop much faster than previously thought due to an unexpected source: the crow. A

Michigan State University’s Ingo Braasch has helped an international research team show that this connection scheme existed in ancient fish at least 450 million years ago, making it about 100 million years older than previously believed.

“This is the first time for me that our publication has truly transformed the textbook I teach,” said Braasch, assistant professor in the Department of Integrative Biology in the College of Natural Sciences.

This work is published in journals. science April 8 also means that this type of eye-brain connection happened before the terrestrial animals. The existing theory is that this connection first developed in terrestrial life and from there to humans, where scientists believe it helps in our depth perception and 3D vision.

And this work, led by researchers from the French public research organization Inserm, does more than just modify our understanding of the past. It also has implications for future health research.

Studying animal models is an invaluable way for researchers to learn about health and disease. But linking to the human condition from these models can be challenging.

For example, Zebrafish is a popular prototype. But walking, eyesight and brain are very different from humans. In fact, that explains why scientists think that human connections first emerged in four-legged terrestrial organisms, or tetrapods.

“In modern fish, they don’t have an eye-to-brain connection,” said Branch, “that’s one of the reasons people think they are new in tetrapods.”

Braasch is one of the world’s leading experts on a different type of fish known as gar gar.It evolves more slowly than zebra fish, meaning that gar is similar to the common ancestor of fish and humans. These similarities could make Gar a powerful animal model for health studies, which is why Braasch and his team are working to understand gar’s biology and genetics.

That is why Inserm researchers searched Braasch for the study.

“Without his help, this project would not have been possible,” said Alain Chédotal, Inserm research director and group head of the Vision Institute in Paris. In Europe and occupies an important position in the tree of life. “

To conduct this study, Chédotal and his colleague Filippo Del Bene used a novel technique to view the nerves that connect the eyes to the brain in many fish species. This includes some very well studied zebrafish. But there are also rare specimens, such as the Australian Braasch and Lung Fish, prepared by collaborators at the University of Queensland.

In each zebra, one nerve is connected to the brain of the opposite fish. That is, one nerve connects the left eye to the right brain and the other right eye to the left brain.

Other “ancient” fish do things differently. They have what is known as the ipsilateral or bilateral projection here.Each eye has two nerves connected by one to either side of the brain, which is also what humans have.

With an understanding of genetics and evolution, the team was able to go back in time to estimate when these bilateral predictions first appeared. Looking ahead, the team is excited to create this work to better understand and explore the biology of imaging systems.

“What we found in this study is just the tip of the iceberg,” Chédotal said. “It was a huge motivation to see Ingo’s enthusiastic reaction and warm support when we presented him with the first results. We can’t wait to continue our project with him.”

Both Braasch and Chédotal noted how effective the study was, thanks to its strong collaboration that allowed the team to examine a number of animals, which Braasch said was a growing trend in the field.

The study also reminded Braasch another trend.

“We have seen more and more that many of the things that we thought were relatively slow evolving were really old,” Braasch said, which made him feel a little more connected to nature. “I learned something about myself looking at these strange fishes and understanding how old our body parts are. I am excited to be able to tell the story of the evolution of the eye with the new changes in the film.” This study in our comparative anatomy class ”

Fish reveal the secret of limb restoration.

More information:
“Bilateral projections exist in non-mobile hard bony fish and preceded the emergence of tetrapods.” science (2021) .sciencemag.org/cgi/doi … 1126 / science.abe7790

Provided by Michigan State University

Reference: Discovery that ‘truly changes the textbook’ (2021, April 8). Retrieved on April 8, 2021 from https://phys.org/news/2021-04-discovery-literally-textbook.html.

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