by An unusual flashing fish is helping scientists understand more about how human ancestors transitioned to life on land from water millions of years ago.
Life on Earth is thought to have first begun in the ocean about 3.5 million years ago.
As the oxygen in the atmosphere increased over time, the descendants of these organisms began living in shallower waters and eventually moved onto land.
Over millions of years, as animals began to adapt to life on land, they developed limbs and swapped gills for lungs.
Scientists believe that the ability to blink in humans and tetrapods (four-legged animals) also evolved during the transition from water to land.
But the researchers said studying this behavior has been challenging because the anatomical changes that enable blinking are mostly in soft tissue, which isn’t preserved in the fossil record.
So experts in the US wanted to investigate whether mudskippers — a type of fish that can live on both land and water — could provide any clues.
Mudskippers are thought to be the only fish that can blink: other aquatic creatures with eyes don’t have moving eyelids.
Instead, they have a clear eye shield in place permanently.
Researchers have found that mudskippers blink for the same reasons humans and other animals do: to clean and protect their eyes.
Thomas Stewart, assistant professor of biology at Penn State University in the US, said: “Animals blink for many reasons.
“It helps us keep our eyes wet and clean, it helps protect our eyes from injury, and we even use blinking for communication.”
He added: “The transition to life on land required many anatomical changes, including changes to nutrition, locomotion and breathing air.
“Based on the fact that mudskipper blinking, which evolved completely independently of our fish ancestors, performs many of the same functions as blinking in our lineage, we think it was probably part of the set of traits that they evolved when tetrapods were adapting to live on land.”
Scientists have analyzed many videos of mudskippers to understand more about the mechanism involved in their blinking.
These fish blink by lowering their eyes into a fleshy lower eyelid — known as a dermal cup — and it lasts about the same duration as a human blink.
Brett Aiello, assistant professor of biology at Seton Hill University, said: ‘Blinking in mudskippers appears to have evolved through a rearrangement of existing muscles that changed their course of action and also from the evolution of a new tissue, the cup. dermal.
“This is a very interesting result because it shows that a very rudimentary, or basic, system can be used to conduct complex behavior.
“You don’t need to evolve a lot of new things to evolve this new behavior. Mudskippers just started using what they already had in a different way.”
The researchers said that despite being a subtle action, blinking is quite complex, because it performs multiple functions, which are crucial for the health and safety of the eye.
The professor. Aiello added: “Our study, which considered the behavior and anatomy of a living fish that underwent a transition to life on land, similar to early tetrapods, helps us reimagine how and why these early tetrapods might have beaten the eyelids.
“Having the opportunity to study how and why this behavior first evolved provides an incredible opportunity to learn more about how humans came to be who they are and gives us insight into the changes associated with major transitions in the history of animals, such as inhabiting the earth. “
The research is published in the Proceedings of the National Academy of Sciences journal.
