What is this strange fish that crawls in the mud and can it be the key to understanding human evolution?

He mudskipper (Boleophthalmus caeruleomaculatus) it’s a species of fish from the family of the Gobiidae in the order of the perciform . THE males They can reach 15.8 cm in total length. It’s a Fish of tropical climate which is in Australia and that it is harmless to humans .

But what makes this fish exceptionally special, is that it spends much of the day out of the water, hence its name .

And it is precisely this feature that provides clues about how and why the transition from water to land may have evolved in our own ancestors . New research shows that these amphibian fish have learned to blink, for the same reasons as humans. The results suggest that eye blinking may be part of the set of traits that evolved to enable the transition to terrestrial life in the tetrapods the group of animals that includes mammals, birds, reptiles and amphibians, around 375 million years ago.

The study was published in the Proceedings of the National Academy of Sciences and was led by Thomas Stuart assistant professor of biology at Penn State, and Brett Aiello, assistant professor of biology at Seton Hill University .

“Animals blink for many reasons,” Stewart said it’s a statement . “It helps us keep our wet and clean eyes For protect them from injury and even we use blinking to communicate. Studying how this behavior first evolved has been difficult because the anatomical changes that enable eye blinking are found primarily in soft tissue, that are not well preserved in the fossil record . The mudskipper, who developed his blinking behavior independently, gives us a chance to test how and why flicker could have evolved in a living fish that regularly leaves water to spend time on land ”.

To understand how this species evolved the ability to blink, the researchers analyzed the behavior with high-speed video and compared the anatomy of mudskippers to that of a closely related non-blinker water-bound fish. Mudskipper’s eyes protrude from the top of his head, like a frog’s eyes . To blink, the fish momentarily retracts its eyes into their sockets, where they are covered by an elastic membrane called “skin cup” . The twinkle of this fish it lasts about the same time as a human blink.

“Flickering among mudskippers seems to have evolved by a reorganization of existing muscles which have changed their line of action and also by the evolution of a new tissue, the dermal cupule Aiello said. “This is a very interesting result because it shows that a very rudimentary or basic system can be used to drive complex behavior. You don’t need to develop a lot of new things to develop this new behavior. : this species just started using what it already had in a different way.

Discover why mudskippers wobble on land, the team examined the roles played by blinking in humans and other tetrapods. In man, tears are essential to keep eye cells healthy and oxygenated the researchers therefore investigated whether grasshoppers also blink to keep their eyes moist.

“We discovered that, like humans, mudskippers blink more frequently when faced with dry eyes yes,” Aiello said. “What is amazing is that they can use their blinks to moisten their eyes, even though these fish have not developed tear glands or ducts. While our tears are made up of glands around our eyes and on our eyelids, grasshoppers seem to mix mucus from the skin with water from their surroundings to produce a tear film.”

The research team also tested whether the blinking of these fish could be activated to protect the eye from potential injury and whether the blinking cleared the fish’s eyes of dust or debris . In both cases the answer was “yes”. Therefore, blinking in fish appears to serve three of the main functions of blinking (protective, cleansing, and maintaining moisture) in humans and other tetrapods.

“Our study, which took into account the behavior and the anatomy of a living fish that has undergone a transition to terrestrial life, similar to early tetrapods, it helps us reimagine how and why these early tetrapods might have blinked,” Aiello said. “Having the opportunity to study how and why this behavior first evolved provides an incredible opportunity for learn more about how humans became who they are and this gives us an idea of ​​the changes associated with the main transitions in the history of animals, such as inhabiting the earth”.

Blinking is something that humans and other tetrapods doing constantly throughout the day , often without even realizing it, explained Aiello. Although a subtle action, eye blinking is quite complex and fascinating, as it is a unique behavior that can perform multiple functions, all of which are essential to the health and safety of the eye of vertebrates, he said.

“The transition to life on earth required many anatomical changes. including changes in feeding, locomotion and respiration,” Stewart said. “Based on the fact that blinking in muckjumpers, which evolved completely independently of our own fish ancestors, fulfills many of the same functions as the blink in our own lineage, we believe it was likely part of the set of traits that evolved when tetrapods were adapting to life on land.