Mudskippers could be key to understanding evolution of blinking - study

Scientists from Georgia Institute of Technology, Seton Hill University and Pennsylvania State University have found that blinking is not only crucial for eye health and protection but also plays a critical role in communication.

The peer-reviewed research was published in the journal Proceedings of the National Academies of Science under the title, "The Origin of Blinking in Both Mudskippers and Tetrapods Is Linked to Life on Land," and shows their study on the mudskipper, an amphibious fish that spends most of its day on land, to gain insights into the origins and significance of blinking in animals.

Researchers have suggested that studying mudskippers, despite being distantly related to tetrapods like humans and other four-limbed vertebrates, could provide insights into the evolution of blinking as these animals transitioned from water to land.

"By comparing the anatomy and behavior of mudskippers to the fossil record of early tetrapods, we argue that blinking emerged in both groups as an adaptation to life on land," one of the authors of the paper and an assistant professor at Penn State, Tom Stewart, said. "These results help us understand our own biology and raise a whole set of new questions about the variety of blinking behaviors we see in living species."

According to the study, mudskippers have evolved a unique way of blinking by using their existing set of eye muscles. 

The uniqueness of blinking

Unlike other animals, mudskippers suck their eyes downward into their sockets to blink, a behavior that did not require the evolution of many new parts such as muscles or special glands. 

"This is a very exciting result because it demonstrates that the evolution of a new, complex behavior can be achieved using a relatively rudimentary set of structures," former postdoctoral fellow in the Agile Systems Lab and assistant professor at Seton Hill, Brett Aiello said.

The research team has taken a step further to investigate the reasons behind mudskippers' blinking behavior. 

In a series of experiments, they identified three primary functions of blinking in these amphibious fish - to wet, clean and protect their eyes. Remarkably, these functions align with the reasons why humans and other land-dwelling vertebrates blink.

"We find that a single behavior can be deployed to accomplish three complex, distinct functions," Aiello said. "These results not only help humans understand our own history, but also help us re-evaluate the adaptations necessary for major transitions in the evolutionary history of vertebrates, like moving from water to land."

Blinking is not only a fascinating research topic but also a crucial mechanism that demands understanding, says Saad Bhamla, an author on the paper and an assistant professor in the School of Chemical and Biomolecular Engineering at Georgia Tech.

"We all blink without thinking and understanding why we blink is just such a beautiful puzzle right in front of our eyes," said Bhamla. "Through our research on mudskippers and by conducting biophysical and morphological analyses, we expose how blinking serves a multitude of functions for adapting to life out of water."

The researchers have turned to the Vertically Integrated Projects (VIP) program at Georgia Tech to delve into the open-ended questions surrounding the evolution and function of blinking. Undergraduates enrolled in the program were given the opportunity to participate in long-term and comprehensive research projects that form part of their coursework. The VIP program has enabled students to gain invaluable experience in conducting scientific research while contributing to the study of fundamental biological mechanisms.

"The structure of the VIP course empowers students to really lean on their own creativity and drive the project in the directions that are most exciting to them," Aiello said. "It helps our students gain the ability to solve unknown problems on the ground as they arise - a lot of people become scientists to push research somewhere where nobody else has tried to go before."

What did the researchers find?

The VIP program at Georgia Tech promotes a multidisciplinary approach to research, allowing students from various fields to contribute their expertise to tackle complex scientific questions. 

While the lead researcher, Aiello, comes from a biology background, the program has attracted many engineering students who bring their distinct skill sets to the table. For instance, Manognya Sripathi, a biomedical engineering major with a minor in computer science, lent her unique perspective to the mudskipper research. The program's diverse student body has enabled researchers to approach problems from different angles and generate innovative solutions.

“I used my computer science skills to gather raw data and analyze and plot them using programs like MATLAB or Python,” said Sripathi. “I also used engineering skills to help build the experimental equipment, allowing us to apply engineering methods to study a biological problem in a unique way.”

The mudskipper research has not only added to the understanding of this unique animal but also helped shape the future aspirations of the students involved. Kendra Washington, for instance, found her trajectory influenced by the two semesters she spent in the lab.

“VIP drew me closer to the programming and device areas of my biomedical engineering major and solidified why I picked up a computer science minor,” she said. “I continued to pursue that fusion through later internships and research, and now work with hemodynamic monitoring. But in a sense, I still help characterize physiology through programming.”

The mudskipper study has proven to be a transformative experience for the students involved, not only enhancing their understanding of the fascinating amphibious fish but also influencing their future aspirations. Kendra Washington, who spent two semesters in the lab, is one example of how the research has impacted the students' career paths.

“Working in an interdisciplinary team like this has allowed me to learn how to understand and communicate ideas between disciplines, which allowed me to be a more well-rounded engineer,” Minoguchi explained. “My work requires a thorough understanding of biology, electrical circuitry, software, firmware, mechanical interactions, and physics. This VIP experience was instrumental for me in being successful at my current job.”

According to Simon Sponberg, an associate professor in the School of Physics and the School of Biological Sciences, the mudskipper research offers a much greater insight into the mechanisms of evolution.

“Blinking is a reflection of a bigger question,” Sponberg explained. “How did major evolutionary transitions occur that enabled organisms to inhabit basically every environment on this planet? What we learned is you don't need the evolution of a lot of specialized musculature or glands; evolution can tinker with the structures that are already there, allowing them to be used in a new way and for a new behavior.”