It may seem like a small action, but blinking is a complex behavior that plays a critical role in the health and safety of vertebrate eyes. And now, a new study has shed light on the evolution of blinking in mudskippers, finding that the behavior evolved by rearranging existing muscles and the development of a novel tissue, the dermal cup.
According to lead researcher Matthew Aiello, “You don’t need to evolve a lot of new stuff to evolve this new behavior — mudskippers just started using what they already had in a different way.”
To understand why mudskippers blink on land, the research team considered the roles that blinking plays in humans and other tetrapods. They found that mudskippers blink more frequently when confronted with dry eyes, and can use their blinks to wet their eyes, despite not having evolved any tear glands or ducts.
Additionally, the researchers found that blinking in mudskippers could be triggered to protect the eye from possible injury and also cleaned the fish’s eyes of dust or debris, fulfilling three of the main functions of blinking in humans and other tetrapods.
This study, which focuses on a living fish that underwent a transition to life on land, provides insight into how and why early tetrapods might have developed the behavior of blinking. As researcher Lindsay Y. Stewart notes, “Based on the fact that mudskipper blinking… serves many of the same functions as blinking in our own lineage, we think that it was likely part of the suite of traits that evolved when tetrapods were adapting to live on land.”
The study’s findings offer a fascinating glimpse into the evolution of even our most basic behaviors and may help us understand the changes associated with major transitions in the history of animals, such as the move from water to land.