The mudskipper is a fascinating animal, in that it's a fish that both swims in the water and crawls on the land. It's probably not unlike the prehistoric fishes that first ventured out of the ocean, hundreds of millions of years ago. Looking at it, you might think that its two pectoral fins do all the work when it's out of the water, while its tail just flaps around. By building a robotic version of the mudskipper, however, scientists have learned that its tail plays a crucial role while it's on the land – the finding could have implications for the design of walking robots.

Known as MuddyBot, the robot was developed as part of a study that included researchers from the Georgia Institute of Technology, Clemson University and Carnegie Mellon University.

Like a lot of limbed robots, it has difficulty climbing up loose, sandy slopes – or at least, it does when it just uses its two front fins, as it tends to just lift itself up off the ground and then slide back downhill. When it adds a flicking motion of its tail as it's off the ground, however, it's much better able to achieve forward motion.

This observation was backed up by analyses of real mudskippers, and by a mathematical model that was subsequently created.

"The fish provided a morphological, functional model," said Clemson student and researcher Benjamin McInroe. "With the robot, we are able to simplify the complexity of the mudskipper and by varying the parameters, understand the physical mechanisms of what was happening. With the mathematical model and its simulations, we were able to understand the physics behind what was going on."

It is now hoped that the knowledge can not only be applied to making better-climbing robots, but also to getting a better understanding of how those first early vertebrates made the transition from water to land.

"We want to ultimately know how natural selection can act to modify structures already present in organisms to allow for locomotion in a fundamentally different environment," said Georgia Tech's Prof. Dan Goldman. "Swimming and walking on land are fundamentally different, yet these early animals had to make the transition."

MuddyBot can be seen in action, in the video below.

Source: Georgia Tech

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