Why are seahorse tails square? A team of researchers has uncovered the answer. Basically, the square cross-section of a seahorse’s tail is more suited for grasping and gripping objects than a circular cross-section tail.

Lead investigator Michael Porter, of Clemson University, said:

“Almost all animal tails have circular or oval cross-sections-but not the seahorse’s. We wondered why. We found that the squared-shaped tails are better when both grasping and armor are needed.”

Porter’s team discovered that square plates move with in only one direction when crushed, they slide. Circular plates, in comparison, have two degrees of freedom, they both slide and they rotate. The result is that the square plates can absorb much more energy before they break.

Researchers used a range of techniques in their invesigation. That includes 3D-printing a simplified model of the seahorse’s tail. They also 3D-printed and ran similar experiments on a tail model made of overlapping round segments that they designed, that is not found in nature.

The researchers took their fabricated tials and subjected them to bending, twisting, compressing and crushing forces. While the square plates squeezed inward and kept their shape, since they could slide over each other, the round plates interfered with each other and distorted the overall shape, and required more energy to return to its original shape.

“New technologies, like 3D-printing, allow us to mimic biological designs, but also build hypothetical models of designs not found in nature,” said Porter “We can then test them against each other to find inspiration for new engineering applications and also explain why biological systems may have evolved.”

Porter looking into how devices based on the structure of the seahorse’s tail could be used in real life.

One idea would be to scale up the structure to build a gripping robotic arm that can be used in hostile environments. Another concept is to scale it down to create a stronger catheter. But the possibilities are many, said study co-author Meyers.

Michael M. Porter, Dominique Adriaens, Ross L. Hatton, Marc A. Meyers, Joanna McKittrick Why the seahorse tail is square Science 3 July 2015: Vol. 349 no. 6243 DOI: 10.1126/science.aaa6683

Illustration: Left: Seahorse skeletons are composed of highly-articulated bony plates that surround a central vertebral column. Right: Bending and twisting performance of the prototypes. Credit: Michael Porter/Clemson University/UC San Diego

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