The seahorse -- whimsical-looking creature of fairytale and myth - is now providing bio-engineers with the inspiration to build a rugged robot arm that could one day rescue sailors who have fallen overboard, grasp medical tools or load equipment in outer space.

That’s because it turns out that the seahorse’s tail is super-strong. Its overlapping armored plates can be squeezed more than 50 percent without damaging the nerves underneath, according to new research at the University of California, San Diego. That helps the animal hold onto undersea grasses and rocks to avoid underwater currents.

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“We’ve been looking at tails and bones,” said Joanna McKittrick, professor of mechanical and aerospace engineering at UCSD’s Jacobs School of Engineering. “We’re interested in the organization from the nano-scale. We looked at bone and antlers, rams’ horns, armadillos, fish scales, porcupine scales and toucan beaks. We’re looking at how an animal can protect itself. It has to be lightweight, but tough and fracture resistant. We're curious as to how Mother Nature can do it. And then maybe we can do it in the lab.”

McKittrick has studied other kinds of natural materials in the past, such as abalone shells, to find possible micro-structures that could be used for armored plates or vests. Armored critters -- whether pangolin, alligator or seahorse - seem to have one thing in common, she said.

“One of the things we discovered that if you are slow moving, you need thick armor,” McKittrick said. “The seahorse has one set of fins and it moves very slowly.”

The seahorse’s skeleton, as well as the bony plates, are shown though a micro CT-scan. acobs School of Engineering

Using a micro-CAT scanner, McKittrick and colleagues at UCSD including graduate student Michael Porter, were able to look at the interlocking plate structure of the seahorse tail armor. The plates slide past each other and bend at several angles.

Most of the seahorse’s predators, including sea turtles, crabs and birds, capture the animals by crushing them.

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Engineers wanted to see if the plates in the tail act as defensive armor. They found the tail could be compressed by nearly 50 percent of its original width before permanent damage occurred. That’s because the connective tissue between the tail’s bony plates and the tail muscles bore most of the load from the displacement. Even when the tail segments were compressed by as much as 60 percent, the seahorse’s spinal column was protected from permanent damage.

The team also found that the plates were composed of mainly soft organic material, rather than harder minerals that are found in animal bond.

The researchers' next step is to construct an artificial seahorse tail with the same geometry using a 3D printer and various polymers. They hope it can be used in various commercial, medical and military applications. Their study was published recently in the journal Acta Biomaterialia.

The armored, prehensile seahorse tail has evolved after millions of years to help it survive in the energetic waters of coral reefs and shallow coastal waters, according to naturalist Helen Scales, author of the new book “Poseidon’s Steed: The Story of Seahorses from Myth to Reality.” The tail grips underwater grasses, keeps it uptight and allows it to camouflage itself.

“The seahorse tail is an extraordinary piece of equipment,” Scales said from Cambridge, England. As a diver conducting marine biological studies, Scales has experienced the strength of the seahorse tail firsthand. “They do hold on really tight.”