This is why a seahorse tail is square

Graham Banton, an Aquarist at the SEALIFE London Aquarium, introduces a new herd of baby Seashorses. Stuart C. Wilson/Getty Images

Engineers have taken a look at the tail of the seahorse, which it uses to hold on to sea grass in a strong current, and find that it’s square because this shape is better at resisting damage and at grasping.

Insights from the study, published in the journal Science, could inspire advances in robotics, the researchers say.

The tails of seahorses are square prisms surrounded by bony plates, while most other animals, including monkeys, lizards and rodents, have soft and cylindrical appendages.

“Human engineers tend to build things that are stiff so they can be controlled easily,” says Ross Hatton, an assistant professor in the College of Engineering at Oregon State University.

“But nature makes things just strong enough not to break, and then flexible enough to do a wide range of tasks. That’s why we can learn a lot from animals that will inspire the next generations of robotics.”

The researchers created a 3D-printed model of the tail as well as a hypothetical cylindrical version. Then they twisted and bent both models, and smashed them with mallets.

The square version was more resistant to twisting and better able to return to its true alignment.

The researchers say the twisting resistance of the square tail may help protect the seahorse’s delicate spinal cord.

The outer surfaces of the square tail also increase contact area when the tail wraps around an object, giving it better grasping control.

The seahorse is the only creature where the male has a reverse pregnancy. The female transfers her eggs to the male which he self fertilises in his pouch.

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