Why seahorses have square tails

seahorse skeleton

The long flexible tails of seahorses (dye-stained skeleton of Hippocampus capensis shown) are made of square segments and are one of the rare exceptions to the round tails of many other animals.

Courtesy of Dominique Adriaens, UGent

Hammering and squishing 3-D printed seahorse tail segments reveals what’s so great about being square.

Angled bones hitched together in a flexible string of squares create protective cages that are four times stronger than rounded ones, researchers report July 3 in Science. That’s the conclusion from squeezing 3-D printed seahorse tails, one made of square segments that had been scaled up and the other an engineer’s best estimate of a round equivalent.

Distant seahorse ancestors had armored tails that could have benefited from such square protection.

Modern seahorse tails have gone prehensile. So there’s now a grip bonus, says study coauthor Michael M. Porter, an engineer at Clemson University in South Carolina. Square segments press more surface area against a perch than round ones, giving squared tails better grip control.

tail types
In a computer-generated image, a stretch of square segments (right) roughly like a seahorse tail gets a better grip than the rounded version (left) by pressing more surface area against a perch. Real seahorse tails build each square segment from four pieces, each bent about 90 degrees. Michael. M. Porter/Clemson Univ.
Susan Milius

Susan Milius is the life sciences writer, covering organismal biology and evolution, and has a special passion for plants, fungi and invertebrates. She studied biology and English literature.

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