The secret of the sea urchin's sharp teeth

The spikes of sea urchins make them look like pins filled with pins, but besides, they also have very strong teeth that can be plugged into stone. Now scientists have discovered the reason why these teeth are so strong: it is due to a very clever arrangement.

Sea urchins use its five hard teeth to burrow in limestone mountains. Scientists have been very curious about how this creature can cut rocks, because both their teeth and limestone are made of calcite, a relatively soft mineral made of calcium carbonate.

Researchers at the Weizmann Institute of Science have investigated this mystery for more than a decade, and have recently made some discoveries.

Sea urchin teeth contain magnesium calcite crystals, which are harder than pure calcite. The closer to the tip of the tooth the greater the presence of magnesium in these crystals, the scientists discovered.

A purple sea urchin (Photo: Claire Fackler)

In addition, the crystalline elements that make up this tooth are aligned, forming a block. Each tooth is made of two blocks. At the top of the teeth, these blocks are woven together. It is these interlocking blocks that form a wave of waves, like a carpenter's file. This sequence has the ability to sharpen itself - when the tooth that grinds into the limestone wall, the crystalline layers move together in a way that helps the tooth remain sharp.

A number of high-resolution imaging techniques were used to observe the structure of the teeth at different ranges.

Knowing more about how sea urchin teeth work can help inventors make cutting tools more advanced, scientists say.

The results were published in the Proceedings of the National Academy of Sciences issued on April 14. The research was supported by the Clore Center for Biological Physics, Kekst Family Medical Genetics Center and a number of other agencies.