U.S. scientists use X-ray technology to reveal mighty strength of Parrotfish teeth

Source: Xinhua| 2017-11-16 06:01:55|Editor: Mu Xuequan
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SAN FRANCISCO, Nov. 15 (Xinhua) -- Scientists at the U.S. University of California Berkeley (UC Berkeley) are using X-ray based technology to unfold the mystery of the mighty coral-crunching ability of Parrotfish's teeth, a UC Berkeley press release said Wednesday.

The scientists at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), a UC-managed institution charged with conducting unclassified research across a wide range of scientific disciplines, found that a chain mail-like woven microstructure gives parrotfish teeth their remarkable bite and resilience.

Parrotfishes are a kind of marine creature that often live in relatively shallow tropical and subtropical oceans throughout the world. They are found in coral reefs, rocky coasts and seagrass beds, and play a significant role in bioerosion that ultimately generates fine and white coral sand characteristic of tropical islands. A single parrotfish can produce hundreds of kilograms of sand each year.

The tropical fish mainly feasts on the polyps and algae that live on the surface of coral skeletons and helps to clean up reefs. The hardness of parrotfish teeth measured near the biting surface is about 530 tons of pressure per square inch (about 6.45 square centimeters), equivalent to a stack of about 88 African elephants compressed to a square inch of space.

With the help of the PIC (polarization-dependent imaging contrast) mapping technology, the scientists were able to study how the fine crystal structure of parrotfish teeth contribute to their incredible strength, and visualize the orientation of individual crystals, which showed their intricately woven structure.

They found the fluorapatite crystals gave parrotfish teeth their extremely powerful strength, with each measuring about 100 nanometers (billionths of a meter) wide and several microns (millionths of a meter) long.

The crystals are assembled into interwoven bundles, which decrease in average diameter from about five microns to about two microns toward the tip of each tooth.

Fluorapatite, which contains calcium, fluorine, phosphorous and oxygen, is the mineral that builds the crystal structure of parrotfish teeth.

The teeth, which grow continuously in rows, form a beaklike structure that constantly replaces older, worn teeth with new ones. No other biomineral is stiffer than parrotfish teeth at their biting tip.

Parrotfish have about 1,000 teeth situated in about 15 rows, and each tooth is cemented to all of the others and surrounded by bone to form a solid beak.

The interwoven characteristics and the crystal orientations of parrotfish teeth may inspire scientists to draw a blueprint for creating ultra-durable synthetic materials that could be useful for mechanical components in electronics, or in other devices that undergo repetitive movement, abrasion and contact stress.