In DepthBiomaterials

Crystalline eyes of chitons inspire materials scientists

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Science  20 Nov 2015:
Vol. 350, Issue 6263, pp. 899
DOI: 10.1126/science.350.6263.899

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For more than a century, biologists have suspected that chitons, slow-moving mollusks common along rocky shorelines, see the world differently from most animals. Though the animals apparently lack a brain, the backs of their hard, turtlelike shells are pockmarked with up to 1000 tiny eyes. Now, a team of materials scientists, engineers, and biologists describes how chitons convert the chalklike aragonite of their shells into transparent lenses that form images. Using high-resolution microscopy and x-ray techniques, as well as computer modeling, these researchers peered deep into the chiton eye and characterized the material and structures of the upper layer of the shell, which in chitons is living tissue. They find the lens consists of bigger, more aligned aragonite crystals than in the rest of the shell and that protective protrusions help compensate for these weak points in the shell. The work offers a striking example of how a single material can perform two jobs—seeing and protecting—at once, and may offer insight to materials scientists seeking to design their own dual-use materials.