February 19, 2004 | David F. Coppedge

Respect the Conch Shell

Engineers and materials scientists seem to never run out of examples in nature that should fill us with awe.  In the Feb. 19 issue of Nature,1 Rosamund Daw brings our attention to the construction ability of the conch shell:

Giant conches are seldom treated with the respect they deserve.  Their impressive shells are prized as holiday souvenirs, but size and aesthetics are only half the story.  At the microscopic scale, they are one of nature’s greatest engineering masterpieces: a stunningly intricate hierarchical architecture of inorganic crystals, interwoven with organic molecules.

Recent experiments have shed light on the ways these marine organisms build and repair their shells.  An organic layer is deposited, providing a base on which fine crystals of aragonite form perpendicular to the organic layer.  Then a three-layered, cross-lamellar structure grows a few millimeters thick, forming the body of the shell.  The result is a strong, exceedingly fine structure, often decorated with streaks or spots of intricate colors, with bumps and horns and geometric spiral shapes.
    Broken shell?  No problem.  When experimenters drilled a hole into the shells of living conches, a new organic layer was formed within 24 hours, upon which new aragonite crystals grew to begin the repair process.
    There’s still much to learn about the “complex process of shell formation,” Daw says.  “It remains to be discovered how the interplay of organic and inorganic components is controlled at the molecular level, in conch shells as well as in other mineralized structures.”

1Rosamund Daw, “Materials Science: Give a shell a break,” Nature 427, 691 (19 February 2004); doi:10.1038/427691a.

This could be a teachable moment on your family’s next trip to the beach.  Tell the kids that this construction project the conch performs is the envy of materials scientists.  Teach them that complex processes that build things do not just happen.  DNA, genes, enzymes, signalling, feedback and quality control all contribute to the work of art that is a seashell.

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