The glass skeleton of the Venus' flower basket is strong and flexible due to the protein-mediated formation of layers of nanoscale silica spheres made up of even smaller nanoscale silica beads.

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The sponge's glass skeleton is made up of spicules, tubule structures of concentric layers of amorphous hydrated silica separated by thin organic layers, like a Parisian pastry with just a tease of sweet cream between flaky crusts. But these thin organic layers go a long way to impart the spicules with considerable toughness. Even the pair of symbiotic shrimp that live their lives trapped within each Venus's woven glass basket can't break out. Unlike biomineralization in other organisms such as the abalone, the mineral portion does not appear to have a regular crystalline pattern. Experiments suggests that the silica layers are made up of colloidal spheres of silica about 50 to 200 nm in diameter, which are in turn made up of smaller spheres about 2.8 nanometers in diameter. By comparison, the smallest sand grains on a beach (also usually silica) are about 60 nm in diameter.

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"Glass is widely used as a building material in the biological world, despite its fragility. Organisms have evolved means to effectively reinforce this inherently brittle material. It has been shown that spicules in siliceous sponges exhibit exceptional flexibility and toughness compared with brittle synthetic glass rods of similar length scales... Consolidated, nanometer-scaled silica spheres are arranged in well-defined microscopic concentric rings glued together by organic matrix to form laminated spicules. The assembly of these spicules into bundles, effected by the laminated silica-based cement, results in the formation of a macroscopic cylindrical square-lattice cagelike structure reinforced by diagonal ridges. The ensuing design overcomes the brittleness of its constituent material, glass, and shows outstanding mechanical rigidity and stability." (Aizenberg et al. 2005: 275)

Journal article
Skeleton of Euplectella sp.: Structural Hierarchy from the Nanoscale to the MacroscaleScienceJuly 7, 2005
J. Aizenberg

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Venus's Flower BasketEuplectella aspergillumSpecies

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