No CrossRef data available.
Published online by Cambridge University Press: 15 February 2011
We report on the structural properties of siliceous spicules, found in the hexactinellid sponge Euplectella. Selective chemical etching of Euplectella spicules in bleach reveals the presence of a striated arrangement of silica spheres (∼50-200 nm in diameter) placed radially around a central, high-organic content cylindrical region. Complementary etching experiments with HF indicate a graded variation of silica content in these shells. The presence of such a multi-layered and variable-composition structure affords these spicules not only with enhanced structural integrity but could also be reflected in their optical properties. Qualitative, index-matched, refractive index measurements are shown to support this expectation.