Silica structure in the spicules of the sponge Suberites domuncula

Accumulation of silica in marine organisms such as diatoms and sponges has been widely reported. The proteins depositing silica in these organisms have been identified and its structure has also been described. The ultrastructure of silica has not been studied in detail, however. Herein we describe the structure of silica in the spicules of the sponge Suberites domuncula. Peroxide treatment was performed to remove the organic compounds, thereby enabling a better study of the silica. Methods used for the study included scanning and transmission electron microscopy. Electron diffraction enabled structural comparison with silica glass at the atomic level. Small-angle X-ray scattering (SAXS) of the spicules was also conducted and structure correlation between these methods attempted. At a lower magnification, spicule needles with a smooth outer surface were visible. Diffraction results suggested a network-like structure in the spicules. Silica particles of 3 nm diameter could be measured by SAXS.