Zoological Studies

Silica Biomineralization in the Radula of a Limpet Notoacmea schrenckii (Gastropoda: Acmaeidae)

Tzu-En Hua and Chia-Wei Li (2007) The radulae of limpets are regarded as an ideal experimental material for studying biologically controlled mineral deposition, because they possess teeth in different mineralization stages.  The pattern of silica precipitation in the limpet, Notoacmea schrenckii (Gastropoda: Acmaeidae), was elucidated in this study using transmission electron microscopy (TEM), electron diffraction, energy-dispersive X-ray (EDX) analysis, and inductively coupled plasma mass spectrometry (ICPMS).  The ICP-MS elemental analysis showed that iron and silica both infiltrate into the radula in early stages of tooth development.  Electron-dense granules in a nanometer size range were observed in ultrathin sections of tooth specimens in early mineral-deposition stage; electron diffraction analysis indicated that silica is the primary component of these granules.  TEM images revealed the intimate association between silica granules and the organic matrix, which implies that the organic matrix may take a more-active role in catalysis besides merely functioning as a physical constraint during mineral deposition.  Exposure of the tooth cusp to NH4F treatment and the appearance of silica spheres after the addition of silicate suggest that the organic molecules embedded within the minerals may assist silica precipitation.