Multiple-front iron-mineralisation in chiton teeth (Acanthopleura echinata: Mollusca: Polyplacophora)

The mineralisation of iron in the major lateral teeth of the chiton Acanthopleura echinata has been examined using light and electron microscopy, together with energy dispersive and Raman spectroscopy. The deposition of magnetite in the posterior region of the tooth cusp has been shown to occur simultaneously on two fronts, from both the anterior and posterior sides. In contrast, in the lepidocrocite region, the mineral is formed by aggregation over the whole region. In addition, evidence is presented for the existence of a thin veneer of ferrihydrite over the surface of the magnetite region. The veneer preserves this region from oxidation prior to use in the mature tooth. Data also suggest that the junction zone plays a vital role in the overall biomineralisation process, contributing large amounts of iron at critical stages of development