Tooth use and wear in three iron-biomineralizing mollusc species.

Chitons and limpets harden their teeth with biominerals in order to scrape algae from hard rock surfaces. To elucidate relationships between tooth structure and function, light and electron microscopy were used to examine naturally worn teeth in three species of mollusc with iron-mineralized teeth and to analyze the grazing marks left by members of these species feeding on wax. For the two chiton species, teeth wore down progressively from the medial to the lateral edge of the cusp, while for the limpet, wear was more evenly distributed across the edges of each cusp.

Ultrastructure of the epithelial cells associated with tooth biomineralization in the chiton Acanthopleura hirtosa.

The cusp epithelium is a specialized branch of the superior epithelium that surrounds the developing teeth of chitons and is responsible for delivering the elements required for the formation of biominerals within the major lateral teeth. These biominerals are deposited within specific regions of the tooth in sequence, making it possible to conduct a row by row examination of cell development in the cusp epithelium as the teeth progress from the unmineralized to the mineralized state. Cusp epithelium from the chiton Acanthopleura hirtosa was prepared using conventional chemical and microwave assisted tissue processing, for observation by light microscopy, conventional transmission electron microscopy (TEM) and energy filtered TEM.

The chiton stylus canal: An element delivery pathway for tooth cusp biomineralization.

A detailed investigation of the stylus canal situated within the iron mineralized major lateral teeth of the chiton Acanthopleura hirtosa was undertaken in conjunction with a row-by-row examination of cusp mineralization. The canal is shown to contain columnar epithelial tissue similar to that surrounding the mineralized cusps, including the presence of iron rich particles characteristic of the iron storage protein ferritin. Within the tooth core, a previously undescribed internal pathway or plume is evident above the stylus canal, between the junction zone and mineralizing posterior face of the cusp.

Fine structure of the mineralized teeth of the chiton Acanthopleura echinata (Mollusca: Polyplacophora).

The major lateral teeth of the chiton Acanthopleura echinata are composite structures composed of three distinct mineral zones: a posterior layer of magnetite; a thin band of lepidocrocite just anterior to this; and apatite throughout the core and anterior regions of the cusp. Biomineralization in these teeth is a matrix-mediated process, in which the minerals are deposited around fibers, with the different biominerals described as occupying architecturally discrete compartments. In this study, a range of scanning electron microscopes was utilized to undertake a detailed in situ investigation of the fine structure of the major lateral teeth.

Contribution of Raman spectroscopy to identification of biominerals present in teeth of Acanthopleura rehderi, Acanthopleura curtisiana, and Onithochiton quercinus.

Raman spectroscopic investigations of the major lateral teeth of the chitons Acanthopleura rehderi and Acanthopleura curtisiana indicate that, in addition to the magnetite of the cutting surface and a carbonated hydroxyapatite in the central tooth core, these species deposit limonite in place of the lepidocrocite reported for other members of the genus Acanthopleura. A comparison of the spectra from these species with those of Onithochiton quercinus, which also deposits limonite, indicates that the current assignment of these species to Acanthopleura may not be appropriate. Biomineralization of the major lateral teeth may be a useful parameter to include in the taxonomic classification of chiton species.

A new biomineral identified in the cores of teeth from the chiton Plaxiphora albida.

The hydrated iron(III) oxide limonite is reported for the first time as a biomineral. In situ laser Raman spectra of the tooth cores from major lateral teeth of the chiton Plaxiphora albida are compared with those of synthetic and mineral iron phosphates and iron oxides. Raman spectra measured on iron phosphate and iron oxide standard materials are shown to be easily distinguishable from one another.