a1 Centre for Microscopy, Characterisation and Analysis, The University of Western Australia, Crawley, WA 6009, Australia
a2 School of Biological Sciences & Biotechnology, Murdoch University, Murdoch, WA 6150, Australia
a3 Faculty of Science, Health and Education, University of the Sunshine Coast, Maroochydore DC, QLD 4558, Australia
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 onset of iron mineralization within the teeth, initiated at row 13, is associated with a number of dramatic changes in the ultrastructure of the apical cusp cell epithelium. Specifically, the presence of ferritin containing siderosomes, the position and number of mitochondria, and the structure of the cell microvilli are each linked to aspects of the mineralization process. These changes in tissue development are discussed in context with their influence over the physiological conditions within both the cells and extracellular compartment of the tooth at the onset of iron mineralization.
(Received October 09 2008)
(Accepted January 14 2009)