Apatite mineralization in teeth of the chiton Acanthopleura echinata

Raman spectroscopy has been used to demonstrate, for the first time, that c alcium mineralization in the core of the major lateral teeth of the chiton Acanthopleura echinata takes place as an ordered process, with crystalline carbonated apatite being the first mineral deposited. Deposition begins at the top of the tooth core, under the so-called tab region, progresses down the interior surface of the tab and lepidocrocite layer, and then extends o utwards to the anterior surface. Mineralization is not initiated until the lepidocrocite layer has isolated the core of the tooth from the magnetite c ap. The last region to be infiltrated is the anterior basal region of the t ooth cusp, immediately above the junction zone. The junction zone is also a region of high ion density, as determined by energy dispersive spectroscop y (EDS) analysis, but we show here for the first time that it is flee of mi neral deposits, acting instead as a transfer and storage region.