Figure 21.

Chiton teeth and their formation. (A) Light micrograph of the radula of the chiton Acanthopleura gaimardi. (B) Detail of progressive stages of radular tooth development. (C) Scheme of the hypothesized mechanism of iron mineral formation (ferrihydrite and magnetite) in chiton teeth. Step 1: Organic tooth matrix around the unmineralized tooth core, which adsorbed Fe³⁺; Step 2: Fe³⁺ is first transformed into ferrihydrite; Step 3: conversion of ferrihydrite into magnetite; Step 4: mineralization of magnetite shell proceeds and the tooth core is also mineralized to phosphates. Image A reproduced from [142] by Brooker and Shaw, 2012, reproduced under the terms of the Creative Commons Attribution 3.0 License. Image B is reproduced from [141] with permission from Springer Nature.