Shell Microstructure, Mineralogy and in Vitro Crystallization Studies on the Shell Soluble Matrix of Abalone, Haliotis Discus Hannai Ino‪.‬

ABSTRACT The shell microstructure of the abalone, Haliotis discus hannai Ino, was studied using scanning electron microscopy. The shell consists of the periostracum, prismatic, and nacreous layers with calcite in the outer prismatic layer and aragonite in the inner nacreous layer. FTIR analysis of the prismatic powder showed characteristic spectra of calcite: 876 [cm.sup.-1] (v2) and 710 [cm.sup.-1] (v4), whereas aragonitic nacreous powder had characteristic spectra of 858 [cm.sup.-1] (v2) and 712 - 700 [cm.sup.-1] (v4). Another absorption area in the range 2520-2650 [cm.sup.-1] in both nacreous and prismatic layers was assigned to HC[O.sub.3.sup.-] groups, residing in the mineral or at the organic mineral interface, which suggests a potential participation of HC[O.sub.3.sub.-] groups as an intermediate in shell formation. In the in vitro crystallization experiment, it was found that the soluble matrix from different shell layers were able to induce different crystals with special morphologies. Soluble matrix, isolated from the prismatic layer, was shown to induce globular calcite formation in vitro, whereas soluble matrix from the nacreous layer induced the formation of almost symmetrical, hedgehog-like, aragonitic aggregates. The regulating mechanism of the formation, morphologic development, and crystallography of minerals in abalone shell is discussed. KEY WORDS: Haliotis discus hannai, shell, microstructure, mineralogy, soluble matrix, in vitro crystallization