Permalink : http://hdl.handle.net/2115/36675

Initial mineralization of the organic membrane-shell utilized in shell regeneration in mussel was studied by electron probe microanalysis and electron microscopy. The organic membrane-shell, not-fully mineralized regenerated shell, is composed of three different layers: laminated, brown and conchiolin membranous layers in regeneration order. The organic matrix of the first and third are very similar, in electron microscopic and histochemical features, to the conchiolin matrix, closely associated with the mineralization of the shell. While the second may be homologous to the periostracum, outermost non-calcified layer of the mussel shell. Initial mineralization of the organic membrane-shell takes place within the conchiolin membranous layer, through the following process: Deposition of particles (nucleus of mineralization?) → Aggregation of particles → Coating of aggregated body with amorphous organic materials (= formation of spherule) (calcium accumulation) → Enlargement of its size (calcium concentration and beginning of mineralization?) → Transformation into double-disk body (accumulation and growth of acicular calcium carbonate crystals) → Exposure of preformed acicular crystals to the spaces between conchiolin membranes → Final formation of crystalline aggregates, structurally organized into well-ordered sheet-like layer (nacreous layer).