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Microstructural Characterization of Shell Components in the Mollusc Physa sp.

Silvia M. de Paula and Marina Silveira

Labroratory of Electron Microscopy, Institute of Physics, University of São Paulo, São Paulo, Brazil

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Summary: Shells of the freshwater, pulmonate snail Physa (Mollusca, Gasteropoda), ranging from 0.5 to 10 mm in length, were studied using scanning microscopy, x-ray analysis, and infrared spectroscopy. Results obtained suggest that the shell is composed of aragonite, which occurs in several distinct crystalline forms. A selective distribution of crystalline forms (hexagonal plates, prisms, rhombohedra, and spherulites) occurred along specific sites of the shell. A variable distribution of the forms was also detected in adult shells and in protoconchs of developing embryos. Qualitative elemental analysis, using an energy-dispersive spectrometer, corroborates the presence of calcium, phosphorus and sulphur ions.

Key words: biomineralization, gasteropoda, Physa, calcium carbonate, microstructures, spectroscopies

PACs: 61.10-i, 61.16 BG, 61.66 Fn, 87.64 Ee, 87.68.+e