Silvia M. de Paula and Marina Silveira
Labroratory of Electron Microscopy, Institute of Physics, University of São Paulo, São Paulo, Brazil
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