Structural and biological characterization of two freshwater mussel shells (Bivalvia: Unionidae)

Authors: HÜLYA ŞEREFLİŞAN

Abstract: The shell of a freshwater mussel (Mollusca: Bivalvia) is a composite biological material that plays an active role in maintaining ecosystem services. Mussel shells have variable structures both within and between species. In this study, the structural and biological characteristics of the shells of Potomida semirugata and Leguminaia wheatleyi were investigated in order to use freshwater mussel shells as a biological material. Close observation of the microstructure of the shells of the two common freshwater bivalves revealed a variation in construction from the outer periostracum to the inner nacreous layer. In P. semirugata, a polygonal arrangement with columnar prisms of different sizes was observed more significantly. In L. wheatleyi the prismatic columns are oval and irregularly polygonal. The nacreous layers of P. semirugata, in which the individual aragonite layers are horizontally overlapped, are more uniformly distributed. The overlapping of the aragonite sheets in L. wheatleyi is more irregular. The presence of calcium carbonate (CaCO$_{3}$) in the shells was confirmed by the identification of the characteristic carbonate bands at 701.9, 713.5, and 865.8 cm$^{-1}$. This information was used to classify and distinguish the different layers of the shells, allowing interspecific comparisons and variations in the different layers. The results clearly showed that shell samples were highly biocompatible and nontoxic compared to the control group. This finding suggests that these materials have promising potential for use in various biomedical applications where biocompatibility is a critical factor. The results indicated that the shells of the freshwater bivalves P. semirugata and L. wheatleyi are biological materials with potential multiple applications for human well-being and environmental quality.

Keywords: Calcification, freshwater bivalve, biomineralization, biological material, nacre, scanning electron microscope

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