Mechanical Characteristics of Bivalve (Mollusc) Shells from the East Coast of India: Implications and Their Significance on the Survival Strategy

Due to natural selection, an increase in biotic and abiotic factors develops an adaptive response in bivalves (molluscs) for survival. Morphological variation in a bivalve is strongly correlated with the changes in the structural and compositional properties of a shell. Therefore, the mechanical characteristics of a shell reflect its morpho-functional adaptation against predation and ecological stresses. An initial investigation into the primary mechanical attributes of predominant bivalve shells from the east coast of India, Tegillarca granosa, Meretrix meretrix, Sunetta meroe, Mactra turgida and Donax scortum, has been documented in this study. The quantitative assessment of the centreline thickness, Vickers hardness and density variation of the shells were measured and correlated along with the preliminary investigation of the microstructural patterns. The results from our study are in agreement with the most vulnerable region of a shell, located just below the umbonal zone, which has been verified through predatory boreholes in other studies. Our data shows a high correlation between shell hardness and density, which could also be the potential properties to consider in detail for future studies, apart from the shell thickness, which could provide a broader perspective on the stability of bivalve shells. Different microstructural patterns observed in the species could be phylogenetically driven based on their life modes.