Abstract: Zhao et al 2017: Delineating the role of calcium in shell formation and elemental composition of Corbicula fluminea (Bivalvia)

 

Calcium is one of the major constituents of bivalve shells. Other element impurities potentially record physical and chemical changes of the ambient environment during growth. It is commonly assumed that Ca2+ and other divalent ions may share the same transport mechanisms because of similar ionic radii and electrochemical properties. However, little effort has been devoted to bolstering this hypothesis. Here, we investigated the effects of Ca2+ on shell formation and element composition of the freshwater bivalve, Corbicula fluminea. Our results showed that increasing aqueous Ca2+ levels from 3 to 6 mM did not facilitate shell production. However, the amounts of Mn, Cu, and Pb incorporated into the shells significantly decreased, indicating the potential competition with Ca2+ in the same transport pathways. Furthermore, blocking the Ca2+ channels by lanthanum and Verapamil significantly reduced Mn, Cu, Zn, and Pb incorporation into the shells, and Mn/Cashell and Cu/Cashell decreased simultaneously when inhibiting the Ca2+-ATPase by ruthenium red. However, the amounts of Mg, Sr, and Ba incorporated into the shells were virtually unaffected, implying that intracellular Ca2+ transport mechanisms are not responsible for their incorporation into the shells. These findings help decipher underlying mechanisms responsible for the element partitioning between the ambient water and the shells.