Seasonal changes in the shell microstructure of the bloody clam, Scapharca broughtonii (Mollusca: Bivalvia: Arcidae)

► We demonstrated seasonal changes in shell microstructures in Scapharca broughtonii. ► Relative thickness of two structures in outer layer changes cyclically with ontogeny. ► Water temperature records in shells were calculated from stable oxygen isotope data. ► Microstructural change was synchronized with seasonal change in water temperature.