Eastern oysters (Crassostrea virginica) are well known for their tolerance of anoxic conditions. Earlier studies revealed biochemical and physiological changes during acclimation to anoxia and some reported the expression of anoxia-responsive genes. Studies summarized here reveal that extended valve closure, valve integrity (no holes), and heart rate reduction/ cessation appear to contribute to long-term anoxic tolerance of the eastern oyster. A single hole drilled into a valve compromised the oysters ability to survive under anoxic conditions. Mechanical and behavioral contributions to anoxic tolerance have not been well studied in bivalves.