[Dentoid]

Gaping is a condition in which a clams shell is open the mantle is retacted a bit and the inhalational and exhalational siphons are wide open. The clam may not react to the shadow test either. A clam that is gaping is a goner.

A healthy clam will be open with its mantle fully extended during lighting periods and will retract quickly if a shadow passes over them. When the lights are off, the clam will retract its mantle and close its shell not necessarily all the way though.