Articulate lampshells are sedentary or sessile in their lifestyle, attaching themselves to a substrate by the use of a cord-like pedicle on their lower valves. The lower valve is usually positioned on top. Lampshells with pedicles tend to orient themselves with regard to the water so that the front-to-back axis of the shell is at right angles to the current, with the commissural plane parallel to the current. The commissure is the line of junction between the edges of two valves. The few species of articulates that lack pedicles attach themselves to the substrate by the lower valve.
Articulate lampshells protect themselves by closing their shells. When disturbed, they will also contract their pedicles and pull themselves downward toward the substrate. They are capable of only limited lateral motion. Most of their movement involves opening the shell for feeding and closing it for protection.
Was this article helpful?