The bivalve nervous system is far less centralized than in other molluscs. A pair of ganglia lie on each side of the esophagus near the mouth leading to the visceral ganglia, which innervate the posterior adductor muscle, and the pedal ganglia, which innervate the foot.
Sensory development is most prevalent in those tissues most directly exposed to the external environment, i.e., the mantle edge and siphons. Photoreceptor cells detect changes in light intensity. Tentacles on the siphons and stiffened cilia perceive touch or vibrations passing through the water. Stronger stimuli cause the valves to close rapidly, either forcing water under high pressure from the siphons or withdrawing the siphons and closing the valves tightly as a defense from predators.
Life History and Biology Introduction
Anatomy and Physiology