Sir, what controls the opening and closing of valves , means adductor muscles on contracting wt happens and on closing wt happens.

Adductors reiaxed- Dorsal vave Adductors contracted Hinge axss- Hinge aKIS Diductots Diductors relaxed contracted Venttal valve Fig. Brachiopod valves are opened and closed by pairs of opposed muscles: (A) Contraction of adductors closes the valvess Relation to substrate