Escape responses of the queen scallopChlamys opercularis(L.) (Mollusca: Bivalvia)

The aversive behaviour patterns of C. opercularis elicited in aquaria depend upon the level of predatory starfish extract and mechanical stimulation applied to the mantle edge. Shell closure is followed by escape adductions and/or swimming. At the escape adduction the scallop moves directly away from the stimulus, the single jet being formed on the velum curtain of both sides even when the mantle edge of only one side is stimulated. Nerve fibres in the radial palliai nerves are responsible for communication between the mantle edge of both sides. The visceroparietal ganglion and adequate stretch of the striated block of the adductor muscle are necessary for the rhythmic sequence of adductions which result in swimming.