The main predators which cause this reaction when detected are the mollusc eating starfish Asterias rubens and Astropecten irregularis .
Starfish which do not feed on molluscs can cause limited jumping or valve - closing reactions .
The main predators which cause this reaction when detected are the mollusc eating starfish Asterias rubens and Astropecten irregularis , although starfish which do not feed on molluscs can cause limited jumping or valve - closing reactions .