Crabs crack the shells with their pincers and starfish use their water vascular system to force the valves apart and then insert part of their stomach between the valves to digest the bivalve's body.
22.
Echinoderms are an exception having both a coelomic circulatory system ( i . e ., the water vascular system ) and a haemal circulatory system ( i . e ., the haemal and perihaemal systems ).
