Mussels

Mussel (Mytilus californicus) the mussel's shell is made up of two blue-black, matching valves, with grooves indicating stages of the mussel's growth. A mussel doesn't have a head! They eat by filtering sand and water through their gills. It can filter up to sixteen gallons of water in a full day of feeding.
When mussels are young, they attach to the sea floor with strong threads called byssus and they spend most of their lives in one spot.
Approximately seventeen species of edible mussels are harvested or cultured worldwide.