Blue Mussels

     Many people who visit the Atlantic Ocean coastline of the Middle Atlantic States, and elsewhere in polar and temperate waters, see varying-sized clusters of blue mussels attached to the green-plant encrusted boulders of rock jetties that extend from the beaches into the tidal area of the ocean.  Jetties are human-made walls constructed to stop waves from washing sand off the beaches.  And the many colonies of mussels find the boulders to be handy homes.  Though they, at first, appear uninteresting, they are more intriguing than they look.  They filter impurities from a lot of sea water, and they are part of several food chains. 
     Blue mussels are animals in the mollusc family of clams, oysters and others.  They are bivalves as many kinds of molluscs are, meaning they have two shells they close with a powerful muscle.  The shells of these mussels are elongated, smooth and purple, blue or brown.  They are attached to the boulders by strong, threadlike byssal threads secreted from glands in the foot of each animal.  But each mussel can release those threads to move on its from one place to another to be in position to get food.  These mussels also use those attachments to immobilize some would-be predators such as whelks, which are a kind of snail. 
     Blue mussels, like clams, are filter feeders that consume plankton and detritus when the tide comes in and cover the rocks.  Cilia of a tube projecting from the partly open shell pull water and food into the mussels' bodies, food is filtered from the water in the body and the water is ejected through another tube.  Each mussel processes ten to eighteen gallons of ocean water each day. Interestingly, mussels, and their relatives, also filter toxins and bacteria from the water, cleansing it.  But when the tide goes out, the mussels are exposed to the drying air and predators.  During that vulnerable time they close their shells to stay moist inside and defend themselves against animals that eat them when they can.  
     Several kinds of animals eat blue mussels, including people, whelks, starfish, gulls, crows, common eider ducks, oystercatchers, which are a kind of long-legged, long-billed shore bird, and other kinds of creatures.  Oystercatchers have thin bills they poke between the shells of molluscs to pry them open to get the soft body inside.   
     Each blue mussel is of one gender.  Each female of this species spawns from five to twelve million eggs sometime between mid-May to late June.  The newly hatched larvae float freely in the ocean for three to four weeks.  Many of them are eaten by jellies and other creatures in the ocean.  The survivors, however, attach themselves with byssal threads to hard surfaces, such as piers, boulders and the like.  And there they spend the rest of their lives, feeding, growing and spawning.
     The next time the reader goes to the seacoast, look for these molluscs on rock jetties protruding into the ocean.  Blue mussels are pretty in their own, plain way and have an interesting life history.