Pile Worm       Nereis vexillosa



Also called the clam worm or mussel worm, this worm-like animal is found in mussel clumps, under docks and in gravelly sediments in low energy environments such as sheltered bays.  It can also be found in high energy areas such as the open coast where it hides within mussel beds for protection from waves and currents.


It is a member of the segmented worm group called the Annelids. Other members are the earthworms (Oligochaeta) and leeches (Hirudinea).  The pile worm belongs to the group called Polychaeta.  The body is made up of a series of identical segments that sprout small bristles and fleshy limbs.  The head sports several tentacles and a mouth housing a powerful, protrusible jaw with which they defend themselves and capture animal prey or tear up algae for food.


During mating season in early summer the males and females, with their fleshy limbs enlarged into paddles for swimming, swarm at the surface where their sperm and eggs are released.  Normally the spawned out animals will die and sink to the bottom or be eaten by fish. However the individual in the picture was found in the early morning intact on the beach near the Boston Harbor Marina. Since the body wall burst releasing reproductive products when the animal was handled, it probably did not participate in the main spawning event.


This species is of medium size ranging anywhere from 2 to 12 inches in length.  A cousin found more in sediments can grow to 16 inches.  Often sought for fish bait, the pile worm is quite common but due to its cryptic colors of blue, green and brown is seldom seen.