RELATIVES

Barnacles are crustaceans and are, therefore, relatives of crabs and shrimp.  Like other crustaceans they must shed their shell, or molt, to grow.  But unlike crabs and shrimp they cannot move or hide.

How do barnacles avoid getting eaten or drying out when the shell is soft?  They have developed a unique additional shell which is not molted but surrounds and protects them.

Close relatives of Balanus glandula include barnacles on a stalk once believed to produce geese, and even barnacles living on whales. 

Gooseneck barnacles

Photos by Bill Austin, Marine Ecology Centre