Barnacles
A barnacle is a type of crustacean that is related to lobsters and crabs. There are over 1,220 species of barnacles that have been discovered and classified. Charles Darwin was the first person to officially study and classify them. In 1851 and 1854 he published a series of monographs.
When an appropriate place is found the cyprid larva cements itself headfirst to the surface and then undergoes metamorphosis into a juvenile barnacle. Typical barnacles develop six hard armour plates to surround and protect their bodies. For the rest of their lives they are cemented to the ground, using their feathery legs (cirri) to capture plankton and gametes when spawning. They are usually found in the intertidal zone.
Once metamorphosis is over and they have reached their adult form, barnacles will continue to grow, but not moult. Instead, they grow by adding new material to the ends of their heavily calcified plates. Like many invertebrates, barnacles are hermaphroditic and alternate male and female roles over time.
Barnacles often attach themselves to man-made structures, sometimes to the structure’s detriment. They even attach themselves to whales. Other members of the class have quite a different mode of life. Some barnacles are edible by humans, and goose barnacles are treasured as a delicacy in Portugal, Spain, and Greece and other Mediterranean countries.
The resemblance of this barnacle’s fleshy stalk to a goose’s neck gave rise in ancient times to the notion that geese, or at least certain seagoing species of wild goose, literally grew from the barnacle. Most notably, the wild Barnacle Goose, whose eggs and young were rarely seen by humans because it breeds in the remote Arctic, got its popular name because it was imagined to grow from gooseneck barnacles.