Barnacle is the common name of the sedentary crustacean animals of the subclass Cirripedia. Barnacles are totally marine and attache themselves to the substrate by means of an adhesive produced by a cement gland and then secrete a shell of limestone plates around themselves. On the outer shores of the coast, you can see such a variety of these wonderful shellfish. Barnacles look like a mollusk but are in fact a crustacean, the only one that attaches itself to a substrate. They are quite fascinating to observe, especial when they are underwater and feeding.
Colonies of such barnacles form thick encrustations on wharves, boats, pilings, and rocky shores. They range in length up to 75 cm. On the outer coast, they are very abundant.
Because of their sedentary life and enclosing shells, barnacles were thought to be shellfish until 1830, when Charles Darwin began to study them. He was fascinated by the barnacle and much of what we know about them is from his studies. We owe so much to the work of this man.
Although nearly all other crustaceans have separate sexes, most barnacles are hermaphrodites. Some species, however, have small parasitic males growing on the side of a females shell. The fertilized egg develops into a free-swimming larva, of the basic crustacean type, with paired antennae. They then molt to become a bivalve larva, which eventually attaches itself to a suitable substrate by its first pair of antennae and undergoes metamorphosis into an adult. The barnacle lives for an average of 3 to 4 years.
Barnacles are very common on all the shores of the Pacific Northwest. I love studying these creatures, they are such a wonder of the sea world. They are such delicate little animals protected by such strong armor.