The more the barnacle eats, the more it grows. And that can create a tight living arrangement for the creature. Like lobsters, barnacles shed their shell when it gets too small for them. But since they never leave their plated homes, they must enlarge their current one. No one is quite sure how the barnacle accomplishes this home renovation, but there is probably a chemical secretion that dissolves the inner layers while new material is added to the outside.
Most barnacles are hermaphrodites, meaning they have both male and female sex organs.
But to create baby barnacles, they must be fertilized by a neighbor. A retractable tube containing sperm can reach outside the shell as far as several inches to fertilize a nearby barnacle. Courtesy of Bullfrog Films and the National Film Board of Canada. Newborn barnacles emerge from their parent's shells as one-eyed larvae. These larvae settle to the bottom, and begin feeling around for a new home, beginning the cycle all over again.