There are more than 1,000 known species of
barnacles spread out in virtually all marine habitats. They are
actually crustaceans, related to lobsters, crabs, and shrimp.
They typically live for between 5 and 10 years, but some of the
larger species are known to be much older.
Barnacle cement, the
substance they use to glue themselves in place, is one of the
strongest known natural adhesives. It is stronger even than
epoxy cement and does not readily dissolve.
Barnacles have evolved some of the longest penises, relative to body size, of any creature. Barnacle penises can stretch to up to eight times the length of their bodies.
Most barnacles are hermaphrodites that may act as either a male or a female. They can't self-fertilize, so they need to find a partner. They are aided by chemosensory bristles that allow barnacles acting as males to detect the chemical signals given out by barnacles acting as females. Once the male barnacle "sniffs out" a receptive partner, it uses its long, stretchy penis to reach out and mate with her.