Barnacles are highly-modified crustaceans (subphylum Crustacea) constitution the subclass Cirripedia. They are hence related to crabs and lobsters ! Barnacles are exclusively marine and tend to live in shallow and tidal waters.
After settlement, adult barnacles become permanently attached to the substratum and encased in a shell. The legs have become long hairy cirri (i.e., hair-like filaments), which are extended through a hole at the apex of the shell and comb the water to filter out food particles. The legs can be withdrawn and the opening of the shell sealed by an operculum of four additional shell plates when the barnacles are threatened or exposed to air.
Barnacles are hermaphroditic, but prefer to cross-fertilize. Being sessile, they can only accomplish this feat by having an extremely long penis – up to three times the length of the animal ! The eggs are brooded and expelled as tiny, shrimp-like planktonic larvae.
F*CK FISH 