Rough Barnacle

• A barnacle is, in truth, a crustacean lying on its back kicking food into its mouth, as Louis Agassiz put it.
• Barnacles are hermaphrodites and, being unable to move, have the longest penis in the animal kingdom relative to body size, in order to reach their neighbours.
• The cement with which they attach is one of the strongest underwater adhesives known.
• It is a cold-water, subtidal barnacle, unlike its intertidal relative: it is rarely left exposed to the air.
• It filters plankton by rhythmically beating its cirri, feathery legs that it extends through the opening at the top of the shell and draws in like a net.
• It attaches to any hard surface, including scallop shells and living lobsters, and is a regular component of the fouling on hulls and marine structures.
• Its plated calcareous shell is so distinctive that marine archaeology uses it to date how long an object has been submerged.

Habitat & environment

Rocks and shells of the cold subtidal of the North Atlantic and the Arctic

Sources consulted: Linneo (1758); Marine Life Information Network; Southward, Barnacles