BARNACLE, popular name for members of the subclass Cirripedia in the class
Crustacea (see CRUSTACEAN). The name was originally applied to the barnacle
goose of northern Europe, and its transfer to these crustaceans was due
to the fable
that the bird develops from the stalked, or "goose," barnacle (Lepas).
Most barnacles are hermaphrodites; all inhabit salt water. The larvae are
free-swimming, but the adults always attach to foreign objects, such as
ship
bottoms, wharf piles, rocks, floating timbers, whales, large fish, and
shellfish. The
subclass is divided into five orders, four of which are minute forms parasitic
on other
shellfish. The other order includes the acorn barnacles common to temperate
and
cold waters, and the stalked barnacles, which are usually found in warm
waters,
but, because they attach themselves to ships, are distributed throughout
the world.
Much expense is involved in the periodical removal of barnacles from the
bottoms of
ships. A method of controlling barnacle infestation by means of ultrasonic
vibrations
was introduced in 1955. The hull of the ship is fitted with thin metal
plates that are
vibrated by a generator at 25,000 cycles per second; the vibrations repel
the
barnacles.
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