Amelia Conley, age 12, of Ashland, Ky. ANG.De Hof, age 12, of Phoenix, Ariz., for their questions:
What are barnacles?
These little shellfish were discovered centuries ago, when the first boats put out to sea. They are still cementing their stony bodies to the undersides of our ocean going ships, to piers and even the backs of whale, deep sea turtles and other living marine animals. But science did not learn the truth about them until about a hundred years ago.
The ocean is home to some 800 different barnacles and as adults they never venture forth from their stony shells. They are crustaceans, cousins of the lobsters and the shrimps and in some ways resemble the insects.
We are used to the idea that a grubby caterpillar can become a glamorous butterfly. The barnacle also develops through four distinct stages. But science was slow to discover this fact because the strange little shellfish spends its youth swimming in the vast ocean and its early stages do not resemble the adult stage any more than a caterpillar resembles a butterfly.
The shell of the adult barnacle is usually dome shaped with a hole in the top which can be closed by a hinged trap door. The smaller varieties are a quarter inch wide and greyish white. The larger varieties are two inches wide and colored purple, red, blue or yellow. The stony house is firmly cemented to a ship or floating log, to a whale or other marine animal, to the underwater posts of a pier or to a rock on the floor of the sea.
A small forest of fringed legs pokes out from the trap door, trawling for scraps of food. Algae and small sea dwellers are caught and stuffed into the barnacles mouth inside the shell.
An adult barnacle is usually both male and a male and the eggs, millions of them, are produced and fertilized inside the shell, The eggs hatch and swim away as tiny larvae which look like water fleas. Each has one eye and six legs. It eats and molts three times in the first week.
After the fourth molt, the barnacle changes its shape. It now has twelve legs, tyro eyes and two feelers and its, fat body grows almost as big as marble. Now it Is ready to settle down. it holds onto a surface with its feelers arid one of these feelers produces a sticky cement to keep it anchored. Then the barnacle builds a shell creates slimy chemicals extracted front the water. For the rest of its life it remains inside the shell, standing on its head.
The hard shell of the barnacle remains cemented where it was built long after the barnacle has died, This is a great problem to marina animals and ocean going liners. A fair sized ship is cluttered with about 30 tons ox barnacle shells after a year of ocean travel. These crusty shells must be scraped away, for they slow down a ship and force it to use extra fuel,