The taxonomy (that is, the classification) of the barnacle family, in addition to placing them in the phylum Arthropoda, also puts them in the class Crustacea and the order Cirripedia. Crustacea, in Latin, means "the shelled ones," and Cirripedia, roughly translated, means an animal with feet that are slender and wispy, like cirrus clouds.
The most common barnacle belongs to the order Balanus. It is called the acorn barnacle (balanos, in Greek, means acorn). The species Balanus nubilus, found in Puget Sound, can reach a diameter of nearly a foot and is said to be good to eat.
Barnacles have existed since Jurassic times, the period in the earth's history during which dinosaurs lived. Fossils more than 150 million years old have revealed the presence of barnacles, whose ancestry can be traced back nearly 400 million years.
An eleventh century myth tells a story about one kind of barnacle, the goose barnacle (Lepas). The monks of those days were forbidden from eating meat during Lent, and they claimed that the barnacle goose, a bird, was simply a "grown up" goose barnacle. They argued that, being a fish, the barnacle goose could be eaten. Perhaps with a little imagination, the stalk, shell, and feathery cirri (feet) of the goose barnacle do look like those of an embryonic bird. in any event, the myth helped out those monks who wanted a hearty meal and gave the barnacle goose its name.
Barnacles live only in salt water. There are two kinds, the stalked barnacle (goose barnacle) and the nonstalked barnacle (acorn, or sessile, barnacle). Most barnacles are hermaphroditic; that is, they have both male and female reproductive organs. However, most barnacles must be fertilized by a neighbor, and that is one reason why they grow in large colonies. One scientist has estimated that the barnacles living along a half mile stretch of coastline can release a trillion young a year; many of these are eaten by other animals.
If barnacles are allowed to accumulate on a ship's hull, the ship will travel slower in the water, or it will have to burn more fuel to keep up its speed, than it would otherwise. A sixmonth growth of barnacles can result in having to burn 40 to 45 percent more fuel to maintain cruising speed. Removing barnacles from ships' hulls costs ship owners more than $125 million a year.
Although many new ideas have been tested, the best way to keep barnacles from growing on a ship's hull is still to paint the hull with copper bottom paint. The paint, which contains copper oxide, forms a toxic film that keeps cyprides (young, swimming barnacles) away from the hull.
The development of a barnacle takes place in two stages: a larval stage called the naupli, and a cyprides stage. In both of these stages of development the barnacles swim about freely, making up part of the mass of microscopic plants and animals collectively called plankton. During the later, cyprides stage they are attracted to other barnacles and use their front two antennae to crawl to a likely spot, where they will glue themselves and remain for life. The life span of most barnacles is from three to five years.
Inside its shell, the barnacle actually stands on its "head" and uses its "feet" to rake the plankton, which it eats. When the shell becomes too small to house the growing animal, a chemical is secreted which dissolves the inside of the shell and simultaneously builds up the outside. The barnacle's shell is made of limestone.
Barnacle cement, the substance the animals use to glue themselves to ships' bottoms and to rocks, has attracted the interest of doctors. A layer of this cement three tenthousandths of an inch thick over one square inch will support a weight of 7000 pounds. It is even stronger than epoxy cement. At temperatures above 6000°F the glue will soften but not melt, and at 380°F the cement will not crack. It does not dissolve in most strong acids, alkalies, organic solvents, or water. If man could learn to manufacture this cement, which barnacles have been using for millions of years, it could be used to mend broken bones and hold fillings in teeth.
14, #3, MayJune 1968
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