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Ocean Watch

By Susan Scott

Monday, May 15, 2000

Counting the ways
to love barnacles

Last week, I wrote about how thrilled I was to find and bring home a big barnacle shell from Chile. After I wrote the story, it occurred to me that readers might wonder what it is, exactly, I like about these creatures. Barnacles, after all, plague boat owners, slice skin like razors and (in my opinion) taste terrible.

But there's another side to these pesky crustaceans. In the world of marine biology, barnacles are famous for being both weird and wonderful.

Take the acorn barnacle. The renowned naturalist Lois Agassiz (1807-1873) described it as "a little shrimplike animal standing on its head in a limestone house and kicking food into its mouth."

Yes, barnacles spend their lives standing on their heads.

A barnacle starts out life as a free-swimming larva but when it matures, it must settle down. The most important factor in choosing a home is the presence of other barnacles of the same species to serve as potential mates.

Barnacle larvae find their kin by recognizing species-specific proteins on adult barnacles' bodies. When a larva detects the neighborhood it's looking for, it lands, then crawls in circles among the relatives, scouting out a "lot." When it finds a spot big enough to grow up in, it settles in.

ONCE in place, barnacle larvae use cement-secreting glands to attach themselves, headfirst and permanently, to the surface.

Because it is incredibly strong and sticks to wet surfaces, barnacle cement is of great interest to dental researchers.

Immediately, the acorn barnacle larva starts reorganizing its body and soon builds its protective limestone house.

A barnacle eats by extending feathery appendages from its house and snagging passing plankton. These appendages sweep together and downward, much like the opening and closing of your two fists with your wrists held together.

Reproduction in barnacles is an amazing example of nature's resourcefulness. Each barnacle has both male and female organs, but they don't fertilize themselves. Instead, a mature barnacle uncoils its long, flexible, snakelike penis and probes around for a mate. When it finds a receptive neighbor, it deposits sperm.

One species of acorn barnacle lives on the backs of sea turtles. In this case, individuals are often too few and far between for the reach-out-and-touch-someone style of mating. Therefore, these barnacles carry tiny males attached to their shells like parasites. These degenerate males are strictly sperm donors.

STALKED or gooseneck barnacles don't construct volcano-style homes. These barnacles have small egglike shells on flexible stalks, which enable the animals to aim toward food sources.

Although these muscular stalks resemble the necks of geese, that's not where the name came from. Rather, in medieval England, people claimed baby geese and ducks hatched from the shells of stalked barnacles. This isn't as wacky as it sounds. If ducks and geese came from barnacles, then during religious meat-fasting days when only seafood was allowed, people could eat ducks and geese.

Barnacles are called pi'oe'oe in Hawaiian. People who were a constant attraction to the opposite sex in ancient Hawaii were said to be clung to by barnacles. The Irish writer James Joyce heard a similar metaphor while dating his future wife, Nora Barnacle. James' father quipped, "She'll never leave him."

How can I love barnacles? How can I not?

Marine science writer Susan Scott's Ocean Watch column
appears Mondays in the Star-Bulletin. Contact her at

E-mail to City Desk

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