Pearls:
A Natural History.
Neil H. Landman, Paula M. Mikkelsen,
Rdiger Bieler, and Bennet Bronson. 2001. Harry Abrams, Inc.,
New York. 232 pp., hardbound. $49.50.
One
of the great challenges of wildlife conservation is persuading
people that some odd species or another matters. Take mussels,
for example. A shrug of indifference, or even a shudder of
impatience, is a more likely response to the news that 16
species of mussels are on the U.S. Endangered Species List
than is a shiver of alarm.
But what would have folks clamoring to save the mussels and oysters and abalones and other mollusks as well? Pearls might just do it. Among these lowly creatures are some that produce gemstones that people have prized for thousands of years. Pearls; A Natural History tells the story in rich detail and lustrous photographs; the book is as beautiful as its subject.
Pearls is not only about the biology of shelled invertebrates, as it encompasses the history, anthropology, and culture of pearls as well. Paleontologist Neil E. Landman and invertebrate zoologist Paula M. Mikkelsen (both of the American Museum of Natural History in New York) and zoologist Rdiger Bieler and anthropologist Bennet Bronson (both of The Field Museum in Chicago) traveled the globe to learn about pearls, from their first appearance in the fossil record more than 200 million years ago to contemporary methods of periculture. Over and over I thought, “Wow, I didn’t know that!” Or said to whomever would listen, “This is great. Did you know. . .?”
Women and men around the world have long adorned themselves with pearls, sometimes extravagantly, as paintings of such luminaries as Elizabeth I and other European Renaissance figures attest. In the 1880s, a strange group of Londoners, led by a street sweeper, began to cover their clothes—head to toe—with mother of pearl buttons. They called themselves the Pearlies, and they still exist in London in small numbers! Rich Indian women were described in the 1830s in these words: “Their heads look too large, from the quantity of pearls with which they load them.” Strands of pearls also dangled from nose and ear rings.
Many legends surround pearls. One tells how Cleopatra wagered Marc Antony that she could offer him the most expensive meal ever prepared. He accepted the bet, then watched Cleopatra dissolve one of her pearl earrings in wine and drink it. He refused her offer of the other earring and, of course, lost the bet. The value of this pearl was reportedly worth 30 tons of gold.
Surprisingly, a pearl will dissolve in wine or vinegar, but only if it is first ground into a powder. Such dissolved pearls, or very small whole ones, were taken as medicine to treat a variety of ailments in Medieval and Renaissance Europe, and are still prescribed in traditional Asian medicine. Being mostly calcium, the authors point out, pearls couldn’t hurt, and may even help. A study of a medicinal mixture with calcium from the Akoya pearl oyster showed that it reduced cholesterol levels in rats.
The authors believe that one reason for pearls’ perceived value is that they are the only gemstones produced by living animals. So what exactly is a pearl? Technically speaking, “. . . a pearl is a calcareous body, composed of concentric layers around a central nucleus, and organically produced by a living mollusk, a soft-shelled invertebrate animal bearing a hard external shell.” The calcareous body is a form of calcium carbonate called nacre, interwoven with an organic membrane called conchiolin, and water.
Not all mollusks produce pearls; neither are pearls exclusively the products of oysters. As noted above, some mussels make pearls, as do some conches, clams, and abalones. On the other hand, not all oysters make pearls; edible oysters do not, for instance, although people eating blue mussels sometimes crack a tooth on this species’ small pearls. Nor are all pearls “pearly white.” The color of a pearl matches that of the inside of the shell (which is also nacre and usually called mother of pearl) of the animal that produced it, and may be black, blue, pink, purple, or red.
Pearl formation begins when something irritates a mollusk’s mantle, a tissue that secretes shell material. The shell material coats the irritant in thin layers. Contrary to popular belief, a grain of sand is only very rarely the stimulus, technically called the nucleus, for pearl formation. More usual stimuli are organic, such as parasites, small crabs, stray food particles, or even small fish. (Mechanical damage that moves mantle tissue to another part of the animal’s body will also stimulate pearl development.) The shape of the nucleus then influences the shape of the pearl. Natural pearls are thus seldom perfectly round like the cultured pearls we see today. The nuclei of cultured pearls are usually tiny beads cut from the shells of mussels. These beads are normally inserted into domesticated oysters, and in a few years’ time the oysters are harvested and the pearls extracted. In China, molds in the shape of Buddhas produce Buddha-shaped pearls for tourists and other trinket lovers.
Pearls concludes fittingly with a chapter entitled “Saving Pearls.” Pearl-producing mollusks have been depleted by over harvesting many times and in many places around the world. While today’s commercial pearls are cultured, millions of wild mussels are harvested for the mother of pearl used as nuclei. What’s more, pollution, invasive species, and habitat loss adversely affect both wild and domesticated mollusks.
The authors do a wonderful job of mixing the more technical information with lighter stories, but all of the text is accessible, engaging, and lively. You can read Pearls straight through, or skip around, dipping into the captions, short features, and chapter subsections as something grabs your attention. In the end, though, I think most people will be drawn into reading every word of this fascinating book. And a plea to save mussels won’t sound so silly anymore.
—Susan Lumpkin
ZooGoer 31(2) 2002. Copyright 2002 Friends of the National Zoo. All rights reserved.
