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National Geographic : 1979 Jun
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A5TEROMPHALUSHOOKERI,1,UUUA Supreme designers: A mini-superdome... A space station... ASTEROLAMPRAVULGARIS,1,165 X ^,'-Ti~tn ,rvD I^' v MICROGRAPHSBYDAVID P. NICOLAS,DANIELW.GATES,ANDRICHARDB. HOOVER A fantasy from outer space. observe under his microscope is reproduc tion. First, the two halves of the pillboxlike shell push apart. The diatom's nucleus then divides, and each new nucleus migrates into one of the half shells. The new diatoms then secrete a new inner half. But a problem remains: The diatom formed from the inner half of the pillbox is slightly smaller, and when it divides, one of its offspring will be smaller still. Eventually the shells would become too small to house the necessary cell parts. So, for most species, occasional sexual re production is essential. I have watched two Pennales come together and envelop them selves in a gelatinous material while they ex changed chromosomes. Later the fertilized protoplasm breaks out of its parent shell and develops into a new full-size diatom. In Ten Days, a Billion Diatoms Diatoms can reproduce at phenomenal rates, some even dividing every four to eight hours. These could become a billion in only ten days' time. Their immense blooms can change the ocean's color for hundreds of square kilometers. Eventually they deplete the available silicon and other nutrients. Great numbers die and sink, carpeting the seafloor with a layer of diatomaceous ooze as deep as 300 meters. Some thirty million square kilometers of the northern Pacific and Antarctic sea bottoms are buried be neath mantles of dead diatoms. Over the aeons, as oceans rise and continents shift, this ooze fossilizes into rich deposits of diato maceous earth, or diatomite. Diatomaceous earth is mined in the American West for use in industry. Its light weight and a multitude of pores make diato mite an ideal filter. Beer and wine pass through its microscopic sieves. It is a fine abrasive, in demand for space-industry components, and a filler for paint, insecti cides, and many other products. We reap a legacy from diatoms, living and dead. And it is not just that these incon spicuous pieces of glass-wrapped proto plasm make the earth a hospitable place on which to live. They fill our minds with won der and teach us to look more closely. I know now I can find perfect beauty any day in almost any mudhole, and in every new clump of brown slime, an adventure. ' NationalGeographic,June 1979 878
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