Horseshoe Crabs and Velvet Worms: The Story of the Animals and Plants That Time Has Left Behind
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From one of the world’s leading natural scientists and the acclaimed author of Trilobite!, Life: A Natural History of Four Billion Years of Life on Earth and Dry Storeroom No. 1 comes a fascinating chronicle of life’s history told not through the fossil record but through the stories of organisms that have survived, almost unchanged, throughout time. Evolution, it seems, has not completely obliterated its tracks as more advanced organisms have evolved; the history of life on earth is far older—and odder—than many of us realize.
Scattered across the globe, these remarkable plants and animals continue to mark seminal events in geological time. From a moonlit beach in Delaware, where the hardy horseshoe crab shuffles its way to a frenzy of mass mating just as it did 450 million years ago, to the dense rainforests of New Zealand, where the elusive, unprepossessing velvet worm has burrowed deep into rotting timber since before the breakup of the ancient supercontinent, to a stretch of Australian coastline with stromatolite formations that bear witness to the Precambrian dawn, the existence of these survivors offers us a tantalizing glimpse of pivotal points in evolutionary history. These are not “living fossils” but rather a handful of tenacious creatures of days long gone.
Written in buoyant, sparkling prose, Horseshoe Crabs and Velvet Worms is a marvelously captivating exploration of the world’s old-timers combining the very best of science writing with an explorer’s sense of adventure and wonder.
dimming light. The forest acts as sponge, absorbing fine water droplets into an orgy of growth. Where the trees have been cleared by importunate loggers, bare gashes of rockslide reveal the volcanic tuffs and ashes weathered to clay and gingerbread-soft mash that underlies the regenerating forest. From hidden glades, whistles and trills betray the birds that happily dance and feed among the apparently endless trees. This is a country of lianas and epiphytes. Every tree trunk is decked with
butterflies to buzz and flit into their respective futures. All mass extinctions ultimately generate winners as well as losers. They help life move on. And so, to a climatic deterioration a mere 1.6 million years ago which brought on the last of the ice ages, in the Pleistocene. As ice sheets grew, they covered great areas in higher latitudes. If animals and plants were able to migrate away from the ice front, then that is exactly what they did; as long as a climatic gradient remained intact,
St. John’s passes several sheltered coves tucked away inside a coastline of magnificent cliffs. The geology is laid bare all along the rim of this island: the only problem is reaching it. Inland, the opposite is true; an endless forest of short conifers interspersed with scattered birch and aspen trees is interrupted only by shallow lakes called “ponds” hereabouts, which are a legacy of the last ice age; the bedrock is hard to see among the scrub. As we approach the end of the Peninsula, the
hint of rotten eggs. In life, Zostera trap fine sediment in their leaves and this is added to the sea floor. Then the dead leaves of the plants themselves, together with any unconsumed organic material, become incorporated as the grasses continue to grow. Decay of this material uses up nearly all the oxygen in the sediment, which soon becomes black and foul. Under these anoxic conditions, certain kinds of bacteria flourish, while organisms that breathe oxygen cannot survive. The smell is hydrogen
appropriate bacteria. Poisonous endotoxins are released into the host organism (you, me or a horseshoe crab) when the bacterial cell wall ruptures. LAL is a highly sensitive chemical able to detect minute quantities of the offending substances. The LAL test is now widely applied, having been sold on to pharmaceutical companies for commercial manufacture. It has to be prepared close to the Limulus populations, but is then exported around the world. This means that there is a tremendous demand for