Posted: Thu Mar 08, 2007 10:46 pm
This was printed in my local newspaper, but it was originally written by Natalie Angier of the New York Times.
Turtles are built for hard times. Through famine, flood, heat wave, ice age and predators' inspections, turtles take adversity in stride, usually by striding as little as possible. "The tale of the tortoise and the hare is the turtles' life story," said Jack Cover, a turtle specialist and general curator of the National Aquarium in Baltimore. "Slow and steady wins the race."
With its miserly metabolism and tranquil temperament, its capacity to forgo food and drink for months at a time, its redwood burl of a body shield, so well engineered it can withstand the impact of a stamping wildebeest, the turtle is one of the longest-lived creatures Earth has known. Individual turtles can survive for centuries, bearing silent witness to epic swaths of human swagger.
Last March, a giant tortoise named Adwaita, said to be as old as 250 years, died in a Calcutta zoo, having been taken to India by British sailors, records suggest, during the reign of King George II. In June, newspapers around the world noted the passing of Harriet, a Galapagos tortoise that died in the Australia Zoo at age 176 - 171 years after Charles Darwin is said, perhaps apocryphally, to have plucked her from her home.
Behind such biblical longevity is the turtle's stobborn refusal to senesce - to grow old. Don't be fooled by the wrinkles, the halting gait and the rheumy gaze. Researchers lately have been astonished to discover that in contrast to nearly every other animal studied, a turtle's organs do not gradually break down or become less efficient over time.
Dr. Christopher Raxworthy, associate curator of herpetology at the American Museum of Natural History, says the liver, lungs and kidneys of a centenarian turtle are virtually indistinguishable from those of its teenage counterpart, a Ponce de Leonic quality that has inspired investigators to begin examining the turtle genome for longevity genes.
"Turtles don't really die of old age," Raxworthy said. In fact, if turtles didn't get eaten, crushed by an automobile or fall prey to a disease, he said, they might live indefinitely.
Turtles have the power to almost stop the ticking of their clock. "Their heart isn't necessarily stimulated by nerves, and it doesn't need to beat constantly," said Dr. George Zug, curator of herpetology at the Smithsonian Institution. "They can turn it on and off essentially at will."
Turtles resist growing old, and they resist growing up. Zug and his co-workers recently determined that among some populations of sea turtles, females do not reach sexual maturity until they are in their 40s or 50s, which Zug proposes could be "a record in the animal kingdom."
Turtles are also ancient as a family. The noble chelonian lineage that includes all living turtles and tortoises extends back 230 million years or more, possibly predating other reptiles as well as birds, mammals, even the dinosaurs.
The turtle's core morphology has changed little over time, and today's 250 or so living species all display an unmistakable resemblance to the earliest turtle fossils. Yet the clan has evolved a dazzling array of variations on its theme, allowing it to colonize every continent save Antarctica and nearly every type of biome nested therein: deserts, rainforests, oceans, rivers, bogs, mountains, New Brunswick, Canada, New Brunswick, N.J.
"Turtles can persist in habitats where little else can survive," said Dr. J. Whitfield Gibbons, a professor of ecology at the University of Georgia in Athens.
The iconic turtle likewise has colonized the human heart. "Turtles are by far the most popular reptile," said Peter C.H. Pritchard, director of the Chelonian Research Institute in Oviedo, Fla. "Unlike snakes, which may threaten you and which move like a flash, turtles are benign and slow, and you can't dislike or distrust the clumsy."
But herpetologists fear that in humans the stalwart survivors from the Mesozoic era may at last have met their mortician. Turtle habitats are fast disappearing, or are being fragmented and transected by roads on which millions of turtles are crushed each year.
Researchers estimate that at least half of all turtle species are in serious trouble, and that some of them, like the Galapagos tortoise, the North American bog turtle, the Pacific leatherback sea turtle and more than a dozen species in China and Southeast Asia, may effectively go extinct in the next decade if extreme measures are not taken. "People love turtles, people find them endearing, but people take turtles for granted," Cover said. "They have no idea how important turtles are to the ecosystems in which they, and we, live."
Box turtles and other forest-dwelling species can spot a lake or pond a mile in the distance, possibly by detecting polarized light glinting off the surface of the water. Female sea turtles migrate across entire oceans every breeding season, unerringly making their way from far-flung feeding grounds right back to the beach where they were born, and where they are instinctively driven to lay their own eggs.
Instinctive does not mean inflexible, however. Should a weary wayfarer arrive at her natal beach in the dead of night and find it has eroded away, Pritchard said, she can adapt, swimming down the coast until she locates a suitably sandy nesting site.
Turtles, it seems, are all ears, all the time. Dr. Ray Ashton, who runs the Finca de la Tortuga biological preserve in Archer, Fla., has highly preliminary evidence that some turtle species may communicate subsonically, just as elephants do, transmitting and detecing ultralow frequency sound waves as vibrations in the ground.
In their new book, "Turtles of the World" (Johns Hopkins Press), Franck Bonin, Bernard Devaux and Alain Dupre seek to loft turtles into the limelight by showcasing the group's diversity.
There is the Indian star tortoise, its shell a vivid basket weave of dark and light veins that dance like spattered sunlight as the tortoise crosses the forest floor; and the Matamata turtle of the Amazon basin, with a flattened, ragged head and neck that look like dead leaves and a bumpy shell that mimics an old log - just try to spot that Matamata at the bottom of a stream, awaiting prey; and the massive alligator snapping turtle of the south-central United States, which lures fish right into its open jaw with a red bleb of flesh on the floor of its mouth that jiggles like a chubby worm.
Some turtles have serpentine necks twice the length of their shells; others sport sweet little snorkeling snouts that look like double-barreled cocktail straws; still others have beaks so fiercely hooked their bearers could easily serve, in the authors' words, as "adornment of the upper reaches of Notre Dame."
Turtles vary considerably in size, from the tiny speckled padloper tortoise of South Africa, which in adulthood is no bigger than a computer mouse, to the great leatherback sea turtle, which can measure 7 feet long and weigh 2,000 pounds.
Many turtles are omnivores, happily consuming fruits, leaves, insects, mollusks, fish, frogs, ice cream. Gibbons told of a friend whose pet box turtle would respond to the sound of a spoon being tapped on a glass ice cream bowl by emerging from behind the couch, walking over to its owner, rearing up on its hind legs and waiting to be spoon-fed its dessert.
Whether they wrest it from sea grass, shellfish or Haagen-Dazs, all turtles need a substantial amount of calcium, all turtles need a substantial amount of calcium, to sustain the structure that marks them as turtles and that remains among the most extraordinary architectural achievements invertebrate evolution: the shell.
In the turtle the skeleton has become the shell. During embryonic development, the bones of the turtle's rib cage grow straight out, rather than curving toward one another as they do in other vertebrates. Those ribs, spinal vertebrae and other skeletal bones are then fused to form the upper shell, called the carapace, the lower shell, or plastron, and the bony bridges that join upstairs with down. In many turtle species, the bony shell is in turn plated over with tough fingernail-like structures called scutes.
As a result of the osteotic overhaul, not only can a turtle not crawl out of its shell, it has trouble crawling, period. "Its legs stick out at bizarre angles, and the only reason it can walk at all is through sheer strength," Pritchard said. "The turtle has enormously strong muscles and extremely thick leg bones." A clumsy gait is a small price to pay for the body armor that protects adult turtles against all kinds of jaws and claws.
The shell very likely helps explain the turtle's elongated storyline. It takes time to consolidate a large, thick shell, but upon reaching adult stature, the turtle is close to invulnerable. At that point, it can compensate for its Darwinically unproductive youth with a very prolonged and zealously fecund adulthood. A female turtle will continue laying eggs until she dies.
There you go! Not the best article ever, but interesting at the least.
Napoleon - Western Painted Turtle
Apollo - Eastern Box Turtle
Moxie - Painted Turtle Mutt
RIP Hercules
Katie
I heart my herpies!
