Thursday, December 14, 2006

The Fountain Of Youth

Is not a fountain. It is the Turtle. Whom it turns out are not only living fossils but the longest living teenagers. And we are it's only real enemy and the reason for its possible extinction.

“Turtles don’t really die of old age,” Dr. Raxworthy said. In fact, if turtles didn’t get eaten, crushed by an automobile or fall prey to a disease, he said, they might just live indefinitely

Turtles resist growing old, and they resist growing up. Dr. 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 Dr. 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 like snakes and crocodiles, 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 blockbuster 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.

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 stampeding 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 equatorial home.

Behind such biblical longevity is the turtle’s stubborn 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.

Imke Lass for The New York Times, at the University of Georgia, Savannah River Ecology Lab

From top, a leopard tortoise, a South African land-based species and a common pet. Center, a New Guinea snakeneck turtle, a carnivorous species found in the river system in the southern part of the country. Above, a big-headed turtle, native to mountain streams in Southern China and related to North American snapping turtles.

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