On a quest for longevity
Centuries ago, Ponce de Leon sailed across the Atlantic Ocean searching for the fountain of eternal youth. But clues to what the fabled Spanish explorer sought may well have been swimming right under his feet.
Some fish simply don’t age, scientists have found, and may live up to 200 years with no loss of vitality. Deciphering the mechanisms that enable these fish to stay robust, says Caleb Finch, a gerontologist at USC, “might shed light on ways of extending our productive lifespan.”
Ultimately, he and others hope to prove that the physical ravages associated with getting older, known as senescence, aren’t inevitable. Thinking that aging was universal “prevented people from looking seriously at the possibility that some creatures don’t age,” he says. “But this research opens up a whole new area in studying the fundamental biology of aging.”
Such research is relatively new.
Most of what we know about aging is derived from experiments on mice, rats, fruit flies and earthworms, which are relatively easy to study because their lives are short. Research on long-lived creatures, such as fish, reptiles and birds, is time-consuming and expensive, and can eat up an entire scientific career with no guarantee of significant results.
As a consequence, “this is the most neglected area of gerontology research, and it’s difficult to get funded,” says Leonard Hayflick, an anatomy professor at UC San Francisco and a pioneering gerontologist.
Already, however, what researchers have discovered in fish and turtles is counter to long-held conceptions about aging.
We do know that human longevity seems to be capped at 120 years, a maximum lifespan that research suggests is programmed genetically into our cells. As we age, fertility declines, our eyesight fails, organ function diminishes, mortality rates accelerate, and the cumulative wear and tear on our cells makes them less resilient, so that we’re more susceptible to serious illnesses, such as heart disease and cancer.
In contrast, studies of the rockfish, a Pacific Ocean perch that can live up to 140 years, indicate they don’t become frail as they get older, and they’re able to reproduce in their 70s and beyond. “Their ovaries at advanced ages continue to generate new eggs, which is completely unlike humans who stop making egg cells even before birth,” says Finch, who has conducted this research.
Other slow-aging organisms include the lobster; fish such as the sturgeon and orange roughy; reptiles such as the Blanding’s turtle and the giant tortoise; and birds such as the albatross, Andean condor, parakeet and parrot. Scientists speculate these creatures have evolved unique mechanisms to resist or even escape aging. Is it chemicals -- hormones, enzymes or proteins -- produced by their cells? Genetic differences controlled by their DNA? Or something else?
Researchers are attempting to answer these questions, but these animals are not divulging their secrets easily. “It will be revolutionary when we understand it,” says Finch, who has sponsored a biennial scientific conference on this subject since 1997.
“The field is in its infancy,” he adds. “But we’re finding new examples of this phenomenon all the time, and now everyone is talking about it because the examples are so compelling.”
If Ponce de Leon had studied fish instead of exploring the coast of Florida, he might have discovered the fountain of youth centuries ago.
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Aging research can be slow -- like the turtles
Research on long-lived creatures is slow and painstaking -- just ask Justin Congdon.
Since 1975, the environmental physiologist has put in 12-hour days, seven days a week, every spring and summer, observing the nesting season of turtles in a University of Michigan nature preserve near Ann Arbor. Continuing work that was started by other researchers in the 1950s, Congdon and his colleagues have tagged and followed more than 12,000 turtles, a group that includes Blanding’s, painted and snapping turtles.
Their arduous research project has yielded some startling results. Females remain fertile into their 70s and are often more productive and have a higher survival rate than succeeding generations of their offspring.
“In the group of painted turtles, the oldest turtles were producing at five times the rate of the youngest ones, and mortality rates for both groups were the same,” he says. Although none of these turtles is immortal, “there is no evidence they die of old age,” says Congdon. “They just get killed eventually -- either in an accident or getting hit by a passing car.”
