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LEWISBURG, Pa. – Chances are, a mouse in the wild will live less than a year before stumbling upon a hungry falcon or feline.
Even if that mouse manages to avoid its natural predators for a couple of years, it will likely develop cancerous tumors before long, bringing an end to its characteristically short life cycle.
Humans stand a much better chance of a living a long life before encountering an unlucky circumstance or illness. But some species seem to defy the odds altogether.
Mark Haussmann, an assistant professor of biology at Bucknell University, was interested in aging and why some animals live longer, healthier lives while others survive only a few years. Haussmann studied cacti and turtles before zeroing in on a small, marine bird that contradicts traditional assumptions about aging.
“Leach’s storm-petrels should die young but live a long life and break the conventional rules,” he said. “First of all, they’re small, and there tends to be a relationship between body size and life span. Elephants live longer than humans. Humans live longer than mice. So this bird shouldn’t live long, but it does.”
Haussmann, 33, stumbled upon some groundbreaking information in his work. His studies of storm-petrels have shown that certain characteristics of DNA – specifically lengths of the protective telomeres at the tips of DNA – are associated with species that live longer lives and possibly with how susceptible they are to cancer-causing tumors.
His work could be used as a springboard for drug companies studying cell division and cancer-treating drugs.
Protective ‘caps’ on DNA figure into age
Haussmann, who joined Bucknell this year, is continuing research he began at Kenyon College in Ohio with the help of a $535,000 National Science Foundation grant. He studied the birds on Kent Island in the Bay of Fundy in Canada, where a colony of storm-petrels comes to nest each spring.
Leach’s storm-petrels, which are about the size of a robin, spend the majority of their lives on the open sea and come to land only to breed. They have a fast metabolism, high body temperature and high glucose level, all of which should shorten their lifespan, but storm-petrels can live to be up to 40 years old.
A colony of the birds has been studied on Kent Island since the mid-1930s, and comprehensive records have been kept since the 1950s.
Previously, Haussmann measured telomere length in five species of birds with life spans ranging from five to 40 years. The studies found that those with shorter life spans, such as zebra finches, lost their protective telomere caps quickly over time. Species such as the common tern, which lives to be about 30 years old, had less shortening over time.
Storm-petrels were in a class of their own.
“Storm-petrels were the only species where the telomeres actually seemed to be getting longer over time,” Haussmann said. An enzyme in cells called telomerase has the job of building telomeres. When telomeres get too short, cells can no longer divide, and this contributes to the aging process. But, unregulated telomerase can result in runaway cell division.
“Turning on telomerase comes with a cost, and the cost is tumor formation,” Haussmann said. “So, telomerase activity has to be closely regulated.”
Even though telomerase levels are high in storm-petrels, the incidence of cancer in storm-petrels and other marine birds appears to be quite low.
“Aging and cancer are rival demons. They result due to a tradeoff. These birds can help us to understand both aging and cancer,” Haussmann said. This is why some cancer drug companies are interested in Haussmann’s research.
Theories on aging
One of the original theories of aging, called the “rate of living theory,” suggested that inactive people and animals live a longer life and that energy consumption – or high metabolism – limits life span. There is some data to support that assumption, Haussmann said, but it is now known that the main cause of aging is oxidative damage.
Cells produce free radicals, which over time break down cells, protein and DNA. Accumulated damage to cells, protein and DNA result in aging. Many age-related diseases such as Parkinson’s and Alzheimer’s and aspects of cancer and heart disease are caused by free radicals and oxidative damage.
There are mitigating factors to aging, such as antioxidants, which detoxify free radicals. Storm-petrels, much like elite athletes, produce more antioxidants, Haussmann said.
“Individuals who are trained athletes have cells that are better able to handle these free radicals that are produced compared to those of us who are couch potatoes,” he said.
In storm-petrels, those with the longest telomeres at the oldest ages also had longer telomeres at a young age, Haussmann said. So, one component to living to a healthy, old age might be beginning life with long telomeres. Telomere length is tied to both genetic and environmental conditions.
“The environment you were exposed to when you were young has large impacts on some of these cellular aging mechanisms,” Haussmann said. “But, the research is showing that the problems of a poor early life environment may not appear until you are much older. It has a way of coming back to haunt you – or age you.”
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