| Summary: | Only about a dozen species of animals are known to achieve maximum ages (Amax) exceeding 100 yrs, including the freshwater pearl shell (Margaritifera margaritifera). This species has a life-span of between 100–200 years depending on latitude and environmental conditions. The difference in Amax is 3–7 times when southern populations, with Amax of 28–40 yrs, are compared to northern Arctic populations, with Amax of 114–190 yrs. Evolutionary and ecological explanations for longevity in the Arctic pearl shell include adaptations to the severe, unstable climatic and hydrological conditions in rivers. Extreme longevity seems to be related not only to the low metabolic rate in the cold climate, but the species can reduce energy expenditure for growth, and can rapidly increase metabolic rate up to 130x the normal level, to regenerate damaged shell or tissue. The physiology of this species may provide valuable clues to understanding the mechanisms that sustain longevity and retard senescence.
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