The exceptional longevity of an egg-laying mammal, the short-beaked echidna (Tachyglossus aculeatus) is associated with peroxidation-resistant membrane composition

The echidna Tachyglossus aculeatus is a monotreme mammal from Australia that is exceptionally long-living. Its documented maximum lifespan of 50 years is 3.7 times that predicted from its body mass. Other exceptionally long-living marturnals (naked mole-rats and humans) are known to have peroxiclationresistant membrane composition, raising the question about echidnas. Phospholipids were extracted from skeletal muscle, liver and liver mitochondria of echidnas and fatty acid composition measured. As with other exceptionally long-living mammals, membrane lipids ofechidna tissues were found to have a lower content of polyunsaturates and a higher content of monounsatu rates than predicted for their body size. The peroxidation index (=peroxidation susceptibility) calculated from this membrane cornposition was lower-than-expected for their body size, indicating that the cellular membranes of echidnas would be peroxiclation-resistant. Additionally when the calculated peroxiclation index was plotted against maximum lifespan, the echidna values conformed to the relationship for mammals in general. These findings support the membrane pacemaker theory of aging and ernphasise the potential importance of membrane fatty acid composition in aging and in the determination of maximum longevity. (c) 2008 Elsevier Inc. All rights reserved.