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Citation. Brunet, A. 2003. Aging and mitochondrial efficiency in the little brown bat, Myotis lucifugus. Ph.D. Thesis, University of Minnesota. 

Abstract. The free radical theory of aging is one of several theories developed to explain differences in aging and longevity among species. According to this theory, aging is the result of oxidative damage to proteins, DNA and membranes of cells due to the inescapable production of free radicals during cellular respiration. I test the free radical theory of aging as an explanation for the extreme longevity of the little brown bat, Myotis lucifugus , which is known to live up to 34 years. One prediction of the free radical theory of aging is that long-lived organisms produce fewer free radicals than short-lived organisms. In a comparative study, I measured whole-organism oxygen consumption, free radical production, and superoxide dismutase activity of M. lucifugus , short-tailed shrews ( Blarina brevicauda ) and white-footed mice ( Peromyscus leucopus ). As predicted, free radical production per unit of oxygen consumed was significantly lower in M. lucifugus compared to the two non-flying mammals. In addition to a lower production, season variation in free radical production of M. lucifugus contributes significantly to reducing the lifetime free radical production of these bats. In fact, after accounting for these seasonal variations, the lifetime free radical production of all three species was very similar (approximately 0.2 mol H 2 O 2 /μg mitochondrial protein). A second prediction of the free radical theory of aging is that free radical production increases with age as a consequence of oxidative damage incurred on mitochondria. I tested this prediction by comparing free radical production in adult, volant juvenile, and non-volant juvenile M. lucifugus . Contrary to prediction, both groups of juveniles had
significantly higher levels of free radical production than adults. I proposed that the decreased free radical production in adults is the result of within-individual selection of efficient mitochondria due to selective pressure created by the energetic demands of flight. Amplified DNA sequences of the mitochondrial control region from adult and juvenile M. lucifugus showed evidence of mitochondrial heteroplasmy (more than one haplotype in an individual). The dominant mitochondrial haplotype in the juveniles varied among individuals but converged on one haplotype in the adults, suggesting that mitochondrial selection may be occurring.

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