title: Exceptional longevity in songbirds is associated with high rates of evolution of cytochrome b, suggesting selection for reduced generation of free radicals.
abstract: In animals, longevity (maximal lifespan) is inversely related to mass-specific basal metabolic rates. However, contrary to expectation, in several mammalian taxa, exceptional longevity is associated with high basal metabolic rate, and also fast evolution of mtDNA-coded proteins. The association of these traits was suggested to result from adaptive selection of mutations in mtDNA-coded proteins, which accelerates basal respiration, thus inhibiting the generation of reactive oxygen species that constrain longevity. In birds, all the genera with high rate of cytochrome b evolution are songbirds (oscines). Within the songbirds group, both longevity residuals and lifetime expenditure of energy are positively correlated with the rate of cytochrome b evolution. Moreover, within the large songbirds family Fringillidae (true finches) mass-specific basal metabolic rates, longevity, longevity residuals and lifetime expenditure of energy are all positively correlated with the rate of evolution of cytochrome b. In Serinus, a genus of finches (canaries) that exhibits the highest rate of cytochrome b evolution, and the highest values of exceptional longevity and lifetime expenditure of energy in all birds, many of the substitutions in cytochrome b are clustered around Qi, a ubiquinone binding site adjacent to the mitochondrial matrix, apparently selected to increase the rate of ubiquinone reduction. We therefore suggest that, in songbirds, the accelerated evolution of cytochrome b involved selection of mutations that reduce the generation of reactive oxygen species, thus contributing to the evolution of exceptional longevity, and possibly also exceptional long-term memory, which is necessary for learning songs.
authors.affiliation: New Hope Biomedical R&D, New Hope, PA 18938, USA. rotteh@hotmail.com
authors.forename: Hagai
authors.initials: H
authors.lastname: Rottenberg
mesh_terms: D000818:Animals; D001483:Base Sequence; D045303:Cytochromes b / Q000235:genetics* / Q000378:metabolism*; D019143:Evolution, Molecular; D006801:Humans; D007858:Learning / Q000502:physiology; D008136:Longevity / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012641:Selection, Genetic; D020308:Songbirds / Q000235:genetics / Q000502:physiology*
chemical_list: D017382:Reactive Oxygen Species; D045303:Cytochromes b