Large-brained birds suffer less oxidative damage.
Large brains (relative to body size) might confer fitness benefits to animals. Although the putative costs of well-developed brains can constrain the majority of species to modest brain sizes, these costs are still poorly understood. Given that the neural tissue is energetically expensive and demands antioxidants, one potential cost of developing and maintaining large brains is increased oxidative stress ('oxidation exposure' hypothesis). Alternatively, because large-brained species exhibit slow-paced life histories, they are expected to invest more into self-maintenance such as an efficacious antioxidative defence machinery ('oxidation avoidance' hypothesis). We predict decreased antioxidant levels and/or increased oxidative damage in large-brained species in case of oxidation exposure, and the contrary in case of oxidation avoidance. We address these contrasting hypotheses for the first time by means of a phylogenetic comparative approach based on an unprecedented data set of four redox state markers from 85 European bird species. Large-brained birds suffered less oxidative damage to lipids (measured as malondialdehyde levels) and exhibited higher total nonenzymatic antioxidant capacity than small-brained birds, whereas uric acid and glutathione levels were independent of brain size. These results were not altered by potentially confounding variables and did not depend on how relative brain size was quantified. Our findings partially support the 'oxidation avoidance' hypothesis and provide a physiological explanation for the linkage of large brains with slow-paced life histories: reduced oxidative stress of large-brained birds can secure brain functionality and healthy life span, which are integral to their lifetime fitness and slow-paced life history.
MTA-DE "Lendület" Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary. csvagasi@gmail.com.|Evolutionary Ecology Group, Hungarian Department of Biology and Ecology, Babeş-Bolyai University, Cluj Napoca, Romania. csvagasi@gmail.com.
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Vágási
MTA-DE "Lendület" Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.|Evolutionary Ecology Group, Hungarian Department of Biology and Ecology, Babeş-Bolyai University, Cluj Napoca, Romania.
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Vincze
Department of Molecular Biology and Biotechnology, Babeş-Bolyai University, Cluj Napoca, Romania.
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Pătraş
Museum of Zoology, Babeş-Bolyai University, Cluj Napoca, Romania.
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Osváth
Evolutionary Ecology Group, Hungarian Department of Biology and Ecology, Babeş-Bolyai University, Cluj Napoca, Romania.|'Milvus Group' Bird and Nature Protection Association, Tîrgu Mureș, Romania.
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Marton
Evolutionary Ecology Group, Hungarian Department of Biology and Ecology, Babeş-Bolyai University, Cluj Napoca, Romania.|'Milvus Group' Bird and Nature Protection Association, Tîrgu Mureș, Romania.
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Bărbos
CREAF, Cerdanyola del Vallès, Spain.|CSIC, Cerdanyola del Vallès, Spain.
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Sol
MTA-DE "Lendület" Behavioural Ecology Research Group, Department of Evolutionary Zoology, University of Debrecen, Debrecen, Hungary.|Evolutionary Ecology Group, Hungarian Department of Biology and Ecology, Babeş-Bolyai University, Cluj Napoca, Romania.
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D000818:Animals; D000975:Antioxidants; D001717:Birds / Q000502:physiology*; D001921:Brain / Q000033:anatomy & histology*; D009929:Organ Size; D018384:Oxidative Stress; D010802:Phylogeny
D000975:Antioxidants
antioxidants; brain size; life history; lipid peroxidation; oxidative stress