Membrane fatty acid composition and longevity of mammals and birds

The fatty acid composition of membrane lipids varies systematically among species in a manner that is consistent with their metabolic rate and longevity. Because the susceptibility of fatty acids to peroxidation relates directly to their extent of unsaturation, it is possible to calculate a peroxidation index (PI) for membranes through characterization of their specific fatty acid composition. Long-living mammals and birds have membrane lipids with a lower PI than shorter-living species. Bird and mammal species with the same maximum life span also have membrane lipids with essentially the same PI. Exceptionally long-living mammals and birds usually have membrane lipids high in monounsaturates, but low in polyunsaturates, with the consequence that the PI of their membrane lipids is as low as expected for their respective longevity. Longevity variation within species (whether due to calorie-restriction, extended longevity associated with specific strains, queen-worker differences in honey bees or inherited longevity differences among humans) is also associated with differences in membrane composition and PI. Membrane composition is specific for each species and PI appears to generally be resistant to dietary manipulation. It is postulated that membrane fatty acid composition is an important influence on aging and the determination of maximum life span

Eggs in the Freezer: Energetic Consequences of Nest Site and Nest Design in Arctic Breeding Shorebirds

Birds construct nests for several reasons. For species that breed in the Arctic, the insulative properties of nests are very important. Incubation is costly there and due to an increasing surface to volume ratio, more so in smaller species. Small species are therefore more likely to place their nests in thermally favourable microhabitats and/or to invest more in nest insulation than large species. To test this hypothesis, we examined characteristics of nests of six Arctic breeding shorebird species. All species chose thermally favourable nesting sites in a higher proportion than expected on the basis of habitat availability. Site choice did not differ between species. Depth to frozen ground, measured near the nests, decreased in the course of the season at similar non-species-specific speeds, but this depth increased with species size. Nest cup depth and nest scrape depth (nest cup without the lining) were unrelated to body mass (we applied an exponent of 0.73, to account for metabolic activity of the differently sized species). Cup depth divided by diameter2 was used as a measure of nest cup shape. Small species had narrow and deep nests, while large species had wide shallow nests. The thickness of nest lining varied between 0.1 cm and 7.6 cm, and decreased significantly with body mass. We reconstruct the combined effect of different nest properties on the egg cooling coefficient using previously published quantitative relationships. The predicted effect of nest cup depth and lining depth on heat loss to the frozen ground did not correlate with body mass, but the sheltering effect of nest cup diameter against wind and the effects of lining material on the cooling coefficient increased with body mass. Our results suggest that small arctic shorebirds invest more in the insulation of their nests than large species

Metabolomics Reveals Target and Off-Target Toxicities of a Model Organophosphate Pesticide to Roach (Rutilus rutilus): Implications for Biomonitoring

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