title: Acyl composition of muscle membranes varies with body size in birds.
abstract: The acyl composition of phospholipids from pectoral muscle of eight species of birds, ranging in size from the 13 g zebra finch to the 34 kg emu, were measured and combined with recent published results for a 3 g hummingbird. This represents an approximately 11000-fold range in body mass. Muscle phospholipids, and thus muscle membrane bilayers, from birds had a relatively constant unsaturated acyl chain content of 62% but exhibited a significant allometric decline in unsaturation index (number of double bonds per 100 acyl chains) with increasing body mass. There was a significant allometric increase in the percentage of mono-unsaturates and a significant allometric decline in the percentage of n-3 polyunsaturates with increasing body mass, whilst there were no significant allometric trends in either percentage of n-6 or percentage of total polyunsaturates in bird muscle. The relative content of the highly polyunsaturated docosahexaenoic acid (22:6 n-3) showed the greatest scaling with body mass, having an allometric exponent of -0.28. The contribution of this n-3 polyunsaturate to the unsaturation index varied with body size, ranging from less than a 6% contribution in the emu to approximately 70% in the hummingbird. Such allometric variation in the acyl composition of bird muscle phospholipids is similar to that observed in mammals, although birds have fewer n-3 polyunsaturates and more n-6 polyunsaturates than do mammalian phospholipids. This allometric variation in phospholipid acyl composition is discussed with respect to both the metabolic intensity and lifespan of different sized bird species.
mesh_terms: D000818:Animals; D001481:Basal Metabolism; D001717:Birds; D001824:Body Constitution; D002462:Cell Membrane / Q000737:chemistry*; D004281:Docosahexaenoic Acids / Q000032:analysis; D005227:Fatty Acids / Q000032:analysis*; D005229:Fatty Acids, Monounsaturated / Q000032:analysis; D015525:Fatty Acids, Omega-3 / Q000032:analysis; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated / Q000032:analysis; D019787:Linoleic Acid / Q000032:analysis; D018482:Muscle, Skeletal / Q000648:ultrastructure*; D010743:Phospholipids / Q000737:chemistry*; D020308:Songbirds
chemical_list: D005227:Fatty Acids; D005229:Fatty Acids, Monounsaturated; D015525:Fatty Acids, Omega-3; D043371:Fatty Acids, Omega-6; D005231:Fatty Acids, Unsaturated; D010743:Phospholipids; D004281:Docosahexaenoic Acids; D019787:Linoleic Acid