The membrane pacemaker hypothesis: novel tests during the ontogeny of endothermy

摘要: ABSTRACT The ‘membrane pacemaker’ hypothesis proposes a biochemical explanation for among-species variation in resting metabolism, based on the positive correlation between membrane docosahexaenoic acid (DHA) and metabolic rate. We tested this using novel model, altricial red-winged blackbird nestlings, predicting that proportion of DHA muscle liver membranes should increase with increasing rate nestling as it develops endothermy. also used dietary manipulation, supplementing natural diet fish oil (high DHA) or sunflower linoleic acid) to alter composition then assessed In support pacemaker hypothesis, proportions increased from pectoralis muscle, mitochondria during post-hatch development. By contrast, elevated had no effect rate, despite causing significant changes lipid composition. During cold challenges, higher rates were achieved by birds lower phospholipids. Given mixed we conclude correlations are likely spurious, be attributed still-unidentified confounding variable.