Incubation behavior and Energetic strategy of female Common Eider (Somateria mollissima).

The aim of this programme will be to study the mechanisms of the regulation of body fuel utilization and energy expenditure during fasting. For this purpose, the ability of eider duck to withstand long periods of starvation will be studied by measuring the variations in plasma of major substrates concentrations (as index of lipid or protein breakdown) and hormones (e. g., leptin) and gene regulation of key targets (ob gene encoding leptin, avian uncoupling protein (UCP), ….) involved in energy metabolism. This will be done by both in vivo and in vitro investigations in fasting eider ducks and the methodological approach will need to develop new molecular tools and methodology. A special emphasis will be put on the putative relationships between body fat, plasma leptin and ob gene expression during fasting in birds to check whether leptin can be viewed as a refeeding signal. Indeed, leptin, the product of the ob gene, is a hormone mainly synthesized in the adipose tissue which is important in the regulation of food intake, adiposity and energy expenditure. The regulation of plasma leptin and ob gene expression by hormones and metabolites will be also investigated in in vivo and in vitro studies. Several metabolic pathways contribute to loss of energy and mitochondria play a central role in energy expenditure by cells. Recently several genes (such as avian UCP) homologous to the gene for brown fat uncoupling protein have been identified and represent candidate genes for the control of energy expenditure. Moreover, energy expenditure will be measured using labelled water and the role and the regulation of avian UCP by hormones and metabolites will be investigated in in vivo studies. The study of duck's adaptation to extended fasts occuring at specific stages of their life might help to understand important underlying mechanisms involved in energy expenditure, long term regulation of body fat storage and mobilization, as well as long term control of food intake.