HSP70 Level in Blood is Associated with Eggshell Blue-green Colouration the Pied Flycatcher

Abstract

Among the cellular pathways conferring protection against oxidative stress, a key role is played by heat-shock proteins, especially HSP70. It has been proposed that blue egg colouration in certain birds, which is related to the deposition of the pigment biliverdin, should be related to basic antioxidant processes in the laying female given the strong antioxidant role of biliverdin. If HSP70 levels express antioxidant defences a higher allocation of the pigment to the clutch could induce a higher response by other components of the antioxidant system like HSP70. In a field study of a breeding population of pied flycatchers Ficedula hypoleuca, a species laying blue-green eggs, we measured spectrometrically the colouration of all eggs and collected blood samples of incubating females one week after clutch completion. We estimated female condition, plasma antioxidant capacity and level of HSP70 in blood cells. HSP70 level was positively related to plasma antioxidant capacity indicating that HSP70 is involved in responses to oxidative stress. Variation in HSP70 level was in good part explained by mean egg blue-green chroma of the clutch when controlling for plasma antioxidant capacity. Results suggest that intensity of eggshell blue colouration in this population is related to a basic system involved in protection against oxidative stress.