title: Does the interaction between glucocorticoids and insulin-like growth factor 1 predict nestling fitness in a wild passerine?
abstract: The crucial question in evolutionary ecology is to find out how physiological traits have coevolved so animals fit their stochastic environments. The plasticity of these different physiological mechanisms is largely mediated by hormones, like glucocorticoids and insulin-like growth factor 1 (IGF-1). Brood size manipulation with nestlings of free-living great tits (Parus major) was carried out to see the way in which plasma IGF-1 and feather corticosterone, a predictor of long-term sustained plasma corticosterone level, are associated across different nutritional conditions and how this association predicts survival during the nestling phase. We showed that the association between levels of IGF-1 and corticosterone depended on physiological condition of nestlings. Namely, there was a positive association between the hormones in nestlings from the decreased broods and a negative association in nestlings from the enlarged broods. Furthermore, we showed that the interaction between levels of IGF-1 and corticosterone was also related with the survival of the nestlings. Our results suggest that signalling pathways of IGF-1 and corticosterone most likely interact with each other in a nutrition-dependent way to maximize the rate of development and survival of nestlings in their stochastic environment.
authors.affiliation: Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, 46 Vanemuise Street, Tartu 51014, Estonia. Electronic address: jaanis.lodjak@ut.ee.
authors.forename: Jaanis
authors.initials: J
authors.lastname: Lodjak
authors.affiliation: Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, 46 Vanemuise Street, Tartu 51014, Estonia.
authors.forename: Vallo
authors.initials: V
authors.lastname: Tilgar
authors.affiliation: Department of Zoology, Institute of Ecology and Earth Sciences, University of Tartu, 46 Vanemuise Street, Tartu 51014, Estonia.
authors.forename: Marko
authors.initials: M
authors.lastname: Mägi
mesh_terms: D000818:Animals; D003345:Corticosterone / Q000032:analysis*; D005241:Feathers / Q000737:chemistry*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D009752:Nutritional Status; D046109:Passeriformes / Q000097:blood / Q000378:metabolism*; D010641:Phenotype
chemical_list: D007334:Insulin-Like Growth Factor I; D003345:Corticosterone
keywords: Feather corticosterone; Fledging success; Growth rate; Life-history; Phenotypic plasticity