title: Plasticity in the adrenocortical response of a free-living vertebrate: the role of pre- and post-natal developmental stress.
abstract: Optimal functioning of the hypothalamo-pituitary-adrenal (HPA) axis is paramount to maximizing fitness in vertebrates. Research in laboratory mammals has suggested that maternally-induced stress can cause significant variation in the responsiveness of an offspring's HPA axis involving both pre- and post-natal developmental mechanisms. However, very little is known regarding effects of maternal stress on the variability of offspring adrenocortical functioning in free-living vertebrates. Here we use an experimental approach that independently lowers the quality of both the pre- and post-natal developmental environment to examine programming and plasticity in the responsiveness of the HPA axis in fledglings of a free-living passerine, the European starling (Sturnus vulgaris). We found that mimicking a hormonal signal of poor maternal condition via an experimental pre-natal increase in yolk corticosterone decreased the subsequent responsiveness of the HPA axis in fledglings. Conversely, decreasing the quality of the post-natal developmental environment (by decreasing maternal provisioning capability via a maternal feather-clipping manipulation) increased subsequent responsiveness of the HPA axis in fledglings, apparently through direct effects on nestling body condition. The plasticity of these responses was sex-specific with smaller female offspring showing the largest increase in HPA reactivity. We suggest that pre-natal, corticosterone-induced, plasticity in the HPA axis may be a 'predictive adaptive response' (PAR): a form of adaptive developmental plasticity where the advantage of the induced phenotype is manifested in a future life-history stage. Further, we introduce a new term to define the condition-driven post-natal plasticity of the HPA axis to an unpredictable post-natal environment, namely a 'reactive adaptive response' (RAR). This study confirms that the quality of both the pre- and post-natal developmental environment can be a significant source of variation in the responsiveness of the HPA axis, and provides a frame-work for examining ecologically-relevant sources of stress-induced programming and plasticity in this endocrine system in a free-living vertebrate, respectively.
authors.affiliation: Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, V5A 1S6 Canada.
authors.forename: Oliver P
authors.initials: OP
authors.lastname: Love
authors.forename: Tony D
authors.initials: TD
authors.lastname: Williams
mesh_terms: D000818:Animals; D000835:Animals, Wild / Q000196:embryology / Q000254:growth & development / Q000378:metabolism / Q000502:physiology; D052284:Clutch Size; D003345:Corticosterone / Q000097:blood / Q000378:metabolism / Q000494:pharmacology; D004625:Embryo, Nonmammalian / Q000187:drug effects; D004924:Escape Reaction / Q000187:drug effects / Q000502:physiology; D005260:Female; D006234:Handling, Psychological; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects / Q000378:metabolism / Q000502:physiology*; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects; D009035:Mothers; D009425:Nesting Behavior / Q000502:physiology; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology*; D046749:Starlings / Q000196:embryology* / Q000254:growth & development* / Q000378:metabolism / Q000502:physiology; D013312:Stress, Physiological / Q000097:blood / Q000196:embryology / Q000378:metabolism / Q000503:physiopathology*
chemical_list: D003345:Corticosterone