Causes and consequences of interindividual variation in glucocorticoid secretion: Experiments in free-living kittiwakes
Abstract: Fluctuation in food availability is a frequently-encountered environmental challenge for seabirds, and secretion of glucocorticoid hormones (corticosterone) is one of the best-studied physiological mediators of the response to food shortages. Elevated corticosterone is assumed to yield sho...
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| Format: | Article in Journal/Newspaper |
| Language: | unknown |
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Underline Science Inc.
2021
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| Online Access: | https://dx.doi.org/10.48448/0v8c-f346 https://underline.io/lecture/34544-causes-and-consequences-of-interindividual-variation-in-glucocorticoid-secretion-experiments-in-free-living-kittiwakes |
| Summary: | Abstract: Fluctuation in food availability is a frequently-encountered environmental challenge for seabirds, and secretion of glucocorticoid hormones (corticosterone) is one of the best-studied physiological mediators of the response to food shortages. Elevated corticosterone is assumed to yield short-term benefits for adults and chicks, yet potentially evoke long-term costs. A unique field station in Alaska permits manipulation of food availability and/or corticosterone in free-living black-legged kittiwake adults and chicks (Rissa tridactyla) to test assumptions about causes and consequences of interindividual variation in glucocorticoid secretion. In breeding known-age adults, we found that a reduction in local food availability (induced by experimentally withdrawing food supplementation) evoked an increase in baseline corticosterone; this increase was lower in birds who spent more time off the colony, presumably foraging. Additionally, much of the inter-individual variation in corticosterone release was explained by telomere length, which may reflect individual quality. An accumulating literature (mostly from captivity) demonstrates potentially costly "programming" effects of developmental exposure to glucocorticoids on phenotype, including telomere length, while benefits of elevated glucocorticoids are rarely tested. In chicks, we found strong correlational, but weaker experimental, support for the common assumption that elevation of glucocorticoids rapidly mobilizes energy - food supplementation reduced circulating corticosterone, glucose and ketones but acute corticosterone administration did not mobilize energy substrates (though catecholamines likely did). In contrast, repeated, acute glucocorticoid elevations induced persistent downregulation of immune genes in chicks. Thus, there is currently stronger evidence for the costs of glucocorticoids than for the benefits, particularly in chicks. In long-lived, late-recruiting species like seabirds, it is challenging to connect long term fitness to non-lethal environmental challenges experienced by chicks. However, our results indicate that monitoring glucocorticoid exposure in seabird chicks may provide valuable insight into the fitness of future cohorts. Authors: Z Morgan Benowitz-Fredericks¹, Scott Hatch², Alexander Kitaysky³ ¹Bucknell University, ²Institute for Seabird Research and Conservation, ³University of Alaska Fairbanks |
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