Determinants of within- and among-clutch variation in yolk corticosterone in the European starling

Department of Biological Sciences, Simon Fraser University, Burnaby, British, Columbia, Canada V5A 1S6.
Hormones and Behavior (Impact Factor: 4.63). 02/2008; 53(1):104-11. DOI: 10.1016/j.yhbeh.2007.09.007
Source: PubMed


Maternal glucocorticoids are known to affect offspring phenotype in numerous vertebrate taxa. In birds, the maternal transfer of corticosterone to eggs was recently proposed as a hormonal mechanism by which offspring phenotype is matched to the relative quality of the maternal environment. However, current hypotheses lack supporting information on both intra- and inter-clutch variation in yolk corticosterone for wild birds. As such, we examined variation in yolk corticosterone levels in a wild population of European starlings (Sturnus vulgaris). Maternal condition, clutch size and nesting density were all negatively related to yolk corticosterone deposition; females with high condition indices, those laying larger clutches and those nesting in high-density associations deposited lower amounts of the hormone into eggs than those with low condition indices, laying small clutches and nesting in isolation. Alternatively, we found no effects of maternal age or human disturbance on yolk corticosterone deposition. Intra-clutch variation of yolk corticosterone was significant, with levels increasing across the laying sequence in all clutch sizes examined, with the difference between first and last-laid eggs being greater in large versus small clutches. Given the reported effects of yolk corticosterone on offspring size and growth, intra-clutch variation in yolk corticosterone has the potential to alter the competitive environment within a brood. Furthermore, our results indicate that variation in yolk corticosterone can originate from variation in both the mother's quality as well as the quality of her breeding environment. The presence of inter-female variation in particular is an important pre-requisite in testing whether the exposure of offspring to maternally-derived corticosterone is a mechanistic link between offspring phenotypic plasticity and maternal quality.

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    • "Additionally, it might be worth mentioning here that the stress hormone corticosterone might also be involved, since the amount of corticosterone within egg yolk is known to increase with laying order in some bird species (e.g. Love et al. 2008). Interestingly, increased yolk corticosterone has been linked to increased oxidative stress and accelerated telomere erosion (Haussmann et al. 2012), a pattern consistent with our results. "
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    ABSTRACT: A trade-off between resource investment toward growth rate and body self-maintenance is likely to occur, but the underlying molecular mediators of such trade-off remain to be determined. In many altricial birds, hatching asynchrony creates a sibling competitive hierarchy within the brood, with first-hatched nestlings enjoying substantial advantages compared to last-hatched nestlings. We used this opportunity to test for a trade-off between growth and self-maintenance processes (oxidative stress, telomere erosion) in great tit nestlings, since resource availability and allocation are likely to differ between first-hatched and last-hatched nestlings. We found that despite their starting competitive handicap (i.e. being smaller/lighter before day 16), last-hatched nestlings exhibited growth rate and mass/size at fledging similar to first-hatched ones. However, last-hatched nestlings suffered more in terms of oxidative stress, and ended growth with shorter telomeres than first-hatched ones. Interestingly, growth rate was positively related to plasma antioxidant capacity and early-life telomere length (i.e. at 7 days old), but among last-hatched nestlings, those exhibiting the faster body size growth were also those exhibiting the greatest telomere erosion. Last-hatched nestlings exhibited elevated levels of plasma testosterone, but only at day 7. Testosterone levels were positively associated with oxidative damage levels and plasma antioxidant capacity, the latter being only significant for first-hatched nestlings. Our results suggest that last-hatched nestlings present a specific trade-off between growth rate and self-maintenance processes, which is possibly driven by their need to compete with their older siblings and potentially mediated by elevated levels of testosterone.
    Oecologia 08/2015; 179(4). DOI:10.1007/s00442-015-3429-9 · 3.09 Impact Factor
    • "Subordinate reproductive females can show either elevated or lowered GCs to dominant females depending on a species' social system (social: Sapolsky 1992; Sapolsky et al. 2000; cooperatively breeding: Young et al. 2006; both: Creel 2001). Aggressive interactions and perceived increases in competition are known to increase maternal GCs in fish (McCormick 1998, 1999, 2006), reptiles (Comendant et al. 2003) and birds (Love et al. 2008). Declines in habitat integrity are often related to elevated maternal GCs; however, complex interactions between resources and other extrinsic variables can complicate this relationship (Madliger & Love 2011). "

    Integrative and Comparative Biology; 04/2015
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    • "Our experimental protocol involved hormonal treatment of mothers assuming transfer of steroids from mothers to yolks (following previous studies [20], [23], [30], [31]), rather than direct manipulation of egg hormone content by egg injection. This raises the possibility that the effects we observed on offspring could have been ‘indirect’, e.g. "
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    ABSTRACT: Maternal effects provide a mechanism to adapt offspring phenotype and optimize the mother's fitness to current environmental conditions. Transferring steroids to the yolk is one way mothers can translate environmental information into potential adaptive signals for offspring. However, maternally-derived hormones might also have adverse effects for offspring. For example, recent data in zebra finch chicks suggested that ageing related-processes (i.e. oxidative stress and telomere loss) were increased after egg-injection of corticosterone (CORT). Still, we have few experimental data describing the effect of maternal effects on the growth-ageing trade-off in offspring. Here, we chronically treated pre-laying zebra finch females (Taeniopygia guttata) with 17-β-estradiol (E2) or CORT, and followed offspring growth and cellular ageing rates (oxidative stress and telomere loss). CORT treatment decreased growth rate in male chicks and increased rate of telomere loss in mothers and female offspring. E2 increased body mass gain in male offspring, while reducing oxidative stress in both sexes but without affecting telomere loss. Since shorter telomeres were previously found to be a proxy of individual lifespan in zebra finches, maternal effects may, through pleiotropic effects, be important determinants of offspring life-expectancy by modulating ageing rate during embryo and post-natal growth.
    PLoS ONE 05/2014; 9(5):e97705. DOI:10.1371/journal.pone.0097705 · 3.23 Impact Factor
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