Stier Antoine, Massemin Sylvie, Zahn Sandrine, Tissier Mathilde L, Criscuolo François
GECCO (Groupe écologie et conservation des vertébrés), University of Angers, Angers, France.
IPHC, Université de Strasbourg, 23 rue Becquerel, 67087, Strasbourg Cedex 2, France.
Oecologia. 2015 Dec;179(4):999-1010. doi: 10.1007/s00442-015-3429-9. Epub 2015 Aug 28.
A trade-off between resource investment into growth rate and body self-maintenance is likely to occur, but the underlying molecular mediators of such a 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 (T), but only at day 7. T 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 T.
在资源投入到生长速率和身体自我维持之间可能会出现权衡，但这种权衡背后的分子介质仍有待确定。在许多晚成鸟中，孵化异步会在一窝雏鸟中形成兄弟姐妹之间的竞争等级制度，与最后孵化的雏鸟相比，最先孵化的雏鸟享有显著优势。我们利用这个机会测试了大山雀雏鸟在生长和自我维持过程（氧化应激、端粒侵蚀）之间的权衡，因为最先孵化和最后孵化的雏鸟的资源可用性和分配可能不同。我们发现，尽管最后孵化的雏鸟一开始处于竞争劣势（即在第16天之前体型更小/更轻），但它们出飞时的生长速率和体重/体型与最先孵化的雏鸟相似。然而，最后孵化的雏鸟在氧化应激方面遭受的痛苦更大，并且在生长结束时端粒比最先孵化的雏鸟短。有趣的是，生长速率与血浆抗氧化能力和早期（即7日龄时）的端粒长度呈正相关，但在最后孵化的雏鸟中，那些体型生长较快的雏鸟也是端粒侵蚀最严重的。最后孵化的雏鸟血浆睾酮（T）水平升高，但仅在第7天。T水平与氧化损伤水平和血浆抗氧化能力呈正相关，后者仅在最先孵化的雏鸟中显著。我们的结果表明，最后孵化的雏鸟在生长速率和自我维持过程之间存在特定的权衡，这可能是由它们与年长兄弟姐妹竞争的需要驱动的，并可能由T水平的升高介导。
