Starting With a Handicap: Effects of Asynchronous Hatching on Growth Rate, Oxidative Stress and Telomere Dynamics in Free-Living Great Tits

Oecologia. 2015 Dec;179(4):999-1010. doi: 10.1007/s00442-015-3429-9. Epub 2015 Aug 28.

Abstract

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.

Keywords: Antioxidant; Intra-brood competition; Oxidative damage; Self-maintenance; Testosterone; Trade-off.

MeSH terms

  • Aging*
  • Animals
  • Antioxidants / metabolism
  • Body Size / physiology*
  • Female
  • Male
  • Nesting Behavior / physiology
  • Oxidative Stress*
  • Passeriformes / blood
  • Passeriformes / growth & development*
  • Reactive Oxygen Species / blood
  • Telomere / physiology*
  • Testosterone / blood

Substances

  • Antioxidants
  • Reactive Oxygen Species
  • Testosterone