The oxidation handicap hypothesis and the carotenoid allocation trade-off.
The oxidation handicap hypothesis proposes that testosterone mediates the trade-off between the expression of secondary sexual traits and the fight against free radicals. Coloured traits controlled by testosterone can be produced by carotenoid pigments (yellow-orange-red traits), but carotenoids also help to quench free radicals. Recently, it has been shown that testosterone increases the amount of circulating carotenoids in birds. Here, a testosterone-mediated trade-off in the carotenoid allocation between colour expression and the fight against oxidative stress is proposed. Male red-legged partridges were treated with testosterone, anti-androgens or manipulated as controls. Testosterone-treated males maintained the highest circulating carotenoid levels, but showed the palest red traits and no evidence of oxidative damage. Increased levels of a key intracellular antioxidant (i.e. glutathione) indicated that an oxidative challenge was in fact induced but controlled. The trade-off was apparently solved by reducing redness, allowing increased carotenoid availability, which could have contributed to buffer oxidative stress.
Alonso-Alvarez
C
C
Instituto de Investigación en Recursos Cinegéticos, IREC, CSIC, UCLM, JCCM, Ciudad Real, Spain. carlos.alonso@uclm.es
Pérez-Rodríguez
L
L
Mateo
R
R
Chastel
O
O
Viñuela
J
J
D000726:Androgen Antagonists / Q000494:pharmacology; D000728:Androgens / Q000494:pharmacology; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D002338:Carotenoids / Q000097:blood / Q000378:metabolism*; D005260:Female; D005485:Flutamide / Q000494:pharmacology; D046094:Galliformes / Q000378:metabolism / Q000502:physiology*; D005978:Glutathione / Q000097:blood; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D010084:Oxidation-Reduction / Q000187:drug effects; D018384:Oxidative Stress / Q000502:physiology; D010858:Pigmentation / Q000187:drug effects / Q000502:physiology*; D011897:Random Allocation; D013739:Testosterone / Q000097:blood / Q000494:pharmacology
D000726:Androgen Antagonists; D000728:Androgens; D002338:Carotenoids; D013739:Testosterone; D005485:Flutamide; D005978:Glutathione