The vitamin A-redox hypothesis: a biochemical basis for honest signaling via carotenoid pigmentation

Am Nat. 2012 Nov;180(5):E127-50. doi: 10.1086/667861. Epub 2012 Oct 5.


Trade-offs in resource allocation have been widely stated as the means by which the honesty of ornamental traits is maintained, but an alternative to this resource trade-off hypothesis is that production of ornamentation is linked to the biochemical efficiency of vital cellular processes. Carotenoids are antioxidants, potentially tying carotenoid-based coloration to the oxidative state of an organism, and some carotenoids are also precursors for vitamin A, which regulates numerous cellular processes. We present a biochemical model for regulation of ornamental coloration based on interdependencies of carotenoid and retinoid biochemistry. We propose that vitamin A regulatory mechanisms, redox systems, and carotenoid pigmentation pathways link carotenoid coloration to oxidative state and to a host of important aspects of performance, such as immune function. The activity of β-carotene ketolase, which catalyzes the oxidation of yellow carotenoids into red carotenoids, is responsive to the states of vitamin A pools and redox systems such that coloration is a direct reflection of the physiological state of an animal. According to the vitamin A-redox hypothesis, feather coloration is associated with a range of performance measures because performance emerges from functionality of the same basic cellular processes that regulate pigmentation. We present the vitamin A-redox hypothesis as a testable alternative hypothesis to the resource trade-off hypothesis for the maintenance of honesty of carotenoid pigmentation.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Feathers / metabolism
  • Finches / immunology
  • Finches / metabolism
  • Finches / physiology*
  • Models, Biological
  • Oxidation-Reduction
  • Oxygenases / metabolism
  • Pigmentation / physiology*
  • Signal Transduction*
  • Vitamin A / metabolism*


  • Vitamin A
  • Oxygenases
  • beta-carotene ketolase