Meeting Abstract

124.4  Monday, Jan. 7  The biochemical basis for honest signaling via carotenoid pigments HILL, G. E.*; JOHNSON, J. D.; Auburn Univ.; Auburn Univ. ghill@auburn.edu

Tradeoffs in allocation of carotenoid pigments between use in immune defense versus use in ornamentation have been widely stated as the means by which the honesty of ornamental coloration is maintained. While this Resource Tradeoff Hypothesis has been supported in some empirical studies showing loss of carotenoid pigmentation following immunostimulation, alternative explanations are equally plausible. Moreover, the quantities of carotenoids used by leukocytes is five orders of magnitude lower than the quantities of carotenoids in circulation, a disparity that is hard to reconcile with a direct tradeoff in carotenoid allocation. An alternative to this Resource Tradeoff Hypothesis is the Shared Pathway Hypothesis, whereby production of ornamentation is linked to the biochemical efficiency of vital 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. Finally, many animals oxidize dietary pigments to produce ornamental coloration. We hypothesize that these oxidation reactions occur in the inner mitochondrial membrane and that pigmentation ultimately reflects the efficiency of cellular respiration.