Studies of ornamental carotenoid coloration suggest that animals may have evolved specialized mechanisms for maximizing color expression and advertising their potential worth as a mate. For example, when given a choice of foods, many carotenoid-pigmented fishes and birds select the more colorful, presumably carotenoid-rich foods, and then accumulate these pigments at high levels in both the integument and systemically, in order to boost their immune system and hence directly advertise their health state with their colors. The majority of animals, however, do not exhibit sexually selected carotenoid coloration, which raises the question of whether they still optimize pigment intake and allocation in ways that boost endogenous accumulation and health. We tested the effect of carotenoid supplementation on food intake, carotenoid accumulation in blood, and both innate and adaptive immunity in male society finches (Lonchura domestica) - a non-carotenoid-colored estrildid finch relative of the zebra finch (Taeniopygia guttata; a species in which males do display sexually attractive and health-revealing carotenoid color). Males fed a carotenoid-rich diet for 2 wk did not consume more food than control males. Still, consumption of the carotenoid-rich diet for 2 wk significantly elevated circulating levels of carotenoids in blood in male society finches, yielding the potential for immune enhancement. In fact, carotenoid-enriched finches performed significantly better than control birds in our assay of constitutive innate immunity (bacterial-killing activity of whole blood), although not in our test of inducible adaptive immunity (response to a mitogenic challenge with phytohemagglutinin). These results suggest that affinities for carotenoid-rich foods may be particular to species with sexually selected carotenoid pigmentation, but that, as in humans and other mammals (e.g. mice, rats) without carotenoid color, the immune-boosting action of carotenoids is conserved regardless of the strength of sexual selection on pigment use.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Animal Science and Zoology