Meeting Abstract
12.4 Monday, Jan. 4 Long-term immune system activation depletes carotenoids from retina of house finches (Carpodacus mexicanus) TOOMEY, M.B.*; BUTLER, M.W.; MCGRAW, K.J.; Arizona State University; Arizona State University; Arizona State University matthew.toomey@asu.edu
The costs of developing, maintaining, and activating the immune system have been cited as an important force shaping life history evolution and maintaining the honesty of sexually selected signals. Immune activation requires energy, nutrients, and time that might otherwise be devoted to other life-history components like reproduction. Carotenoid pigments in animals provide a unique opportunity to track the costs of immune activation, because they are dietarily derived, modulate the immune system, and are used in sexually selected signals of quality. In several bird species, carotenoid supplementation enhances health, and immune activation depletes carotenoid levels in circulation and colorful ornaments. Carotenoids also accumulate in the retinas of birds, where they tune spectral sensitivity and provide photoprotection. If carotenoid accumulation in the retina follows the patterns of other tissues, then immune activation may deplete retinal levels impacting visual health and function. To test this hypothesis, we challenged molting wild-caught captive house finches (Carpodacus mexicanus) with weekly injections of lipopolysaccharide and phytohaemagglutinin over an eight-week period. Immunostimulated adult males and females produced significant antibody responses and molted slower than uninjected control birds. After eight weeks, immune-challenged birds had significantly lower levels of two major retinal carotenoid types (galloxanthin and zeaxanthin), but there were no significant differences in the plasma or liver carotenoid levels between the treatment groups. These results indicate that immune activation depletes retinal carotenoids, which may compromise visual health and performance representing an additional cost of immune activation.
