Selective absorption of carotenoids in the common green iguana (Iguana iguana)

In the animal kingdom, species-specific differences with regard to the absorption of intact carotenoids are observed. The causes of these differences are not entirely understood. To investigate the absorption of selected carotenoids, 20 juvenile green iguanas (Iguana iguana) were fed a carotenoid deficient basal diet for 56 days. Thereafter, the iguanas were assigned to receive a basal diet supplemented with different carotenoids (80 mg/kg diet) such as beta-carotene, canthaxanthin and apo-8'-carotenoic acid ethyl ester for 28 days. Changes in plasma carotinoid concentrations associated with the individual diets were used as indicators of carotenoid absorption. In both the experimental and control groups, only the oxygenated carotenoids (xanthophylls), lutein, zeaxanthin and canthaxanthin, were found in the plasma. Canthaxanthin and apo-8'-carotenoic acid ethyl ester were readily absorbed and recovered from the plasma. However, the supplementation of beta-carotene caused no increase in plasma beta-carotene concentration. Additionally, beta-carotene, canthaxanthin or apo-8'-carotenoic acid ethyl ester did not affect the concentrations of retinol and alpha-tocopherol in plasma. In conclusion, the study demonstrates that iguanas appear to be selective accumulators of polar xanthophylls. The iguana might, therefore, be a valuable model to investigate the selectiveness of carotenoid absorption as well as the function of xanthophylls in animals.