Investigation of the genetic mechanisms involved in the absorbtion, depositin and degradation of Astaxanthin in white and red Chinook salmon (Oncorhynchus tshawytscha) phenotypes

Astaxantin (Ax) is a xanthophyll carotenoid naturally produced from microalgae, phytoplankton, and yeast. The accumulation of this pigment in the muscle of Atlantic salmon and other salmonids species is the reason of their characteristic red/pink flesh. The effect of Ax on muscle coloration assume a noteworthy importance in the fish industry, since the color intensity of the fillet, together with fat content and texture are the major parameters that determine the satisfaction of the costumer and thus the fish value on the market. Furthermore, in fish xanthophylls act as precursor for vitamin A production. Ax is also one of the most powerful natural antioxidant and researches have already proved its positive effect on stress and disease resistance in both aquatic and non-aquatic species. Fish cannot produce carotenoids de novo and in farmed conditions diet supply is the only source of carotenoids. However, despite fed with Ax enriched feeds, salmonids approximately retain only between 2 and 22 % of the pigment in the flesh (12% A. salmon). Intestinal absorption, transport and metabolism of Ax are the main factors responsible for the pigments retention in the muscle. Nevertheless, the mechanism involved in these processes are jet far to be clear. To better study the mechanism involved in the muscle pigmentation, we chose a Salmonid specie, Chinook salmon (Oncorhynchus tshawytscha) that in nature display two phenotype characterized by white (unpigmented) and red (pigmented) muscle. By comparing these two Chinook phenotype we aim to investigate possible difference on the absorption (gut), degradation (lever) and deposition (muscle) of astaxanthin.