Dietary carotenoids and skin melanin content influence the coloration of farmed red porgy (Pagrus pagrus)

The present study investigates the effects of dietary carotenoid sources on the coloration of the red porgy, Pagrus pagrus. Red porgies (131.9 +/- 16.2 g; mean +/- SD) were fed for 12 weeks on five different diets supplemented with red carotenoids (mainly astaxanthin esters) supplied from Haematococcus pluvialis algae and yellow carotenoids (mainly beta-carotene, lutein, and zeaxanthin) supplied from Alfalfa, Medicago sativa L. and Spirulina, Spirulina pacifica. The carotenoid-supplemented diets did not have any marked effect on the growth rate, the feed conversion ratio, the daily feeding rate, or the hepatosomatic index of red porgy. The biochemical indices measured in plasma including cholesterol, total proteins, glucose, lactate, phospholipids, non-esterified fatty acids, triglycerides, and thyroid hormones did not differ significantly among groups. Diet did not affect significantly the melanophore-area coverage, the melanin skin concentration and skin lightness. Carotenoid-supplemented diets affected significantly the carotenoid deposition in the skin, the presence and distribution of erythorphores and xanthophores, and skin hue and chroma. Overall, data have shown the efficacy of Haematococcus algae in promoting a reddish coloration in red porgy.