Effects of light intensity on erythrophore number and astaxanthin amount in the skin of coral trout Plectropomus leopardus

Numerous studies have reported that environmental background color alters the skin color of aquaculture fish. In the present study, we investigated the effects of light intensity on skin coloration, chromatophores numbers, astaxanthin content and gene expression in 7-month-old coral trout Plectropomus leopardus . After been feeding astaxanthin-free diet (AFD) for 30 days, the fish in control group (under natural light) showed little change in skin color. In contrast, the skin color of fish in light-treat group (under 300 lux white light) changed from dark-brown to orange-red, associated with erythrophores number increase, xanhtrophores number reduction and astaxanthin amount increase on the skin. Transcriptomic analysis indicated that several genes related to carotenoid transport, metabolism, cell apoptosis and autophagy show significant variation between the light-treat and control groups. These results suggest that background light intensity affect the proliferation of erythrophores and the acquisition of astaxanthin in the skin of coral trout. • Coral trout reared under 300 lux light intensity showed increased erythrophores number and decreased xanthophores number. • 300 lux light intensity promoted astaxanthin accumulation in coral trout skin during the non-astaxanthin uptake phase. • 300 lux group showed up-regulated expression levels of genes related to carotenoid transport and metabolism. • The ultrastructural similarity implies the possibility of conversion of xanthophores into erythrophores.