Response of body color change rearing under different light intensity conditions in farmed red spotted grouper, Epinephelus akaara

Abstract

Abstract Background Fish body color is one of the major factors that determine the commercial value of farmed fish, to understand for coloration mechanisms. The expression of melanin-related genes is according to the developmental stage and light intensity in the red spotted grouper, Epinephelus akaara. Methods To investigate changes in melanin formation and melanin-related genes in the larval development stage, fish larvae were reared from fertilized egg stage to 50 days after hatching (DAH). Experiment of body color changes was performed under each different light intensity conditions. Melanin-related genes expression was analyzed by real-time qPCR, and body coloration difference was represented by RGB (red, green, blue) code value. Results Expression levels of melanin-concentrating hormone (MCH) mRNA, pro-opiomelanocortin (POMC) mRNA, and melanocortin 1 receptor (MC1R) mRNA were at their highest 5 DAH (days after hatching). Expression levels of agouti-signaling protein (ASIP) mRNA were at their highest 10 DAH. Results of body color changes according to changes in light intensity conditions showed that the expression level of MCH mRNA in the 2000 lx group was the highest at 6 weeks. The expression levels of POMC mRNA and MC1R mRNA in the 1000 lx group were at their lowest at 9 weeks. RGB color code value under different light intensities were the brightest under 1000 lx and the darkest under 0 lx. Conclusion Our research suggests that POMC mRNA and MC1R mRNA in the red spotted grouper are involved in melanin synthesis, and these genes are thought to be controlled by light intensity. To better understand the molecular mechanism of coloration in the red spotted grouper, further studies are needed to clarify the relationship between melanophore development and melanin-related genes.