Molecular Mechanisms of Natural Carotenoid-based Pigmentation of Queen Loach, Botia dario (Hamilton, 1822) Under Captive Condition.

The genetic basis and expression patterns of key genes are important aspects of study to understand the colouration. This trait differs between wild and domesticated fish which is a matter of research. Botia dario is an indigenous fish, having ornamental and aesthetic value, which shows faded appearance in terms of colour in domesticated condition than wild. In the present study the carotenoid-fed B. dario were examined through incorporation of marigold petal meal in the diets at the rate of 5, 10 and 15% w/w along with wild fish. The carotenoid content of tissues that is skin, muscle and intestine along with intensity of colouration increased in a dose dependant manner of carotenoid in the diet. Important carotenoid-based colouration genes that is csf1r, BCDO2, SR-B1, MLN64, STAR5, GSTA2 and PLIN2 were characterized in the fish, to find out their role in fish pigmentation. The significant difference (p < 0.05) in the expression of these genes in different tissues, when compared among carotenoid-fed domesticated and wild fish, revealed the mechanism responsible for faded colouration and also revealed the means to enhance colour in the fish.