Unraveling the coloration pattern of male bitterling (Rhodeus ocellatus) with implications for ornamental fish industry

Bitterling ( Rhodeus ocellatus ), particularly in male, is renowned for its vibrant color and the potential stronger aesthetic appeal. However, their biological coloration mechanism is still unclear. In this study, we first compared the cytological differences of body color between the female and male bitterling, and the results indicate that the specific distributional features of erythrophores play a fundamental role in forming the sexual dimorphism of body color in bitterling. By analyzing the transcriptomic data from different body color areas of male bitterling, it is further revealed that the genes associated with carotenoid metabolism ( scarb1 , bco1 , plin2 , cyp2j4 ), melanin synthesis ( wnt2 ), and pteridine synthesis ( spr , gch1 ) are closely related to the body color formation of male bitterling. Particularly, myh1s gene is identified to be associated with formation of the red and yellow body color in the fish. Clearly, these findings can provide insights into the cellular basis of body color formation and highlight the potential roles of myh1s gene in deepening understanding pigment cell development and farming ornamental fish. • Depicting the coloration patterns of sexual dimorphism in bitterling ( Rhodeus ocellatus ). • Association of body color patterns with the specific distribution of erythrophores in male bitterling. • Regulation of the myh1s gene in forming the red and yellow body color patterns.