Observation and regression models on body colour inheritance and development in crucian carp and carp

Abstract

Body colour and pattern are the important characteristics for ornamental fish. Owing to the complexity of colour heredity in fish, this study attempts to reveal the rule of red and black body colour formation in crucian carp, carp and their hybrids by observation and statistical analysis. It is found that melanocytes occur during the stage of embryo or larva in the skin of red crucian carp, and then, the body colour changes from dark grey to red-orange after about 3 months old. For Kohaku and Yamabaki ogon, which are two kinds of koi carp without melanocyte in the body colour of the adults, no melanocyte is observed in skin during the stage of embryo or larva. However, for the hybrids originating from red crucian carp and Kohaku or from red crucian carp and Yamabaki ogon, the body colours are dark grey. By statistical methods, regression models are constructed to describe the inheritance rule on the red and black body colours in fish. In virtue of the models, some interesting properties in inheritance are revealed for crucian carp and carp: (1) the percentage of the black colour in parents generates negative cross-correlation with the red colour of offspring for both of crucian carp and carp. (2) The negative effect on the percentage of the red colour in offspring by the black colour in parents is stronger for carp than that for crucian carp.