Inheritance of Long Fins in Ornamental Koi Carp

Inheritance of long fins in ornamental koi carp Cyprinus carpio was studied. Fish segregations with regard to the presence or absence of long fins in two progenies were recorded and analyzed. In progeny 1, produced by crossing a long‐fin koi female with a short‐fin (wild‐type) koi male, the observed segregation of long‐fin fish : short‐fin fish did not differ significantly from the 1:1 Mendelian ratio. In progeny 2, produced by crossing the same long‐fin female with a long‐fin male, the observed segregation of long‐fin fish : short‐fin fish did not differ significantly from the 3:1 Mendelian ratio. Based on these data, it was concluded that the appearance of long fins in koi is under the control of a dominant mutation of one gene (Lf/lf). Fish with genotypes LfLf and Lflf have long fins, while fish with genotype lflf do not have this trait. Since the appearance of long fins in koi is controlled by a dominant mutation, the development of a true‐bred, long‐fin line could be achieved only by identifying heterozygotes Lflf by means of test crosses and removing them from the stock. Received April 14, 2010; accepted June 16, 2010