Inheritance and Expression of Koi Color Dominant Mutations in Koi × Goldfish Hybrids

• Published in: North American journal of aquaculture 2023-01, Vol.85 (1), p.48-52
• Main Authors: Gomelsky, Boris, Novelo, Noel D., Warner, Jeffrey L.
• Format: Article
• Language: English
• ISSN: 1522-2055; 1548-8454
• DOI: 10.1002/naaq.10270

The purpose of the study was to investigate the inheritance and expression of the koi color dominant mutations “design” and “red eyes” in koi × Goldfish hybrids (koi Cyprinus carpio × Goldfish Carassius auratus). The mutation “design” manifests as a yellow stripe along the dorsal fin and a specific ornament on the head; this trait is controlled by a dominant allele of one gene (D/d). In four progenies that were obtained by crosses of koi females having the “design” trait with Goldfish males, the segregations of so‐called "ghost fish," having a melanin‐pigmented body with the “design” pattern, and fish having wild‐type color, without the “design” pattern, were close to the Mendelian 1:1 ratio. This indicates that koi females with the “design” trait that are used for the production of these progenies had the genotype Dd, whereas the Goldfish males had the genotype dd. In one progeny that was obtained by crossing a koi female having the “design” trait with a Goldfish male, 420 ghost fish (99.8%) and one fish with wild‐type color (0.2%) were recorded. The koi female from which this progeny originated was apparently homozygous for the dominant allele (genotype DD). Earlier, it was shown that the appearance of red eyes in koi is caused not by the albino mutation, but by another dominant demelanization mutation (R). In three progenies that were obtained by crossing koi females having red eyes with Goldfish males, the segregations of the larvae with unpigmented bodies and light eye lenses and those with dark bodies and black eye lenses were close to 1:1. Later, three types of body color were observed in the juveniles of these progenies: yellow, brown, and wild‐type; all of the juveniles had black eyes. The segregations of colored (yellow + brown) and wild‐type‐color juveniles were close to 1:1. This shows that that the red‐eyed koi females that were used in the crosses were heterozygous (genotype Rr), whereas the Goldfish males had genotype rr. The described colored forms of koi × Goldfish hybrids can be used for weed control.