Coloration in crosses between two variants of goldfish, Carassius auratus

Two varieties of goldfish (Carassius auratus), the red comet and the variegated or the transparent-white blue shubunkin, were crossed to test coloration in their offspring. Three cross-combinations were performed in each triplicate (a, b and c), in which the comet always served as the female spawner: (1) comet x comet (CGFxCGF), (2) comet x white-transparent blue shubunkin (CGFxWBS) and (3) comet x variegated blue shubunkin (CGFxVBS). The hatched-out offspring were maintained in flow-through 30 I Zuger incubators. Random samples of fish from each group were examined in 2-4 week intervals. In progenies derived from spawners where one or both of the parents was a blue shubunkin, the light colored larvae appeared soon after incubation was completed and could easily be identified at hatching. All offspring of the CGFxCGF combination had wild-type coloration during the first three months of development. All offspring of the CGFxWBS cross were light-colored at hatching. Progeny of the CGFxVBS cross segregated into wild-type and light-colored fish in a Mendelian 1:1 ratio. Fish from crosses belonging to triplicate a were divided into two parts. Half of each cross was maintained in a Zuger and half in a 1 m³ cage suspended in an earthen pond to compare environment-dependent coloration. After one month, the fish grown in the cages were 2-3 times larger than their siblings in Zugers. Half of the light-colored fish, offspring of CGFxWBS and CGFxVBS, developed red patches and colors, similar to fish popularly named Jericho shubunkin by aquarists, while the rest remained transparent-white. Some of the wild-type colored fish in groups CGFxCGF and CGFxVBS developed the orange coloration characterizing the red comet. However, no color changes were observed in any groups grown in Zugers. The results suggest that at least three different interacting loci control the colors in crosses between the comet and the shubunkin. Further investigation is recommended to determine more precisely the genetic model of color inheritance in these goldfish variants.