4.5. Complexity of color inheritance
Koi have a wide variety of colors and color-pattems, which evolved during a rather short period of domestication in Japan ( ~ 200 years, Balon, 1995). Selection of new mutants probably introduced new varieties. Given the short time of color evolution and the rate of mutations, one might expect that color phenotypes would be controlled by single genes. However, we found a quite complex genetic control for colors in koi. For the zebra fish, it has been shown that the development and migration of two different melanocyte populations are controlled in part by duplicated genes, each controlling one type of melanocytes (Mellgren and Johnson, 2002). Cyprinus carpio was suggested to be a tetraploid (Ohno et al., 1967) and we have previously suggested that about 60% of the common carp genome is in duplicates (David et al., 2003 ). In koi, we have suggested two developmental stages for the Bekko and บtsuri patterns and also provided evidence for association between red color phenotypes and a duplicated microsatellite locus (koi89- 90). Thus, it is possible that the complexity of color inheritance in koi may result in part from a duplicated nature of color loci.