A team of researchers from Hiroshima University and other institutions has conducted extensive genome DNA analysis on ornamental medaka, leading to a significant discovery regarding their origins. The study involved analyzing 181 individuals from 86 varieties of ornamental medaka, including black varieties known as 'Orochi' and those resembling Nishikigoi with red and white colors. The analysis revealed a close genetic relationship between the analyzed ornamental medaka and wild medaka from regions bordering the Seto Inland Sea, particularly Osaka, Hiroshima, and Takamatsu.

The researchers compared the genomic data of ornamental medaka with previous reports to determine their closest wild relatives. Their findings indicate that most ornamental medaka varieties examined are genetically similar to wild medaka found in the Kansai and Setouchi areas, while showing significant differences from those found in other regions of Japan, such as the eastern Pacific and Sea of Japan coasts. This could suggest that the breeding practices and environmental factors unique to the Setouchi region may have played a vital role in the development of ornamental medaka.

The implications of this research extend beyond mere genetic curiosity; it could have significant consequences for understanding biodiversity and conservation in Japan. By tracing the lineage and origins of ornamental medaka, researchers can better appreciate the genetic diversity among these species. Moreover, this knowledge may inform breeding programs focusing on preserving the unique traits of these fish while contributing to biodiversity conservation efforts in the region.