Genetics and Goldfish

By Myron Huang

Today, there are dozens of goldfish breeds sold in pet stores around the world. Most goldfish are divided into two groups, the “common” varieties, and the “fancy” varieties. Common varieties retain the streamlined fish body, but differ from their river carp ancestors in their extravagant hues of orange, yellow, calico or red patterns. Fancy varieties are those which in addition to colors, also have unique morphological traits. These include but are not limited to: double tails (also found in a few common varieties), head growths, bubble or telescope eyes, distinct body shapes, and many more.

The illustrious history of goldfish has left behind many tangible legacies. The beautiful red/orange of today’s fish was first recorded during the Jin dynasty among Crucian river carp, the ancestor of goldfish and koi. The predominance of red/orange goldfish owes to the reservation of yellow fish for the Song dynasty imperial family. The shift from the idea of majestic dragon-fish to cute domestic ornaments rings of the introduction of goldfish from China to Japan, around 1603 AD. The eventual spread of goldfish to Europe and the Americas from the 16th century onward gave rise to the global hobby now enjoyed by professional breeders and amateur enthusiasts alike.

Another important legacy was only recently articulated. The genetic implications of the heavy artificial selection behind the historical development of goldfish breeds are being studied. According to (Wang, Luo, Murphy, Wu, Zhu, Gao, Zhang, 2013), the millenia-old human practice of selectively breeding carp led to a loss in genetic diversity. The Grass/Wen/Egg classification is reflective mainly of body and fin shapes. “Grass” breeds were the most genetically similar to the carp ancestor, with the most genetic diversity, while the “Egg” breeds were developed through extensive culling to suit particular human preferences, and thus had the lowest genetic diversity, contrary to what their phenotypic variety suggests. Similar decreases in genetic diversity have been noted among other domesticated species, including maize, rice and pigs. Together, these are but a few examples which ring of the effects from the shared history between humans and many other species.