An evolutionary origin and selection process of goldfish

Many different physical characteristics of goldfish (Carassius auratus auratus), such as celestial and telescopic eyes, fancy but uncontrollable shapes of tail fin, an unfittingly fat body, and loss of dorsal fins, provide us with a unique opportunity of studying artificial selection on phenotypic changes on the basis of molecular evolution. The aim of the present study is to elucidate the evolutionary origin and history of goldfish, taking into account the different characteristics of goldfish and human culture. Collecting 44 samples of a variety of goldfish from Japan and China as well as common and Crucian carps, we determined the nucleotide sequences for a substantial portion of mitochondrial genome including eight gene regions (D-loop, 12SrRNA, 16SrRNA, ND1, ND2, COI, ND5 and Cyt b) of approximately 11,180 bps. We, then, constructed phylogenetic trees for a total of 78 fishes, adding the 19 sequence data available in the international DNA database DDBJ/EMBL/GenBank to our 59 sequence data determined. From the phylogenetic trees obtained, we found that Japanese goldfish are not relative to Japanese Crucian carp (Carassius auratus langsdorfi) and that all the goldfish examined were originated from one of the two groups of the Chinese Crucian carp “Gibelio” (Carassius auratus gibelio). Moreover, we found that the process of artificial selection began from losing the dorsal fin followed by diversification of other characters such as eyes. This is supported by our further observations that the improvement of celestial and telescope eyes took place independently at different times, implying that goldfish was imposed by strong artificial selection only to meet diversified needs of human preferences in a unsystematic way.