Scientists from Japan have undertaken a study to examine how varieties of fancy goldfish were produced thousands of years ago.
The study, which is due to be published in the journal Gene, was undertaken by biologists from Tokai University School of Medicine, who examined nucleotide sequences from a substantial portion of the mitochondrial genome.
In an attempt to elucidate the evolutionary origins and history of goldfish varieties they scientists examined genetic material from 44 different goldfish, including many popular strains.
They then added 19 more sets of data from DNA databases and used computer software to analyse the sequences and produce phylogenetic trees showing the evolutionary history of the fishes.
The results showed that Japanese goldfish are not related to Japanese Crucian carp, Carassius auratus langsdorfi, and that they instead originated from one of the two groups of Chinese Crucian carp, Carassius auratus gibelio, also known as the Gibel carp.
The study claims that the first stage of artificial selection early breeders achieved was fixing strains that were missing their dorsal fins.
They then subsequently focused on breeding fishes with unusual eye features.
The authors said: "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 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."
For more information see the paper: Komiyama T, Kobayashi H, Tateno Y, Inoko H, Gojobori T, Ikeo K (2008) - An evolutionary origin and selection process of goldfish. Gene, In press.