The domesticated goldfish, Carassius auratus, is known by a color-specific name despite being available in a spectrum of hues, including black, white, and calico. This raises the question of why the descriptor “goldfish” persisted as the common name for the entire species. The answer lies in the animal’s ancient history, a spontaneous genetic event, and cultural selection.
The Origin of the Species and Color Mutation
The goldfish traces its lineage back to a wild ancestor, the dull, olive-brown Prussian carp (Carassius gibelio), native to East Asia. For millennia, carp were cultivated in China as a food source in ponds and water gardens. Although these wild fish were not colorful, a spontaneous genetic mutation occasionally occurred in the population.
This mutation resulted in a loss of dark pigment, allowing reddish-orange or yellow coloration to become visible. While brightly colored individuals would have been easily eaten in the wild, they survived in controlled ponds. Records of these color variants date back to the Jin Dynasty (266–420 AD). During the Tang and Song Dynasties, keeping these mutated fish for ornamental value increased significantly, and this initial bright, reddish-gold variant served as the basis for their common name.
The Biological Basis of Gold Coloration
The gold or reddish-orange color is a direct result of specialized pigment cells, known as chromatophores, located in the dermis. Different types of chromatophores produce different colors. The gold appearance is primarily generated by xanthophores (yellow pigment) and erythrophores (red pigment).
The brilliance of the gold color depends on the presence or absence of melanophores, which produce the black and brown pigment melanin that dominates the wild ancestor. The genetic mutation caused a significant reduction or complete loss of these melanophores. Removing the dark pigment allowed the underlying red and yellow pigments to express themselves fully, resulting in the characteristic gold sheen. Subsequent selective breeding intensified these mutations, establishing the bright gold color.
How the Name Was Established and Spread
The name “goldfish” was solidified during the Song Dynasty when the fish were officially bred for ornamental purposes. The dominant and most desired color at this time was the red-orange, or gold, variation. During the Ming Dynasty, cultivation exploded, and the fish were kept indoors in ceramic bowls, emphasizing their color.
When the fish arrived in Portugal in the early 17th century, the exported specimens were predominantly the brightly colored variety. The term “goldfish” became the standardized English name applied to the entire species, Carassius auratus, upon its global introduction. Even as breeders developed new color morphs, such as the black moor or the spotted shubunkin, the original name persisted because the vibrant, gold-like color had already cemented the common name in the global consciousness.