Goldfish were bred from Prussian carp (Carassius auratus gibelio) in China, and these usually olive green fsh remain the closest wild relative of the goldfish.[19][20] Previously, some sources claimed the Crucian carp (Carassius carassius) as the wild version of the goldfish. However, they are differentiated by several characteristics. C. auratus have a more pointed snout while the snout of a C. carassius is well rounded. C. a. gibelio often has a grey/greenish colour, while crucian carp are always golden bronze. Juvenile crucian carp have a black spot on the base of the tail which disappears with age. In C. auratus this tail spot is never present. C. auratus have fewer than 31 scales along the lateral line while crucian carp have 33 scales or more.
Like their wild ancestors, common and comet goldfish as well as Shubunkin can survive, and even thrive, in any climate that can support a pond, whereas fancy goldfish are unlikely to survive in the wild as their bright colours and long fins make them easy prey. Goldfish can hybridise with certain other species of carp as well as C. a. gibelio. Within three breeding generations, the vast majority of the hybrid spawn revert to the wild type colour. Koi may also interbreed with the goldfish to produce sterile hybrids.
Biology