Goldfish aren't the ho-hum fish you thought they were

Carassius auratus

There are many breeds of goldfish (Carassius auratus). This is a celestial eye goldfish, which has large eyes turned upward.

Thank the Chinese for today’s beloved aquarium mainstay, the goldfish. A type of carp, goldfish were domesticated nearly 2,000 years ago for use as ornamental fish in ponds and tanks. They were seen as a symbol of luck and fortune, and they could only be owned by members of the Song Dynasty.

The fish are now ubiquitous in bowls throughout homes, classrooms, and doctor’s offices. They even share a name with a cracker, fondly known as the “snack that smiles back.”

Don’t confuse goldfish with its oversized cousin koi, another type of domesticated carp. There’s a common misconception that koi are large goldfish, but they are distinct species.

Not always gold

Goldfish weren’t always, well, gold.

Prussian carp, from which goldfish were domesticated, are traditionally a dull, gray-green hue. But mutations and breeding over the years created goldfish' signature orange, red, and yellow pigments found in the over a hundred varieties of the fish today. Goldfish first arrived in Europe in the 1600s and the United States in the 1800s, becoming what is likely the first foreign fish species introduced to North America. (Read more about the history of goldfish here.)

Goldfish have two sets of paired fins and three sets of single fins. They don’t have barbels, sensory organs some fish have that act like taste buds. Nor do they have scales on their heads. They also don’t have teeth and instead crush their food in their throats.

The fish are known for having large eyes and great senses...

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