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Posts Tagged ‘Prussian carp’

This is a feral goldfish caught in the US. It strongly resembles its ancestor, the Prussian carp.

This is a feral goldfish caught in the US. It strongly resembles its ancestor, the Prussian carp.

It is often pointed out how much domestication and selective breeding have changed the domestic dog.  But they are far from the only species in which our selective breeding has changed dramatically. Dogs have been with us for a very long time, and because of tandem repeats, they can evolve into various different forms rather quickly.

However, if you would like to see another species that has dramatically changed because of domestication, look no further than the goldfish. Goldfish are species of carp, and believe it or not, there are two wild subspecies of this carp that still exist in the wild. These are the Prussian carp (Carassius auratus gibelio) and the Crucian carp (Carassius auratus carassius). These fish can all produce fertile offspring with the goldfish, and the Crucian carp is known to come in a yellow mutation. It was thought that the goldfish descended from the Crucian subspecies, when now it is generally accepted that it descends from the Prussian subspecies.

Prussian carp

Prussian carp

crucian-carp

Over a thousand years ago, the Chinese were breeding carp in ponds. Some of these fish were yellow in color, a common mutation in carp.

yellow-crucian

A yellow Crucian carp.

In 1162, an Empress of the Song Dynasty had a pond constructed solely for yellow and reddish fish. Yellow fish were the sole domain of the imperial family, so the gold colored were bred more often. As a result, the main color of the domesticated goldfish would become gold, not yellow.

Within a 150 years, the Chinese began to breed veil-tailed varieties of the fish, and soon, goldfish began to change dramatically.

This fancy breeding happened in East Asia first, but it soon spread to Japan, where the fancy breeding really took off.

My favorite type of Japanese goldfish is the ranchu. The ranchu has a large head with an arched back that dips down before it reaches its tail. And, like many fancy goldfish, it has two tails. On its head, it has lots of growths that are considered absolutely necessary for its breed standard. It also has no dorsal fin.

ranchu

The ranchu, like most double-tailed “fancy” goldfish, cannot really live in a pond as its less exaggerated relatives can. The double tail and unstreamlined body prevent these fancy goldfish from swimming fast. They need to swim fast if they are to be pond fish, because they will be unable to compete with faster swimming goldfish in their school. Also, these fish have lost their ancestors’ tolerance for very cold water.

However, I would not count the ranchu as the most bizarrely exaggerated goldfish. That title goes to the bubble-eye.

bubble-eye

The bubble eye also has no dorsal fin. It has a double-tail, which does slow the fish down. But its most striking feature are the fluid filled sacks that come off the bottom of its eyes. It cannot ever be pond fish or ever kept with fast moving goldfish. Those sacks and the double tail make it really slow in the water. It is very hard to keep in a fish tank, because the chances are very high that it might damage its eye sacks. I once purchased one of these and it lasted about a week in my goldfish tank. I had a common feeder-type goldfish in that same tank that lasted several years, so that should tell you which races of goldfish are the hardiest.

So our selective breeding has not changed only dogs. We like to really mess around with selective breeding, and if we can find novelty in our stock, we’ll breed for it. It is because of this almost inherited tendency in our species that we must draw the line at some point. Interest in novelty of all sorts may have been a great advantage for our species, allowing us to develop all sorts of new technology and art, but like everything else, our tendency to select for novelty can be excessive.

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