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
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.
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.
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.
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.
And in the case of some breeds of dog, the excessive selection for novelty has made finding a sound, healthy representative of that breed a novelty in and of itself!
“And in the case of some breeds of dog, the excessive selection for novelty has made finding a sound, healthy representative of that breed a novelty in and of itself!”
How true, how painfully true! And no, those fancy goldfish would only survive in a covered pond. Any self respecting Great Blue heron would wipe out the breeding stock in a few gulps otherwise.
What is interesting is that basic goldfish if released into the wild will revert. There is a small quarry not far from me with a captive collection of goldfish/carp that were released there about 25 years ago. It’s deep enough the fish can bury in the sediment to survive the winter. The original fish were all store bought goldfish. Now, there are are fish whose phenotype looks pure carp, and all combinations in between.
Now, if only dog breeders would start selecting for larger muzzles, less domed skulls, less dwarfism, shorter backs,less coat, less bulk and return to the type of an earlier age, a lot of today’s novelties would be so much better off!
I’ve caught wild goldfish in the rivers in West Virginia, and almost none of them are gold. They are like that feral specimen.
It’s kind of like how dogs would eventually either evolve into the typcial street dog or a dingo-like animal if left to their own devices. And the availability of carrion or garbage is the factor that determines what type evolves. However, there have been no dingoes evolving from domestic dogs in modern history. We are that dirty.
The problem with fancy goldfish is that they might do okay in a pond in temperate conditions, like in North Carolina or the South of England. However, if they are housed with single-tailed races that are stream-lined, like common goldfish or comets, they can’t eat enough food to thrive. The faster ones simply swim and eat all the food before the slow-movers can get to it.
Mmm… one of my favorite computers games growing up was a simulation for breeding fish. Shows what a huge geek I am. It was actually quite versatile for it’s time, and it was fascinating to see how selective breeding could get some extreme results.
I think some breeders would actually be better off playing simulation games like that and not messing with live animals at all.