Goldfish Has Unique Genome That Makes It Purely Decorative

People have trained countless animals throughout history -- some for food and others as friends or defenders. Also, there are animals like rabbits and guinea pigs that can be food or prey and pets.

But there is one specific domesticated animal that left its past as a food source and ended up serving as purely decorative, according to Ars Technica. This animal is the goldfish, a popular pet, in which scientists have studied its genome to investigate what's unique in their genome.

Weird Genes of a Goldfish

Goldfish is a slightly colored variant of the carp that is used for aquaculture, but soon it completely removed from the food chain and became pets. Unlike dogs or cats, goldfish are not the interactive kind of cats because their purpose is just for decoration, and in turn, humans breed more varieties of far less functional fish.

But the goldfish of today is actually not the golden goldfish after its domestication in China. During that time, only the emperor is allowed to have the gold-colored fish making them rare. So the public has started breeding strains of multiple tails and dorsal fins which makes them weirder than they were.

On the other hand, scientists have suggested that goldfish do have genomes that are relatively unique to them compared to their ancestors, the common carp. A huge consortium dropped an analysis of the 185 strain of goldfish and 16 various wild carp genomes.

The raw sequence needed to analyze all of this ran out to 4.3 trillion bases which is an astonishing feat given that goldfish has only 1.8 billion base pairs long.

The researchers published their study in PNAS.

Selection of Unusual Features for the Goldfish

Goldfish and carp have 25 chromosomes, but each of them carries 100 chromosomes which are four copies or rather two sets of two copies of genes, unlike most animals that have 23 chromosomes and carry 46 of them.

As a consequence, some copies of the genes were deleted or disabled by mutation like DNA repair genes wherein one set of copies has been eliminated. Scientists were unable to pinpoint the exact workings of the four sets of genes of a goldfish, but they believe it is not simple to explain it.

It has not been long yet that goldfish have undergone selection for unusual features to produce various strains. Many of them are likely the result of recent selection that physical traits have become unique to a specific strain, creating the "selective sweep" wherein only the variant and others present nearby are the only ones present in a population.

Upon checking for selection sweeps in the fish, the scientists found that there are quite a number of them with 1% of possible sweeps, which has nearly 1,000 genes. While the zebrafish, a fish not distantly related to carp, has 173 of these genes deleted. Those who carry the deleted genes have pigmentation and body shape that differed from most carp.

They also tested genomes of egg goldfish that do not make the dorsal fin. They identified over 400 genes responsible for the deletion of the dorsal fin.