Photo/IllutrationThe “wakin” goldfish breed, whose whole genome was decoded (Kazuya Goto)

  • Photo/Illustraion

Some are frilly, some have protruding eyes and some are shaped like eggs. In fact, there are about 80 species of goldfish, but why?

Researchers have decoded the creature's entire genome, which may help explain the mystery behind the sheer variety.

A team of scientists from Osaka University and other institutes said they found that goldfish have 70,000 genes, far exceeding the number for other types of fish.

The findings were published in the U.S. scientific journal Science Advances.

According to team member Yoshihiro Omori, an invited professor of developmental biology at Osaka University, a crucian species mutated into a reddish one in China more than 1,000 years ago.

The red fish repeatedly bred to become goldfish and have been selectively bred over generations in China, Japan and elsewhere, resulting in more than 80 goldfish breeds with unique body colors, fin shapes, eyes and other body parts, said Omori.

The scientists decoded the entire genome of the “wakin” goldfish breed, typically kept as a pet in Japan. The results showed the species has as many as 70,000 genes, far surpassing the 26,000 of zebrafish, which is often used in scientific experiments.

The findings also revealed the number of chromosomes of the ancestor of goldfish doubled 14 million years ago, with genes inside also doubling.

Chromosomes frequently double over the course of evolution. While the ancestor of salmon underwent such a mutation 80 million years ago, unnecessary genes have been lost in evolution phases.

“Goldfish are also in the process of losing genes, but many of them still remain,” said Omori. “This characteristic likely helped so many breeds to emerge through repeated breeding.”