Scientists found that the fish were gradually domesticated like dog breedsinto the beautiful shapes and colors that turn up today in pet stores.

For centuries, humans have been captivated by the beauty of the betta. Theirslender bodies and oversized fins, which hang like bolts of silk, come in avariety of vibrant colors seldom seen in nature.

However, bettas, also known as the Siamese fighting fish, did not becomeliving works of art on their own. The betta’s elaborate colors and long,flowing fins are the product of a millennium of careful selective breeding. Oras Yi-Kai Tea, a doctoral candidate at the University of Sydney who studiesthe evolution and speciation of fishes, put it, “quite literally the fishequivalent of dog domestication.”

A new study, uploaded in April to the preprint service BioRxiv, shows throughgenome sequencing that humans began domesticating bettas at least 1,000 yearsago. The years of breeding gave rise to the stunning diversity of domesticbetta fishes alive today, but also caused both wild and domestic betta fish toundergo vast genetic changes. By studying the genes of these fish, the study’sauthors argue, scientists can learn a great deal about how domesticationalters the genes of wild animals.

Tea, who was not involved in the analysis, praised the research for being “thefirst major study to tease apart the genetic basis for this remarkablephenomenon” in fish.

All 73 species of bettas originated in Southeast Asia. But the ubiquitousspecies sold in pet shops and at flea markets is Betta splendens. Domesticatedbettas of this species are far more colorful than most wild species.

“Wild bettas can look very different from ornamental bettas,” said Young MiKwon, a researcher at Columbia University and lead author of the study. “Theyhave short fins, duller coloration and lack the striking fin-nage that you canfind in ornamental varieties.”

Domestic bettas are also “very aggressive,” she said. “You can’t put two bettamales in the same tank, they will attack each other and will fight to thedeath.”

Wild bettas are far less aggressive. This is likely because the ornamentalspecies “were initially domesticated for fighting, similar to cockfights,”Kwon said.

By the end of the 19th century, breeders began focusing on creating ornamentalvarieties of the fish, which had become extremely popular in the West. “Thishistory has shaped the ornamental bettas we see today — a really beautifulfish with a temper,” she said.

To determine exactly how this history shaped the ornamental bettas we seetoday, Kwon and a team of scientists collected DNA samples from wild anddomestic betta and sequenced their genomes.

“We were surprised by how long bettas have been part of human history — it’sbeen domesticated for at least 1,000 years, making it one of the oldest fishdomestications known,” said Kwon. That is further back than earlier anecdotalresearch cited in the study suggesting that bettas had been bred for fightingas early as the 13th century.

The research also highlighted why breeders have been able to create dozens ofdifferent varieties of betta. There are red, yellow and blue bettas, bettaswith big fins and small fins and even bettas that resemble Thailand’s flag. Ifyou can imagine it, it probably exists.

“Many of the traits that breeders are selecting are regulated by very fewgenes that have a major effect,” Kwon said. “This means it doesn’t take thatextensive a number of crosses to get the trait or traits that you want foryour fish.”

As expected, the researchers also discovered that domestic bettas aregenetically dissimilar to their wild cousins. However, they were surprised tofind that, in past and recent years, domestic bettas have interbred with wildones. This hybridization, which was likely the result of domestic bettas beingreleased into the wild, could undermine conservation efforts.

“Feral domestics — if they are more fit than their wild counterparts — cantake over the wild populations,” Kwon said. Many wild species of betta arethreatened with extinction, mainly as a result of habitat loss.

By studying the evolutionary history of these fish in greater detail, theresearchers hope to improve our understanding of how domestication alters thegenes of species.

Although there is still much to be learned about how domestication isaffecting bettas, the process has produced a plethora of pretty fish whosefantastical colors and shapes may never have existed otherwise.

Bettas as extravagant as the domestic variety “are unlikely to occur in thewild,” Tea said. “It’s like expecting Chihuahuas to naturally exist in thewild without human interference.”

Source: USA StarTribune

Image: Bigstock

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