Scientists in a laboratory have created a strange new type of fish called ‘bullfish’ which is a cross between a Russian sturgeon and an American spoonbill.
A team from the Fisheries and Aquaculture Research Institute, Hungary, was using spatula fish sperm to try to get the eggs of the endangered sturgeon to reproduce asexually, in a process called gynegenesis.
They chose the American spatula fish sperm because they assumed that the two species would not be able to reproduce, due to the fact that they had never come into contact with each other, and the process of gynegenesis requires the ‘sperm but not its DNA’.
However, despite the closest common ancestor of the two fish dating back to 184 million years ago, the oarfish’s DNA managed to fertilize sturgeon eggs.
The researchers said the resulting fish are infertile, like many hybrid species, and that they have no plans to produce more, but the survivors could live more than 100 years.
Two examples of the ‘offspring’ of the Russian sturgeon and the American spoonbill fish. Some of the surviving descendants were more like sturgeon and others more like oarfish.
Russian sturgeons feed on the soil of seas, lakes, and rivers in Eastern Europe, Siberia, and the Middle East, but are not found in the United States.
In contrast, the American spoonbill is found in the rivers of the US and not in Eastern Europe, Siberia, and the Middle East. The two have never been mixed.
Despite this, a new species of sturddlefish – a female sturgeon and a male swordfish – has been created in a lab “ accidentally ” despite researchers predicting that it would be impossible for the two to produce offspring.
The team says this could be due to the fact that they are both ‘living fossil’ species, meaning they have changed little since their last common ancestor was alive.
“These phenomena could lead to greater similarity, compatibility, and flexibility between sturgeon genomes,” the authors wrote in their article published in Genes.
Adding that it could “allow for hybridization between the Russian sturgeon and the American spoonbill fish despite the great geographical, physiological and morphological distances.”
This is a significant discovery since other ‘mixtures’ of distant species from families similar to these two have been unable to reproduce.
The researchers say their descendants look even stranger than their parental species, with some resembling their mother, father, and others like them both.
Some have classic sturgeon fins and snouts with the typical oarfish mouth.
“I did a double take when I saw it,” aquatic ecologist Solomon David told the New York Times.
‘I just didn’t believe it. I thought, hybridization between sturgeon and oarfish? There is no way.’
Sturgeons and paddlefish share some things in common. They are among the largest, longest-living and slowest-growing freshwater fish species.
They are also critically endangered due to habitat loss, overfishing, and pollution that wreaked havoc on both species over the past century.
Attila Mozsar and colleagues in Hungary were trying to find a way to breed both fish in captivity by inducing gynegenesis, a form of asexual reproduction.
This works by requiring the presence of sperm to trick the egg into fertilizing, but it only works if there is no compatible DNA contained in the sperm.
The top is a typical American spoonbill fish and the bottom is an image of a typical Russian sturgeon like those used to produce the spatula.
‘We never wanted to play with hybridization. It was absolutely involuntary, “said Dr. Mozsár.
The unexpected fertilization resulted in hundreds of hybrid fish that emerged from the eggs, and the team says two-thirds of them survived.
This suggests that the two species are more alike than previously thought, despite never mixing and being separated by thousands of miles of ocean.
This is likely due to the extremely slow rate of evolution of fish species, so while they evolved independently, they have many characteristics of their last common ancestor that existed during the time of the dinosaurs 184 million years ago.
The team said the fish were likely sterile and therefore could not continue to reproduce and that they had no plans to create more hybrid species.
They said they would continue to study how sturgeon and oarfish and how they reproduce in hopes of saving them on the brink of extinction.
Both fish are in serious danger of extinction as the Chinese spoonbill went extinct earlier this year and the sturgeon is “in greater danger than any other group.”
The study was published in the journal Genes.
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