Fish

Get to know the “Sturddlefish”, a bizarre hybrid

A group of Hungarian water scientists in search of sturgeon for caviar accidentally created this bizarre hybrid. The study “Sturddlefish”, which consists partly of American paddle fish and partly of Russian sturgeon, was published this month in the journal Genes.

How it happened

The original aim of the study was to encourage the endangered sturgeon to reproduce asexually. Instead, the Russian sturgeon hybridized with the American paddle fish, the first time the two successfully hybridized in captivity.

The paddle fish was originally supposed to provide sperm, not its DNA, to help the sturgeon reproduce itself. Genetically, the sturgeon is not that different from paddle fish – it belongs to the same group, Acipenseriformes.

Previous attempts at hybridization between American paddle fish and other sturgeons would not have worked, the authors wrote. And because of their evolutionary similarities, the two have very different dietary habits, preferred habitats, and physical properties.

The Sturddlefish hybrids differ in their resemblance to their parent sturgeon, but most of them share the same ridged back and short snout. By J. Kaldy, A. Mozsar, G. Fazekas, M. Farkas, D. Lilla Fazekas, G. Lea Fazekas et al.

“In addition, the two fish would never have met naturally. The American paddle fish lives in the Mississippi Basin, and the Russian sturgeon inhabits Russian rivers. The Russian sturgeon is considered extremely valuable for its roe or eggs.

Both species are threatened by shrinking habitats and overfishing. While the caviar, which comes from sturgeon, is a delicacy, the fish are extremely rare even in Russian waters.

For this reason, the researchers from Hungary wanted to encourage the sturgeon to reproduce through gynogenesis, which uses the treated sperm of a different species to induce the sample’s eggs to develop. In gynogenesis, however, the DNA of the sperm sample should not be transferred to the offspring

What the hybrids could do next

There were two types of hybrid fish: one of them is part paddle fish, two parts sturgeon, and the other part is part paddle fish, four parts sturgeon. Most of them, between 62% and 74%, survived one month after hatching. Both hybrids resembled the sturgeon with their ridged back and short nose, although one of them had a more pointed snout reminiscent of its paddlefish parents. “The how and why are still questions open? “Said lead author Jen. Káldy, aquaculture researcher at the Hungarian Research Institute for Fisheries and Aquaculture of the National Agricultural Research and Innovation Center. The two probably hybridized because the sturgeon developed slowly. This means there are likely to be fewer differences between its morphology and genes and those of other species, including what appears to be the American paddle fish.

The “Sturddlefish” live in a Hungarian research facility, where there is no chance of them entering natural waters.

Sturgeon hybrids are typically used in aquaculture and account for about 20% of global caviar production, the researchers said. However, if the hybrids adopt the habits of the paddlefish parents and learn to feed on plankton and other microscopic organisms rather than the more sophisticated sturgeon diets of crustaceans and higher forage, they can “play an important role in adapting pond aquaculture to the challenges of climate change, “the authors wrote.

Put simply, if these “Sturddlefish” no longer need to be fed and instead rely on natural plankton in their habitats, the carbon emissions that would have been caused by feeding will decrease. Coupled with their high market value, the random hybrids could be more valuable than their creators imagined.

In terms of saving the endangered sturgeon, the study “brought us closer to our goals,” said Káldy. Currently, however, the hybrids live peacefully in a research facility in Hungary, where there is no risk of them entering non-native waters. [CNN]

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