Amazing that these species have been separated by 184 million year but can still mix their genes.

>>In the experiment, some of the sperm were irradiated to damage the genetic material inside. But in another group, the scientists mixed sturgeon eggs with untreated, healthy paddlefish sperm. Several past attempts to mix the two species “failed to result in viable offspring,” and the laundry list of differences between the fish “suggests an inability to hybridize,” the scientists wrote in their paper, published on July 6 in the journal Genes.

The top fish is a Russian sturgeon and the bottom is an American paddlefish. In between, two varieties of hybrid ‘sturddlefish’ created by accident. (Kaldy et al., Genes 2020)

All that to say, the resulting school of hybrid offspring came as a surprise. About two thirds of the fish survived the first month, and about 100 are still alive today, Annie Roth reports for the New York Times.

Bercesényi adds that such a hybrid would be impossible in the wild. For one thing, Russian sturgeon and American paddlefish live on opposite sides of the globe. They have been evolving separately for over 184 million years, and have vastly different survival strategies. Papa paddlefish is a filter feeder with a long, sensitive nose that enjoys large, slow-moving rivers. Meanwhile, the Russian sturgeon mother is carnivorous and highly valued for its eggs.

Both fish species are exceptionally rare. The American paddlefish may be the last paddlefish species left, as its nearest cousin, the Chinese paddlefish, probably went extinct between 2005 and 2010, according to a study published in March. And sturgeon as a group of species are critically endangered, with Russian sturgeon even more rare among them.

“These living fossil fishes have extremely slow evolutionary rates, so what might seem like a long time to us isn’t quite as long of a time to them,” Nicholls State University aquatic ecologist Solomon David tells the New York Times. So even though the fish have been evolving independently for twice as long as humans and mice, they still had enough in common for their genes to mingle.

The scientists suspect that the sturddlefish are sterile, like other man-made hybrids like mules and ligers. That means they wouldn’t be useful for caviar production. And while the fish are doing well in captivity, the researchers don’t plan to make more.<<

https://www.smithsonianmag.com/smart-news/scientists-accidentally-bred-school-sturddlefish-180975375/

> Amazing that these species have been separated by 184 million year but can still mix their genes.

I’d like to see more proof. That timespan looks impossible.

A 2 million years split for interbreeding is not impossible, eg. donkeys and horses.
A 15 million years split for interbreeding has been observed among the wild cats.
Hybrids among plants may go back further than that.

The timing gets confused by the issue of polyploidy. Human-mice hybrids have given rise to transgenic mice. As each organism develops it loses some of the human genetic information. And that split goes back more than 66 million years.

mollwollfumble said:

> Amazing that these species have been separated by 184 million year but can still mix their genes.

I’d like to see more proof. That timespan looks impossible.

A 2 million years split for interbreeding is not impossible, eg. donkeys and horses.
A 15 million years split for interbreeding has been observed among the wild cats.
Hybrids among plants may go back further than that.

The timing gets confused by the issue of polyploidy. Human-mice hybrids have given rise to transgenic mice. As each organism develops it loses some of the human genetic information. And that split goes back more than 66 million years.

What do you mean that you need more proof? The fact that you have these hybrid fish is the proof, which why they wrote the paper.

dv said:

We’ve all been there.