Hidden DNA found in blue whales shows they interbreed with other species and their hybrid offspring
These are the exciting revelations that scientists have made in the journal Conservation Genetics. By analyzing the genomes of blue whales – an endangered species – they discovered that they carry previously unknown DNA, indicating that they will mate with fin whales as well as their hybrid offspring.
Hybrid blue whale
The study’s authors explain that they analyzed the DNA of blue whales living in the North Atlantic, looking for possible signs of inbreeding that could hinder the group’s recovery. What they discovered surprised them: every whale sampled contained fin whale DNA (Balaenoptera physalus) is hidden in its genome. About 3.5% of the group’s DNA came from an average fin whale.
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Scientists have long known that these two whale species can sometimes interbreed, giving birth to individuals with the appearance of an unusually large fin whale with the coloration and jaw structure of a blue whale.
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It was long believed that these hybrid whales were sterile. But a 2018 study found that some of them can breed with blue whales, producing “backcross” offspring — mostly with blue whale DNA and some fin whale DNA. This phenomenon of gene transfer from one species to another after repeated hybridization is called “introgression”.
If the study’s authors suspected they would find fin whale DNA in the sequenced genome, they were surprised by its quantity. “The degree of introgression between species we found was unexpected and far greater than previously reported.”co-author Mark Engstrom, an ecological geneticist at the University of Toronto (Canada), told LiveScience.
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Hybridization, a threat?
In contrast, scientists have identified no evidence that fin whales inherit blue whale DNA through introgression. “So it appears that only blue whales are able, or perhaps willing, to breed with these hybrids. Mark Engstrom notes. We do not know why the conscience feels directionless. However, this may be because there are many more fin whales than blue whales.”
Furthermore, the interaction between fin whales and blue whales does not occur anywhere else in the world. “As far as we know, this is a phenomenon that only affects the North Atlantic, although the cause is not clear”The scientist added.
Finally, while there are no signs that this will have a negative impact on blue whales, Mark Engstrom fears that if the invasion continues, “This could reduce the amount of DNA from these whales in the population, which could make them less resilient to adapt to new challenges such as human-induced climate change.”.
