Discoveries

February 21, 2024

Mixing to Thrive

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Blue whales are the largest animals on Earth, capable of reaching lengths of 110 feet long.

Unfortunately, they are also listed as an endangered species as a result of intense commercial whaling over the 20th century.

But even as their numbers rebound, there is a blue whale subspecies, Balaenoptera musculus musculus, that is most at risk.

Now, marine scientists discovered that members of this subspecies have found ways to multiply their numbers without inbreeding, Live Science reported.

In a new study, researchers meticulously analyzed the genomes of B. musculus musculus whales in the North Atlantic, painstakingly piecing together DNA from different individuals to create a comprehensive genetic blueprint.

Their findings showed that each sampled whale harbored DNA from fin whales, their smaller counterparts.

On average, around 3.5 percent of blue whale DNA originated from fin whales, indicating extensive introgression between the two species – described as the transfer of DNA from one species to another via interbreeding.

While scientists previously believed that hybrids resulting from blue and fin whales were infertile, recent studies – including this one – have challenged this notion.

The new analysis suggested that the hybrids have been successfully mating with blue whales and creating “backcrossed” offspring – which exhibit mostly blue whale and some fin whale DNA.

Even so, past research has found no evidence that fin whales have inherited any blue DNA via introgression, which means that this introgression seems to be “unidirectional,” according to the authors.

They noted that this introgression could reduce the genetic diversity of blue whale populations, potentially impacting their resilience to future challenges, such as climate change.

Still, the good news is that inbreeding between the North Atlantic marine mammals is less than expected and there is a substantial gene flow between western and eastern Atlantic blue whale populations.

This story originally appeared in the February 21, 2024 newsletter, A Popular Resistance.