Long life of bowhead whales partially deciphered | Polarjournal
Apart from beluga and narwhals, bowhead whales are the only whale species that can migrate far into the pack ice of the Arctic Ocean. With their reinforced upper jaw and arched back of the head/back, the animals can seemingly effortlessly break through the pack ice to breathe, thanks to 80 tons of weight. Image: Screenshot documentary “Sanfte Riesen” via Youtube

One of the most spectacular, but also most mysterious inhabitants of the Arctic certainly is the bowhead whale. This giant marine mammal has been known for centuries due to whaling, but it still puzzles researchers. One of secrets is its longevity and its reasons and mechanisms. A research group has now probably discovered a key clue as to how these animals manage to become the oldest known mammal in the world.

A whopping 211 years is the age record set by the oldest known mammal, a bowhead whale. For comparison, the remaining large whales live between 60 and 70 years (with exceptions, like humans). And according to research by Juan Vazquez of the University of California Berkeley, Morgan Kraft and Vincent Lynch, University at Buffalo, a single specific gene is likely responsible, the CDKN2C gene. The three scientists published their study on the bioRxiv preprint server, a reputable server for advance publications for life sciences.

In 2015, the genetic material of bowhead whales was completely sequenced and has been known since. The genes can be divided into functionality groups, so the research team was able to pick and analyze those that are affected in cancer. This is how they discovered the whale-specific gene CDKN2C. Image: Vazquez et al (2022)

Longevity in mammalian species is often associated with cancer formation. The longer a species lives, the more likely it is that cells will develop into cancer cells due to mutation accumulation. But interestingly, this finding cannot be applied across species boundaries. It has long been suspected that the secret to the longevity of bowhead whales lies in their genetic predisposition to reduce such mutations even at an advanced age. To investigate this, Vazquez, Kraft and Lynch studied the genome of bowhead whales, which has been open to research like a book since 2015. The genes can be divided into groups according to their functions. This helped the research team to study only those genes involved in the various aging and cancer formation processes.

Using evolutionary genomics and comparison with other cetaceans, the three researchers discovered the cetacean-specific gene, but it only appears strongly in bowhead whales. The team found that, on the one hand, the gene likely slows down cell division because it successfully duplicates itself (i.e., has a copy of itself), and at the same time, it positively affects the repair of damaged DNA (which can occur when genetic information is copied and is the mutation), thus protecting the cell from cell death. Thus, bowhead whales are probably much less susceptible to cancer than other mammals, the researchers conclude.

Due to the remoteness of their habitat, much is still unknown about the biology of bowhead whales. However, it is known that on the one hand the animals can become very old, but on the other hand they only raise a calf every 3 – 4 years and also need a long time until they can successfully raise a calf for the first time. According to researchers, the gene that promotes longevity may also have an effect on reproductive organs, at least in bulls. Image: NOAA Fisheries

Another finding of the study by Vazquez, Kraft and Lynch that CDKN2C also affects testicular development in bulls in ways that are still unknown. That’s because the team’s research showed that the testes of bowhead whale bulls are only about 20 percent of the size known in their closest relatives, right whales. According to the team, there are numerous known examples in nature where there is a trade-off between body size, longevity, health and reproduction. In the case of bowhead whales, the team speculates, the extra copy and overexpression of the gene may be responsible. However, the researchers write nothing in their paper about whether this induces, for example, changes in the genitalia of female animals, a slowing of oocyte maturation, or a reduction of oocytes at all. But bowhead whales at least do not seem to mind, because the number of animals is increasing thanks to more offspring.

Dr Michael Wenger, PolarJournal

Study link: Vazquet et al (2022) bioRxiv 2022.09.07.506958 A CDKN2C retroduplication in Bowhead whales is associated with the evolution of extremely long lifespans and alerted cell cycle dynamics; https://doi.org/10.1101/2022.09.07.506958

A documentary about the longevity of bowhead whales can be found here.

The approximately 45-minute documentary shows what the longevity of bowhead whales means.

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