Lowest mutation rate: Shark genetic material changes extremely slowly

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According to a report in the journal “Nature Communications” by researchers led by Manfred Schartl of the University of Würzburg, the rate of change in epaulette sharks in particular is only one twentieth of the rate in humans.

This has advantages and disadvantages for fish living off Australia, as the research team explains: The fact that changes in the animals’ genetic makeup occur so rarely is a possible explanation for the extraordinarily low risk of cancer. However, for the same reason, they can adapt to environmental changes more slowly than other animals.

Genetic changes are the basis of evolution: some give affected animals a survival advantage and are therefore more likely to be preserved because these specimens have a better chance of producing more offspring. But cancer disease is also based on spontaneous small changes in DNA that lead to malfunctions and unbridled cell proliferation in affected cells.

As the researchers explain, the low mutation rate could be a disadvantage for sharks; especially if their populations are already significantly reduced and they must adapt to a rapidly changing environment. For the research, the team from Germany, Australia, Sweden and the USA compared the genomes of a pair of parents with the genomes of nine children, recording the genetic differences and thus determining the mutation rate.

Sharks are very old in terms of evolutionary history. They have lived in the world’s oceans for approximately 400 to 500 million years, and their basic appearance has remained virtually unchanged throughout this enormous span of time. Sharks reach sexual maturity late, have a slow metabolism, live to very old ages, and have few offspring. Overfishing, habitat loss and climate change are causing population declines of many shark species.

Epaulette sharks (Hemiscyllium ocellatum) live in coral reefs up to 60 meters deep. They are just over a meter long, are mostly out at night and rarely swim. Instead, they use their fins as feet and “walk” on the seabed.

Scientists explain that epaulette sharks are restricted to warm tropical waters, while lower mutation rates can be expected in shark species in cold waters, which have lower metabolic rates. A possible example is the Greenland shark (Somniosus microcephalus), which can live about 400 years.

(SDA)

Source : Blick