Sharks occupy diverse ecological niches and play critical roles in marine ecosystems, often acting as apex predators. They are considered a slow-evolving lineage and have been suggested to exhibit exceptionally low cancer rates. These two features could be explained by a low nuclear mutation rate. To estimate the nuclear mutation rate, a team of marine biologists generated a high-quality reference genome of the epaulette shark (Hemiscyllium ocellatum); they also resequenced the whole genomes of epaulette shark parents and nine offspring to detect new mutations.
Sharks are members of one of the earliest vertebrate clades that emerged from mass extinction events in the Permian and Jurassic periods to radiate and dominate many marine food webs.
Modern sharks play important functional roles in the regulation and maintenance of a diverse range of marine ecosystems.
However, little is known about the evolutionary rate and adaptive potential of shark populations, a fact that has come into sharper focus with the emergence of the dual ecological pressures of overfishing and habitat loss.
In the new study, Professor Manfred Schartl from the Julius-Maximilians-Universität Würzburg and his colleagues focused on the epaulette shark, a small, oviparous species that inhabits coral reef environments in the waters north-east of Australia.
First, they were able to create a high-quality reference genome and sequence the entire genomes of the parents and then the nine offspring to discover new mutations occurring in the progeny.
They we estimate a mutation rate of 7*10-10 per base pair, per generation — 10 to 20 times lower than in mammals.
This represents one of the lowest directly estimated mutation rates for any vertebrate clade.
“Sharks have long been said to have an exceptionally low cancer rate,” Professor Schartl said.
“The low mutation rate could play a decisive role in this.”
“What initially sounds like good news for the animals, however, also brings with…
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