It’s an apex predator, one of the most fearsome fish in the sea, and now scientists know just what it’s made of.
Researchers have decoded the genome of the great white shark. Containing roughly one-and-a-half times as much DNA as the human genome, the white shark’s genetic code revealed a wealth of insight — and a few surprises — about what makes these creatures so successful from an evolutionary standpoint.
Sharks have been around a long time. Scientists estimate that they’ve terrorized the oceans for some 500 million years. (For comparison, great apes have existed for something like 20 million years.) Surviving that long isn’t easy. Scientists at Nova Southeastern University, Clemson University, and elsewhere wanted to find out how sharks have done it.
“Sharks represent an ancient vertebrate line which has been very successful in an evolutionary persistence sense,” Mahmood Shivji, director of the Save Our Seas Foundation Shark Research Center and Guy Harvey Research Institute at Nova Southeastern, told Digital Trends. “The impetus for decoding a shark genome was to gain an understanding of what makes a shark a shark, at the most fundamental level — their DNA — and see what unique genetic features might explain their biological success.”
To better understand sharks as a whole, Shivji and his colleagues decided to focus on the white shark due to its unique characteristics. The white shark exemplifies extremes. It grows to an extraordinary size, migrates huge distances, and they’re partially warm-bodied, which is uncommon in fish. Beyond that, the great white is a popular and recognizable — if widely feared — species.
Within the white shark genome, the researchers discovered a few surprises. For one, the shark genome was about 50 percent larger than the human genome. They also uncovered a high number of adaptive changes in genes linked to DNA repair, damage tolerance, and damage response. In short, the findings suggest that sharks have developed a certain “genetic defense mechanism” that helps maintain the long term integrity of their genetic code. In humans, an absence of these genes have been linked to increased rates of cancer and age-related diseases.
The researchers also compared the genome to that of the giant whale shark, another large-bodied and long-lived creature, to see what similarities they could find.
“The study sheds light not only on the genomes and gene contents of white sharks but also whale sharks,” Shivji said. “The findings suggest that it’s the genetic adaptations in genome stability maintenance genes in both the white and whale sharks that may underlie the attainments of such large bodies and long lives in these species. Furthermore, knowledge of the genetic innovations facilitating genome stability in sharks provides us with gene targets to study in more detail to potentially help with the many human diseases caused by genome instability. “
The scientists have merely scratched the surface of studying shark genomes, Shivji said. Moving forward they plan to continue to decode genomes of various shark species and investigate whether genetic traits present in white and whale sharks occur across all sharks or just in those with large bodies.
A paper detailing the study was published this week in the journal Proceedings of the National Academy of Sciences.
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