Despite widespread fascination with sharks, the world's oldest ocean predators have long been a genetic mystery. The first deep dive into a great white shark's genetic code has fished up big surprises behind a design so effective it has barely changed since before dinosaurs roamed.
Cornell researchers have discovered that many of the endangered great white shark's proteins involved in an array of different functions -- including metabolism -- match humans more closely than they do zebrafish, the quintessential fish model.
Michael Stanhope, professor of evolutionary genomics at Cornell's College of Veterinary Medicine, and scientists at the Save Our Seas Shark Research Center at Nova Southeastern University published the study in the November issue of BMC Genomics. It lays the foundation for genomic exploration of sharks and vastly expands genetic tools for their conservation, said Stanhope.
"We were very surprised to find, that for many categories of proteins, sharks share more similarities with humans than zebrafish," Stanhope said. "Although sharks and bony fishes are not closely related, they are nonetheless both fish … while mammals have very different anatomies and physiologies. Nevertheless, our findings open the possibility that some aspects of white shark metabolism, as well as other aspects of its overall biochemistry, might be more similar to that of a mammal than to that of a bony fish."
The study launched when Stanhope and Nova Southeastern professor Mahmood Shivji received a Save Our Seas Foundation grant and a rare gift of a great white shark heart. The heart had been autopsied from an illegally fished shark, confiscated by government authorities and donated to their project.
Of particular interest was that white shark had a closer match to humans for proteins involved in metabolism.
"Sharks have many fascinating characteristics," said Stanhope. "Some give live birth to fully formed young, while some lay eggs. In some species, the embryos eat the remaining eggs or even other embryos while still developing in the uterus. Some can dive very deep, others cannot. Some stay local; others migrate across the entire ocean basins. White sharks dive deep, migrate very long distances and give live birth. We will use what we've learned in this species in a broader comparative study of genes involved in these diverse behaviors."
Because sharks are apex predators, their decreasing number threatens the stability of marine ecosystems, on which millions of people rely for food. This study also increased the number of genetic markers scientist can use to study the population biology of great white and related sharks, Stanhope said, by a thousandfold, from which they hope to further expand knowledge of these fascinating animals, many of which are in urgent need of conservation.
- Vincent P Richards, Haruo Suzuki, Michael J Stanhope, Mahmood S Shivji. Characterization of the heart transcriptome of the white shark (Carcharodon carcharias). BMC Genomics, 2013; 14 (1): 697 DOI: 10.1186/1471-2164-14-697
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