A team of genetic researchers from Cornell University and Nova Southeastern University have discovered that many of the great white shark’s (Carcharodon carcharias) proteins match humans more closely than they do zebrafish, the quintessential fish model.
Prof Michael Stanhope of Cornell University with colleagues compared the transcriptome – the set of RNA sequences expressed by the organism’s genes – from the white shark heart to the transcriptomes from the zebrafish and humans to look for similarities and significant differences that might explain the distinctiveness of the white shark.
Surprisingly, they found that the proportion of white shark gene products associated with metabolism had fewer differences from humans than zebrafish.
“We were very surprised to find, that for many categories of proteins, sharks share more similarities with humans than zebrafish,” said Prof Stanhope, a co-author of the study published in the journal BMC Genomics.
“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.”
“Sharks have many fascinating characteristics. 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,” Dr Stanhope said.
“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 scientists can use to study the population biology of great white and related sharks by a thousandfold, from which they hope to further expand knowledge of these fascinating animals, many of which are in urgent need of conservation,” Dr Stanhope said.
Richards VP et al. 2013. Characterization of the heart transcriptome of the white shark (Carcharodon carcharias). BMC Genomics, 14: 697; doi: 10.1186/1471-2164-14-697