Great White Sharks More Closely Related to Humans Than Zebrafish--Sort of

First Posted: Nov 19, 2013 09:02 AM EST
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The great white shark is one of the deadliest and most efficient predators in our oceans. Now, scientists have learned a little bit more about this species. They've explored the genetic makeup of this remarkable animal, revealing further insight into the great white's distinctive features.

In order to learn a bit more about the shark, the scientists compared the transcriptome, the set of RNA sequences expressed by the organism's genes, from the great white shark heart to the transcriptomes from zebrafish and humans. They then looked for similarities and significant differences that might explain the distinctiveness of the shark. In order to have a common comparative basis, the researchers compared gene products that had known functions in all three species.

So what did they find? It turns out that the proportion of white shark gene products associated with metabolism had fewer differences from humans than zebrafish. That's extremely unusual considering that bony fishes are evolutionarily much more closely related to sharks. The scientists also found that other aspects of the great white shark heart transcriptome, including molecular functions as well as the cellular locations of these functions, also showed greater similarities to humans than zebrafish.

"It's intriguing why there are these fewer differences in the proportion of gene products between white sharks and humans, than white sharks and zebrafish, when the complete opposite was expected based on evolutionary affinities," said Mahmood Shivji, one of the researchers, in a news release. "One possibility for the apparent great similarity between white sharks and humans in the proportion of gene products associated with metabolism might be due partly to the fact that the white shark has a higher metabolism because it is not a true cold-blooded fish like bony fishes; however this explanation remains a hypothesis to be further tested."

The findings reveal a little bit more about this massive animal. This, in particular, could be important for future conservation efforts. In addition, it reveals a bit more about the species as a whole, which could give further insights into the process of evolution.

"Our results, along with other distinctive shark genome features reported by the very few studies in this area by others, are suggesting that we may be in for some surprises as we further explore sharks at their most fundamental level--their genes," said Shivji in a news release. "We've just scratched the surface in terms of investigating what makes these evolutionary marvels, and in many cases threatened species, tick."

The findings are published in the journal BMC Genomics.

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