Researchers have discovered that the genes of the Great white shark match humans more closely than Zebra danios.
This came as something of a surprise, seeing than bony fishes like the Zebrafish — which is genetically, one of the best understood fish — are evolutionarily much more closely related to sharks.
Researchers primarily interested in the conservation of this iconic shark made the discovery following the donation of the heart of a Great white, which had been illegally fished and confiscated by authorities.
Seeking genetic similarities and differences that might explain the characteristics of the Great white shark, its genetic makeup was compared to that of Zebrafish and human genes — and the results raised more questions than it provided answers.
They discovered that many of the shark’s proteins involved in metabolism, as well as other aspects of its overall biochemistry were more similar to that of a mammal.
"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, director of NSU’s Save Our Seas Shark Research Centre and Guy Harvey Research Institute, who was co-author of the study.
"One possibility for the apparent greater 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 Great white shark is one of few fish that is regionally warm-bodied, with parts of its body being kept at a higher temperature than the surrounding water (known as regional endothermy). This warm-body property is associated with elevated metabolic rates compared to true cold-blooded bony fishes.
Shivji suggests that more surprises lie ahead with further genetic exploration of the Great white shark.
"We've just scratched the surface in terms of investigating what makes these evolutionary marvels, and in many cases threatened species, tick," he said.
The study is published in BMC Genomics.
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