Great whites ended up in Mediterranean after ‘wrong turn’ 450,000yrs ago

Wednesday, November 17, 2010

LONDON - A genetic study has suggested that the great white shark may have ended in the Mediterranean after it took a wrong turn 450,000 years ago, from the seas around Australia.

Researchers believe the arrival may have been simply a migratory “wrong turn” by a few pregnant females, brought about by a tumultuous climate between ice ages.

It had previously been assumed that the great whites in the Mediterranean were most closely related to their cousins in the Atlantic Ocean, but a team led by Les Noble of the University of Aberdeen found something else.

They examined several groups of sharks’ mitochondrial DNA - genetic material passed through the maternal line that is particularly suited to tracing lineages - and found that the Mediterranean sharks were very different to the Atlantic group and more like sharks from Australia and New Zealand.

Although changes to the DNA in the different populations happen randomly, they do happen with a regular average rate.

And the few differences between the Australian and Mediterranean sharks indicated how long ago they parted ways: 450,000 years ago - a time between ice ages that would have seen many effects of a changing climate.

“That was a time of interglacials, when you would’ve had all kinds of changes in the currents going down the east and up the western coast of Africa,” the BBC quoted Dr Noble as saying.

The team hypothesises that strong, warm currents pushing the sharks northward would have put them far off course.

“They might have gone a considerable way up there before the warmth ran out. Then they start trying to turn east and north and the first place you can go east, of course, is the Straits of Gibraltar,” the team said.

Dr Noble explained that perhaps only a few pregnant great whites would have needed to make the journey.

“The reason we still have a genetic signature of that with the great whites is because they’re like salmon - where the pups are dropped, they recognise as their home - that’s where they always return to,” he said.

The findings have been published in Proceedings of the Royal Society B. (ANI)

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