Hybrid sharks 'evolution in action'

Last updated 09:38 04/01/2012
Black-tip shark
Wikimedia Commons
A common black-tip shark.

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The world's first hybrid sharks have been discovered off the Australian coast, scientists say.

Researchers found 57 of the new sharks along 1200 miles of coastline between New South Wales and Queensland, with the interbreeding possibly a response to climate change or fishing patterns.

The mating of the two species - local Australian black-tip shark with its global counterpart, the common black-tip - was an unprecedented discovery with implications for the entire shark world, said lead researcher Jess Morgan.

"It's very surprising because no one's ever seen shark hybrids before, this is not a common occurrence by any stretch of the imagination," Morgan, from the University of Queensland, told AFP.

"This is evolution in action."

Like its two parent species, the new shark is not considered dangerous - and scientists say there is no risk of the hybrids leading to a Jaws-style "mega-shark".

The hybrids were found at five locations and identified using genetic testing and body measurements.

While the two parent black-tip species are closely related, they grow to different maximum sizes and are genetically distinct.

Colin Simfendorfer, a research partner from James Cook University, finding the hybrids was "very unusual".

"Telling the hybrids is extremely difficult, which is why it has never been done before," he told ABC Radio.

"It came very much out of leftfield. We didn't think it was a possibility, but lo and behold there it was."

Simfendorfer said hybrids were often sterile but there was evidence the new sharks have been breeding both with each other and with members of the separate black-tip species.

Surprisingly, he said, the hybrids are not the average size of the two interbred species but tend to be roughly the same length as one species or the other.

A Queensland marine scientist, Dr Jennifer Ovenden, told the Telegraph the sharks may be adapting to changes in the environment and other closely related sharks and rays may also be interbreeding.

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"Wild hybrids are usually hard to find, so detecting hybrids and their offspring is extraordinary," she said.

"Hybridisation could enable the sharks to adapt to environmental change as the smaller Australian black tip currently favours tropical waters in the north. The larger common black tip is more abundant in sub-tropical and temperate waters along the south-eastern Australian coastline."

Asked whether there was any risk of a "mega-shark" developing, Simfendorfer said: "We don't think there's any issue with that at all. Both of these species we don't consider a danger to humans. Given that they keep the same sort of morphology of one or other of the parents, we should see no visible change in terms of what we see out there in the ocean."

- Stuff

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