DNA from sharks' teeth may help protect the endangered species

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London, August 12 : Scientists have developed a new technique that can analyze DNA from sharks' teeth, which would help conservation biologists to study endangered species of the poorly understood fish.

Until now, scientists have not been able to extract DNA from old shark samples, as the fish do not have the bony skeletons that are essential for conventional methods. lthough biopsies of flesh from live sharks are possible, the fish are generally quite uncooperative research subjects.

According to a report in Nature News, the new technique, developed by scientists at Macquarie University in Sydney, Australia, is allowing them to assess genetic variation in both modern and historical populations of shark, which is crucial for conservation assessments.

"Sadly, trophy jaws and teeth from sharks are relatively commonplace, whereas living sharks are becoming increasingly rare," said Heidi Ahonen, one of the researchers. This method allows information locked away within the teeth and jaws to be exploited to assist with conservation management," she added.

Using a hand drill, Ahonen and her colleague Adam Stow extracted about a quarter of a teaspoon (1.5 millilitres) of material from a shark's tooth or jaw.

They mixed the material with just the right cocktail of detergents and enzymes to break open cells and release the DNA.

"Sharks have continual turnover of dentition throughout their lifespan, and consequently teeth may be collected from the seafloor in areas where sharks aggregate without the need to use invasive sampling methods such as biopsy," said Ahonen.

So, the method can be applied to museum specimens and trophy samples as well as for endangered or elusive living sharks.

The team is collecting samples from several species to determine whether declines in shark populations are being exacerbated by low genetic variation.

The technique has already yielded useful results for the highly endangered east Australian population of grey nurse sharks (Carcharias taurus), which were heavily fished in the 1960s and 1970s.

Using their new method, the researchers amplified DNA from nine specimens aged 20 to 40 years old, and found low levels of genetic variation.

"These data support our hunch that low genetic variation in grey nurse shark is probably due to longer term processes than the recent human-induced population crash," said Ahonen.

According to Les Noble, of the University of Aberdeen, UK, "We also have plans to use approaches like this to identify rogue individuals."

Noble said that scientists could analyze fragments of tooth found in a survivor's wound after a shark attack.

It should be possible to compare that sample with any sharks killed in the subsequent hunt - confirming that the rogue fish had been bagged.

ANI

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