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Joined: Mon Apr 11, 2011 6:55 pm
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Post Longevity
Wondering if we can use the Greenland shark to study how to live longer.

Radiocarbon dating finds a Greenland shark that could be 400 years old

At four to five meters in length, the Greenland shark (Squaliformes, Somniosus microcephalus) is the largest fish native to the Arctic waters. Getting that big must take a while, and scientists have long known that these sharks grow less than one cm per year. So these sharks probably live a very long time, but little was known about their longevity and maturation.

In an investigation recently published in Science, a team of researchers used radiocarbon dating to put together a timeline of the Greenland shark's lifespan.

Because Greenland sharks lack bones—they’re cartilaginous fish—conventional methods of tracking growth, like carbon dating of bones, won't work. Instead, the team used a modified radiocarbon dating technique that has worked before on other boneless animals: tracking the chronology of the eye lens. The eye lens nucleus is composed of inert proteins. The central portion of the lens is formed during prenatal development, and during growth, the tissue retains the original proteins, which were largely made before birth.

As a result, carbon-dating these proteins can help determine how long ago the shark was born. For this work, researchers performed radiocarbon dating on the eyes of 28 female sharks that were collected in Greenland during scientific surveys that took place between 2010 and 2013. According to the radiocarbon dating, these sharks live at least 272 years.

In the past, atmospheric testing of thermonuclear weapons caused bomb-produced radiocarbon. This radiocarbon subsequently assimilated into the marine environment. The occurrence of these events created a “bomb pulse” that is visible in radiocarbon dating data. In the field, it’s well-established that the presence of the radiocarbon bomb pulse is a time marker for the early 1960s.

The two smallest sharks in the survey (220 cm or less) are presumably the youngest, and they exhibited the highest radiocarbon levels (>99 pMC). The scientists think this indicates these two sharks were affected by the bomb pulse. Unfortunately, due to variability of bomb pulse curves that model its effect on radiocarbon dating, assigning an age to these animals is impossible, though it's likely that they were born later than the early 1960s.
http://arstechnica.com/science/2016/08/ ... years-old/

Sat Aug 13, 2016 2:01 am
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