Wednesday, August 24, 2016

[Ichthyology • 2016] Eye Lens Radiocarbon reveals Centuries of Longevity in the Greenland Shark Somniosus microcephalus


Greenland Shark Somniosus microcephalus 
photo: Nick Caloyianis DOI:  10.1126/science.aaf1703

Deep living for centuries
We tend to think of vertebrates as living about as long as we do, give or take 50 to 100 years. Marine species are likely to be very long-lived, but determining their age is particularly difficult. Nielsen et al. used the pulse of carbon-14 produced by nuclear tests in the 1950s—specifically, its incorporation into the eye during development—to determine the age of Greenland sharks. This species is large yet slow-growing. The oldest of the animals that they sampled had lived for nearly 400 years, and they conclude that the species reaches maturity at about 150 years of age.

A Greenland Shark Somniosus microcephalus off Baffin Island, Canada. 
photo: Nick Caloyianis 


 Abstract

The Greenland shark (Somniosus microcephalus), an iconic species of the Arctic Seas, grows slowly and reaches >500 centimeters (cm) in total length, suggesting a life span well beyond those of other vertebrates. Radiocarbon dating of eye lens nuclei from 28 female Greenland sharks (81 to 502 cm in total length) revealed a life span of at least 272 years. Only the smallest sharks (220 cm or less) showed signs of the radiocarbon bomb pulse, a time marker of the early 1960s. The age ranges of prebomb sharks (reported as midpoint and extent of the 95.4% probability range) revealed the age at sexual maturity to be at least 156 ± 22 years, and the largest animal (502 cm) to be 392 ± 120 years old. Our results show that the Greenland shark is the longest-lived vertebrate known, and they raise concerns about species conservation.


Julius Nielsen, Rasmus B. Hedeholm, Jan Heinemeier, Peter G. Bushnell, Jørgen S. Christiansen, Jesper Olsen, Christopher Bronk Ramsey, Richard W. Brill, Malene Simon, Kirstine F. Steffensen and John F. Steffensen. 2016. Eye Lens Radiocarbon reveals Centuries of Longevity in the Greenland Shark (Somniosus microcephalus). Science. 353(6300); 702-704. DOI:  10.1126/science.aaf1703

Slow Sharks Sneak Up on Sleeping Seals (and Eat Them)? http://on.natgeo.com/LOdEP3 via @NatGeo


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