Somniosus microcephalus, ‘The Greenland Shark’ commonly known as ‘the sleeper shark’ is the vertebrate of cold oceans with the longest lifespan. Living in the depths of cooler oceans, this member of the scavenger family swims in the depths of the North Atlantic and Arctic oceans. Human encounters are rare for this vertebrate because of its deeper habitats. Being the center of attraction for our researchers once caught in fishing nets; sleeper sharks benefit scientists by becoming their subject of research.
During research on this charismatic organism, among 28 Greenland sharks, one female sleeper shark turned out to be 5 meters long, hence the oldest among all. Though the exact age of the female is not known, carbon dating estimates the age of Greenland sharks with the proteins inside their eyes. before their birth and do not degrade. The scientists were sure that the age of this oldest female was between 272 and over 500 years old. Though radiocarbon dating can’t result in the exact time, according to the researcher, the female was around 400 years old.
A team of European and United States scientists is eager to find the ability of the sleeper shark to live for a long time and, therefore, have mapped the genome of this vertebrate. The findings on the genome provide approximately 6.5 billion base pairs, about twice as many as humans. Repeated genes compose more than two-thirds of the genome. The exact reasons for the longer lifespan of sleeper sharks are yet unknown, but the assumptions are many. Sometimes their longevity relates to their adaptation in cold environments of the ocean at temperatures below 29° Fahrenheit, while other assumptions say the slower growth rate of the species. Sleeper sharks reach the size of 6 meters due to their slower growth rate and grow less than 1 cm per year. After becoming 4 meters long, Greenland sharks attain sexual maturity in about 150 years. Having a slow metabolism, these Greenland sharks not only grow slowly but also move slowly, with an average speed of 0.3 meters per second. Scientists assume that cold environments are responsible for anti-aging effects and slow metabolism, and this slow or stable metabolism of Greenland sharks can be the only reason besides their longer lifespan.
The increase in global warming could be a great concern for Greenland sharks' longer lifespan. The impact might be worse as the warm oceans would increase their metabolism and might affect the longevity of Greenland sharks.
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