Scientists tested the radiocarbon method for age determination from whale sharks. It turned out that they accumulate an isotope of carbon as well as other inhabitants of the surface layers of the ocean and corals. The researchers also found that the previous method of age estimation using the counting of layers in vertebrates — gives the correct assessment. In addition, they constructed a growth curve for whale sharks and defined the period in which animals may be particularly vulnerable to poachers — it takes up almost half of their lives. Work published in the journal Frontiers in Marine Science.
Among the many types of sharks, long-lived, but to find out for sure how long they actually live — not an easy task. And if small fish more suitable option with all sorts of labels — for example, substances that can be injected into the body of the animal, and then catch it again and measure the concentration of large sharks rarely catch so biologists could use some way to determine their age at one time.
From bony fishes to the point of such definitions provide salt deposits in the otolith crystals in the inner ear. We can also analyze the composition of proteins in the lens — so found out that the Greenland shark can live up to 400 years. But for cartilaginous fish often use the Dating of the vertebrae: the cartilage is deposited on them layers resembling the annual rings of trees. However, scientists still were not sure how often there is a new layer every year or two, and how this method is generally reliable.
Joyce Ong (Ong Joyce) from Rutgers University with colleagues from Australia, Iceland, Pakistan and Saudi Arabia worked with the vertebrae of the whale sharks from Taiwan and Pakistan. The researchers counted the stripes on the vertebrae of 20 individuals and determined that their ages ranged from 15 to 50 years.
To check these calculations, they were going through radiocarbon Dating. As a result of nuclear weapons testing in the 1950-ies and 1960-ies in the ocean dramatically increased the amount of radioactive isotope of carbon. Therefore, knowing its concentration in the environment, you can make a scale age determination for individual species. Such scale already known for other animals, including corals and other species of sharks.
The authors determined the concentration of heavy carbon in samples from different bands of two vertebrae of sharks. They compared the amount of carbon and the estimated age of the strips (on the basis of its sequence number), and then checked his calculations with the age scales for other species. They found that they received points approximately coincide with the curve for the sharks from the North Atlantic. On this basis, they concluded that the method of counting the stripes authentic whale sharks, and they are formed one at a year.