Age Determination of Mammals in the Arctic ocean – University of Copenhagen


Age Determination of Mammals in the Arctic ocean

World-wide biologists are concerned with counting animals, uncover migration patterns, and collect tissue samples. However, it is not easy to estimate the age of wild animals. For toothed animals the most widespread method is counting layers of teeth. Teeth however are worn and some animals do not have teeth (baleen whales e.g.) and older animals usually have worn teeth.

Exploiting the fact that amino acids in proteins racemise at constant speed (under constant conditions), one can – by determining the ratio of D- to L-amino acids estimate the age of the animal. Of the common amino acids aspartic acid (aspartate) racemises fastest and is therefore utilised for age determination to obtain the best sensitivity. This can only work if some proteins at the time around the birth of the animal are incapsulated with no exchange to the surroundings. Two tissue candidates are teeth and the lens in the eyes of mammals.

Racemisation of Aspartate is facilitated by the formation of a special intermediate due to the free carboxylate group of the side-chain. Aspartate from hydrolysed lens protein from the eye of a caught animal is derivatised with ortho-phthalic aldehyde and N-acetyl Cysteine. The derivatives are analysed using HPLC with fluorescence detection.





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It turns out that arctic whales are older than previously estimated and have a life span of up to about 200 years. This is confirmed by the discovery of several very old spear heads embedded in the blubber of the oldest whales examined. The project is extended from narwhales to include e.g. polar bears and Greenland sharks.