Lobsters are one of the small number of species that might be ageless, or at the very least age very slowly and exhibit little to no decline until very late life. There is little money for aging research in lobsters, however: until now researchers possessed no way to accurately determine the age of a lobster, and no good estimate as to average or maximum life span in these species. This new development should hopefully lead to a better grasp of the degree to which lobsters do or do not age, and pin down numbers for life span:

For the first time, scientists have figured out how to determine the age of a lobster - by counting its rings, like a tree. Nobody knows how old lobsters can live to be; some people estimate they live to more than 100.

Scientists already could tell a fish's age by counting the growth rings found in a bony part of its inner ear, a shark's age from the rings in its vertebrae and a scallop or clam's age from the rings of its shell. But crustaceans posed a problem because of the apparent absence of any permanent growth structures. It was thought that when lobsters and other crustaceans molt, they shed all calcified body parts that might record annual growth bands.

[Researchers] took a closer look at lobsters, snow crabs, northern shrimp and sculptured shrimp. They found that growth rings, in fact, could be found in the eyestalk - a stalk connected to the body with an eyeball on the end - of lobsters, crabs and shrimp. In lobsters and crabs, the rings were also found in the so-called "gastric mills," parts of the stomach with three teeth-like structures used to grind up food.

http://www.huffingtonpost.com/huff-wires/20121130/us-lobster-aging/

Source:
http://www.fightaging.org/archives/2012/11/a-method-of-determining-lobster-age.php