It is believed that lobsters can live for up to 100 years and reach 4 ft. in length, qualities that rank them among the largest and most long-lived creatures of the sea. Marine biologists actually have a term to refer to such large and long-lived beings: biological immortality.
Lobster species vary considerably in size. The carapace of the smallest lobster species is less than 1.5 inches long, measured from the eye socket to the rear of the carapace, while the largest lobsters grow up to 4 ft. long and can measure up to 20 pounds in weight (the largest lobster ever caught was captured in Canada, in Nova Scotia, and it weighed 44.4 pounds).
Biological mortality, the term frequently used when discussing the lifespan of lobsters, refers to the fact that lobsters do not seem to die because of cellular aging. Most lobster species retain their strength and fertility through their entire life. One of the physical features that account for this incredible longevity is the production of an enzyme called telomerase. This enzyme is able to repair the telomeres, which are parts of DNA sequences. Telomerase is present in the majority of the tissues in the lobster’s body.
Though scientists call them immortal, lobsters still die. Even if the natural causes do not include aging, these animals also die, the main causes being injuries, diseases and exhaustion. Lobsters continue to grow all their life. Being crustaceans, they are covered in a hard and rigid shell called an exoskeleton. When the animal grows, it sheds its exoskeleton in a tedious process called moulting that involves the growth of a relatively soft new shell underneath the old exoskeleton, followed by the actual shedding of the old shell. The process is very exhausting for the lobster. The larger the animal, the longer and the more tedious it actually becomes, leading to the death of the lobster if it cannot supply the metabolic energy necessary for getting rid of the exoskeleton. Actually, about 10-15% percent of lobsters die because of moulting exhaustion.
In order to avoid the exhaustion related to moulting, some lobster species are known to stop shedding their old shells, but they do not stop feeding and, as a result, growing. The lobsters belonging to these species usually die because the exoskeleton kept on for too long will eventually become damaged, leading to infections and other diseases and to the lobster’s death, eventually. There is another aspect of moulting that also accounts for increased mortality. The new carapace that covers the lobster’s body immediately after the animal has moulted the old shell is softer and leaves the animal more vulnerable to predation. Lobsters do go into hiding for a while after shedding, but even if hidden, they make easy prey.
Determining the weight of a lobster is simple – you only need to place it on scales – but determining a lobster’s age is much more difficult. Age is usually assessed by examining the animal’s eyestalks and measuring the growth bands on the stalks, but scientists are still looking for more accurate methods.