Are lobsters immortal? | Natural History Museum

Working out how old lobsters are can be very tricky, but despite all the memes, we know they can’t actually live forever. © OSDG/ Shutterstock

What on Earth?Are lobsters immortal?<br>By Emily Osterloff

Biological immortality is exceptionally rare.

Despite numerous memes that suggest lobsters can live forever, these crustaceans are bound to a mortal existence, just like us.

Discover how long lobsters live, how big they get and why scientists think they don’t act their age.

What is a lobster?

While lots of animals are known as lobsters, for example, spiny lobsters, squat lobsters and slipper lobsters, this term is more formally used to refer to the true lobsters – crustaceans in the taxonomic family Nephropidae.

This group includes well known, commercially valuable species, such as the European lobster, Homarus gammarus, and American lobster, Homarus americanus.

How long do lobsters live?

Working out how old lobsters are can be difficult and scientists have tried a variety of methods. In lots of other animals, experts can use growth bands left behind on hard structures, such as bones or scales, to determine the age of an individual.

But this method doesn’t really work for lobsters. Lobsters shed their entire exoskeleton when they grow and retain no hard structures. The size and weight of the animal helps us guess their age, but it’s not a reliable way to determine it accurately.

Instead, scientists have tried looking at the fat residue on the eyestalks, assuming older lobsters would have stored up more fat.

They found that, on average, male European lobsters live to 31 years old, and females to 54. There were a few exceptions – one particularly long-lived female had was found to be 72 years old.

The idea that lobsters live forever is a myth. These animals can face death from predation, disease or even exhaustion when they moult, for example. © Becky Gill/ Shutterstock

Lobsters certainly do not live forever. It’s not entirely clear where this myth originated, but it’s a claim that persists online, often in the form of memes. Given the right circumstances, some animals could be considered immortal, but lobsters are not among them.

Like many other decapod – ten-footed – crustaceans, lobsters continue to grow throughout their lives. Scientists call this indeterminate growth. This contrasts with people, for example – we stop growing when we reach adulthood.

But lobsters and other decapods do eventually reach the end of their lives.

Lobsters can face death from predation, including by humans, or health issues such as shell disease.

Another potential cause of death is inherently linked to their continuous growth. When they’re young, lobsters grow rapidly, shedding their exoskeleton multiple times a year. Over time, growth slows down and moulting becomes less frequent. But for each successive moult, increasing amounts of energy are needed and eventually the cost is too high and lobsters can die from exhaustion. One lobster expert has suggested that that 10–15% of lobsters go out this way.

A female lobster carrying eggs on its underside. The lobster life cycle begins with a female producing thousands of eggs, but only a few will survive to adulthood, and even fewer to enormous sizes. © Lost_in_the_Midwest/ Shutterstock

How big can lobsters get?

Lobsters may not be able to grow forever, but they can reach impressive sizes.

American lobsters are larger and heavier than their European relatives. A metre-long specimen, caught off the coast of Nova Scotia, Canada in 1977, weighed in at 20.14 kilogrammes (44lbs 6oz). This is the largest lobster ever caught and currently holds the record as the world’s heaviest marine crustacean.

This isn’t the only big lobster to have been pulled from the ocean. Two individuals from the Virginia Capes, affectionately known as Mike and Ike, are held in the collection at the Museum of Science, Boston. These colossal crustaceans weighed in at 19 kilogrammes (42lbs) and 17.2 kilogrammes (38lbs) respectively.

Rumours of heavier specimens have come and gone. Most have been unconfirmed, such as a 1939 claim of a 21.3-kilogramme (47lbs) giant lobster living off the coast of New Jersey, and a huge 21.7 kilogramme (48lbs) individual said to have been caught near Chatham, Massachusetts.

To imagine just how huge these lobsters would have been, we can compare to ones diners might be familiar with. For example, in Maine, a state with a large commercial lobster industry, there are now fishing regulations that detail a minimum and maximum size for lobsters that can be caught and kept. Any lobsters found to have a carapace – the part of the hardened exoskeleton that protects the head and thorax – of over 12.7 centimetres long must be returned to the ocean. Lobsters this size often weigh around 1.3–1.8 kilogrammes (3-4 lbs).

From the thousands of eggs female lobsters can produce, only a small number will make it to adulthood, and far...