Decline is an accepted part of old age for most people, even for those still searching for the fountain of youth. We expect the same in our pets and in the flies that buzz around us, albeit at a different rate. So why are lobsters different? A study conducted in 1998 showed that lobsters maintain telomerase activation late in life. But before we explain that, let's talk briefly about cell division.
Telomeres are like caps or sheathes that encase the ends of chromosomes. When cells divide, telomeres get shorter. When telomeres get to a certain length, they can no longer protect chromosomes and the chromosomes start to suffer damage. The number of cell divisions before damage sets in is called the Hayflick limit.
Telomerase is an enzyme that adds length to telomeres, extending their life span. In humans, telomerase is abundant in embryonic stem cells and then declines later in life. This is actually a good thing because when cells re-activate telomerase after reaching the Hayflick limit, they become cancerous (in other words, they don't die when they're supposed to). The downside is that cells with short telomeres weaken and die, so we eventually die, too.
In humans, telomerase levels decline later in life and are only found in some types of tissue, but in lobsters, telomerase is found in all types of tissue. That likely accounts for lobsters' ability to grow throughout their lives. And because lobsters' skeletons are on the outside and the molting process allows them to periodically shed their exoskeletons in favor of a new, larger one, their constant growth isn't a problem. With a steady, evenly distributed supply of telomerase, lobsters don't approach the Hayflick limit, which means that their cells stay pristine, young and dividing.
The dual role of telomerase in keeping cells healthy and in cancer growth means that it's an important area of research for both anti-aging and cancer treatments. Further study of lobsters may teach us more about their longevity, how long they can actually live and what that knowledge may mean for human health.
Scientists are also studying a variety of other animals that are long-lived. Like lobsters, many types of turtles don't show compromised immunity or physical breakdown because of age. They also become more fertile with age and usually die because of a predator or malady unrelated to age.
A bird known as Leach's storm petrel fits into a human hand yet lives more than 30 years. They're also the only known animal in which telomeres grow longer with age. Related animal species with vastly different life spans are also a point of interest. Conventional mice live only three years, but naked mole rats can live for 28.
Other animals being studied include whales, bats, rockfish, zebrafish and clams, the oldest of which, a quahog clam, lived to be 220 years old. In many of these animals, the rate of telomere deterioration corresponds with their lifespan. The longer the telomeres last, the longer the animals live. Studying these creatures may tell us much about human aging and lead to treatments for aging-related diseases. Exciting research is being conducted on many fronts -- on the molecular and genetic levels and regarding lifestyle, diet and habitat. If one day humans discover an important new treatment for cancer, it may be due to one of these creatures -- or to a 200-pound lobster living peacefully in a tank at Boston University.
For more information about lobsters and aging, and to hear a song about Leroy, the Uninterrupted Lobster, please check out the links on the next page.