Crustacean Conundrum: A Lobster’s Accurate Age
By Paul Erickson, COSMOS Science Contributor, with Chris Munkholm
American lobster on the Rockport Breakwater
One evening, years ago, when I lived beside Cape Ann’s Folly Cove, a 14-pound lobster arrived at our back door. Hefting the bright-red, cooked crustacean, Eric, our neighbor and a lobster fisherman said, “Dinner, anyone?”
Later, as our friends and family dined on Eric’s big catch, someone asked, “So how old is a 14-pound lobster?”
Lobzilla
“I have no idea,” said Eric. The rest of us were just as clueless and most likely preoccupied by a more urgent concern: our supply of melted butter.
Lobzilla of Maine
Most lobsters that you see in a grocery store or at a restaurant are roughly 5-7 years old and weigh about 1-2 pounds. Unlike we humans, lobsters grow throughout their entire lifespan, and the bigger the lobster the older the specimen.
While the 14-pound lobster of Folly Cove was large, I once knew an arthropod who weighed around 35 pounds and sported a lifetime of battle scars etched into its colossal claws. He or she—we never determined its gender—lived in a cave in a century-old granite wharf on the coast of Maine.
Back in the 1970s and 80s, my dive buddies and I often encountered Lobzilla during our Downeast scuba adventures. We were pretty sure that our old friend’s massive claws could easily break our arms. But out of respect for this local, increasingly famous, king (or queen) of beasts, we never ventured close enough to risk any appendages.
How old was Lobzilla? Again, I hadn’t a clue. Although I assumed that a lobster in the 30-40 pound weight class was probably more than 50 years old.
A Lobster’s Age Matters to the Industry
Half-and-half lobster—a rare genetic variation
So, who cares how old a lobster is? For one thing, fisheries management experts care. Knowing the ages of lobsters helps them assess the long-term population trends of our local American lobster Homarus americanus. That’s important to an industry worth more than $90 million, per year, to Cape Ann’s home state of Massachusetts, alone.
But size is not always an accurate measure of a lobster’s age. Varying diets and sea temperatures are factors that add uncertainty to a size/age curve on a scientific growth chart.
Then, a breakthrough occurred about ten years ago when scientists at Canada’s University of New Brunswick discovered how to estimate a lobster’s age by counting growth rings in its eyestalks, which connect its beadlike eyeballs to the body.1
But is there a way to calculate a lobster’s age without removing and dissecting one of its eyestalks?
DNA as an Age Marker
Scientists at the University of East Anglia, in Norwich, England have been probing changes in lobster DNA as a function of aging.2
To refresh your high school biology, a DNA (deoxyribonucleic acid) molecule primarily exists as a twisted ladder (double helix), held together by ladder rungs formed by the precise coupling of 4 nitrogen bases: adenine and thymine pairs (A-T) and guanine and cytosine pairs (G-C). The interplay of these base pairs with RNA then codes for the proteins forming all of our tissues, functions, and structures. A change in any one of these four nitrogen bases can have a profound effect.
That’s about as complicated as we’ll get here.
In their aging breakthrough, the University of East Anglia scientists observed changes in the European lobster’s cytosine. With age, methyl groups increasingly attached to cytosine, forming methylcytosine. A lobster’s advancing age showed excellent correlation with increased methylcytosine in its DNA structure.
The scientists then developed a technique for measuring the percentage of DNA in a fragment of a live lobster’s antennae. Without sacrificing the animal, they could determine the age of a lobster, almost to the month, up to about 4.5 years. More work is needed to extend the study beyond these first years, as well as to test their technique on the closely related American lobster, Homarus americanus.
Tracking Human Methylcytosine
But the outlook for measuring the age of Lobzilla-type oldsters is favorable. Other species, including Homo sapiens, have demonstrated correlation of DNA alterations with aging. In fact, DNA methylation biomarkers can determine biological age of any tissue throughout the entire human lifespan. Even more exciting is the use of DNA methylation-based clocks as predictors of age-related diseases and life expectancy.3
More Cool Stuff
Deconstructing the lobster genome was once considered unsolvable because of the molecule’s extreme length, with many long repetitive sections of base pairs. After nearly six years of intense work, Gloucester Marine Genomics Institute (GMGI), with scientists from several other institutes, finally unraveled the complete genome of the American lobster.*
The lobsters used for the GMGI genome study were acquired by fishing professionals at the Steve Connolly Seafood Company, who certified the three historic specimens as truly Gloucester lobsters. Connolly’s also packed them in dry ice for their trip to California, where the sequencing scientists were awaiting their arrival.
Each human DNA molecule is almost six feet long, with one double helix molecule in each of a human’s 37.2 trillion cells. For the total combined length of DNA in one Homo sapiens, do the math.
*The American lobster genome reveals insights on longevity, neural, and immune adaptations. Science Advances, Volume 7, Issue 26. June 23, 2021.
Researchers are now exploring factors that decrease methylation and can possibly reverse disease. At Harvard University, David Sinclair’s lab recently reported on a very exciting mouse study relative to vision deterioration. The lab researchers used genes to restore youthful DNA methylation in retinal ganglion cells and observed a reversal of vision loss in glaucoma-modeled mice.4 The Sinclair lab is in the forefront of this important new science.
Lobsters in Labs – A Delicacy or Not?
Okay, all of that is cool if you’re interested in lobster’s ages. Yet a burning question remains: Do lobster scientists ever consume their research subjects?
Having worked at a public aquarium for many years, the aquarists I have known would never consider dining on their charges. Curators easily grow emotionally attached to their lobsters. For example, one of my coworkers suffered considerable pain and injury when his arm accidentally drifted into a massive claw of a 35-pounder on exhibit. He blamed himself for the mishap, not the lobster, “who was just reaching for some food.”
As one lobster aquarist once told me, “They’re not pets, but they are my friends.”
References
1. Direct determination of age in shrimps, crabs, and lobsters. Canadian Journal of Fisheries and Aquatic Sciences, Volume 69, Number 11, November 2012.
2. Ageing European lobsters (Homarus gammarus) using DNA methylation of evolutionarily conserved ribosomal DNA. Evolutionary Applications, Volume 14, Issue 9, 2305-2318, August 30, 2021.
3. DNA methylation biomarkers in aging and age-related diseases. Frontiers Genetics, Volume 10, March 2020.
4. Reprogramming to recover youthful epigenetic information and restore vision. Nature, Volume 588, pages 124-129, December 02, 2020.
