Print This Page

May 30, 2013

United States

Virginia—Lobster Longevity

 

This exchange took place on Crust-L, a mailing for crustacean scientists, which is similar to the Shrimp List, but covers all crustaceans:

 

Hi there,

 

My name is Marina Koren and I write for Smithsonian magazine’s blog, Surprising Science.  I’m working on a story about lobsters’ incredible longevity.  A Smithsonian researcher pointed me to this listserv as a way to find good background information from experts.  I’ve included several questions below—if you’re interested, do respond!

 

1. Is it true lobsters get more fertile, stronger and bigger as they age, and if so, why is that?

2. Which species of lobsters exhibit this ability?

3. What contributes to lobsters’ longevity?  Is it something in their DNA?

4. How long could lobsters live if left undisturbed?

5. If lobsters don’t die from aging alone, what kills them (barring us eating them!)?

6. Is there an evolutionary purpose/benefit for them to live so long?

7. Do other marine species exhibit similar features?

 

Information: Marina Koren, Smithsonian Magazine (phone 1-202-633-5957, email korenm@si.edu).

 

 

Jeff Shields, Manager of Crust-L, Responded

 

Hi Marina,

 

I’ll take a shot at some of your questions.  My responses are mainly to get the ball rolling.  I’m sure others will have additional comments.

 

1. Is it true lobsters get more fertile, stronger and bigger as they age, and if so, why is that?

 

Female lobsters produce more eggs as they increase in size (as body volume) because fecundity is related to size in decapod crustaceans.  There are many examples of this in the literature.  I can provide a few references for lobsters if needed, but think of it as an increase in size corresponds to an increase in volume and that volume is increasingly taken up by ovaries.  There is a maximum size supported by the exoskeleton.  I don’t work in this area, but some one on Crust-L may have some insights into it.

 

2. Which species of lobsters exhibit this ability?

 

Virtually all female lobsters exhibit this relationship between fecundity and size.  While the same is generally true for males, it’s not nearly as impressive as occurs in females.  I exaggerate a little when I say that virtually the entire hemocoel [the body cavity in crustaceans through which the blood or hemolymph circulates] of females can be filled with ovaries.  The values for the relationship will change between species, but the relationship is pretty solid.

 

3. What contributes to lobsters’ longevity?  Is it something in their DNA?

 

Cell growth is mostly under hormonal control in crustaceans that exhibit indeterminate growth (continuous molting with no terminal molt).  With some exceptions, tissue growth increases during the molt cycle and less so at other times.  Sparks and Lightner speculated on why lobsters don’t obtain cancers in a 1973 paper.  Because cell growth is under hormonal control and because lobsters may only molt 25-30 times, their chromosomes don’t exhibit the signs of ageing seen in vertebrates, and cancers tend to increase with ageing for a number of reasons. I haven’t looked at much recent literature on this, but Vogt (2008 or 2009) discusses the cancer angle from the point of view of crayfish.

 

4. How long could lobsters live if left undisturbed?

 

We cannot accurately determine the age of lobsters like we can with fish because molting leaves few signs of ageing.  Most studies of ageing focus on metabolic or physiological age.  There is a recent paper indicating that lobster aging may be measurable via “ossicles” in the foregut, but more studies are needed to fully understand this as it may be measuring molting and not ageing.  For clawed lobsters there have been several estimates of maximum age, some up to 100 years, but 50-60 years may be more likely in large lobsters.

 

5. If lobsters don’t die from aging alone, what kills them (barring us eating them!)?

 

Lobsters are susceptible to disease, predation and senescence.  If the cuticle (or shell) is damaged and cannot be replaced by molting, then the animal can become susceptible to bacterial diseases or cannot molt properly as can happen in lobsters with epizootic shell disease. Moreover, if you think of each successful molt as requiring more and more energy, then older lobsters may need to store a great deal of energy (in terms of metabolic reserves) in order to molt successfully. Many probably don’t do this, hence they eventually die from senescence (old age) or an inability to molt successfully.

 

6. Is there an evolutionary purpose/benefit for them to live so long?

 

Cold-water species tend to live a long time in comparison to tropical and some temperate species.  It may simply be a function of cold-blooded metabolism at lower temperatures, but I’m probably not the one to address this question.

 

7. Do other marine species exhibit similar features?

 

Some temperate and boreal species of gastropods are thought to live 50-60 years.  I think the same is true for cold water bivalves.  I don’t know about fishes.

 

Source: Crust-L.  Subject: Questions for a Science Story for Smithsonian Magazine.  May 28 and 29, 2013.  Information: Crust-L is an email-based mailing list for crustacean scientists.   Subscribing to Crust-L is easy.   Send an email to sympa@vims.edu from the email address where you want to receive messages.  In the subject line of your message, type in “subscribe Crust-L YourFirstName YourLastName”.  Don’t enter anything into the body of the message.  If you have any questions or problems, Click Here.

 

Print This Page