Is it impossible to tell a lobster's age?

Question

^Source

Stephen Fry said in the QI episode "I-Spy":

"You can't tell the age of a lobster "

(watch video)

From the American Lobster FAQ:

There is no foolproof way to determine a lobster’s age.
One can only make an educated guess by looking at the lobster’s size.

From Visit Maine:

No one has yet found a way to determine the exact age of a lobster because it sheds its shell so often.

A lobster's age is approximately his weight [in pounds ] multiplied by 4, plus 3 years.

(add to that, Lobsters might be able to live forever, as mentioned by Sandi Toksvig in the QI episode)

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My Question:

• Is body size/weight the only biological indicator we can use to make an "educated guess " about a lobster's age?

Answer 1

In many species, small granules of waste material - called "lipofuscin" - build up in the body over time. As it turns out, this can be used to measure the metabolic age of lobsters, and to give a good estimate of their chronological age.

Wahle, Tully & O'Donovan (1996) found a strong correlation between lipofuscin area (corrected for carapace size) and lobster age in American lobsters (Homarus americanus). Metabolic age is not a precise measure of chronological age - it is affected by several other factors, including temperature, and this study controlled temperature, so they caution about using it to measure age in natural populations.

Sheehy et. al. (1996) released 3-month old European lobsters (Homarus gammarus) (after tagging them) into the wild and then recaptured them 5.4-9.6 years later. Extrapolating from their results led them to suggest that lipofuscin concentration could age 43% of lobsters to within 1yr and 95% to within 3.5yrs - not brilliant but better than carapace length, which other studies have found only age 3% to within 1yr and 95% to within 82(!) years (what was that about lobster immortality, again?).

Maxwell et. al. (2007) conclude:

We show that neurolipofuscin concentration, measured histologically in the central nervous system of laboratory-reared Caribbean spiny lobsters, Panulirus argus, is correlated with the chronological age of both males and females. These results suggest that the neurolipofuscin technique holds great promise for use in estimating age of wild-caught spiny lobsters.

Sheehy et. al. (2011) described lipofuscin accumulation as "remarkably constant" at 0.31% (by volume) per year in wild western rock lobsters (Panulirus cygnus).

Of course, using a fluorescence microscope to measure the concentration of micrometre-sized granules in a lobster's eyestalk is a bit of effort to go to to find out how long it took your dinner to grow.

Answer 2

For any creature, there is only one way to know how old it is: record its time of birth.

However, there are plenty of proxy measurements that are strongly correlated to age - the wear of the teeth of a horse, whether an insect is still a larvae, etc. They may not give perfect values, but provide a reasonable estimate.

For many animals, size is a reasonable proxy for age (e.g. corn snake length). In such cases, maybe further research could develop other techniques - blood chemistry, bone density, etc., but why bother searching hard for it when you already have a reasonable technique?

So, why should we find it odd that - given you can get a reasonable age estimate for a lobster age by size - no-one has developed another technique?

Is it the only technique? Marine biologist and lobster expert Jell Atema is quoted as confirming this:

KRULWICH: [...] with lobsters, the bigger you are, the older you are. That's how you age a lobster, by size.

Prof. ATEMA: That's right. Yeah.

[...]

Prof. ATEMA: There's absolutely no indication that this lobster is showing signs of old age.

KRULWICH: In fact, lobsters in general show no discernable signs of aging. They don't lose appetite, sex drive, energy, no change in metabolism.

Prof. ATEMA: Something we could all be jealous of.

Source: NPR

Having seen Jivlain's answer, posted while I wrote this, I am not so sure Atem is correct here.