I should point out that the idea that metabolic rate negatively
correlates with longevity has now been disproved.Â It’s not only
that bats and birds are an exception to the idea that high metabolic
rate is associated with short lifespan.Â There is no correlation at
all between metabolic rate and longevity in mammals or birds.Â we
have shown this, and so have others (Speakman, Austad, etc.):http://ift.tt/1D1DIlG
to repeat, Kleiber’s rule is wrong.
There is a small negative correlation between temperature and
longevity, however.Â Could this be a contributing factor to the long
lifespan of the naked mole rat and, to a smaller degree, of the
bowhead whale?Â yes, absolutely, but if you extrapolate from known
modulations of longevity by temperature in model systems it is a
relatively small contribution.Â so the longevity of the naked mole
rat is still very interesting when compared to other rodents (but
maybe not as exceptional when compared to humans) and their cancer
resistance is fascinating.Â As for the bowhead whale, as the longest
lived mammal, these animals must cope with a higher degree of damage
and insults over a longer period of time than any other mammalian
species, and I have no doubt that unraveling the mechanisms
responsible will be of great value to understand aging, longevity
and age-related diseases. this was why we went out to sequence the
genomes of the naked mole rat and bowhead whale:http://ift.tt/1D1DJG5
Lastly, my view is that species evolved different ‘tricks’ to have a
longer lifespan, and by discovering the ‘tricks’ used by the
bowhead, naked mole rats, bats, etc. we may be able to apply those
findings to humans in order to fight age-related diseases.Â so
really what we need is to study multiple long-lived lineages.
On 01/02/2015 03:16, sbharris1 wrote:
Greg, et al.
Bowheads don’t excite me for the same reason
that naked mole rats don’t. Large animals have slow metabolic
rates. Bowheads have only 1/3rd the metabolic rate you’d
expect for an animal of their size, possibly because they keep
their heat losses so low from all that blubber.
Bowheads are the second largest whale (only
blue whales are larger) and can get up to 50 to 100 tons. So
let’s say they weigh 1000 times what a human does. We’d expect
them to have a specific metabolic rate 1000^-(.25) = .178 that
of a human. If it’s really only 1/3 of what you’d expect from
the Kleiber equation that’s only 0.044 that of a human– down
in the reptilian range. Multiply that by 200 years and you get
only 9 years. Over a 200 year old lifespanÂ a kg of bowhead
muscle burns only 10% of whatÂ kg of human muscle does.
Even using Kleiber, the bowhead MLS comes out
only 36 years. These are just really gigantic cows, like
elephants but bigger and longer lasting. The excitement of
scientists at their long life really mystifies me. Nobody gets
that excited over 200 year old tortoises, but the whales are
just as slow-motion when it comes to making calories.
I can’t grow to a size of 100 tons, or put on
that much blubber (though I admit I do find it chasing me).
The bowhead is not likely to have anything really interesting
in its slow cells. And if they can’t find any cancer in
bowheads, it’s because the ones they’ve seen are only 9 to 36
years old in human terms.
Sorry, it’s still the 100 year-old macawsÂ that
interestÂ me. Their cells have some trick that you’re
notÂ likely to find in a whale, a mole rat,Â or even a bat. I
hope the simple math I’ve given has shown this.