I tend to agree that bats are
aging models that are overlooked, and I’ve been saying this for 20 years now.
And so have others, but somewhat indiscriminately on the basis of hibernating
bats banded in (say) Siberia.
I also tend to agree with Greg that
looking at bats that undergo daily torpor and longer hibernation (basically
extended torpor) are less interesting from the aging point of view, as a large
part of their longevity is explained by the 1928 Pearl “rate of living theory.”
It’s not terribly interesting to humans unless they want to be astronauts, at
the same time as being unwilling to give up large fractions of
lifetime needed to travel long distances. And (of course) people who want
to see the future by effectively traveling in time past their allotted maximal
life span. But the ultimate goal of gerontology is have your cake and eat it,
too– you want to live longer than present human maximal life span AND be
healthy and awake for it.
I might add the basic fact that 30% of
bat species are vegetarian and live only on fruit and nectar.
A few drink blood. The other 70% are insectivores, and it’s only
in this class that temperature regulation goes by different rules, and resting
metabolic rates are lower than predicted by the Kleiber 3/4 exponent law for
body weight. Insects in the temperate zones of the world are very seasonal
and nocturnal, and thus are a variable food source, so temperate zone
insectivores (the two discussed in the lecture below, for example) NEED to
undergo diel torpor (“diapause”) and hibernation.
By contrast, in the tropics where all
the frugivores live, there is fruit available all year and at anytime of the day
(though frugivores may need to migrate to get it), so I am unaware of any
frugivore bat that undergoes torpor or hibernation in the wild (at least
three species do so in the lab when forced by lack or
food). Frugivores and nectarivores regulate their body temperatures (36-40
C) more closely, and have a higher BMR which is more or less predicted
by the Kleiber’s 3/4 power law, unlike the insectivores, which tend to fall
below the Kleiber prediction. So frugivore bats are like humans. (Frugivores
also keep blood sugar in the human diabetic range without suffering any diabetic
consequences, which is interesting.)
Frugivore bats also live a long time