On Bat Exceptionalism

Comparative biology is a field gathering momentum these days. The tools of biotechnology have advanced to the point at which it is worth asking exactly how it is that some species are longer-lived, or more resistant to cancer, or capable of regenerating organ damage and lost limbs. It is especially useful to find similar species in which one is very different from the other in one of these aspects, as that gives a better chance of pinning down the important mechanisms. The end goal is better medicine: is there any possibility of deriving the basis for enhancements or therapies for humans from the longevity of whales, or the cancer immunity of naked mole-rats, or the regenerative prowess of salamanders? The answer will probably vary on a case by case basis: it is not unreasonable to expect that some aspects of biology in another species will be very hard to recreate in humans. The only way to find out is to make further progress in research.

Bats are on the list of exceptional species for many of the same reasons as those mentioned above, though not yet as well studied as naked mole-rats or salamanders. The evolution of flight has necessitated a set of unusual metabolic adaptations for a mammal, and as a result there are bats that are certainly unusually long-lived for their size, possibly cancer resistant, and so forth. This is an opportunity for researchers to learn more about how the operation of metabolism determines these outcomes:

The bat immune system is astonishingly tolerant of most pathogens. Evidence is mounting that bats can serve as reservoirs of many of the world's deadliest viruses, yet bats appear largely immune to the many viruses they carry and rarely show signs of the diseases that will rapidly overwhelm any human, monkey, horse, pig or other mammalian host the microbes manage to infiltrate. Scientists have also learned that bats live a seriously long time for creatures of their small size. The insectivorous Brandt's bat of Eurasia, for example, weighs an average of just six grams, compared with 20 grams for a mouse. But while a mouse is lucky to live for a year, the Brandt's bat can survive well into its 40s. Bats may be girded against cancer, too. "At this stage, the evidence is anecdotal. But of all the bat biologists I've spoken with, I've only heard of one or two cases of bat tumors."

Researchers found an "unexpected concentration" of genes involved in repairing damaged DNA. Those fix-it factors, the scientists proposed, are the bat's solution to the blistering demands of flight. When a bat flies, its heart beats an impressive 1,000 times a minute, and its metabolism ramps up 15-fold over resting rate. By contrast the metabolism of a running rodent is seven times normal, "and that's only for a short burst, whereas a bat can fly at 15-fold metabolic rate for hours." All that fiery flapping ends up generating a huge number of metabolic byproducts called free radicals, which could mutilate the bat's DNA were it not for its extra-strength molecular repair crew. And countering DNA damage happens to be a great strategy for overall health, which could explain bats' exceptional longevity and apparent resistance to cancer. Researchers suggest that changes to the bat's immune system originated as part of the heightened demand for DNA repair, and later proved valuable for its general life strategy.

Link: http://www.nytimes.com/2015/01/13/science/no-time-for-bats-to-rest-easy.html


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