Did learning to fly give bats super-immunity?

http://www.newscientist.com/article/dn23020-did-learning-to-fly-give-bats-superimmunity.html

by betadreamer • 14 years ago

62 16 14 years ago

csense3• 14 years ago

I assumed from the headline that this would be a stupid article, but I took the time to read it anyway and found that this assumption was wrong.

The premise sounds quite solid: The unique challenges of being a flying mammal require spending lots of energy. Which leads to lots of free radicals. Which leads to lots of DNA damage. Which increases selective pressure for DNA repair.

Evolution normally doesn't select for organisms that are able to survive aging, because, from the standpoint of natural selection, once your reproductive years are past, your survival doesn't matter.

That aging resistance would be an incidental benefit of general DNA repair mechanisms that evolved in response to a lifestyle that encourages free radical formation makes a lot of sense. The specific molecules and reactions involved in bats probably will provide important clues to the aging process in mammals, even if the adaptations in bats can't be translated directly into treatments for humans.

How immunity and disease fits into this picture is less clear from the article. But the aging angle alone is enough to make this research very interesting.

thaumasiotes2• 14 years ago

> Evolution normally doesn't select for organisms that are able to survive aging, because, from the standpoint of natural selection, once your reproductive years are past, your survival doesn't matter.

The logic is actually a bit deeper than this. There's no reason you couldn't have an organism that "survived aging", and that could reproduce indefinitely. Obviously, given a potentially unlimited reproductive span, selection would come in on the side of longer lifetimes.

As I've seen it presented, the logic of organism deterioration with age is that accidents happen, which means that, if you happen to have a life strategy which makes you momentarily better off, but permanently worse off, you may die of unrelated causes before suffering a net loss. As long as that can happen, we should observe aging: young organisms boosting their performance at the expense of their own future selves.

(as an example: imagine you impress a girl by doing some death-defying stunt, and suffer more physical strain than your body is really designed for. If you were going to live forever, that might be a bad idea. If you're not, then maybe impressing the girl is worth the lower physical fitness you have afterwards.)

csense3• 14 years ago

> if you happen to have a life strategy which makes you momentarily better off, but permanently worse off, you may die of unrelated causes before suffering a net loss

This is true, but irrelevant to the present discussion. If you can live and reproduce forever -- or for a very long time -- then the -EV of "permanently worse off" exceeds the +EV of "temporarily better off."

My understanding of why we didn't evolve to have better gene repair and longer lives is that the ideal death and mutation rates in terms of species survival is some finite number greater than zero. Near-immortality, eternal youth and perfect genome repair would be great from an individual perspective, but from a species perspective, those things reduce the ability for genetic innovation. Too many mutations are bad, but not enough mutations are also bad.

I would guess that the bats get around this by getting so much extra EV from occupying the unique ecological niche of "flying mammal" that the ability to occupy that niche overwhelms the negative aspects of a smaller mutation rate.

sukuriant• 14 years ago

Why are bats the litmus test for rabies, then? That just seems a bit odd. And why is rabies so prevalent/dangerous in bats that even breathing the air in bat caves can get you the disease?

blhack• 14 years ago

>breathing the air in bat caves can get you the disease?

For reference, there are two possible cases of this.

Two.

This is not a common thing.

NickNameNick• 14 years ago

The article doesn't say the bats dont get infected, it says infection has very little affect on the bats health.

huggah• 14 years ago

Dangerous for humans, you mean. The fact that a species can survive while being so disease-ridden that they routinely kill the animals they infect seems to lend credence to the "super-immunity" claim.

I'm not sure this is actually the case for bats, but assuming your statement is true, it seems to be evidence for the presence of super-immunity, rather than against.

executive• 14 years ago

Dangerous for some humans, you mean. Clearly not dangerous for Mr. Wayne.

wisty• 14 years ago

Bats live in massive colonies, so diseases can spread like wildfire. That's probably why their immune systems are good, too.

hughlomas• 14 years ago

Consider it from the disease's perspective.

Ebola doesn't 'target' humans. Ebola's obvious symptoms and mortality rate in humans limit its ability to spread efficiently. The flu virus or cold virus has been far more successful in penetrating the human ecosystem. Perhaps Ebola has been selected for being stable in the bat ecosystem. The mobility of bats also makes them an excellent transmission vector, which a virus would ideally want to be non-symptomatic.

gus_massa• 14 years ago

Very strange, I'd like to see more evidence.

Is there some analogous adaptation for birds? Flying / non-flying birds?

abecedarius• 14 years ago

Birds are also long-lived, compared to mammals of similar size. One of Nick Lane's books discussed this and something about their adaptations against damage from respiration -- either Oxygen or Power, Sex, Suicide, I forget which.

lostlogin• 14 years ago

Given the massive die offs from the fungal infection that is completely devastating US bat populations, I'd say their immune systems may be unique, but they aren't miraculous. The outlook for North American bats is very grim. http://en.m.wikipedia.org/wiki/White_nose_syndrome

Did learning to fly give bats super-immunity?

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