That is, under conditions of low extrinsic mortality (no predators, no seasonal drying-up), Daphnia were able to evolve the capacity to octuple their lifespan.
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In fact, there are *two* lineages in Lake Czarny: a short-lived, exclusively asexual strain (asexual reproduction accumulates more deleterious mutations than sexual reproduction; it seems to be another r-selected adaptation) and the long-lived sexually-reproducing strain.
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The long-lived Daphnia are larger, and have more fat reserves to help them survive the winter. They are orange, possibly due to beta-carotene. And they stay in deeper, colder water, lowering their metabolic rates, which makes them live longer.
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Small aquatic animals are governed by the Arrhenius equation: if you cool them down, *all* their chemical reactions go slower, including the ones that make their bodies break down with age. This obviously doesn't apply directly to warm-blooded mammals like us.
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The connection between metabolic rate and lifespan does extend to mammals though. Smaller, short-lived, more r-selected mammals (like mice) have higher metabolic rates than long-lived K-selected mammals.
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Vertebrates with exceptional longevity (tortoises and sharks can live centuries) are all cold-blooded; the naked mole rat (a mammal that appears not to senesce with age) is a rare example of a cold-blooded mammal; and mammals that hibernate age slower than mammals that don't.
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Also, inducing hypothyroidism in rats (which lowers their metabolic rate) makes them live 30% longer. http://sci-hub.tw/https://doi.org/10.1016/0047-6374(86)90052-7 …
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Genetic differences between short- and long-lived strains of similar species could point the way towards mechanisms to delay aging in humans. I don't expect simply lowering metabolism to be a good trade-off, but there may be other resilience mechanisms that we could "borrow."
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The "bad" news is that humans are already pretty K-selected; we may already have most of the long-life adaptations we see in other animals. (Though it's worth doing a lot more comparative genomics to find out!)
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Replying to @s_r_constantin
"Lower metabolic rate" seems like a plausible explanation for why extreme caloric restriction seems to increase lifespan.
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