At One Extreme of the Aging PhenomenaScientists have identified the pygmy goby as the shortest lived vertebrate animal, with a livespan of just 59 days. That creature, and another fish that was the previous record-holder for shortgevity, Nothobranchius furzeri, may shed light on why we age as we do. Taking the Nothobranchius furzeri first, which lives a whopping 75 days, there is a clear environmental reason why the fish should evolve to fill such a short timespan -- the climate they live in dries out the ephemeral ponds where they reside. The fish lay eggs in the mud that do not hatch until the rains come -- then they live out their brief lifespan growing, mating and repeating the cycle. This short life cycle has been so encoded into their genes that even when raised in the laboratory, they complete their life cycle in two and a half months then die of senescence. The pygmy goby, on the other hand, never gets old. It lives in the hectic environment of a coral reef. The female lays three batches of more than 100 eggs each, which the male fans to provide them extra oxygen. When the baby fish hatch they spend three weeks - almost half their entire life -- in the open ocean. Then they find a coral reef and settle down to mate. Perhaps they slow down a little and fall prey to one of the numerous predators of the reef. "For example, they are still reproductively capable and active at 59 days. In the absence of predation they would age like any vertebrate animal, although science still doesn't yet fully know why vertebrates (including humans) actually age, despite there being many tractable and realistic theories from spontaneous mutations in cells, damage from free radicals, weakened defense systems, to simple wear and tear." No doubt if they can be successfully raised in a lab setting they would live longer than 59 days -- but as the preceding example shows, probably not much longer. Nature conserves resources. Why design a fish to live for years if it only survives a couple months in its natural habitat? We too are victims of our past. Adaptations to those primitive lifestyles are the ones encoded in our genes. Through technological and medical advances we have had great success at increasing the percentage of people who reach old age -- thus the 'average' lifespan has increased. But the maximum age has changed little or not at all (past records are too unreliable to accurately identify the oldest individuals from past centuries). We are just reaching the point in technological advancements where we may beging to see that maximum lifespan increase, and just perhaps, what we learn from studying these little fishes may contribute to that advance. |
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