Early life growth rate determines lifespan
Early life growth rates significantly shorten or prolong the lifespan of fish used in an experiment researchers from the University of Glasgow. They found that manipulating growth rates of stickleback fish bodies can extend their lifespan by nearly a third or reduce it by 15 percent.
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The team from the University's Institute of Biodiversity, Animal Health and Comparative Medicine used increased and decreased temperatures as a way to alter the growth rate of 240 fish, which put groups of them behind or ahead their normal growth schedule. As soon as the environmental temperature was turned back to normal, the fish got back on track by accelerating or slowing their growth accordingly.
It turned out that the accelerated-growth fish had a lifespan that was 15% shorter than the normal lifespan of sticklebacks, which is around two years. On the other hand, the slow-growth fish lived more than 30 percent longer, and died only after a about 1000 days.
Professor Neil Metcalfe, who worked on the study, said: "The results of the study are striking. It appears that bodies which grow quickly accumulate greater tissue damage than those that grow more slowly and their lifespan is substantially reduced as a result. The study also demonstrates the surprising ways in which a slight change in environmental conditions in early life can have long-term consequences."
The effects were even stronger when the rate of growth was additionally increased by artificially manipulating the length of daylight the fish were exposed to, "tricking" their bodies into growing faster to reach their target size before the start of the breeding season. The causal relationship observed occurred despite all fish reaching the same adult size.
"These findings are likely to apply to many other species, including humans, since the manner in which organs and tissues grow and age is similar across very different kinds of animal. It has already been documented in humans, for example, that rapid growth in early childhood is associated with a greater risk of developing ailments later in life such as cardiovascular disease in middle or old age, possibly because of the way in which the tissues of a fast-grown heart are laid down."
Earlier attempts to test the now observed link between growth rates and lifespan by altering diet have been inconclusive, since the diet was a heavily influencing factor. This caveat was avoided in the current study by the approach to use temperature as the regulating instrument.
Study: Who-Seung Lee, Pat Monaghan and Neil B. Metcalfe, Experimental demonstration of the growth rate-lifespan trade-off, Proceedings of the Royal Society B, 2012, DOI: 10.1098/rspb.2012.2370 (open access)