Dendrobates leucomelas, a poisonous frog from Venezuelan Guiana. Photo courtesy of Cesar Barrio-Amoros (www.andigena.org)
Frog fitness tests reveals whose genomes change faster.
A new study of poison frogs from Central and South America has found that fitter frogs have faster changing genomes. The study published in Molecular Biology and Evolution could help explain the varying rates of genome changes between.
Previous studies have tried to explain these different rates through body size, generation time, fecundity and lifespan. However, these tests based their measurements of metabolism on animals at rest, rather than during normal physical activity, according to lead author Juan C. Santos from the National Evolutionary Synthesis Center in the US.
“Animals rarely just sit there,” Santos said. “If you go to the wild, you’ll see animals hunting, reproducing, and running to avoid being eaten.”
To test his theory, Santos and his colleagues collected 500 poison frogs from Panama, Ecuador, Colombia and Venezuela, and gave them a fitness test. The subjects ran in a rotating plastic tube, which resembled an exercise wheel used by mice, and their oxygen uptake was measured after four minutes.
The fitter frogs could run longer before they got tired and had aerobic capacities five times higher than the most sluggish species. “Physically fit species are more efficient at extracting oxygen from each breath and delivering it to working muscles,” Santos said.
He then used DNA sequences from fifteen frog genes reconstruct the poison frog family tree and estimate the rate at which each species’ genome changed. A clear pattern emerged as he tested the changes- fitter frogs tended to have faster changing genomes.
Santos also tested other factors, such as body size, but fitness was the only one that correlated with genomic changes. However, the reason behind these changes is still a mystery.
One theory is that harmful free radicals, which are produced as a by-product of exercise, could cause wear and tear on DNA. This could eventually lead to genetic changes that can be passed on to the next generation, if the DNA of egg or sperm cells are affected.
But don’t change your exercise routine just yet, as the results don’t debunk the benefits of regular physical exercise. “What applies to cold-blooded animals such as poison frogs doesn’t necessarily apply to warm-blooded animals such as humans,” Santos said.
Source: Eureka Alert
