Durham, NC Physically fit frogs have faster-changing genomes, says a new study of poison frogs from Central and South America.
Stretches of DNA accumulate changes over time, but the rate at which those changes build up varies considerably between species, said author Juan C. Santos of the National Evolutionary Synthesis Center in Durham, North Carolina.
In the past, biologists trying to explain why some species have faster-changing genomes than others have focused on features such as body size, generation time, fecundity and lifespan. According to one theory, first proposed in the 1990s, species with higher resting metabolic rates are likely to accumulate DNA changes at a faster rate, especially among cold-blooded animals such as frogs, snakes, lizards and fishes. But subsequent studies failed to find support for the idea.
The problem with previous tests is that they based their measurements of metabolism on animals at rest, rather than during normal physical activity, Santos said.
"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. The energetic cost of these activities is far beyond the minimum amount of energy an animal needs to function."
To test the idea, Santos scoured forests in Colombia, Ecuador, Venezuela, and Panama in search of poison frogs, subjecting nearly 500 frogs representing more than 50 species to a frog fitness test.
He had the frogs run in a rotating plastic tube resembling a hamster wheel, and measured their oxygen uptake after four minutes of exercise.
The friskiest frogs had aerobic capacities that were five times higher than the most sluggish species, and were able to run longer before they got tired.
"Physically fit species are more efficient at extracting oxygen from each breath and delivering it to working muscles," Santos said.
To estimate the rate at wh
|Contact: Robin Ann Smith|
National Evolutionary Synthesis Center (NESCent)