Contributing Monkie Sarah Backhouse
Published on July 18, 2008
Evolution is a fascinating thing. It’s amazing to think that animals can physically breed out organs their bodies deem unnecessary, while some “scarred for life” humans can’t even seem to shake traumatic events from their lives. Granted, the evolution of animals happens over a much longer period of time, but it’s still an amazing concept. And it makes you wonder if there’s something we could learn from the smaller creatures that share our planet.
Clearly, we couldn’t survive without lungs. But a frog called the Barbourula kalimantanensis that can was recently found in a cold-water stream on the island of Borneo in Indonesia. According to David Bickford, a biologist at the National University of Singapore, the lunglessness was discovered accidentally in a routine dissection.
Tetrapods (or four-limbed creatures) that don’t have lungs is a rare occurrence in nature. Until now, salamanders and caecilians (an earthworm-like creature) were the only two creatures thought to lack them. Amphibians may have developed their ability to respire through their skin as a response to a life lived between water and land. Researchers point out several factors that might explain why this particular frog evolved into a lung-free species: a higher oxygen content in cold water; the frog’s low metabolic rate which requires less oxygen; the increased surface area caused by flatness of the frog; and the interesting fact that, according to Bickford, “having lungs makes you more likely to be swept away in a fast-flowing stream — because you would float.”
David Wake, a biologist and expert in amphibian evolution at the University of California, Berkeley, isn’t surprised by the discovery of the lungless frog, as most tailed frog varieties have reduced lung capacity. In the case of amphibians, respiration usually takes place through the skin rather than the sac-like lungs. However, he noted that most species “have mating calls that require lungs.” Interesting.
Further studies into the frog may be restricted by “the species’ rarity and endangered habitat,” says Bickford. The lungless frog’s habitat is being contaminated by illegal gold mining, which clouds the water with sediment and pollutes it with mercury. What’s more, the area is also under threat by logging, which creates runoff into the streams.
The Barbourula kalimantanensis may not have lungs, but unless we protect its environment, it won’t be breathing easy through any organ.
(via National Geographic) Photo by David Bickford, National University of Singapore