Science Questions

How is it possible for a Bornean flat-headed frog to have no lungs and breathe through its skin? Jason Flakes, Virginia

David Bickford, Associate Professor at National University of Singapore.

The ecology of the animal, where it lives are extremely fast flowing streams that are clear and cold. They’re coming right down off of the largest mountain in Kalimantan, where the colder water holds more oxygen than the warmer water. When it’s travelling very fast the frog is able to basically run into more molecules of oxygen as it’s carried in the water. Also most amphibians are able to do most of their gas exchange through their skin anyhow. The lungs in amphibia are fairly primitive and they mostly just get a little bit of oxygen through their lungs. They get rid of most of the carbon dioxide through their skin anyhow. What is probably the real kicker, the real reason these guys don’t have lungs is that same very fast-flowing water could be detrimental  to you if you got swept away. A good way to get swept away is to be buoyant or to float in the water. Having lungs makes you a lot more buoyant. It’s kind of in the context of very fast-flowing streams that these frogs need to so everything that they do. It’s easy to imagine that being a very strong selective force.

July 2008