Airdate: Nov 07, 2006
Scientist: Valerie C. Clark
Poison Frogs - Toxic Lunch
Where does the poison in toxic frogs come from?
ambience: Madagascar forest
We've all heard of poison frogs those colorful rainforest dwellers whose skin secretes toxins, making them unpalatable to predators. The question is, where do the frogs get their poison from? I'm Jim Metzner, and this is the Pulse of the Planet. Valerie Clark is a chemistry graduate student at Cornell University. She thinks the answer might lie with the frog's diet. In particular, ants.
"70% of the frog's diet consists of ants, which is important because a lot of ants have alkaloids. There are over 800 different alkaloids, or nitrogen containing compounds, that are known from poison frogs around the world and they all vary greatly in toxicity. So, any single frog that I would find at any one of my study sites could have from 10 to 30 different alkaloid chemicals in their skin. So basically, the frogs are going to be acquiring more and more different alkaloids as they age because they just keep eating more and more insects. Some of which contain alkaloids and some of which don't. And whether or not they are selective for things that are bitter tasting, that would have alkaloids, or not, is not quite clear yet. In two very similar ecosystems, one that I studied in Madagascar, and one in Panama - both first had to have a lot of ants present with toxins. So that the frogs could start eating them, slowly gaining resistance to them, and probably in the same step that they are gaining resistance to them, they're also developing their alkaloid uptake system to localize them into skin glands. Rather than pass the toxins through, like we do when we take drugs, we metabolize them and excrete them through our urine, but instead of doing that, they have some sort of system to actually take them up into their skin, and use them for their own defense."
We'll here more about poison frogs and the role they play in medicine in future programs. Please visit our website at pulseplanet.com. Pulse of the Planet is made possible by the National Science Foundation. I'm Jim Metzner.