Interestingly, we have two articles on the link between frogs and pollution, with seemingly contradictory results. First the BBC reports that the spate of deformed frogs with missing limbs, a phenomenon which had always been thought to result from man-made environmental pollution, is actually caused by predatory dragonfly nymphs that actually eat the limb-buds from tadpoles, before they develop proper limbs when they metamorphose into frogs.
And then we have this column from Nicholas Kristof, telling us that It’s Time to Learn From Frogs. And what should we learn exactly? That industrial chemicals used in agriculture or in daily household products such as hairspray act as a weak form of estrogen on the body, causing significant sexual organ deformities in embryos of various species. It is well known that frogs are particularly sensitive to environmental pollution, which is why the aforementioned missing limb phenomenon was long thought to have a chemical trigger, but the evidence is mounting that these sorts of environmental pollution are also causing a stark increase in cases of human sexual organ deformity, particularly among young boys.
I can easily imagine some reactionary “conservative” making a pseudo-scientific argument that because we recently disproved a link between industrial chemicals and missing frog legs, we might as well dismiss the second case out of hand. This would of course be a logical fallacy, as the mechanism is clear and the evidence is plentiful, not to mention relevant so far more animal species than frogs, but don’t be surprised if you see someone trying to make such a claim.
2 thoughts on “Legless frogs mystery solved”
And don’t forget about metabolic by-products of pharmaceuticals, which are usually excreted in urine. US stats seem to indicate leading contaminants are psychiatric drugs and human hormones such as estrogen, levonorgestrel, and testosterone. .
The study by Ballengee and Sessions puts forward an interesting potential explanation for some types of frog deformities. Unfortunately, their research fails to live up to the media hype; it does not solve the mystery of deformed frogs. In the laboratory, they found that some dragonfly larvae will remove limbs of tadpoles. However, Ballengee and Sessions did not actually test the predictions of the dragonfly hypothesis with rigorous data from the field. For example, a clear prediction of their hypothesis is that as the frequency of dragonfly larvae in wetlands increases, the frequency of missing-limb deformities in those wetlands is also expected to increase. Ballengee and Sessions did not test this prediction. Testing such predictions is a fundamental component of science. Until there are well-designed studies that examine the relationship between dragonfly density and frogs with missing limbs in nature, the relative importance of the role of predation in amphibian deformities will remain unknown.
Comments are closed.