The mystery of the deformed frogs is a news story that pops up every now and then on the evening news or PBS “" supposedly, we like to be reminded every few months about how each of us is personally responsible for slowly but surely ruining the entire planet. Up until this point, scientists had proposed that the chemicals we were leeching into the environment and therefore into the frogs’ watery homes was interfering with their development, causing frogs to be born without limbs, with extra limbs, or other abnormalities.
While in pictures these malformed frogs were obviously eye catching for the environmentalist crowd, it turns out there’s actually a much more benign and biological explanation beyond all the fear mongering. The missing limbs and the extra limbs actually have two completely separate causes. While some scientists are still firmly entrenched in the “chemical cause” camp, biologists Stanley Sessions and Brandon Ballengee observed tadpoles in the wild for a few years, and noted that the tadpoles were actually being predated on by dragon fly nymphs.
The scientists observed back in their lab that the dragon fly nymphs would, more often than not, eat only parts of the tadpoles, usually just removing a limb. The tadpoles would then return back, and grow up, sans said limb. Despite missing parts of their bodies, many of the tadpoles were still able to grow up, metamorphosizing into frogs, who managed to live quite a long time.
While frogs with missing limbs have a rather mundane explanation, the frogs with extra limbs have a much more exotic explanation. Sessions established that the frogs had been infested by small parasitic flatworms called Riberoria trematodes. These works burrowed into the rapidly developing tadpoles and actually rearranged the cellular structure of the frogs as they were developing, resulting in their leg precursor cells to actually spawn multiple limbs.
Of course, the fact that this problem turned out not to be our fault doesn’t mean we’re off the hook. Pollution is still a problem, even if its effects aren’t as obvious as a three-legged frog.