About those Extra and Missing Frog Limbs….
Remember how concerned we all were about frog limbs? Answers!:
In the late 1980s and early 1990s, researchers started getting reports of numerous wild frogs or toads being found with extra legs or arms, or with limbs that were partly formed or missing completely.
The cause of these deformities soon became a hotly contested issue.
Some researchers believed they might be caused naturally, by predators or parasites.
Others thought that was highly unlikely, fearing that chemical pollution, or UV-B radiation caused by the thinning of the ozone layer, was triggering the deformations.
“Deformed frogs became one of the most contentious environmental issues of all time, with the parasite researchers on one side, and the ‘chemical company’ as I call them, on the other,” says Stanley Sessions, an amphibian specialist and professor of biology at Hartwick College, in Oneonta, New York.
“There was a veritable media firestorm, with millions of dollars of grant money at stake.”
Somehow, the voices of the latter group were much more prevalent in the media than the former. (Surprise!). Well, the mystery of the missing legs was resolved a few years ago (what, you didn’t know?). Just like we all thought, it was we humans who were to blame…..!:
Sessions and other researchers established that many amphibians with extra limbs were actually infected by small parasitic flatworms called Riberoria trematodes.
These creatures burrow into the hindquarters of tadpoles where they physically rearrange the limb bud cells and thereby interfere with limb development.
Er…oh. OK, but what about all of those poor three-limbed frogs. Surely we did it to ’em!
The mystery of what causes frogs to have missing or deformed limbs remained unsolved until Sessions teamed up with colleague Brandon Ballengee of the University of Plymouth, UK….While surveying, Ballengee also discovered a range of natural predators he suspected could be to blame, including stickleback fish, newts, diving beetles, water scorpions and predatory dragonfly nymphs.
So Ballengee and Sessions decide to test how each predator preyed upon the tadpoles, by placing them together in fish tanks in the lab.
None did, except three species of dragonfly nymph.
Crucially though, the nymphs rarely ate the tadpoles whole. More often than not, they would grab the tadpole and chew at a hind limb, often removing it altogether.
“Once they grab the tadpole, they use their front legs to turn it around, searching for the tender bits, in this case the hind limb buds, which they then snip off with their mandibles,” says Sessions.
Hm. So bugs eat frogs. Payback is a b$%#&! I wonder if there are other environmental claims out there that could use some further research?