Friday, June 26, 2009

Frogs, deformed and fanciful

I held off on blogging about frog deformities as symptomatic of the pollution of the ecosystem, and I'm glad I did. Just this week, British researchers have revealed that the cause is not chemicals or a thinning ozone layer, but dragonfly nymphs. The frogs with extra limbs have been attacked by small parasitic flatworms, which rearrange the cells of their limb buds. But the far more common missing or truncated limbs are the result of dragonfly nymphs nipping off the limb buds of tadpoles with their mandibles. The scientists characterize the limb buds as the "tender bits" and the hind legs are favored for two reasons: the front limb buds are protected because they develop within the gills and the hind legs are the last to develop poison glands and therefore may make a tastier meal. Tadpoles that are attacked when they are very young can regenerate the limb, but even those with missing legs survive in great numbers, which is why so many are found - and not just in North America.

It's also nice to know, as so many other species are facing imminent extinction, that new frogs are being discovered by the hundreds:
And all of these discoveries have been made within the last few years! The species found in Borneo has the requisite number of legs, but no lungs. The frog found in Peru is the world's smallest. And the males of the Costa Rican species are orange, and the females black. I dreaded dissecting a frog in high school, but there is a place for these colorful creatures in Quigley's Cabinet.

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