" We are skeptical of claims for the ability of random mutation and natural selection to account for the complexity of life. Careful examination of the evidence for Darwinian theory should be encouraged." - Dissent from Darwin

Natural selection [is used] carelessly as a mantra, as in the evidence-free “just-so stories” concocted out of thin air by mentally lazy adaptationists. (Stephen Jay Gould)

In the absence of any other proof, the thumb alone would convince me of God's existence. (Isaac newton)

Saturday, April 7, 2007

How FROG got her poison

The golden poison frog has enough venom in its skin to kill 12 people.
Why else would a creature coveted by everything from snakes and birds to Jacques Pépin evolve an extravagantly colored skin, except to warn any would-be predators of bitter toxins embedded therein?
Now it turns out that it is no mean feat for a frog to earn its mean feet, and that one of the surest routes to optimal toxicity is through a highly specialized form of ant eating.

Writing in the current issue of The Proceedings of the National Academy of Sciences, researchers report that poison frogs in Africa and the Neotropics of Central and South America appear to have converged on the same difficult method of harvesting the toxic chemicals they need to defend themselves against predators. Both the famed poison-dart frogs of the New World and the Mantella poison frogs of Madagascar dine largely though not exclusively on ants, and many of those ants, the researchers have determined, contain toxic chemicals called alkaloids.

Through entirely independent pathways, it seems, the two unrelated groups of frogs evolved a similar capacity to store, or sequester, the ingested alkaloids in their skin sacs without being harmed by the pungent substances themselves. And once the unrelated amphibian clans had succeeded in caching the ant bane in their glands, they autonomously evolved bright coloration to broadcast to potential frog-eaters their possession of distasteful alkaloids. The evolution of chemical protection and concomitant advertising gave the poison frogs a considerable leg up on the competition. Whereas most frogs dare only emerge at night to feed and will skitter for cover at the slightest breeze, a majority of poison frogs are diurnal, brazenly hopping around the sunlit forest floor like scattered gems on pogo sticks.

Storyteller: Natalie Angier, science journalist for the
New York Times.

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